Article

A head-to-head comparison of poly(sarcosine) and poly(ethylene glycol) in peptidic, amphiphilic block copolymers

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  • Leiden Academic Center for Drug Research
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Abstract

In this work we compare chemical and solution properties, like critical aggregate concentrations (CAC) and hydrodynamic radii of aggregates based on either poly(ethylene glycol) or poly(sarcosine) block copolymers in aqueous solution. The amine functionalized, hydrophilic polymers poly(sarcosine) (degree of polymerization, Xn = 100 and 200) and PEG (Xn = 121 and 242) of comparable hydrodynamic volume were used to initiate the ring opening polymerization of α-amino acid-N-carboxyanhydrides based on ɣ-benzyl-l-glutamate (Glu(OBn)) or ε-carboxybenzyl-l-lysine (Lys(Z)). The second, hydrophobic block was kept at a degree of polymerization of 25 and 50 to enable a direct comparison of solution properties of block copolymers. In both cases block length could be precisely adjusted and all synthesized block copolymers have narrow molecular weight distributions and dispersities between 1.1 and 1.2. Both types of block copolymers display critical aggregate concentrations in the range of 6*10−8–3*10−7 mol/L and aggregates possess hydrodynamic radii in a range of 40–100 nm. PEG based systems, however, have a slightly lower CAC and tend to form smaller micelles, while PSar based systems have commonly smaller μ2 parameter indication more uniform aggregates.

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... 1 In particular, polysarcosine (PSar) holds outstanding promise as a biomedical polymer due to its hydrophilicity, the controllable manner in which its synthesis proceeds, 2,3 and the exclusive H-bond acceptor repeat units that offer it resistance to protein fouling. 4 Consequently, PSar offers a real alternative to poly(ethylene glycol) (PEG) for numerous applications, 5 including its use as a non-fouling coating, 6 and therapeutic protein conjugation. 7 The precise control over PSar synthesis has enabled the accurate synthesis of block copolymers that contain PSar conjugated to other polypeptoids, [8][9][10] poly(e-caprolactone), 11,12 tertiary amine-containing molecules, 13 PEG, 14 and poly(amino acids)/polyamides. ...
... Although the particles disclosed in this paper may readily be applied as materials that enable the controlled release of a range of molecular cargoes, the loading, and release, of an anticancer drug (Dox) into/from the particles was selected for further evaluation. The particles are deemed suitable candidates as drug delivery vehicles owing to their limited nondegradable polymer content, which is restricted to five repeat units on average per polymer chain in the case of PSar 136 -b-PHPMA 5 . Dox loading into polymer nanoparticles was achieved by 'dropping in' a solution of polymer dissolved in DMF to vigorously stirred phosphate buffered saline (PBS) solution that contained Dox. 30 Table S3, ESI †). ...
... This offers validation that the reported nanoparticles are pharmacologically relevant; payload release can be actuated by nanoparticle heating to a temperature that is not detrimental to cell survival. Pharmacological studies were undertaken whereby the cytotoxicity of the nanoparticles formed from PSar 136 -b-PHPMA 5 were assessed on MCF-7 breast cancer cells, triple-negative breast cancer cells (MDA-MB-231), and Her2-enriched (ER and PR negative) breast cancer cells (MDA-MB-453), to assess the capability of the materials to potentially treat chemo-refractory disease. Free Dox was used as a positive control (Tables S5 and S6, ESI †). ...
Article
Polysarcosine holds great promise as an alternative to poly(ethylene glycol) for use within both biomedical and non-biomedical applications owing to its hydrophilicity and non-cytoxicity, amongst other features. The grafting of a limited quantity of (N-(2-hydroxypropyl)methacrylamide) to polysarcosine, for instance 3.5% of the total copolymer in terms of the number of repeat units, has a profound effect on the properties of the copolymer formed; polymer self-assembly to yield thermoreponsive nanoparticles can now be realised. Such nanoparticles are non-cytotoxic against a range of human breast cancer cell lines, able to withhold the therapeutic compound doxorubicin, and allow pronounced doxorubicin release in response to subtle thermal stimulation. This research informs of how the straightforward modification of polysarcosine with a nominal molar amount of poly(N-(2-hydroxypropyl)methacrylamide) can yield stimuli-responsive polymers that are suitable for use within controlled release applications.
... The use of macroinitiators has several advantages besides the plain availability of amine functionalized polymers. A major advantage is that the synthesis of different block copolymers sharing an identical block is straightforward, which enables researchers to obtain reliable structure-property relationships [138,139]. The major hurdle of the macroinitiator approach is the purity of the initiator itself. ...
... In 2014, Huesmann et al. compared the solution properties like critical aggregate concentrations (CAC) and D h of PEG-or pSarb-pGlu(OBn) or -b-pLys(Z) copolymers in aqueous solution [138]. Both types of block copolymers displayed almost identical CACs, which are in the range of 6.0 × 10 −8 to 3.0 × 10 −7 mol/L. ...
... These structures are much larger than the micelles reported by Barz and coworkers [194] and may indicate the formation of disordered structures likely due to the preparation method. Nevertheless, CAC values are 3.6 × 10 −7 and 4 × 10 −6 mol/L, which is in line with the findings reported by Huesmann et al. [138]. ...
Article
Although the first polysarcosine (pSar) synthesis by Wesseley et al. was reported almost a century ago, it was only recently that pSar gained broader attention and is considered a potential alternative of poly(ethylene glycol) (PEG). In contrast to polyethers, such as PEG, pSar is a polypeptoid based on the amino acid sarcosine, i.e. N-methylated glycine. As a polymer, pSar combines PEG-like properties, e.g., excellent solubility in water, protein resistance, low cellular toxicity and a non-immunogenic character, while being based on endogenous material. Sarcosine can be obtained in a simple one-step reaction of bromoacetic acid and methylamine, easily transferred into the sarcosine N-(thio)carboxyanhydride and polymerized under living condition. This review provides a first comprehensive overview on pSar-containing block copolymers, which comprises of copolymers with polyesters, polyethers, polypeptides, polypeptoids, polyacrylates, others, as well as graft copolymers. The synthesis, characteristics and application of such polymers will be presented and discussed in detail. Finally, solution self-assembly and applications of pSar-containing block copolymers are reviewed underlining the enormous potential of this recently rediscovered polypeptoidic material.
... acid-derived polypeptoid, has been of particular interest in the biomedical field due to its poly(ethylene glycol) (PEG) properties (i.e., hydrophilicity, limited non-specific organ uptake, extended circulation times etc.), indicating its potential as a replacement for PEG. [17][18][19] This unique property has significantly increased interest in the development of polypept(o) ide nanoparticles for applications in drug delivery. ...
... Finally, poly(sarcosine) was selected as a non-reactive hydrophilic polymer with "PEGlike" properties. [18] The successful synthesis of amphiphilic block copolymers via surface initiated NCA-ROP was confirmed by 1 H NMR and FT-IR spectroscopy. It was found by 1 H NMR spectroscopy that before chain extension with sar-NCA, signals attributed to poly(tryptophan-co-phenylalanine) (P(W-co-F)) backbone and aromatic groups were present. ...
Article
Owing to their wide range of inherent functionality, hydrolytic stability, biodegradability, and low toxicity, polypeptide‐based materials have been increasingly exploited for controlled drug release applications. More recently, the incorporation of poly(α‐peptoid)s such as poly(sarcosine) into polypeptide‐based materials has been investigated owing to their potential as naturally derived “stealth polymers.” Here the synthesis of novel amphiphilic polypept(o)ide nanoparticles is described utilizing silica templates as a macroinitiator for the ring‐opening copolymerization of l‐tryptophan and d/l‐phenylalanine NCAs and subsequent chain extension with sarcosine NCA. These particles are subsequently crosslinked utilizing the TAD‐indole “click” chemistry and the silica templates are eroded via treatment with HF yielding core crosslinked amphiphilic polypept(o)ide nanostructures. This synthetic strategy offers a unique platform to yield naturally‐derived degradable core‐crosslinked nanostructures, which may have the potential to be utilized in the future as delivery vehicles for hydrophobic small molecules.
... A further comparison between PSar and PEG in block copolypept(o)ides revealed that they presented similar hydrophilicity and solution properties. [34] In our previous study, it was found that polypeptide with amide bonds present in both main chain and side residue, that is, poly(Nisopropyl-L-glutamine) (PIGA), exhibited a helical conformation and poor water-solubility due to an intensive H-bonding packing of side groups [35] . With the development on polypeptoid synthesis, [36] it is now possible to alter the H-bonding in the main chain of polypeptides simply by copolymerization. ...
... temperature. Therefore, both measurements suggested that PEG copolypeptide exhibited thermo-sensitivity while PSar remained relatively thermo-stable [34] . ...
Article
Full-text available
Copolypept(o)ides of polysarcosine (PSar) and poly(N-isopropyl-L-glutamine) (PIGA) with random and block sequence structures were synthesized by ring-opening polymerization (ROP) of sarco-sine N-carboxyanhydrides (Sar-NCA) and g-benzyl-L-glutamate N-carboxyanhydrides (BLG-NCA) and post modification. With different distribution of Sar along the main chain, H-bonding pattern and secondary structure of polypeptides were turned, as well as aggregation and gelation behavior. Both copolypept(o)ides formed hydrogels above their critical gelation concentrations (CGCs) without thermo-sensitivity, which was normally reserved for PEG copolypeptides (eg, PEG-b-PIGA). In particular, a different mechanism from previously reported micellar percolation or fibrillar entanglement was suggested for gelation of the random copolypept(o)ide. Therefore, hydrogels from copolymers of PSar and PIGA represented a new approach to construct easy-handling, bio-compatible, biodegradable and thermo-stable gels that could potentially be applied in biomedical fields. K E Y W O R D S copolypept(o)ide, gelation, ring-opening polymerization
... The synthesis of pGlu(O t Bu)-b-pSar was performed by sequential ring-opening polymerization (ROP) of the corresponding NCAs (see Scheme 1). The tert-butyl protection Scheme 1. Synthesis of pGlu(COONa) 11 -r-pGlu(CODopa) 22 group was chosen for polymerizations as substitution for the benzyl protection group used previously 24,46 since it allows relatively mild removal in TFA without fragmentation of the pSar block. 47 After full conversion of the Glu(O t Bu)NCA was ensured by Fourier-transform infrared (FTIR) spectroscopy, the SarNCA was added, and the polymerization was again allowed to proceed until full conversion. ...
... Moreover, negatively charged coatings control the slow release of Ag + ions resulting in improved cell viability ( Figure S9). 55 The size of Ag NPs in our system is smaller than hydrodynamic diameter of polymer, 46 resulting in complete coverage of Ag NPs with polymers. We suppose that the negative charges of the glutamic acid block at physiological pH contribute to a controlled Ag + release since there was no significant difference in biocompatibility between bare and Ag NPs-P(A)-modified surfaces ( Figure 6C). ...
Article
Prevention of biofouling and microbial contamination of implanted biomedical devices is essential to maintain their functionality and biocompatibility. For this purpose, polypept(o)ide block copolymers have been developed, in which a protein-resistant polysarcosine (pSar) block is combined with a dopamine-modified poly(glutamic acid) block for surface coating and silver nanoparticles (Ag NPs) formation. In the development of a novel, versatile and biocompatible antibacterial surface coating, block lengths pSar were varied to derive structure property relationships. Notably, the catechol moiety performs two important tasks in parallel; primarily it acts as an efficient anchoring group to metal oxide surfaces, while it furthermore induces the formation of Ag NPs. Attributing to the dual function of catechol moieties, antifouling pSar brush and antimicrobial Ag NPs can not only adhere stably on metal oxide surfaces, but also display passive antifouling and active antimicrobial activity, showing good biocompatibility simultaneously. The developed strategy seems to provide a promising platform for functional modification of biomaterials surface to preserve their performance while reducing the risk of bacterial infections.
... This debate has prompted exploration into novel materials that resemble PEG, retaining its positive attributes, but add biodegradability. Two of such classes of polymers that would form viable alternatives are polyoxazolines and polypeptides [10,11], both of which possess biodegradable and biocompatible properties. Moreover, these materials offer versatility in their synthesis, allowing for the incorporation of various building blocks to tailor the polymers to desired specifications. ...
Article
Full-text available
Polysarcosine emerges as a promising alternative to polyethylene glycol (PEG) in biomedical applications, boasting advantages in biocompatibility and degradability. While the self-assembly behavior of block copolymers containing polysarcosine-containing polymers has been reported, their potential for shape transformation remains largely untapped, limiting their versatility across various applications. In this study, we present a comprehensive methodology for synthesizing, self-assembling, and transforming polysarcosine-poly(benzyl glutamate) block copolymers, resulting in the formation of bowl-shaped vesicles, disks, and stomatocytes. Under ambient conditions, the shape transformation is restricted to bowl-shaped vesicles due to the membrane's flexibility and permeability. However, dehydration of the polysarcosine broadens the possibilities for shape transformation. These novel structures exhibit asymmetry and possess the capability to encapsulate smaller structures, thereby broadening their potential applications in drug delivery and nanotechnology. Our findings shed light on the unique capabilities of polysarcosine-based polymers, paving the way for further exploration and harnessing of their distinctive properties in biomedical research.
... An alternative to PEG is a polypeptoid of the amino acid sarcosine (N-methylated glycine) [29]. Prior studies compared the critical aggregate concentration of PEG or polysarcosine (pSar) and found that these two polymers behave similarly, which suggests that pSar can serve similar functionality as PEG for antifouling applications [30,31]. Polysarcosine has been previously investigated as a PEG substitute for therapeutic protein conjugation [32]. ...
Article
Full-text available
Since the approval of the lipid nanoparticles (LNP)-mRNA vaccines against the SARS-CoV-2 virus, there has been an increased interest in the delivery of mRNA through LNPs. However, current LNP formulations contain PEG lipids, which can stimulate the generation of anti-PEG antibodies. The presence of these antibodies can potentially cause adverse reactions and reduce therapeutic efficacy after administration. Given the widespread deployment of the COVID-19 vaccines, the increased exposure to PEG may necessitate the evaluation of alternative LNP formulations without PEG components. In this study, we investigated a series of polysarcosine (pSar) lipids as alternatives to the PEG lipids to determine whether pSar lipids could still provide the functionality of the PEG lipids in the ALC-0315 and SM-102 LNP systems. We found that complete replacement of the PEG lipid with a pSar lipid can increase or maintain mRNA delivery efficiency and exhibit similar safety profiles in vivo.
... This model indicates that there is a critical length at which a secondary structure transition occurs, driving in aggregation. 71 Based on dispersity, there would always be a peak at the same high elution volume which represents the part of the molecular weight distribution that is below the secondary structure transition. This would explain why the minor peaks from KEY20 and KEY30 roughly align with the major peak of KEY10. ...
Article
Full-text available
The drug overdose epidemic in America has intensified over the past 20 years and has led to hundreds of thousands of deaths. Opioids account for most of these deaths, but overdose can be effectively reversed using naloxone, an FDA-approved medication. The rate of non-opioid drug fatalities has also risen in recent years—but unlike opioids—many of these drugs do not have specialized treatments in cases of overdose. Instead, activated charcoal is ingested to decontaminate the gastrointestinal tract before the drug is absorbed by the blood. Although activated charcoal is an effective drug adsorbent, there are many adverse side effects following respiratory and oral exposure. To address the drawbacks of this treatment, a new class of aromatic polypeptide amphiphiles (termed “KEYs”) were developed to adsorb drugs from the stomach and intestines without harmful side effects. This manuscript details the rational design and synthesis of KEY polypeptide adsorbents. KEYs were evaluated against model compounds acid yellow 3 and amitriptyline in simulated biological media and compared to activated charcoal. Adsorption studies indicate that KEYs are capable of adsorbing drugs. KEYs adsorb molecules as rapidly as activated charcoal and adsorb certain compounds with comparable or higher adsorption capacity in a pH-dependent manner. This work represents a novel application of aromatic polypeptide amphiphiles as a gastrointestinal decontamination technology. Further, these studies provide insight for how future generations of polypeptide-based adsorbents can be rationally designed to selectively target and improve drug adsorption from the gastrointestinal tract.
... Like PEG, it is flexible and hydrophilic, allowing entropic exclusion of opsonins and has been recognized as a prime candidate for PEG substitution [202,203]. PSR has been identified as anti-fouling and appropriate for inclusion in nanoparticles as a "stealth" component [204,205]. A recent study also shows that it can protect conjugated proteins from proteolysis [206]. ...
... A nanoprecipitation process was reported for PEG-b-PLGluOBn copolymers using a mixture of DMF and tetrahydrofuran (THF) (3/7, v/ v) (Jeong et al., 2005), pure THF (Barbosa et al., 2007;Segura-Sánchez et al., 2010), or dimethyl sulfoxide (DMSO) Goñi-de-Cerio, 2013;Kakkar et al., 2015). For PSar-b-PLGluOBn copolymers, Barz et al. reported a nanoprecipitation method , dialysis method (Huesmann et al., 2015), and a centrifugation technique (Weber et al., 2017). Since paclitaxel and the different PSar-b-PGluOBn copolymers described above were all soluble in pure DMF, we decided to perform a nanoprecipitation procedure similar to the literature , in which a solution of copolymer and paclitaxel in DMF at a feed weight ratio of 10 % is injected into water in conditions well-above their CMC (Fig. S38). ...
Article
New stealth amphiphilic copolymers based on polysarcosine (PSar) rather than poly(ethylene glycol) (PEG) have gained more attention for their use as excipients in nanomedicine. In this study, several polysarcosine-b-poly(γ-benzyl glutamate) (PSar-b-PGluOBn) block copolymers were synthesized by ring opening polymerization (ROP) of the respective N-carboxyanhydrides (NCAs) and were characterized by Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR) and size-exclusion chromatography (SEC). Copolymers had different PGluOBn block configuration (racemic L/D, pure L or pure D), degrees of polymerization of PSar between 28 and 76 and PGluOBn between 9 and 93, molar masses (Mn) between 5.0 and 24.6 kg.mol⁻¹ and dispersities (Đ) lower than 1.4. Nanoparticles of PSar-b-PGluOBn loaded with paclitaxel (PTX), a hydrophobic anti-cancer drug, were obtained by nanoprecipitation. Their hydrodynamic diameter (Dh) ranged from 27 to 118 nm with polydispersity indexes (PDI) between 0.01 and 0.20, as determined by dynamic light scattering (DLS). Their morphology was more spherical for copolymers with a racemic L/D PGluOBn block configuration synthesized at 5 °C. PTX loading efficiency was between 63 and 92% and loading contents between 7 and 15%. Using PSar-b-PGluOBn copolymers as excipients, PTX apparent water-solubility was significantly improved by a factor up to 6600 to 660 µg.mL⁻¹.
... [32][33][34] Many researches have been reported in recent years that the biocompatible, non-cytotoxic and stealth-like PSar does well in biomedicine. [25][26][35][36][37][38][39][40] With the same problem as PEG has, PSar is non-biodegradable and there has been no successful enzymolysis of PSar so far, indicating the excretion of PSar is nonnegligible. 41 Another methylated glycine, L-alanine (Ala), is one of the native amino acids as an isomer of sarcosine. ...
Preprint
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Polysarcosine (PSar), a water-soluble polypeptoid, is gifted with biodegradability via random ring-opening copolymerization of sarcosine- and alanine-N-thiocarboxyanhydrides catalyzed by acetic acid in controlled manners. Kinetic investigation reveals the copolymerization behavior of the two monomers. The random copolymers, named PAS, with high molecular weights between 22.0 and 43.6 kg/mol and tunable Ala molar fractions varying from 6% to 43% are able to be degraded by porcine pancreatic elastase within 50 days in mild conditions (pH=8.0 at 37 °C). Both the biodegradation rate and water solubility of PAS depend on the content of Ala residues. PAS with Ala fractions below 43% are soluble in water while the one with 43% Ala self-assembles in water into nanoparticles. Moreover, PAS are non-cytotoxic at the concentration of 5 mg/mL. The biodegradability and biocompatibility endow the Ala-containing PSar with potential to replace PEG as protective shield in drug-delivery.
... 34 PSar properties are similar to PEG, in that it has high water solubility and exhibits hydrogen bond acceptor attributes as a result of methylation at the amide nitrogen atom. 35,36 In addition, it is a nonionic zero charge polypeptoid with a nonimmunogenic profile and is associated with low cellular toxicity. 34 These features, along with minimal interactions with proteins, render PSar as a biocompatible material providing "stealth-like" properties similar to PEG. ...
Article
Mucosal delivery across the gastrointestinal (GI) tract, airway, and buccal epithelium is an attractive mode of therapeutic administration, but the challenge is to overcome mucus- and epithelial barriers. Here, we present degradable star polypept(o)ides capable of permeating both barriers as a promising biomaterial platform for mucosal delivery. Star polypept(o)ides were obtained by initiation of benzyl-L-glutamate N-carboxyanhydride (NCA) from an 8-arm polypropylene dendrimer, with subsequent chain extension with sarcosine NCA. The hydrophobic poly(benzyl-L-glutamate) block length was maintained at 20 monomers, while the length of the hydrophilic poly(sarcosine) block ranged from 20 - 640 monomers to produce star polypept(o)ides with increasing hydrophilic : hydrophobic ratios. Transmision Electron Microscopy (TEM) images revealed elongated particles of ~120 nm length, while Dynamic Light Scattering (DLS) provides evidence of a decrease in the size of polymer aggregates in water with increasing poly(sarcosine) block length, with the smallest size obtained for the star PBLG20-b-PSar640. Fluorescein isothiocyanate (FITC)-conjugated PBLG20-b-PSar640 permeated artificial mucus and isolated rat mucus, as well as rat intestinal jejunal tissue mounted in Franz diffusion cells. A permeability coefficient (Papp) of 15.4 ± 3.1 x 10 -6 cm/sec for FITC-PBLG20-b-PSar640 was calculated from the flux obtained with apical-side addition of 7.5 mg polypept(o)ide to jejunal tissue. The Papp could not be accounted for by flux of unconjugated FITC. Exposure to trypsin demonstrated enzymatic stability of FITC labeled polypept(o)ide over 2 h, but enzymatic degradation at the mucus-epithelial interface or during flux cannot be ruled out as contributing to the increased Papp. The absence of any histological damage to the jejunal tissue during the 2 h exposure suggests that flux was not associated with toxicity.
... As model systems we selected polymer micelles and a molecular polymer brush, which are close to established nanocarriers concerning their hydrophilic shell (see Figure 1). As shell material we chose either i) poly(ethylene glycol) (PEG), [25,32] ii) poly(N-2-hydroxypropylmethacrylamide) (pHPMA) [18,33,34] or iii) polysarcosine (pSar), [35,36] as they are not only considered protein resistant but furthermore are part of drugs in preclinical or clinical investigations. [21,[37][38][39] Moreover, all these polymers ...
Article
Full-text available
The current understanding of nanoparticle–protein interactions indicates that they rapidly adsorb proteins upon introduction into a living organism. The formed protein corona determines thereafter identity and fate of nanoparticles in the body. The present study evaluates the protein affinity of three core‐crosslinked polymeric nanoparticles with long circulation times, differing in the hydrophilic polymer material forming the particle surface, namely poly(N‐2‐hydroxypropylmethacrylamide) (pHPMA), polysarcosine (pSar), and poly(ethylene glycol) (PEG). This includes the nanotherapeutic CPC634, which is currently in clinical phase II evaluation. To investigate possible protein corona formation, the nanoparticles are incubated in human blood plasma and separated by asymmetrical flow field‐flow fractionation (AF4). Notably, light scattering shows no detectable differences in particle size or polydispersity upon incubation with plasma for all nanoparticles, while in gel electrophoresis, minor amounts of proteins can be detected in the particle fraction. Label‐free quantitative proteomics is additionally applied to analyze and quantify the composition of the proteins. It proves that some proteins are enriched, but their concentration is significantly less than one protein per particle. Thus, most of the nanoparticles are not associated with any proteins. Therefore, this work underlines that polymeric nanoparticles can be synthesized, for which a protein corona formation does not take place.
... Furthermore, PEG can enhance intracellular drug accumulation by reversing multidrug resistance in tumor cells [11]. PEG has been well developed for a hydrophilic shielding agent when combining with other hydrophobic substances as drug carriers, such as poly(lactic-co-glycolic acid)(PLGA) [12][13][14], poly(e-caprolactone)(PCL) [15,16], and poly(amino acid) [17][18][19]. ...
Article
Keratin-based drug carriers have attracted great interest due to their intrinsic biocompatibility and tumor micro-environmental responsiveness. In the study, keratin was first extracted from human hair with reduction method. The reduced keratin was successively conjugated with poly(ethylene glycol) (PEG) via thiol Michael addition reaction and iodoacetic acid (IAA) via substitution reaction to impart both physical stability and acidity responsiveness. Subsequently, the conjugated keratin was fabricated into micelles and loaded with doxorubicin (DOX) by self-assembly. The micelles exhibited pH, glutathione (GSH) and enzyme (trypsin) triple-responsiveness as well as charge reversibility under the simulated tumor microenvironment. These drug-loaded micelles exhibited high toxicity against A549 cells with low side effect on normal cells. Furthermore, anticancer efficacy in vivo revealed DOX-loaded micelles presented higher therapeutic efficiency than free DOX. Moreover, these micelles were stable under physiological conditions, and could be internalized through endocytosis without hemolysis. Based on the results, the drug-loaded micelles were satisfactory candidates for drug carriers.
... Furthermore, PEG can enhance intracellular drug accumulation by reversing multidrug resistance in tumor cells [11]. PEG has been well developed for a hydrophilic shielding agent when combining with other hydrophobic substances as drug carriers, such as poly(lactic-co-glycolic acid)(PLGA) [12][13][14], poly(e-caprolactone)(PCL) [15,16], and poly(amino acid) [17][18][19]. ...
Article
Drug-loaded micelles with long circulation time in blood and stimuli-responsiveness under tumor microenvironment can significantly enhance the therapeutic efficacy. In this report, human hair keratin was extracted with a reduction method and then conjugated with zwitterionic poly(2-methacryloxyethyl phosphatidylcholine, MPC) via thiol chain transfer polymerization(Thiol CTP). Subsequently, keratin-polyMPC conjugates (KPC) were prepared into micelles and loaded with doxorubicin (DOX) by self-assembly. These micelles exhibited pH, glutathione (GSH), and enzyme triple-responsiveness as well as charge reversibility under the tumor microenvironment. In addition, these micelles showed high toxicity against A549 cells while low toxicity to normal cells. In vivo anticancer efficacy results revealed that these micelles performed better therapeutic efficiency than free DOX. Furthermore, these carriers exhibited the prolonged circulation time, good stability, and no hemolysis in blood. Based on the results, these drug delivery systems of micelles were proper candidates as drug carriers.
... [16] Nonionic polyglycine is similar to PEG, but potentially offers in vivo degradability as suggested by in vitro studies under physiologically relevant conditions. [17] Another goal of the study was to investigate in vitro cellular response of the particles. The effect of nanoparticles as drug carrier was determined using human bone marrow stromal cells (hMSCs) or tumor glioblastoma cell line GaMG and primary glioblastoma cells isolated from patients (GBM), and compared with that of free Dox. ...
Article
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With the aim to develop a new anticancer agent, we prepared poly[N‐(2‐hydroxypropyl)methacrylamide‐co‐methyl 2‐methacrylamidoacetate] [P(HP‐MMAA)], which was reacted with hydrazine to poly[N‐(2‐hydroxypropyl)methacrylamide‐co‐N‐(2‐hydrazinyl‐2‐oxoethyl)methacrylamide] [P(HP‐MAH)] to conjugate doxorubicin (Dox) via hydrazone bond. The resulting P(HP‐MAH)‐Dox conjugate was used as a coating of magnetic γ‐Fe2O3 nanoparticles obtained by the coprecipitation method. In vitro toxicity of various concentrations of Dox, P(HP‐MAH)‐Dox, and γ‐Fe2O3@P(HP‐MAH)‐Dox nanoparticles was determined on somatic healthy cells (human bone marrow stromal cells hMSC), human glioblastoma line (GaMG), and primary human glioblastoma (GBM) cells isolated from GBM patients both at a short and prolonged exposition time (up to 7 days). Due to hydrolysis of the hydrazone bond in acid milieu of tumor cells and Dox release, the γ‐Fe2O3@P(HP‐MAH)‐Dox nanoparticles significantly decreased the GaMG and GBM cell growth compared to free Dox and P(HP‐MAH)‐Dox in low concentration (10 nM), whereas in hMSCs it remained without effect. γ‐F2O3@PHP nanoparticles alone did not affect the viability of any of the tested cells.
... pH-or redox-responsive) or act as a core-forming block due to their tendency to form secondary structures [26,27]. pSar has been proposed as a promising alternative to PEG because of their many commonalities such as zero net charge, hydrophilicity, and the inability to serve as a hydrogen bond donor, and as a result, they strictly follows Whitesides' rules for protein-resistant surfaces [28][29][30][31][32]. In addition, it was recently demonstrated that PEG and pSar possess identical Kuhn-lengths and second virial coefficients in aqueous solutions [33]. ...
Article
Amphiphilic miktoarm star copolymers have a unique internal structure and many attractive properties with respect to solution self-assembly, such as a high density of internal and peripheral functionalities, low CMC values, and high loading efficiency. However, compared to their linear analogs, the complex architecture demands asymmetric polymer arms emanating from a single core, which poses a significant synthetic challenge. Herein, we demonstrate an approach for the synthesis of polypept(o)ide-based AB3- and A3B-type miktoarm PeptoStars consisting of polypeptidic poly(γ-benzyl-l-glutamate (pGlu(OBn)) as the hydrophobic A arm and polypeptoidic polysarcosine (pSar) as the hydrophilic B arm. These structures, which are completely derived from endogenous amino acids, were realized by the core-first method using a tetrafunctional initiator and the corresponding N-carboxyanhydrides (NCAs) via a controlled, living nucleophilic ring-opening polymerization (ROP). The asymmetric architecture was achieved through an orthogonal protecting group strategy with multiple protection/deprotection steps. Characterization via ¹H NMR-, ¹H DOSY-spectroscopy, and size-exclusion chromatography (SEC) indicate the presence of well-formed miktoarm PeptoStars with low dispersities (Đ = 1.09–1.14), the precise control over the degree of polymerization and Poisson-like molecular weight distributions.
... Neutral water-soluble PAAs are competitive alternatives of PEG [17][18][19]. For instance, polysarcosine (PSar) and poly(N-ethylglycine) (PNEG) are favored as the hydrophilic block for biomedical applications due to their non-toxicity and biocompatibility [20,21]. ...
... We selected the 10 kDa PEG for conjugation because it has a comparable hydrodynamic radius with our PSar of 12 kDa. 26 Size exclusion chromatography (SEC) analysis of the two conjugates gave the same elution time, suggesting the two conjugates shared a similar hydrodynamic volume ( Figure 1B). This notion was also well supported by the dynamic light scattering (DLS) measurement, which gave a 12.6 ± 0.7 and 12.8 ± 0.4 nm diameter for PSar-IFN and PEG-IFN, respectively ( Figure 1C). ...
Article
Full-text available
The performances of many therapeutic proteins, including human interferon-α2b (IFN), are often impeded by their intrinsic instability to protease, poor pharmacokinetics, and strong immunity. Although PEGylation has been an effective approach improving the pharmacokinetics of many proteins, a few noticeable limitations have aroused vast research efforts in seeking alternatives of PEG for bioconjugation. Herein, we report our investigation on the use of polysarcosine (PSar), a non-ionic and hydrophilic polypeptoids, for IFN modification. The site-specific conjugate PSar-IFN, generated by native chemical ligation in high yield, is systematically compared with a similarly produced PEG-interferon conjugate (PEG-IFN) to evaluate the in vitro and in vivo behaviors. PSar is found to show comparable ability in stabilizing IFN from protease digestion in vitro and prolonging the circulation half-life in vivo. Interestingly, PSar-IFN retains more activity in vitro and accumulates more in the tumor sites upon systemic administration than PEG-IFN. Most importantly, PSar-IFN is significantly more potent in inhibiting tumor growth and elicits considerably less anti-IFN antibodies in mouse than PEG-IFN. Together, our results demonstrate for the first time that PSar is an outstanding candidate for therapeutic protein conjugation. Considering the low toxicity, biodegradability, and excellent stealth effect of PSar, this study suggests that such polypeptoids hold enormous potential for many biomedical applications including protein delivery, colloidal stabilization, and nanomedicine.
... 1−7 Neutral water-soluble polypeptides and polypeptoids are remarkably competitive alternatives of PEG. 8,9 For instance, water-soluble polypeptoids, polysarcosine (PSar) and poly(N-ethylglycine) (PNEG), are favored as the hydrophilic block for biomedical applications due to their nontoxicity and biocompatibility. 10−18 Furthermore, PSar with special functional end groups are used for block copolymer synthesis 19,20 or as ligands to stabilize quantum dots 21 and gold nanoparticles 22,23 in aqueous solution, which enhances the colloidal stability and biocompatibility at the same time. ...
Article
N-Carboxyanhydride (NCA) polymerization cannot tolerate nucleophilic groups that have the ability of initiation, e.g., hydroxyl group. In contrast, N-thiocarboxyanhydride (NTA) is a much more stable monomer to tolerate them. In this contribution, we investigate aminoalcohols including 2-amino-1-ethanol (AE), 3-amino-1-propanol (AP), 4-aminomethylbenzyl alcohol (AMB), 6-amino-1-hexanol (AH), and 12-amino-1-dodecanol (AD) as initiators for ring-opening polymerization of N-substituted glycine N-thiocarboxyanhydride (NNTA) to prepare α-hydroxyl-ω-aminotelechelic water-soluble polypeptoids. Hydroxyl groups of AE, AP, and AMB are activated by hydrogen bonding with amino groups, which results in a mixture of α,ω-diaminotelechelic and α-hydroxyl-ω-aminotelechelic polypeptoids confirmed by ¹H NMR, MALDI-ToF, and SEC measurements. Pure α-hydroxyl-ω-aminotelechelic polypeptoids are synthesized for the first time initiated by AH and AD with controlled molecular weights (1.3–12.4 kg/mol) and low polydispersity indices (<1.30). Hydroxyl groups in AH and AD remain inactive to generate hydrogen bonding due to the long distance from amino groups. Water-soluble polypeptoids with special functional end groups are attractive alternatives of PEG for their nontoxicity and biocompatibility having great potential in biomedical applications.
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Polysarcosine emerges as a promising alternative to polyethylene glycol (PEG) in biomedical applications, boasting advantages in biocompatibility and degradability. While the self-assembly behavior of block copolymers containing polysarcosine containing polymers has been reported, their potential for shape transformation remains largely untapped, limiting their versatility across various applications. In this study, we present a comprehensive methodology for synthesizing, self-assembling, and transforming polysarcosine-polybenzylglutamate block copolymers, resulting in the formation of bowl-shaped vesicles, disks, and stomatocytes. Under ambient conditions, the shape transformation is restricted to bowl-shaped vesicles due to the membrane's flexibility and permeability. However, dehydration of the polysarcosine broadens the possibilities for shape transformation. These novel structures exhibit asymmetry and possess the capability to encapsulate smaller structures, thereby broadening their potential applications in drug delivery and nanotechnology. Our findings shed light on the unique capabilities of polysarcosine-based polymers, paving the way for further exploration and harnessing of their distinctive properties in biomedical research.
Article
Protein‐polymer conjugates and polymeric nanomaterials hold great promise in many applications including biomaterials, medicine or nanoelectronics. In this work, we present the first PISA (polymerization‐induced self‐assembly) approach performed in aqueous medium enabling protein‐polymer conjugates and nanoparticles entirely composed of amino acids by using ring‐opening polymerization (ROP). We indeed show that aqueous ROPISA can be used with protein or peptidic macroinitiators without prior chemical modification and afford the simple preparation of nanomaterials with protein‐like property, for example to implement biomimetic thermoresponsivity in drug delivery. This article is protected by copyright. All rights reserved
Article
N‐carboxyanhydride ring‐opening polymerisation‐induced self‐assembly (NCA ROPISA) offers a convenient route for generating poly(amino acid)‐based nanoparticles in a single step, crucially avoiding the need for post‐polymerisation self‐assembly. Most examples of NCA ROPISA make use of a poly(ethylene glycol) hydrophilic stabilising block, however this non‐biodegradable, oil‐derived, polymer and may cause an immunological response in some individuals. Alternative water‐soluble polymers are therefore highly sought. We report the synthesis of wholly poly(amino acid)‐based nanoparticles, through the chain‐extension of a polysarcosine macroinitiator with L‐Phenylalanine‐NCA (L‐Phe‐NCA) and Alanine‐NCA (Ala‐NCA), via aqueous NCA ROPISA. The resulting polymeric structures comprise of predominantly anisotropic, rod‐like nanoparticles, with morphologies primarily influenced by the secondary structure of the hydrophobic poly(amino acid) that enables their formation. This article is protected by copyright. All rights reserved
Article
Introduction: Due to the concerns raised by the extensive application of PEGylation, polypeptides have stood out as excellent candidates with adequate biocompatibility and biodegradability with tunable hydrophilicity. Areas covered: In this review, polypeptides with the potential to replace PEGylation have been summarized and their application has been reviewed, including XTEN, PASylation, polysarcosine, zwitterion polypeptides, ELPylation, etc. Besides their strengths, the remaining challenges have also been discussed and the future perspectives have been provided. Expert opinion: Polypeptides have been applied in the designing of peptide/protein drugs as well as nanomedicines, and some of the pharmaceutics have made it into the clinical trials and got approved. These polypeptides showed similar hydrophilic properties to PEGylation, which increased the hydrodynamic volumes of protein drugs, reduced kidney elimination, decreased protein-polymer interaction and potentially improved the drug delivery efficiency due to the extended circulation time in the system. Moreover, they demonstrated superior biodegradability and biocompatibility, compensating for the deficiencies for polymers such as PEG.
Chapter
Polymers are the backbone for generating and developing newer drug delivery systems for human welfare against dreadful diseases. Designed polymers should be biocompatible, nonimmunogenic, and nontoxic and are acceptable for biomedical applications. Block copolymers have several applications in drug delivery. Over time, different types of polymers have been synthesized to suit specific drug formulations and requirements. These polymers include homopolymers (composed of similar small molecules), heteropolymers, or copolymers (composed of dissimilar small molecules), alternating copolymers, and random copolymers. Block copolymer micelles are a kind of nanosized particle that has gained significant attention in drug delivery, predominantly for enhancing the solubility of hydrophobic drugs and altering their biopharmaceutical profile. The current chapter includes the general classification and structural information of block copolymers. Besides, emphasis is given to the use of diblock copolymer systems in drug delivery systems.
Article
Core cross-linked polymeric micelles (CCPMs) are designed to improve the therapeutic profile of hydrophobic drugs, reduce or completely avoid protein corona formation, and offer prolonged circulation times, a prerequisite for passive or active targeting. In this study, we tuned the CCPM stability by using bifunctional or trifunctional cross-linkers and varying the cross-linkable polymer block length. For CCPMs, amphiphilic thiol-reactive polypept(o)ides of polysarcosine-block-poly(S-ethylsulfonyl-l-cysteine) [pSar-b-pCys(SO2Et)] were employed. While the pCys(SO2Et) chain lengths varied from Xn = 17 to 30, bivalent (derivatives of dihydrolipoic acid) and trivalent (sarcosine/cysteine pentapeptide) cross-linkers have been applied. Asymmetrical flow field-flow fraction (AF4) displayed the absence of aggregates in human plasma, yet for non-cross-linked PM and CCPMs cross-linked with dihydrolipoic acid at [pCys(SO2Et)]17, increasing the cross-linking density or the pCys(SO2Et) chain lengths led to stable CCPMs. Interestingly, circulation time and biodistribution in mice of non-cross-linked and bivalently cross-linked CCPMs are comparable, while the trivalent peptide cross-linkers enhance the circulation half-life from 11 to 19 h.
Article
Polysarcosine (PSar) is an electrically neutral and excellently hydrophilic polypeptoid showing limited interaction with proteins and cells, which possesses better biocompatibility compared with polyethylene glycol. However, the immobilization of PSar is difficult due to the high water solubility. Herein, lysine-sarcosine PiPo, which was the random copolymer of lysine and sarcosine (PLS), was synthesized via a phosgene-free and water-tolerable polymerization of N-phenyloxycarbonyl-amino acids for the first time. PLS was immobilized by tannic acid (TA) on the polysulfone (PSf) membrane for a short time to obtain a neutral surface. The modified membrane showed improved hydrophilicity, decreased protein adsorption, and low cytotoxicity. Moreover, barely any hemolysis, no platelet adhesion, prolonged clotting time, and low complement activation further suggested good hemocompatibility. In order to improve the antifouling ability of the membrane under pressure, the neutral surface was oxidized by sodium periodate, which accelerated the chemical reaction between amino groups in PLS and phenolic hydroxyl groups in TA. Meanwhile, carboxyl groups generated due to the decomposition of TA and a negatively charged surface were obtained. While maintaining the good properties of the unoxidized one, the hydrophilicity of the oxidized membrane was improved and the clotting time was further prolonged. Besides, the filtration recovery of the oxidized membrane was improved remarkably. This approach of rapid immobilization of PSar has great potential for applications in the biomedical area, especially for blood-contacting materials.
Article
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Many therapeutic formulations incorporate poly(ethylene glycol) (PEG) as a stealth component to minimize early clearance. However, PEG is immunogenic and susceptible to accelerated clearance after multiple administrations. Here, we present two novel reformulations of a polyion complex (PIC), originally composed of poly(ethylene glycol)113-b-poly(glutamic acid)50 (PEG-PLE) and brain-derived neurotrophic factor (BDNF), termed Nano-BDNF (Nano-BDNF PEG-PLE). We replace the PEG based block copolymer with two new polymers, poly(sarcosine)127-b-poly(glutamic acid)50 (PSR-PLE) and poly(methyl-2-oxazolines)38-b-poly(oxazolepropanoic acid)27-b-poly(methyl-2-oxazoline)38 (PMeOx-PPaOx-PMeOx), which are driven to association with BDNF via electrostatic interactions and hydrogen bonding to form a PIC. Formulation using a microfluidic mixer yields small and narrowly disperse nanoparticles which associate following similar principles. Additionally, we demonstrate that encapsulation does not inhibit access by the receptor kinase, which affects BDNF’s physiologic benefits. Finally, we investigate the formation of nascent nanoparticles through a series of characterization experiments and isothermal titration experiments which show the effects of pH in the context of particle self-assembly. Our findings indicate that thoughtful reformulation of PEG based, therapeutic PICs with non-PEG alternatives can be accomplished without compromising the self-assembly of the PIC.
Preprint
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Many therapeutic formulations incorporate poly(ethylene glycol) (PEG) as a stealth component to minimize early clearance. However, PEG is immunogenic and susceptible to accelerated clearance after multiple administrations. Here, we present two novel reformulations of a polyion complex (PIC), originally comprised of poly(ethylene glycol) 113 -b-poly(glutamic acid) 50 (PEG-PLE) and brain derived neurotrophic factor (BDNF), termed Nano-BDNF (Nano-BDNF PEG-PLE). We replace the PEG based block copolymer with two new polymers, poly(sarcosine) 127 -b-poly(glutamic acid) 50 (PSR-PLE) and poly(methyl-2-oxazolines) 38 - b -poly(oxazolepropanoic acid) 27 - b -(poly(methyl-2-oxazoline) 38 (PMeOx-PPaOx-PMeOx) which are driven to association with BDNF via electrostatic interactions and hydrogen bonding to form a PIC. Formulation using a microfluidic mixer yields small and narrowly disperse nanoparticles which associate following similar principles. Additionally, we demonstrate that encapsulation does not inhibit access by the receptor kinase, which effects BDNF’s physiologic benefits. Finally, we investigate the formation of nascent nanoparticles through a series of characterization experiments and isothermal titration experiments which show the effects of pH in the context of particle self-assembly. Our findings indicate that thoughtful reformulation of PEG based, therapeutic PICs with non-PEG alternatives can be accomplished without compromising the self-assembly of the PIC.
Article
Polypeptoids, with similar structure to polypeptides, are nowadays rising stars due to their excellent solubility, processibility, enzymatic stability, and biocompatibility. Attractive properties of polypeptoid-containing copolymers endow them with various applications in surface antifouling, biosensing, microreactor, drug delivery, and stimuli–response. The syntheses of block copolymers containing polypeptoids have attracted a great amount of interest so far. The review summarizes the synthetic strategies of polypeptoid-containing copolymers, that is, polypeptoid-b-polypeptoid, −polypeptide, −polyester, −polyether and -polyolefin developed recently, as well as their phase-separation, assembly and stimuli–response properties. Abstract
Article
Polymeric micelles are promising vehicles for drug delivery these years. The stability of micelles in blood system is very important for the encapsulated therapeutic agents reaching the targeting area. However, generally, micelles are not stable in the presence of proteins and ions after being injected intravenously. The topology of polymer chain on the surface of micelles plays a key role on the stability of micelles. Here we have prepared flower micelles and the traditional micelles via self-assembly of triblock and diblock copolymer of polyethylene glycol (PEG) and poly(ε-caprolactone) (PCL) in water. The special PEG shell of flower micelles prevents micelles from ions and proteins, which endows the micelles with the ability to resist aggregation. The experiment results show that flower micelles are much more stable in the presence of serum and salt than traditional micelles, which indicates these micelles would be promising in drug delivery in the future.
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Polysarcosine (psar) is a non-ionic hydrophilic polypeptoid with numerous biologically relevant properties. Polysarcosine is poly (n-methylated glycine) and has been reported first by wesley and co-workers in the 1920s. Polysarcosine was first synthesized via ring-opening polymerization (rop) of sarcosine n-carboxyanhydride, using high-vacuum techniques. Overall, findings highlight the potential of poly(sarcosine) as an alternative corona-forming polymer to poly (ethylene glycol)-based analogues of (polymerization-induced self-assembly) pisa assemblies for use in various pharmaceutical and biomedical applications. Numerous studies suggested that such polypeptoids hold enormous potential for many biomedical applications, including protein delivery, colloidal stabilization, and nanomedicine.
Article
Riboflavin carrier protein (RCP) and riboflavin transporters (RFVTs) have been reported to be highly overexpressed in various cancer cells. Hence, targeting RCP and RFVTs using riboflavin may enhance tumor accumulation and internalization of drug delivery systems. To test this hypothesis, butyl-based 3-arm peptostar polymers were synthesized consisting of a lysine core (10 units per arm) and a sarcosine shell (100 units per arm). The end groups of the arms and the core were successfully modified with riboflavin and the Cy5.5 fluorescent dye, respectively. While in phosphate buffered saline the functionalized peptostars showed a bimodal behavior and formed supramolecular structures over time, they were stable in the serum maintaining their hydrodynamic diameter of 12 nm. Moreover, the polymers were biocompatible and the uptake of riboflavin targeted peptostars in A431 and PC3 cells was higher than in nontargeted controls and could be blocked competitively. In vivo, the polymers showed a moderate passive tumor accumulation, which was not significantly different between targeted and nontargeted peptostars. Nonetheless, at the histological level, internalization into tumor cells was strongly enhanced for the riboflavin-targeted peptostars. Based on these results, we conclude that passive accumulation is dominating the accumulation of peptostars, while tumor cell internalization is strongly promoted by riboflavin targeting.
Article
Over the last three decades, polymeric micelles have emerged as a highly promising drug delivery platform for therapeutic compounds. Particularly, poorly soluble small molecules with high potency and significant toxicity were encapsulated in polymeric micelles. Polymeric micelles have shown improved pharmacokinetic profiles in preclinical animal models and enhanced efficacy with a superior safety profile for therapeutic drugs. Several polymeric micelle formulations have reached the clinical stage and are either in clinical trials or are approved for human use. This furthers interest in this field and underscores the need for additional learning of how to best design and apply these micellar carriers to improve the clinical outcomes of many drugs. In this review, we provide detailed information on polymeric micelles for the solubilization of poorly soluble small molecules in topics such as the design of block copolymers, experimental and theoretical analysis of drug encapsulation in polymeric micelles, pharmacokinetics of drugs in polymeric micelles, regulatory approval pathways of nanomedicines, and current outcomes from micelle formulations in clinical trials. We aim to describe the latest information on advanced analytical approaches for elucidating molecular interactions within the core of polymeric micelles for effective solubilization as well as for analyzing nanomedicine's pharmacokinetic profiles. Taking into account the considerations described within, academic and industrial researchers can continue to elucidate novel interactions in polymeric micelles and capitalize on their potential as drug delivery vehicles to help improve therapeutic outcomes in systemic delivery.
Chapter
Recent advances in synthetic chemistry has led to the increasingly sophisticated design and preparation of biofunctional polymeric surfaces and materials. In this regard, synthetic poly-(N-substituted glycine) “peptoids” which mimic the structure and function of peptides play an important role, since they may attain functionalities similar to natural biopolymers. This chapter reviews efforts by our group and others to develop “antifouling” peptoid coatings that resist the nonspecific and undesired adsorption of proteins and attachment of mammalian and microbial cells. We have found that the simplest peptoid—polysarcosine—has been found to be well hydrated and therefore well-suited for antifouling applications. We show that the synthetic convenience of peptoids in general greatly facilitates studies on how polymer chain length, chain density, sidechain chemistry, and specific peptoid sequences may control surface interactions. Indeed, specific peptoids and sequence arrangements have been found to exhibit long-term antifouling properties and excellent resistance against different strains of bacteria. Addition of simple sugar groups to peptoid chains may further enhance resistance against bacterial attachment. Combined with peptoid’s resistance against enzymatic degradation, antifouling peptoids have excellent potential in biomedical applications. These range from coatings of catheters and other biological devices to biosensing and nanomedicine that require a non-fouling interface to achieve improved device performance.
Article
Stimuli-responsive polymersomes formed by amphiphilic block copolymers have attracted substantial attention as smart and robust containers for drug delivery and nano/micro-reactors. Bio-sourced amphiphilic diblock copolypeptoids were developed that can self-assemble into oxidation-responsive unilamellar vesicles. These vesicles can burst under the action of reactive oxygen species which can be the hydrogen peroxide, or the singlet oxygen produced by light-activation of photosensitizer with spatiotemporal control. Polysarcosine (PSar, also called poly(N-methyl glycine)) was selected as the hydrophilic block, due to its resistance to protein adsorption and low toxicity, similar to PEG. We designed and synthesized poly(N-3-(methylthio)propyl glycine) as the hydrophobic block. Its polyglycine backbone is the same as that of PSar, and especially its hydrophobic N-substituents, thioether side-chains, can be oxidized to hydrophilic sulfoxides. These oxidation-responsive polymersomes entirely based on N-substituted poly(amino acid)s were biocompatible as confirmed by cell viability tests, and may find applications in drug delivery, biosensing, biodetection, and nano-/micro-reactors.
Thesis
Geringe Wasserlöslichkeiten kleiner organischer Wirkstoffkandidaten, sogenannter Leitstrukturen, sind in der Medikamentenentwicklung häufig für das Scheitern vielversprechender Projekte verantwortlich. Um diese Kandidaten dennoch zur Marktreife bringen zu können, wurden verschiedene Strategien entwickelt. Neben der kostenintensiven Strukturoptimierung rücken Formulierungsadditive in den Fokus, die in der Lage sind, Wirkstoffe zu solubilisieren, transportieren und gezielt freizusetzen. In dieser Arbeit wird eine Hochdurchsatz-Screening-Methode präsentiert, die eine schnelle und arbeitsextensive Identifizierung maßgeschneiderter Binder für wasserunlösliche, niedermolekulare Wirkstoffe ermöglicht und mithilfe derer Löslichkeitsvermittler in Form von Peptid-Polymer-Konjugaten mit definierten Solubilisierungs- und Freisetzungseigenschaften realisiert werden können. Dazu werden Peptidbibliotheken in einem zweistufigen Prozess auf Wirkstoffbindung und auf Wirkstofffreisetzung durchsucht. Das Screening kann aufgrund einer innovativen on-chip Immobilisierung der Peptidbibliothek und der intrinsischen Fluoreszenz der niedermolekularen Wirkstoffe halbautomatisiert durchgeführt werden. Vielversprechende Peptidsequenzen können anschließend direkt on-chip mittels MALDI-ToF-MS/MS bzw. fragmentierungsfrei sequenziert und löslichkeitsvermittelnde Peptid-PEG-Konjugate hergestellt werden. In einem Testsystem wurden maßgeschneiderte Peptid-PEG-Konjugate mit unterschiedlichen Freisetzungseigenschaften für einen potentiellen Alzheimer-Wirkstoff realisiert und sowohl Solubilisierungseigenschaften, als auch die Freisetzungseigenschaften in einem vereinfachten Blutplasmamodell mittels Fluoreszenzanisotropie und Fluoreszenzkorrelationsspektroskopie bestätigt. In Zelltests mit einer Neuro-2a-Zelllinie konnten durch Zugabe der Wirkstoff-Transporter-Komplexe effektiv die Ausbildung der bei einer Alzheimer-Erkrankung auftretenden Tau-Protein-Aggregate bis zu 55 % reduziert werden.
Article
Metal-organic framework nanoparticles (MOF NPs) are of growing interest in diagnostic and therapeutic applications and due to their hybrid nature, they display enhanced properties compared to more established nanomaterials. The effective application of MOF NPs, however, is often hampered by limited control of their surface chemistry and understanding of their interactions at the biointerface. Using a surface coating approach, we found that coordinative polymer binding to Zr-fum NPs is a convenient way for peripheral surface functionalization. Different polymers with biomedical relevance were assessed for the ability to bind to the MOF surface. Carboxylic acid and amine containing polymers turned out to be potent surface coatings and a modulator replacement reaction was identified as the underlying mechanism. The strong binding of polycarboxylates was then used to shield the MOF surface with a double amphiphilic polyglutamate-polysarcosine block co-polymer, which resulted in an exceptional high colloidal stability of the nanoparticles. The effect of polymer coating on interactions at the biointerface was tested with regard to cellular association and protein binding which has, to the best of our knowledge, never been discussed in literature for functionalized MOF NPs. We conclude that the applied approach enables a high degree of chemical surface confinement, which could be used as a universal strategy for MOF NP functionalization. In this way, the physicochemical properties of MOF NPs could be tuned, which allows for control over their behavior in biological systems.
Article
Poly(sarcosine) (PSar) is a non-ionic hydrophilic poly(peptoid) with numerous biologically relevant properties, making it an appealing candidate for the development of amphiphilic block copolymer nanostructures. In this work, the fabrication of poly(sarcosine)-based diblock copolymer nano-objects with various morphologies via aqueous reversible addition-fragmentation chain-transfer (RAFT)-mediated photoinitiated polymerization-induced self-assembly (photo-PISA) is reported. Poly(sarcosine) was first synthesized via ring-opening polymerization (ROP) of sarcosine N-carboxyanhydride, using high-vacuum techniques. A small molecule chain transfer agent (CTA) was then coupled to the active ω-amino chain end of the telechelic polymer for the synthesis of a poly(sarcosine)-based macro-CTA. Controlled chain-extensions of a commercially available water-miscible methacrylate monomer (2-hydroxypropyl methacrylate) were achieved via photo-PISA under mild reaction conditions, using PSar macro-CTA. Upon varying the degree of polymerization and concentration of the core-forming monomer, morphologies evolving from spherical micelles to worm-like micelles and vesicles were accessed, as determined by dynamic light scattering and transmission electron microscopy, resulting in the construction of a detailed phase diagram. The resistance of both colloidally stable empty vesicles and enzyme-loaded nanoreactors against degradation by a series of proteases was finally assessed. Overall, our findings underline the potential of poly(sarcosine) as an alternative corona-forming polymer to poly(ethylene glycol)-based analogues of PISA assemblies for use in various pharmaceutical and biomedical applications.
Article
Polymeric micelles are demonstrating high potential as nanomedicines capable of controlling the distribution and function of loaded bioactive agents in the body, effectively overcoming biological barriers, and various formulations are engaged in intensive preclinical and clinical testing. This Review focuses on polymeric micelles assembled through multimolecular interactions between block copolymers and the loaded drugs, proteins, or nucleic acids as translationable nanomedicines. The aspects involved in the design of successful micellar carriers are described in detail on the basis of the type of polymer/payload interaction, as well as the interplay of micelles with the biological interface, emphasizing on the chemistry and engineering of the block copolymers. By shaping these features, polymeric micelles have been propitious for delivering a wide range of therapeutics through effective sensing of targets in the body and adjustment of their properties in response to particular stimuli, modulating the activity of the loaded drugs at the targeted sites, even at the subcellular level. Finally, the future perspectives and imminent challenges for polymeric micelles as nanomedicines are discussed, anticipating to spur further innovations.
Article
Because of the high reactivity, N-carboxyanhydride (NCA) can be initiated by the thiol group. On the contrary, N-thiocarboxyanhydride (NTA) is more stable and is able to tolerate it. Herein, we apply cysteamine as a regioselective initiator for ring-opening polymerization (ROP) of N-substituted glycine N-thiocarboxyanhydride (NNTA) to synthesize well-defined thiol-capped polypeptoids. ROPs of sarcosine NTA (Sar-NTA) and N-ethylglycine NTA (NEG-NTA) are well controlled when [M]/[I] ≤ 100 with high yields (>87.5%) producing polypeptoids with designable molecular weights and low polydispersity indices (<1.2). All the polypeptoid chains contain a thiol end group, which is confirmed by NMR analyses, MALDI-ToF MS spectra, and Ellman's assay. Through radical-mediated thiol-ene reaction with styrene, all the thiol chain ends are transferred to oligostyrene, revealing the convenience of further modification. Benefiting from the thiol-ene click chemistry, thiol-capped polysarcosine (PSar) and poly(N-ethylglycine) (PNEG) are promising candidates to replace PEG for their nontoxicity and biocompatibility.
Article
Polysarcosine (pSar) was one of the first polymers synthesized in a controlled living manner, but it was only recently when it was reconsidered as a promising alternative for poly(ethylene glycol) (PEG) in biomedical applications. Despite receiving more and more attention, very little is known about the solution properties of pSar, such as coil dimensions and thermodynamic interactions. In this article, we report on these properties of pSar with degrees of polymerization 50 < Xn < 400 that were prepared by controlled living ring-opening polymerization. The polymers are characterized by gel permeation chromatography (GPC), MALDI-TOF mass spectrometry, dynamic and static light scattering (SLS), and viscometry. The chain stiffness of pSar in PBS in terms of the Kuhn statistical segment length, lk, was estimated to lk = 1.5 nm by application of the Yamakawa–Fujii wormlike chain theory to the experimentally determined hydrodynamic radii, Rh, thus being higher than lk = 1.1 nm for PEG in PBS. Also, the second virial coefficients, A2, of pSar and PEG in PBS were similar and reflect their good solubility in aqueous solution. While the universal calibration of GPC elution volumes failed for pSar in HFIP utilizing PMMA standards, it worked better in PBS buffer with PEG standards. Alternatively, an Rh–Mw relation is established in the present work, which enables the determination of molar masses of pSar by simple DLS measurements. In addition, it is demonstrated that pSar independent from its chain length (50 < Xn < 400) does not induce any detectable complement activation (C5a) in human serum.
Article
Poly(sarcosine) displayed on polymeric micelle is reported to trigger a T cell-independent type2 reaction with B1a cells in the mice to produce IgM and IgG3 antibodies. In addition to polymeric micelle, three kinds of vesicles displaying poly(sarcosine) on surface were prepared here to evaluate the amounts and avidities of IgM and IgG3, which were produced in mice, to correlate them with physical properties of the molecular assemblies. The largest amount of IgM was produced after twice administrations of a polymeric micelle of 35 nm diameter (G1). On the other hand, the production amount of IgG3 became the largest after twice administrations of G3 (vesicle of 229 nm diameter) or G4 (vesicle of 85 nm diameter). The augmented avidity of IgG3 after the twice administrations compared with that at the single administration was the highest with G3. These differences in immune responses are discussed in terms of surface density of poly(sarcosine) chains, nanoparticle size, hydrophobic component of poly(L-lactic acid) or (Leu- or Val-Aib)n, and membrane elasticity of the nanoparticles. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.
Article
Therapeutic nucleic acids such as pDNA hold great promise for the treatment of multiple diseases. These therapeutic interventions are, however, compromised by the lack of efficient and safe non-viral delivery systems, which guarantee stability during blood circulation together with high transfection efficiency. To provide these desired properties within one system, we propose the use of reactive triblock copolypept(o)ides, which include a stealth-like block for efficient shielding, a hydrophobic block based on reactive disulfides for cross-linking and a cationic block for complexation of pDNA. After the complexation step, bifunctional cross-linkers can be employed to bio-reversibly stabilize derived polyplexes by disulfide bond formation and to introduce endosomolytic moieties at the same time. Cross-linked polyplexes show no aggregation in human blood serum. Upon cellular uptake and cleavage of disulfide bonds, the cross-linkers can interact with the endosomal membrane, leading to lysis and efficient endosomal translocation. In principal, the approach allows for the combination of one polymer with various different cross-linkers and thus enables the fast forward creation of a polyplex library.
Article
Gene therapies enable therapeutic interventions at gene transcription and translation level, providing enormous potential to improve standards of care for multiple diseases. Nonviral transfection agents and in particular polyplexes based on block ionomers are-besides viral vectors and cationic lipid formulations-among the most promising systems for this purpose. Block ionomers combine a hydrophilic noncharged block, e.g., polyethylene glycol (PEG), with a hydrophilic cationic block. For efficient transfection, however, endosomolytic moieties, e.g., imidazoles, are additionally required to facilitate endosomal escape, which raises the general question how to distribute these functionalities within the block copolymer. Combining molecular dynamics simulation with physicochemical and biological characterization, this work aims to provide a first rational for the influence of block ionomer microstructure on polyplex properties, e.g., size, shape, and transfection efficiency. Our findings underline that a triblock microstructure is most efficient in compacting pDNA, which reduces polyplex size, enhances stability against degradation by DNase I, and thus provides better transfection performance.
Article
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Polypeptides are envisaged to achieve a major impact on a number of different relevant areas such as biomedicine and biotechnology. Acquired knowledge and the increasing interest on amino acids, peptides and proteins is establishing a large panel of these biopolymers whose physical, chemical and biological properties are ruled by their controlled sequences and composition. Polymer therapeutics has helped to establish these polypeptide-based constructs as polymeric nanomedicines for different applications, such as disease treatment and diagnostics. Herein, we provide an overview of the advantages of these systems and the main methodologies for their synthesis, highlighting the different polypeptide architectures and the current research towards clinical applications. Keywords: polymer therapeutics; polypeptides; drug delivery; nanomedicine
Article
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Synthetic methods in polymer chemistry have evolved tremendously during the last decade. Nowadays more and more attention is devoted to the application of those tools in the development of the next generation of nanomedicines. Nevertheless, poly(ethylene glycol) (PEG) remains the most frequently used polymer for biomedical applications. In this review, we try to summarize recent efforts and developments in controlled polymerisation techniques that may allow alternatives to PEG based systems and can be used to improve the properties of future polymer therapeutics.
Article
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Poly(ethylene glycol) (PEG) is the most used polymer and also the gold standard for stealth polymers in the emerging field of polymer-based drug delivery. The properties that account for the overwhelming use of PEG in biomedical applications are outlined in this Review. The first approved PEGylated products have already been on the market for 20 years. A vast amount of clinical experience has since been gained with this polymer--not only benefits, but possible side effects and complications have also been found. The areas that might need consideration and more intensive and careful examination can be divided into the following categories: hypersensitivity, unexpected changes in pharmacokinetic behavior, toxic side products, and an antagonism arising from the easy degradation of the polymer under mechanical stress as a result of its ether structure and its non-biodegradability, as well as the resulting possible accumulation in the body. These possible side effects will be discussed in this Review and alternative polymers will be evaluated.
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In the course of the routine use of NMR as an aid for organic chemistry, a day-to-day problem is the identification of signals deriving from common contaminants (water, solvents, stabilizers, oils) in less-than-analytically-pure samples. This data may be available in the literature, but the time involved in searching for it may be considerable. Another issue is the concentration dependence of chemical shifts (especially 1H); results obtained two or three decades ago usually refer to much more concentrated samples, and run at lower magnetic fields, than today’s practice. We therefore decided to collect 1H and 13C chemical shifts of what are, in our experience, the most popular “extra peaks” in a variety of commonly used NMR solvents, in the hope that this will be of assistance to the practicing chemist.
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7-Ethyl-10-hydroxy-camptothecin (SN-38), a biological active metabolite of irinotecan hydrochloride (CPT-11), has potent antitumor activity but has not been used clinically because it is a water-insoluble drug. For delivery by i.v. injection, we have successfully developed NK012, a SN-38-releasing nanodevice. The purpose of this study is to investigate the pharmacologic character of NK012 as an anticancer agent, especially in a vascular endothelial growth factor (VEGF)-secreting tumor model. The particle size of NK012 was approximately 20 nm with a narrow size distribution. NK012 exhibited a much higher cytotoxic effect against lung and colon cancer cell lines as compared with CPT-11. NK012 showed significantly potent antitumor activity against a human colorectal cancer HT-29 xenograft as compared with CPT-11. Enhanced and prolonged distribution of free SN-38 in the tumor was observed after the injection of NK012. NK012 also had significant antitumor activity against bulky SBC-3/Neo (1,533.1 +/- 1,204.7 mm(3)) and SBC-3/VEGF tumors (1,620.7 +/- 834.0 mm(3)) compared with CPT-11. Furthermore, NK012 eradicated bulky SBC-3/VEGF tumors in all mice but did not eradicate SBC-3/Neo tumors. In the drug distribution analysis, an increased accumulation of SN-38 in SBC-3/VEGF tumors was observed as compared with that in SBC-3/Neo tumors. NK012 markedly enhanced the antitumor activity of SN-38, especially in highly VEGF-secreting tumors, and could be a promising SN-38-based formulation.
Chapter
This unique text discusses the solution self-assembly of block copolymers and covers all aspects from basic physical chemistry to applications in soft nanotechnology. Recent advances have enabled the preparation of new materials with novel self-assembling structures, functionality and responsiveness and there have also been concomitant advances in theory and modelling. The present text covers the principles of self-assembly in both dilute and concentrated solution, for example micellization and mesophase formation, etc., in chapters 2 and 3 respectively. Chapter 4 covers polyelectrolyte block copolymers - these materials are attracting significant attention from researchers and a solid basis for understanding their physical chemistry is emerging, and this is discussed. The next chapter discusses adsorption of block copolymers from solution at liquid and solid interfaces. The concluding chapter presents a discussion of selected applications, focussing on several important new concepts. The book is aimed at researchers in polymer science as well as industrial scientists involved in the polymer and coatings industries. It will also be of interest to scientists working in soft matter self-assembly and self-organizing polymers.
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Recently, colloidal carrier systems have been receiving much attention in the field of drug targeting because of their high loading capacity for drugs as well as their unique disposition characteristics in the body. This paper highlights the utility of polymeric micelles formed through the multimolecular assembly of block copolymers as novel core-shell typed colloidal carriers for drug and gene targeting. The process of micellization in aqueous milieu is described in detail based on differences in the driving force of core segregation, including hydrophobic interaction, electrostatic interaction, metal complexation, and hydrogen bonding of constituent block copolymers. The segregated core embedded in the hydrophilic palisade is shown to function as a reservoir for genes, enzymes, and a variety of drugs with diverse characteristics. Functionalization of the outer surface of the polymeric micelle to modify its physicochemical and biological properties is reviewed from the standpoint of designing micellar carrier systems for receptor-mediated drug delivery. Further, the distribution of polymeric micelles is described to demonstrate their long-circulating characteristics and significant tumor accumulation, emphasizing their promising utility in tumor-targeting therapy. As an important perspective on carrier systems based on polymeric micelles, their feasibility as non-viral gene vectors is also summarized in this review article. (C) 2012 Published by Elsevier B.V.
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Core-shell structures based on polypept(o)ides combine stealth-like properties of the corona material polysarcosine with adjustable functionalities of the polypeptidic core. Mannose-bearing block copolypept(o)ides (PSar-block-PGlu(OBn)) have been synthesized using 11-amino-3,6,9-trioxa-undecyl-2,3,4,6-tetra-O-acetyl-O-α-D-mannopyranoside as initiator in the sequential ring-opening polymerization of α-amino acid N-carboxyanhydrides. These amphiphilic block copolypept(o)ides self-assemble into multivalent PeptoMicelles and bind to mannose-binding receptors as expressed by dendritic cells. Mannosylated micelles showed enhanced cell uptake in DC 2.4 cells and in bone marrow-derived dendritic cells (BMDCs) and therefore appear to be a suitable platform for immune modulation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
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The synthesis of triblock copolymers based on polysarcosine, poly-N-ε-t-butyloxycarbonyl-l-lysine, and poly-N-ε-t-trifluoroacetyl-l-lysine by ring-opening polymerization of the corresponding α-amino acid N-carboxyanhydrides (NCAs) is described. For the synthesis of N-ε-t-butyloxycarbonyl-l-lysine (lysine(Boc)) NCAs, an acid-free method using trimethylsilylchloride/triethylamine as hydrochloric acid (HCl) scavengers is presented. This approach enables the synthesis of lysine(Boc) NCA of high purity (melting point 138.3 °C) in high yields. For triblock copolypept(o)ides, the degree of polymerization (Xn ) of the polysarcosine block is varied between 200 and 600; poly-N-ε-t-butyloxycarbonyl-l-lysine and poly-N-ε-t-trifluoroacetyl-l-lysine blocks are designed to have a Xn in the range of 10-50. The polypeptide-polypeptoid hybrids (polypept(o)ides) can be synthesized with precise control of molecular weight, high end group integrity, and dispersities indices between 1.1 and 1.2. But more important, the use of tert-butyloxycarbonyl- and trifluoroacetyl-protecting groups allows the selective, orthogonal deprotection of both blocks, which enables further postpolymerization modification reactions in a block-selective manner. Therefore, the presented synthetic approach provides a versatile pathway to triblock copolypept(o)ides, in which functionalities can be separated in specific blocks.
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A series of well-defined polypeptide-polypeptoid block copolymers based on the body's own amino acids sarcosine and lysine are prepared by ring opening polymerization of N-carboxyanhydrides. Block lengths were varied between 200-300 for the shielding polysarcosine block and 20-70 for the complexing polylysine block. Dispersity indexes ranged from 1.05 to 1.18. Polylysine is polymerized with benzyloxycarbonyl as well as trifluoroacetyl protecting groups at the ϵ-amine group and optimized deprotection protocols for both groups are reported. The obtained block ionomers are used to complex pDNA resulting in the formation of polyplexes (PeptoPlexes). The PeptoPlexes can be successfully applied in the transfection of HEK 293T cells and are able to transfect up to 50% of cells in vitro (FACS assay), while causing no detectable toxicity in an Annexin V assay. These findings are a first indication that PeptoPlexes may be a suitable alternative to PEG based non-viral transfection systems.
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Nanoparticles are expected to be applicable for the theranostics as a carrier of the diagnostic and therapeutic agents. Lactosome is a polymeric micelle composed of amphiphilic polydepsipeptide, poly(sarcosine)64-block-poly(l-lactic acid)30, which was found to accumulate in solid tumors through the enhanced permeability and retention effect. However, lactosome was captured by liver on the second administration to a mouse. This phenomenon is called as the accelerated blood clearance phenomenon. On the other hand, peptide-nanosheet composed of amphiphilic polypeptide, poly(sarcosine)60-block-(l-Leu-Aib)6, where the poly(l-lactic acid) block in lactosome was replaced with the (l-Leu-Aib)6 block, abolished the accelerated blood clearance phenomenon. The ELISA and in vivo near-infrared fluorescence imaging revealed that peptide-nanosheets did not activate the immune system despite the same hydrophilic block being used. The high surface density of poly(sarcosine) chains on the peptide-nanosheet may be one of the causes of the suppressive immune response. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.
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Poly[N-(2-hydroxypropyl) methacrylamide] (HPMA) was one of the first polymers applied as polymer drug conjugate in the clinics. Since then many attempts have been made to expand the functionality of HPMA-based copolymers from advanced synthetic pathways to multiple biomedical applications. This Feature Article highlights multifunctional HPMA based copolymers prepared by controlled radical polymerization and subsequent post-polymerization modification of activated ester precursor polymers via aminolysis. This approach combines precise control of the polymer's microstructure (molecular weight, dispersity, block copolymer formation, end group functionalization) with an easy introduction of various multifunctional groups. The obtained polymers can be used as versatile targeted drug carriers for sophisticated molecular imaging techniques that provide detailed information about structure property relationships both in vitro as well as in vivo. Moreover, recent studies have shown that such multifunctional HPMA copolymers may have high potential as advanced carriers in the field of tumor immunotherapy.
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Two series (degree of polymerization: 20−200) of polylysines with Z and TFA protecting groups were synthesized, and their behavior in a range of analytical methods was investigated. Gel permeation chromatography of the smaller polypeptides reveals a bimodal distribution, which is lost in larger polymers. With the help of GPC, NMR, circular dichroism (CD), and MALDI-TOF, it was demon- strated that the bimodal distribution is not due to terminated chains or other side reactions. Our results indicate that the bimodality is caused by a change in secondary structure of the growing peptide chain that occurs around a degree of polymerization of about 15. This change in secondary structure interferes strongly with the most used analysis method for polymersGPCby producing a bimodal distribution as an artifact. After deprotection, the polypeptides were found to exhibit exclusively random coil conformation, and thus a monomodal GPC elugram was obtained. The effect can be explained by a 1.6-fold increase in the hydrodynamic volume at the coil−helix transition. This work demostrates that secondary structures need to be carefully considered when performing standard analysis on polypeptidic systems.
Article
We report the synthesis of polysarcosine-block-polyglutamic acid benzylester (PSar-block-PGlu(OBn)) and polysarcosine-block-polylysine-ε-N-benzyloxycarbonyl (PSar-block-PLys(Z)) copolymers. The novel polypeptoid-block-polypeptide copolymers have been synthesized by ring opening polymerization (ROP) of N-carboxyanhydrides (NCAs). Polymerization conditions were optimized regarding protecting groups, block sequence and length. While the degree of polymerization of the PSar block length was set to be around 200 or 400, PGlu(OBn) and PLys(Z) block lengths were varied between 20 to 75. The obtained block copolypeptides had a total degree of polymerization of 220-475 and dispersity indices between 1.1 and 1.2. Having ensured a non-toxic behavior up to a concentration of 3 mg/mL in HEK293 cells the novel block copolymers have been applied to the synthesis of organic colloids (by miniemulsion polymerization and miniemulsion solvent evaporation process). Colloids of around 100 nm (miniemulsion polymerization) to 200 nm (miniemulsion process) have been prepared. Additionally, PSar-block-PGlu(OBn) copolymers have been used in a drug formulation of an adenylate cyclase inhibitor increasing solubility of the drug, which enhances its bioavailability reducing of intracellular cAMP levels.
Article
N-Carboxy-α-amino acid anhydrides were prepared by the reaction of α-amino acids with trichloromethyl chloroformate. The yields were good to moderate, and the products obtained were as pure as those obtained by a conventional way using phosgene.
Article
AB block copolymers of (KtSa) were synthesized and studied by X-ray diffraction. In order to obtain copolymers with a polydispersity small enough to allow the formation of mesophases, the first block of was fractionated before using it as a macromolecular initiator of the polymerization of the second block of polysarcosine. Block copolymers of KtSa exhibit lamellar mesophases in the solid state and in concentrated aqueous solution. Each sheet of the lamellar structure results from the superposition of two layers: one formed by the hydrophilic polysarcosine chains in a disordered conformation, the other formed by the hydrophobic chains in an α-helix type conformation arranged in a hexagonal array and tilted. The influence of the water content of the mesophase and of the composition of the copolymers on the structural parameters of the lamellar structure was analysed and it was shown that the angle of tilt of the helices increases with both the water content of the mesophases and the length of the polysarcosine chains.
Article
Precision synthesis of polymers has been a hot topic in recent years. While this is notoriously difficult to address for polymers with a C-C backbone, Merrifield has discovered a way many decades ago for polypeptides. Using a similar approach, N-substituted polypeptides, so-called poly-peptoids have been synthesized and studied for about 20 years. In contrast, the living ring-opening polymerization (ROP) of N-substituted N-carboxyanhydrides was among the first liv-ing polymerizations to be discovered. More recently, a surge in new synthetic approaches led to the efficient synthesis of cyclic or linear multiblock copolypeptoids. Thus, polypeptoids can be synthesized either by solid phase synthesis to yield complex and exactly defined oligo-and small polymers or by ROP of appropriately N-substituted N-carboxyanhydrides (NNCA) to give linear, cyclic, or star-like polymers. Together with an excellent biocompatibility, this polymer family may have a bright future ahead as biomaterials. V C 2013 Wiley Periodicals, Inc.
Article
Bioinspired polymeric materials are attracting increasing attention due to significant advantages over their natural counterparts: the ability to precisely tune their structures over a broad range of chemical and physical properties, increased stability, and improved processability. Polypeptoids, a promising class of bioinspired polymer based on a N-substituted glycine backbone, have a number of unique properties that bridge the material gap between proteins and bulk polymers. Peptoids combine the sequence specificity of biopolymers with the simpler intra/intermolecular interactions and robustness of traditional synthetic polymers. They are highly designable because hundreds of chemically diverse side chains can be introduced from simple building blocks. Peptoid polymers can be prepared by two distinct synthetic techniques offering access to two material subclasses: (1) automated solid-phase synthesis which enables precision sequence control and near absolute monodispersity up to chain lengths of ∼50 monomers, and (2) a classical polymerization approach which allows access to higher molecular weights and larger-scale yields, but with less control over length and sequence. This combination of facile synthetic approaches makes polypeptoids a highly tunable, rapid polymer prototyping platform to investigate new materials that are intermediate between proteins and bulk polymers, in both their structure and their properties. In this paper, we review the methods to synthesize peptoid polymers and their applications in biomedicine and nanoscience, as both sequence-specific materials and as bulk polymers.
Article
Background: Nanoparticle of Lactosome, which is composed of poly(l-lactic acid)-base depsipeptide with diameter of 35nm, accumulates in solid tumors by the enhanced permeability and retention (EPR) effect. However, a pharmacokinetic alteration of Lactosome was observed when Lactosome was repeatedly administered. This phenomenon is named as the Lactosome accelerated blood clearance (ABC) phenomenon. In this study, the effect of Lactosome dose on the ABC phenomenon was examined and discussed in terms of immune tolerance. Methods: To tumor transplanted mice, Lactosome (0-350mg/kg) was administrated. At 7days after the first administration, indocyanine green (ICG)-labeled Lactosome (ICG-Lactosome, 0-350mg/kg) was injected. Near-infrared fluorescence imaging was performed, and biodistribution of ICG-Lactosome was evaluated. Further, the produced amounts of anti-Lactosome IgM were determined by enzyme-linked immunosorbent assay (ELISA). Results: ICG-Lactosome accumulated in the tumor region when the first Lactosome dose exceeded over 150mg/kg. The amounts of anti-Lactosome IgM were inversely correlated with the first Lactosome doses. Even after establishment of the Lactosome ABC phenomenon with the first Lactosome dose as low as 5.0mg/kg, the Lactosome ABC phenomenon can be evaded apparently by dosing ICG-Lactosome over 50mg/kg regardless of anti-Lactosome IgM production. Conclusions: There are two different mechanisms for evasion from the Lactosome ABC phenomenon before and after its establishment. In either mechanism, however, the Lactosome ABC phenomenon can be evaded by excessive administration of Lactosome. General significance: Lactosome is a potential nanocarrier for drug and/or imaging agent delivery, which can be used for frequent administrations without significant pharmacokinetic alterations.
Article
Poly(N-substituted glycine) "peptoids" are a class of peptidomimetic molecules receiving significant interest as engineered biomolecules. Sarcosine (i.e. poly(N-methyl glycine)) has the simplest sidechain chemical structure of this family. In this contribution, we demonstrate that surface-grafted polysarcosine (PSAR) brushes exhibit excellent resistance to non-specific protein adsorption and cell attachment. Polysarcosine was coupled to a mussel adhesive protein inspired DOPA-Lys pentapeptide, which enabled solution grafting and control of the surface chain density of the PSAR brushes. Protein adsorption was found to decrease monotonically with increasing grafted chain densities, and protein adsorption could be completely inhibited above certain critical chain densities specific to different polysarcosine chain-lengths. The dependence of protein adsorption on chain length and density was also investigated by a molecular theory. PSAR brushes at high chain length and density were shown to resist fibroblast cell attachment over a 7 wk period, as well as resist the attachment of some clinically relevant bacteria strains. The excellent antifouling performance of PSAR may be related to the highly hydrophilic character of polysarcosine, which was evident from high-pressure liquid chromatography measurements of polysarcosine and water contact angle measurements of the PSAR brushes. Peptoids have been shown to resist proteolytic degradation and polysarcosine can be produced in large quantities by N-carboxy anhydride polymerization. In summary, surface grafted polysarcosine peptoid brushes hold great promise for antifouling applications.
Article
This paper describes the use of surface plasmon resonance (SPR) spectroscopy and self-assembled monolayers (SAMs) to determine the characteristics of functional groups that give surfaces the ability to resist the nonspecific adsorption of proteins from solution. Mixed SAMs presenting different functional groups were prepared for screening using a synthetic protocol based on the reaction of organic amines with a SAM terminated by interchain carboxylic anhydride groups. Surfaces that presented derivatives of oligo(sarcosine), N-acetylpiperazine, and permethylated sorbitol groups were particularly effective in resisting the adsorption of proteins. Incorporation of these groups into single-component SAMs resulted in surfaces that are comparable to (but slightly less good than) single-component SAMs that present oligo(ethylene glycol) in their ability to resist the adsorption of proteins. In the group of surfaces examined, those that resisted the adsorption of proteins had the following properties:  they were hydrophilic; they contained groups that were hydrogen-bond acceptors but not hydrogen-bond donors; and they were overall electrically neutral.
Article
Lactosome, which is a polymer micelle composed of poly(lactic acid)-b-poly(sarcosine), was applied successfully for solid tumor imaging. Lactosome is considered to escape from the reticuloendothelial system recognition, and shows prolonged in vivo blood clearance time. In vivo disposition of Lactosome, however, changed upon multiple dosages. Lactosome at the 2nd dosage was cleared from the blood stream by trapping at liver. This accelerated blood clearance (ABC) phenomenon is explained by production of anti-Lactosome IgM and IgG(3) through the immune response related with B-lymphocyte cells. The memory effect of B-lymphocyte cells lasted nearly for six months in mouse. The epitope moiety of Lactosome is concluded to be poly(sarcosine) based on the competitive inhibition assay. Since the ABC phenomenon was also reported with PEGylated liposome, nanoparticles in general may be potential in triggering the immune system.
Article
Well-defined α-methoxy-ω-amino and α-hydroxy-ω-amino poly(ethylene oxides) (PEOs), obtained by chemical modifications of α-hydroxy-ω-amino PEO, were studied for block copolymerization with β-benzyl-L-aspartate-N-carboxy anhydride (BLA-NCA); the block copolymers were obtained via polymerization of BLA-NCA with the primary amino end-groups of the PEOs as initiator in the mixture CHCl3/N,N-dimethylformamide (DMF) (vol. ratio10/1). Gel-permeation chromatography (GPC) of both block copolymers showed the presence of BLA oligomers. α-Methoxy PEO/PBLA and α-hydroxy PEO/PBLA block copolymers were submitted to selective precipitation in 2-propanol; this method allowed total elimination of oligomers as shown by GPC of the purified block copolymers. Moreover, for each block copolymer, the number of BLA units determined by 1H NMR spectroscopy (in CDCl3) was in good agreement with the number calculated from the ratio BLA-NCA/amino end-groups of PEO. The polymeric micelles having hydroxy functions or methoxy groups on the outer-shell were prepared by dialysis against water of the corresponding solution of the pure block copolymers. These polymeric micelles were characterized by dynamic light scattering (diameter) and by fluorescence spectroscopy (critical micellar concentration, cmc) using pyrene as a fluorescence probe. Both polymeric micelles have a small diameter (<50nm) and a very low cmc (<20 mg/L in water).
Article
A block copolymer (6) with both hydrophilic and hydrophobic regions was synthesized, in order to examine its interaction with model membranes and its uptake by living cells. The copolymer comprised poly(ethylene oxide) and poly(L-lysine) with 50 mol-% substitution of the ε-amino groups with palmitoyl groups. To permit 125I-labelling, p-methoxyphenyl residues (1–4 mol-%) were incorporated into the block copolymer and into a poly(ethylene oxide) used for comparison. Sudan Red 7 B solubilization studies indicated that the block copolymer, but not the homopolymer, forms micelles. Differential scanning calorimetry of dipalmitoyl-phosphatidylcholine liposomes indicated that the block copolymer interacts with and probably penetrates lipid membranes. Both poly(ethylene oxide) and the block copolymer were captured by rat peritoneal macrophages in vitro, and inhibitor studies indicated that uptake of both polymers was by pinocytosis. Rates of uptake were indicative of adsorptive pinocytosis, and it is concluded that both poly(ethylene oxide) and the block copolymer present a largely hydrophilic aspect which interacts positively with the cell surface.
Chapter
PEG is used to improve pharmacokinetic properties of biologicals. Concern has been expressed about the toxicological effect and/or fate of the PEG. This paper reviews the available toxicity, metabolism and clearance data of PEG and PEGylated products in order to place such concerns in to appropriate context. The available data demonstrates that PEG itself only shows toxicity at high, parenteral doses and the usual target organ is the kidney as this is the route of excretion for unchanged PEG. A large therapeutic window (approximately 600-fold) exists between the maximum PEG burden from a current biological agent and the doses of PEG associated with human toxicity. Pathological changes which results in no functional deficit, PEG containing vacuoles in cells, have been observed with PEGylated biologicals. There is evidence that these PEG vesicle can resolve with time. In conclusion the doses used clinically for current and many future PEGylated biologicals are low and will result in exposures to PEG significantly lower than that required to elicit PEG toxicity. In all cases the routine regulatory toxicology studies would identify relevant pathology should it occur.
Article
Amphiphilic diblock copolymers, poly(n-butyl acrylate)-block-poly(acrylic acid) (PnBA-PAA), with narrow molecular weight distribution (PDI <= 1.07) were prepared by atom transfer radical polymerization (ATRP) of n-butyl acrylate and tert-butyl acrylate (tBA), followed by selective acidolysis of the PtBA block. These polymers possess a soft PnBA hydrophobic block with a constant chain length of 90-100 monomer units and pH- and ionic strength-sensitive hydrophilic PAA block with DPPAA = 33-300 AA monomer units. They were expected to form stimuli-responsive micelles. The block copolymers with DPPAA ! 100 are directly soluble in water at pH > 4.7. Pyrene steady-state fluorescence spectroscopy and fluorescence correlation spectroscopy (FCS) studies indicate the existence of a very low critical micelle concentration (cmc similar to 10(-8) mol/L). The number-average hydrodynamic radii of the micelles, as determined by FCS, range from 28 to 55 urn, depending on the PAA block length. FCS data indicate that micellar sizes significantly decrease upon dilution for salt-free systems. This is attributed to a dynamic, but kinetically controlled, behavior of these self-assembled nanostructures. In saline solutions the micellar sizes remain constant above the "apparent" cmc (cmc*), which is attributed to slower dynamics of unimer exchange between micelles.
Article
Preparation of defined and functional polymers has been one of the hottest topics in polymer science and drug delivery in the recent decade. Also, research on (bio)degradable polymers gains more and more interest, in particular at the interface of these two disciplines. However, in the majority of cases, combination of definition, functionality and degradability, is problematic. Here we present the preparation and characterization (MALDI-ToF MS, NMR, GPC) of nonionic hydrophilic, hydrophobic, and amphiphilic N-substituted polyglycines (polypeptoids), which are expected to be main-chain degradable and are able to disperse a hydrophobic model compound in aqueous media. Polymerization kinetics suggest that the polymerization is well controlled with strictly linear pseudo first-order kinetic plots to high monomer consumption. Moreover, molar mass distributions of products are Poisson-type and molar mass can be controlled by the monomer to initiator ratio. The presented polymer platform is nonionic, backbone degradable, and synthetically highly flexible and may therefore be valuable for a broad range of applications, in particular as a biomaterial.
Article
Estimates of the daily rate of methionine utilization by adult humans, published previously, were under-estimated because available data did not permit quantitative assessment of the rate at which the methyl moiety of methionine is oxidized.1 The present paper reports efforts to measure the rate of oxidation of methionine methyl by the two pathways that proceed through the intermediate N-methylglycine (sarcosine). Two sarcosinemic, sarcosinuric patients, proven or presumed to have specific genetic defects in the sarcosine-oxidizing system, were studied while maintained on constant diets containing differing amounts of methionine, choline (or choline derivatives), and glycine. The steadystate excretions of sarcosine, creatinine, creatine, and a number of other materials were determined. The results obtained suggest that sarcosine is formed in 2 ways: (1) In an amount equivalent to the dietary intake of choline (or choline derivative)—this pathway would make a net positive contribution to the methionine-methyl pool due to the transfer of a methyl group from betaine to homocysteine; and (2) By processes requiring net consumption of methionine methyl. For the single patient for whom reasonably complete data were attained, it appears that 2 such processes may be occurring. One proceeds at a rate (approximately 2 mmole/24 hr) that changed little as total intake of labile methyl groups∗ was altered. The second became prominent (and accounted for the bulk of the incremental intake of labile methyl groups) when this intake exceeded the combined amounts required for the synthesis of creatine (10.2 mmole/24 hr), other transmethylation reactions (1.4 mmole/24 hr), polyamine synthesis (0.5 mmole/24 hr), and the “basal” process of sarcosine formation just mentioned (2 mmole/24 hr). It is possible that such “basal” sarcosine formation is due chiefly to endogenous choline synthesis, balanced by degradation, whereas the more responsive process of sarcosine formation may be due chiefly to methylation of glycine. Together with available data, these new data on methionine consumption due to sarcosine formation permit calculation of a turnover time for S-adenosylmethionine in human liver (no more than 3.5–7 min), as well as upward revision of previous minimal estimates1 of the rate of methylneogenesis, the number of times that the average homocysteinyl moiety cycles between methionine and homocysteine during its passage through the body, and the partitioning of homocysteine between the remethylation and the transsulfuration pathways.
Article
Depending on the context, nanotechnologies developed as nanomedicines (nanosized therapeutics and imaging agents) are presented as either a remarkable technological revolution already capable of delivering new diagnostics, treatments for unmanageable diseases, and opportunities for tissue repair or highly dangerous nanoparticles, nanorobots, or nanoelectronic devices that will wreak havoc in the body. The truth lies firmly between these two extremes. Rational design of "nanomedicines" began almost half a century ago, and >40 products have completed the complex journey from lab to routine clinical use. Here we critically review both nanomedicines in clinical use and emerging nanosized drugs, drug delivery systems, imaging agents, and theranostics with unique properties that promise much for the future. Key factors relevant to the design of practical nanomedicines and the regulatory mechanisms designed to ensure safe and timely realization of healthcare benefits are discussed.
Article
Poly(ethylene glycol) (PEG) and poly(2-methyl-2-oxazoline) (PMOx) are water-soluble, biocompatible polymers with stealth hemolytic activities. Poly(amino acid) (PAA) end-capped PEG and PMOx were prepared using amino-terminated derivatives of PEG and PMOx as macroinitiators for the ring-opening polymerization of γ-benzyl protected l-glutamate N-carboxyanhydride and S-benzyloxycarbonyl protected l-cysteine N-carboxyanhydride, respectively, in the presence of urea, at room temperature. The molecular weight of the PAA moiety was kept between M(n) = 2200 and 3000 g mol(-1). PMOx was polymerized by cationic ring-opening polymerization resulting in molecular weights of M(n) = 5000 and 10,000 g mol(-1), and PEG was a commercial product with M(n) = 5000 g mol(-1). Here, we investigate the self-assembly of the resulting amphiphilic block copolymers in water and the effect of the chemical structure of the block copolymers on the solution properties of self-assembled nanostructures. The PEG-block-poly(amino acid), PEG-b-PAA, and PMOx-block-poly(amino acid), PMOx-b-PAA, block copolymers have a narrow and monomodal molecular weight distribution (PDI < 1.3). Their self-assembly in water was studied by dynamic light scattering and fluorescence spectroscopy. In aqueous solution, the block copolymers associate into particles with hydrodynamic radii (R(H)) ranging in size from R(H) 70 to 130 nm, depending on the block copolymer architecture and the polymer molecular weight. Larger R(H) and critical association concentration values were obtained for copolymers containing poly(S-benzyloxycarbonyl-l-cysteine) compared to their poly(γ-benzyl-L-glutamate) analogue. FTIR investigations revealed that the poly(γ-benzyl-L-glutamate) block adopts a helical conformation, while the poly(S-benzyloxycarbonyl-L-cysteine) block exists as β-sheet.
Article
The increasing importance of nanotechnology in the biomedical field and the recent progress of nanomedicines into clinical testing have spurred the development of even more sophisticated nanoscale drug carriers. Current nanocarriers can successfully target cells, release their cargo in response to stimuli, and selectively deliver drugs. More sophisticated nanoscale carriers should evolve into fully integrated vehicles with more complex capabilities. First, they should be able to sense targets inside the body and adapt their functions based on these targets. Such devices will also have processing capabilities, modulating their properties and functions in response to internal or external stimuli. Finally, they will direct their function to the aimed site through both subcellular targeting and delivery of loaded drugs. These nanoscale, multifunctional drug carriers are defined here as nanodevices. Through the integration of various imaging elements into their design, the nanodevices can be made visible, which is an essential feature for the validation. The visualization of nanodevices also facilitates their use in the clinic: clinicians can observe the effectiveness of the devices and gain insights into both the disease progression and the therapeutic response. Nanodevices with this dual diagnostic and therapeutic function are called theranostic nanodevices.
Article
This chapter summarizes methods for the synthesis of polypeptides by ring-opening polymerization. Traditional and recently improved methods used to polymerize α-amino acid N-carboxyanhydrides (NCAs) for the synthesis of homopolypeptides are described. Use of these methods and strategies for the preparation of block copolypeptides and side-chain-functionalized polypeptides are also presented, as well as an analysis of the synthetic scope of different approaches. Finally, issues relating to obtaining highly functional polypeptides in pure form are detailed. Graphical Abstract
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The fluorescence intensities for various vibronic fine structures in the pyrene monomer fluorescence show strong solvent dependence. In the presence of polar solvents, there is a significant enhancement in the intensity of the 0--0 vibronic band at the expense of other bands. This strong perturbation in the vibronic band intensities is more dependent on the solvent dipole moment than on the bulk solvent dielectric constant. This suggests the operation of some specific solute--solvent dipole--dipole interaction mechanism. The strong perturbation of the vibronic band intensities has been used as a probe to accurately determine critical micelle concentrations and also to investigate the extent of water penetration in micellar systems.
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