[show abstract][hide abstract] ABSTRACT: Oral delivery is the preferred route to deliver therapeutics via nanoparticles due to ease of administration and patient acceptance. Here, we report on the findings of the absorption pathway of taurocholic acid (TCA)-linked heparin and docetaxel (DTX) conjugate, which we refer to as HDTA. We studied the oral absorption of HDTA using a Caco-2 cell transport system and an animal model. We have also used other absorption enhancers, such as ethylene glycol tetraacetic acid (EGTA), or inhibitors, such as sodium azide, to compare the relative permeability of HDTA conjugates. In vivo comparative studies were conducted using free TCA as a pre-administration and exhibited the maximum absorption site of the organ after oral administration of HDTA conjugates. HDTA was found to be absorbed mainly in the ileum and Caco-2 cell monolayer through passive diffusion and bile acid transporters. High fluorescence intensity of HDTA in mice came from the ileum, and it was eliminated from the body through colon. This novel formulation could be further investigated by clinical trials to find the prospect of oral anti-cancer drug delivery through anti-angiogenic treatment strategies.
Journal of Controlled Release 01/2014; · 7.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: In our previous study, a histidine-based AB2 miktoarm polymer, methoxy poly(ethylene glycol)-b-poly(l-histidine)2 (mPEG-b-(PolyHis)2), was designed to construct pH-sensitive polymersomes that transform in acidic pH; the polymer self-assembles into a structure that mimics phospholipids. In this study, the polymersomes further imitated liposomes due to the incorporation of cholesterol (CL). The hydrodynamic radii of the polymersomes increased with increasing CLwt% (e.g., 70nm for 0wt% vs. 91nm for 1wt%), resulting in an increased capacity for encapsulating hydrophilic drugs (e.g., 0.92μL/mg for 0wt% vs. 1.42μL/mg for 1wt%). The CL incorporation enhanced the colloidal stability of the polymersomes in the presence of serum protein and retarded their payload release. However, CL-incorporating polymersomes still demonstrated accelerated release of a hydrophilic dye (e.g., 5(6)-carboxyfluorescein (CF)) below pH 6.8 without losing their desirable pH sensitivity. CF-loaded CL-incorporating polymersomes showed better cellular internalization than the hydrophilic CF, whereas doxorubicin (DOX)-loaded CL-incorporating polymersomes presented similar or somewhat lower anti-tumor effects than free hydrophobic DOX. The findings suggest that CL-incorporating mPEG-b-(PolyHis)2-based polymersomes may have potential for intracellular drug delivery of chemical drugs due to their improved colloidal stability, lower drug loss during circulation, acidic pH-induced drug release, and endosomal disruption.
[show abstract][hide abstract] ABSTRACT: A cancer-recognizable MRI contrast agents (CR-CAs) has been developed using pH-responsive polymeric micelles. The CR-CAs with pH sensitivity were self-assembled based on well-defined amphiphilic block copolymers, consisting of methoxy poly(ethylene glycol)-b-poly(l-histidine) (PEG-p(l-His)) and methoxy poly(ethylene glycol)-b-poly(l-lactic acid)-diethylenetriaminopentaacetic acid dianhydride-gadolinium chelate (PEG-p(l-LA)-DTPA-Gd). The CR-CAs have a spherical shape with a uniform size of ∼40 nm at physiological pH (pH 7.4). However, in acidic tumoral environment (pH 6.5), the CR-CAs were destabilized due to the protonation of the imidazole groups of p(l-His) blocks, causing them to break apart into positively charged water-soluble polymers. As a result, the CR-CAs exhibit highly effective T1 MR contrast enhancement in the tumor region, which enabled the detection of small tumors of ∼3 mm(3)in vivo at 1.5 T within a few minutes.
[show abstract][hide abstract] ABSTRACT: With countless research papers using preclinical models and showing the superiority of nanoparticle design over current drug therapies used to treat cancers, it is surprising how deficient the translation of these nano-sized drug carriers into the clinical setting is. This review article seeks to compare the preclinical and clinical results for Doxil®, PK1, Abraxane®, Genexol-PM®, Xyotax™, NC-6004, Mylotarg®, PK2, and CALAA-01. While not comprehensive, it covers nano-sized drug carriers designed to improve the efficacy of common drugs used in chemotherapy. While not always available or comparable, effort was made to compare the pharmacokinetics, toxicity, and efficacy between the animal and human studies. Discussion is provided to suggest what might be causing the gap. Finally, suggestions and encouragement are dispensed for the potential that nano-sized drug carriers hold.
Journal of Controlled Release 10/2013; · 7.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: To address cancer cell heterogeneity while endowing tumor specificity, the approach of charge shielding/deshielding was tested in vitro and in vivo with a paclitaxel loaded cationic micelle from a block copolymer of poly(L-histidine) (3.7kDa) and short branched polyethyleneimine (1.8kDa). The cationic micelle surface was shielded by electrostatically complexing with a negatively charged mPEG (2kDa)-block-polysulfadimethoxine (4kDa) (mPEG-b-PSDM) at pH7.4. Unshielded micelle at pH7.4 and deshielded micelle at tumor extracellular pH were readily taken up by two wild types of human cancer cell lines, MCF-7 breast adenocarcinoma and SKOV-3 ovarian carcinoma, while the uptake of the shielded micelle at pH7.4 was minimal. The preliminary in vivo results from a mouse model xenografted with MCF-7 showed significant anticancer therapeutic efficacy and deep penetration of the micelle into tumor tissues after deshielding, supporting the unique pH-responsive mechanism to treat acidic cancer.
Journal of Controlled Release 08/2013; · 7.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: To enhance limited drug penetration that mediated drug resistance and heterogeneity within the tumour microenvironment, we designed a paclitaxel (PTX) loaded degradable cationic nanogel (DpNG) consisted with acetylated pullulan and low molecular weight polyethyleneimine (LowbPEI, 1.8 kDa). The restoration of cationic charge on the DpNG was achieved via HA degradation by hyaluronidase which is secreted in tumour. The size and surface charge of HA-coated DpNG loaded with PTX (HA/DpNG-PTX) was 200-250 nm and 0 mV, respectively. The DpNG-PTX was showed significant cytotoxicity in heterogeneous cancer cells. The IC50 value of DpNG-PTX was 100 times less than that of free PTX. The growth of heterogeneous tumour in Balb/c mice was inhibited via intravenous injection of HA/DpNG-PTX. Furthermore, the invasive distance and amount of HA/DpNG-PTX localised within the deep tissue regions were increased two times than that of PA-PTX. Therefore, the DpNG based drug delivery system could be useful for treatment of heterogeneous tumour.
[show abstract][hide abstract] ABSTRACT: Despite the numerous vital functions of proteins in the cytosolic compartment, less attention has been paid to the delivery of protein drugs to the cytosol than to the plasma membrane. To address this issue and effectively deliver charged proteins into the cytoplasm, we used endosomolytic, thiol-triggered degradable polyelectrolytes as carriers. The cationic, reducible polyelectrolyte RPC-bPEI0.8 kDa2 was synthesized by the oxidative polymerization of thiolated branched polyethyleneimine (bPEI). The polymer was converted to the anionic, reducible polyelectrolyte RPA-bPEI0.8 kDa2 by introducing carboxylic acids. The two reducible polyelectrolytes (RPC-bPEI0.8 kDa2 and RPA-bPEI0.8 kDa2) were complexed with counter-charged model proteins (bovine serum albumin (BSA) and lysozyme (LYZ)), forming polyelectrolyte/protein complexes of less than 200 nm in size at weight ratios (WR) of ≥1. The resultant complexes maintained a proton buffering capacity nearly equivalent to that of the polyelectrolytes in the absence of protein complexation and were cytocompatible with MCF7 human breast carcinoma cells. Under cytosol-mimicking thiol-rich conditions, RPC-bPEI0.8 kDa2/BSA and RPA-bPEI0.8 kDa2/LYZ complexes increased significantly in size and released the loaded protein, unlike the protein complexes with nonreducible polyelectrolytes (bPEI25 kDa and bPEI25 kDaCOOH). The polyelectrolyte/protein complexes showed cellular uptake similar to that of the corresponding proteins alone, but the former allowed more protein to escape into the cytosol from endolysosomes than the latter as a result of the endosomolytic function of the polyelectrolytes. In addition, the proteins in the polyelectrolyte/protein complexes kept their intrinsic secondary structures. In conclusion, the results show the potential of the designed endosomolytic, reducible polyelectrolytes for the delivery of proteins to the cytosol.
[show abstract][hide abstract] ABSTRACT: No chemotherapeutic drug can be effective until it is delivered to its target site. Nano-sized drug carriers are designed to transport therapeutic or diagnostic materials from the point of administration to the drug's site of action. This task requires the nanoparticle carrying the drug to complete a journey from the injection site to the site of action. The journey begins with the injection of the drug carrier into the bloodstream and continues through stages of circulation, extravasation, accumulation, distribution, endocytosis, endosomal escape, intracellular localization and-finally-action. Effective nanoparticle design should consider all of these stages to maximize drug delivery to the entire tumor and effectiveness of the treatment.
[show abstract][hide abstract] ABSTRACT: For long-term, sustained protein delivery, a new, star-shaped block copolymer composed of methoxy poly(ethylene glycol) (mPEG), branched oligoethylenimine (bOEI), and poly(l-histidine) (pHis) was synthesized via the multi-initiation and ring-opening polymerization (ROP) of His N-carboxy anhydride (NCA) on bOEI with a PEG conjugation. The resulting mPEG-bOEI-pHis (POH) had strong buffering capacity within the neutral-to-acidic pH range and was complexed with insulin (Ins) via an electrostatic attraction plus hydrophobic interactions, resulting in the formation of a dual-interaction complex (DIC, weight ratio 2) of approximately 30-60 nm in size. This DIC tolerated high salt concentrations without destabilization, supporting the existence of hydrophobic interactions, and protected Ins from the organic solvent/water interface. The DIC in poly(lactide-co-glycolide) microspheres (PLGA MS) as a long-term Ins delivery formulation was evenly distributed via a double-emulsion method. The DIC-loaded PLGA MS offered a higher Ins loading and a lower initial burst than Ins-loaded PLGA MS. This formulation possessed near zero-order release kinetics (for at least one month). In streptozotocin (STZ)-induced diabetic rats, a DIC-loaded PLGA MS formulation was able to maintain blood-glucose levels at 200-350 mg/dL for the first two weeks and even lower levels (100-200 mg/dL) for the next two weeks. Thus, a new POH polymer and its complex with a drug protein could have potential biological application as a long-term, sustained protein delivery system.
[show abstract][hide abstract] ABSTRACT: Motivated by the limitations of liposomal drug delivery systems, we designed a novel histidine-based AB2-miktoarm polymer (mPEG-b-(polyHis)2) equipped with a phospholipid-mimic structure, low cytotoxicity, and pH-sensitivity. Using “core-first” click chemistry and ring-opening polymerization, mPEG2kDa-b-(polyHis29kDa)2 was successfully synthesized with a narrow molecular weight distribution (1.14). In borate buffer (pH 9), the miktoarm polymer self-assembled to form a nano-sized polymersome with a hydrodynamic radius of 70.2 nm and a very narrow size polydispersity (0.05). At 4.2 μmol per mg polymer, mPEG2kDa-b-(polyHis29kDa)2 strongly buffered against acidification in the endolysosomal pH range and exhibited low cytotoxicity on 5 days exposure. Below pH 7.4 the polymersome transitioned to cylindrical micelles, spherical micelles, and finally unimers as the pH was decreased. The pH-induced structural transition of mPEG2kDa-b-(polyHis29kDa)2 nanostructures may be caused by the increasing hydrophilic weight fraction of mPEG2kDa-b-(polyHis29kDa)2 and can help to disrupt the endosomal membrane through proton buffering and membrane fusion of mPEG2kDa-b-(polyHis29kDa)2. In addition, a hydrophilic model dye 5(6)-carboxyfluorescein encapsulated into the aqueous lumen of the polymersome showed a slow, sustained release at pH 7.4 but greatly accelerated release below pH 6.8, indicating a desirable pH sensitivity of the system in the range of endosomal pH. Therefore, this polymersome that is based on a biocompatible histidine-based miktoarm polymer and undergoes acid-induced transformations could serve as a drug delivery vehicle for chemical and biological drugs.
Journal of Materials Chemistry 08/2012; 22(36):19168-19178. · 5.97 Impact Factor
[show abstract][hide abstract] ABSTRACT: To overcome the limitations of monomeric pH probes for acidic tumor environments, this study designed a mixed micelle pH probe composed of polyethylene glycol (PEG)-b-poly(l-histidine) (PHis) and PEG-b-poly(l-lactic acid) (PLLA), which is well-known as an effective antitumor drug carrier. Unlike monomeric histidine and PHis derivatives, the mixed micelles can be structurally destabilized by changes in pH, leading to a better pH sensing system in nuclear magnetic resonance (NMR) techniques. The acidic pH-induced transformation of the mixed micelles allowed pH detection and pH mapping of 0.2-0.3 pH unit differences by pH-induced "on/off"-like sensing of NMR and magnetic resonance spectroscopy. The micellar pH probes sensed pH differences in nonbiological phosphate buffer and biological buffers such as cell culture medium and rat whole blood. In addition, the pH-sensing ability of the mixed micelles was not compromised by loaded doxorubicin. In conclusion, PHis-based micelles could have potential as a tool to simultaneously treat and map the pH of solid tumors in vivo.
[show abstract][hide abstract] ABSTRACT: To deliver nucleic acids including plasmid DNA (pDNA) and short interfering RNA (siRNA), polymeric gene carriers equipped with various functionalities have been extensively investigated. The functionalities of these polymeric vectors have been designed to overcome various extracellular and intracellular hurdles that nucleic acids and their carriers encounter during their journey from injection site to intracellular target site. This review briefly introduces known extracellular and intracellular issues of nucleic acid delivery and their solution strategies. We examine significant yet overlooked factors affecting nucleic acid delivery (e.g., microenvironmental pH, polymer/siRNA complexation, and pharmaceutical formulation) and highlight our reported approaches to solve these problems.
Journal of Controlled Release 07/2012; · 7.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: Evidence continues to accumulate that patient tumors contain heterogeneous cell populations, each of which may contribute differently in extent and mechanism to the progression of malignancy. However, the field of tumor drug delivery research, while continually presenting new and innovative approaches, in many ways continues to operate on the premise that essentially all tumor cells are identical. In some in vivo models, xenograft tumors using cell lines may actually be comparatively homogeneous, and thus result in overly encouraging results when a particular drug or delivery system is reported to successfully treat tumors in mice. It is well known, however, that many drugs that show success in preclinical studies will fail in clinical trials. Tumor heterogeneity is possibly one of the most significant factors that most treatment methods fail to address sufficiently. While a particular drug may exhibit initial success, the eventual relapse of tumor growth is due in many cases to subpopulations of cells that are either not affected by the drug mechanism, possess or acquire a greater drug resistance, or have a localized condition in their microenvironment that enables them to evade or withstand the drug. These various subpopulations may include cancer stem cells, mutated clonal variants, and tumor-associated stromal cells, as well as cells experiencing a spatially different condition such as hypoxia within a diffusion-limited tumor region. This review briefly discusses some of the many aspects of tumor heterogeneity and their potential implications for future drug design and delivery methods.
Journal of Controlled Release 04/2012; · 7.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: The objective of this study was to investigate the efficiency of multifunctional poly(ethylene glycol)-based hemoglobin conjugates crosslinked with antioxidant enzymes for their ability to protect an oxygen carrier (hemoglobin) and insulin secreting islets from the combination of hypoxic and free radical stress under simulated transplantation conditions. In this study, RINm5F cells and isolated pancreatic islets were challenged with oxidants (H(2)O(2) or xanthine and xanthine oxidase) and incubated with conjugates (hemoglobin-hemoglobin or superoxide dismutase-catalase-hemoglobin) in normoxia (21% oxygen) or hypoxia (6% or 1% oxygen). Hemoglobin protection, intracellular free radical activity and cell viability in RINm5F cells measured by methemoglobin, dichlorofluorescein-diacetate, and (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay, respectively, showed that cells were better protected by conjugates containing antioxidant enzymes. Insulin secretion from islets and qualitative confocal evaluation of viability showed beta cells were protected by conjugates containing antioxidant enzymes when exposed to induced stress. Our study suggested that antioxidant enzymes play a significant role in hemoglobin protection and thus extended cell protection.
Biotechnology and Bioengineering 03/2012; 109(9):2392-401. · 3.65 Impact Factor
[show abstract][hide abstract] ABSTRACT: Poly(lactide-co-glycolide) (PLGA) has most often been employed for the controlled release of protein formulations because of its safety profile with non-toxic degradation products. Nevertheless, such formulations have been plagued by a local acidic microenvironment and protein-polymer interactions, which result in chemical and physical denaturation of loaded proteins and often unfavorable release profiles. This study investigated the pH change of inner PLGA microsphere (MS) using charged (PLGA)(n)-b-branched polyethyleneimine (bPEI) micelles. The designed micelles can be transformed into either micelle or reverse micelle (RM) depending on the solvent and RM can form microspheres. In addition, (PLGA)(n)-b-bPEI can be modified into (PLGA)(n)-b-(carboxylated bPEI) via carboxylation of the primary amines. Cationic micelle (CM) or anionic micelle (AM) was complexed with counter-charged proteins leading to nanosized particles (approximately 100nm). In the micelle/protein complexes, the micelles mostly maintained their proton buffering capacity, and consequently, prevented or delayed the typical decrease in pH caused by degradation of PLGA in aqueous solution. Reconstitutable micelle/protein complexes allowed for increased and fine-tuned protein loading (~20wt.% when using CM1 (CM prepared from PLGA(36kDa)-b-bPEI(25kDa))/insulin complexes) in PLGA MS. In CM2 (CM prepared from (PLGA(36kDa))(2)-b-bPEI(25kDa))/insulin (4 of weight ratio (WR) of micelle to protein; WR4)-loaded PLGA MS, CM2 strongly prevented the micellar nanoenvironmental pH (pH 6.6 within 5days and then approximately pH 8.5) to be acidified in PLGA MS for 9weeks, unlike CM2-free PLGA MS. In conclusion, our findings propose that the proton buffering capacity and protein loading in PLGA MS can be tuned by controlling the complexation ratios of micelles and proteins, polymeric architectures of (PLGA)(n)-b-bPEI copolymers and WR of micelle/protein complexes and PLGA (or RM).
Journal of Controlled Release 03/2012; 160(3):440-50. · 7.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: Although polymers, polyplexes, and cells are exposed to various extracellular and intracellular pH environments during polyplex preparation and polymeric transfection, the impact of environmental pH on polymeric transfection has not yet been investigated. This study aims to understand the influence of environmental pH on polymeric transfection by modulating the pH of the transfection medium or the culture medium. Changes in the extracellular pH affected polymeric transfection by way of complex factors such as pH-induced changes in polymer characteristics (e.g., proton buffering capacity and ionization), polyplex characteristics (e.g., size, surface charge, and decomplexation), and cellular characteristics (e.g., cellular uptake, cell cycle phases, and intracellular pH environment). Notably, acidic medium delayed endocytosis, endosomal acidification, cytosolic release, and decomplexation of polyplexes, thereby negatively affecting gene expression. However, acidic medium inhibited mitosis and reduced dilution of gene expression, resulting in increased transfection efficiency. Compared to pH 7.4 medium, acidic transfection medium reduced gene expression 1.6-7.7-fold whereas acidic culture medium enhanced transfection efficiency 2.1-2.6-fold. Polymeric transfection was affected more by the culture medium than by the transfection medium. Understanding the effects of extracellular pH during polymeric transfection may stimulate new strategies for determining effective and safe polymeric gene carriers.
[show abstract][hide abstract] ABSTRACT: Tumors have been a highlight in the research of nanomedicine for decades. Despite all the efforts in the decoration of the nano systems, tumor specific targeting is still an issue due to the heterogeneous nature of tumors. Hypoxia is frequently observed in solid tumors. The consequent acidification of tumor extracellular matrices may bring new insight to tumor targeting. In this review, we present the polymeric nano systems that target tumor extracellular pH (pH(e)).
[show abstract][hide abstract] ABSTRACT: The magnetic resonance (MR) functionalities of pullulan-conjugated gadolinium diethylene triamine pentaacetate (Gd-DTPA-Pullulan) as a new hepatocyte-specific contrast agent were evaluated. Pullulan, which specifically accumulates on hepatocytes via asialoglycoprotein receptors, was chemically linked with Gd-DTPA. Gd-DTPA-Pullulan displayed three times greater contrast enhancement than Gd-DTPA-BMA (Omniscan) in delayed MR imaging (MRI) on orthotopic rat hepatocarcinoma (HCC). This contrast effect lasted up to 24h. In particular, Gd-DTPA-Pullulan displayed a discriminative MR contrast on the regenerative and malignant hepatic nodules sequentially observed during the progress of cirrhotic HCC. Approximately 50% of injected Gd-DTPA-Pullulan was eliminated via the hepato-biliary system. IC(50) of Gd-DTPA-Pullulan on Chang liver cells was much higher than Gd-DTPA and Gd-DTPA-BMA (309.1 ± 11.2, 173.5 ± 15.5 and 49.4 ± 8.9 μM, respectively). Any significant toxicities of Gd-DTPA-Pullulan at the conventional dose on the rats weren't detected on histology studies. Gd-DTPA-Pullulan worked as a hepatocyte-specific MR contrast agent with increased MR functionalities and an acceptable safety profile setting the scene for future clinical trials.