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Abstract
Hemoglobin (Hb) protein microcapsules held together by cross-linker, glutaraldehyde (GA), were successfully fabricated by covalent layer-by-layer (LbL) technique. The Schiff base reaction occurred on the colloid templates between the aldehyde groups of GA and free amino sites of Hb results in the formation of GA/Hb microcapsules after the removal of the templates. The structure of obtained monodisperse protein microcapsule was characterized by transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). The UV-Vis spectra measurements demonstrate the existence of Hb in the assembled capsules. Cyclic voltammetry (CV) and potential-controlled amperometric measurements (I-t curve) confirm that hemoglobin microcapsules after fabrication remain their heme electroactivity. Moreover, direct electron transfer process from protein to electrode surface was performed to detect the heme electrochemistry without using any mediator or promoter. The experiments of fluorescence recovery after photobleaching (FRAP) by CLSM demonstrate that the hemoglobin protein microcapsules have an improved permeability comparing to the conventional polyelectrolyte microcapsules.
... The studies showed that the protein nanotubes prepared in this way could remain the electroactivity and catalytic activity. Later, our group extended this strategy to sacrificial 3-D colloidal particles and hollow protein capsules were obtained without the use of any polymer [23][24][25][26], different from the assembly of proteins and oppositely charged polyelectrolytes. Here, we mainly introduce the fabrication of this kind of microcapsules and their applications in biomedical engineering and biologically related chemistry, in which they can be flexibly designed to be stimuli-responsive under physiological conditions and allow for the incorporation of uncharged species, which is important for capsule's multifunctionalization. ...
... Our group has recently prepared hemoglobin (Hb) protein microcapsules by using a covalent LbL technique [24]. The use of covalent bonds to assemble LbL microcapsules can provide significant advantages compared to traditional electrostatic assembly [27]. ...
... In addition, the LbL technique can further help the loading of Hb by coating the external surface of CaCO 3 with encapsulated Hb inside (Fig. 5.7c). Both factors contribute to the high loading of Hb in the spheres, and also present adjustable permeability [24], which is of great importance for maintaining the normal functionalities of natural RBCs, allowing life-sustaining small molecules such as oxygen, carbon dioxide, glucose, reducing agents and metabolic products to diffuse into/out of the system. More importantly, such Hb protein after covalently cross-linked and modified by PEG retains well its whole structure and especially its oxygen-carrying function. ...
Development of protein-based molecular devices is an active area of research due to their broad applications in biotechnology, biorelated chemistry, bioelectronics, and biomedical engineering. Hemoglobin (Hb) is a physiologically important oxygen-transport metalloprotein present in the red blood cells. In this chapter, we present the recent development in fabrication and tailoring of a variety of hemoglobin protein shells via covalent layer-by-layer (LbL) assembly combined with template technique. Also, the developed strategy is effective and flexible, advantageous for avoiding denaturation of proteins. The as-fabricated Hb shells have better applications in drug delivery and controlled release, biosensors, biocatalysis, and bioreactors due to the enhancement of biological availability. In view of the carrying-oxygen function of Hb protein in blood, we particularly focus on the potential applications of hemoglobin-based nanoarchitectonic assemblies as artificial blood substitutes. These novel oxygen carriers exhibit advantages over traditional carriers and will greatly promote research on reliable and feasible artificial blood substitutes.
... Since proteins contain many amino groups, we fabricate hollow hemoglobin (Hb) microcapsules by using GA as a cross-linker ( Figure 2A). 36 Manganese carbonate (MnCO 3 ) particles were chosen as sacrificial templates. The GA and Hb were alternately adsorbed onto the surfaces of MnCO 3 particles. ...
... Cyclic voltammetry and potential-controlled amperometric measurements confirmed that the Hb assembled in the microcapsules remained its native structure and showed a good electroactivity. 36 Since the stability of Schiff base bond decreases with the decreased pH, the permeability of Hb microcapsules to fluorescence probe FITC-dextran (M w 2000 kDa) were studied by incubating with different pH buffers. When the pH is lower than 5.8, the fluorescence intensities of the exterior and interior of microcapsules are almost same, indicating that FITC-dextran could penetrate into microcapsules through the wall. ...
Layer-by-layer (LbL) assembly is a most commonly used method to prepare various microcapsules based on the electrostatic interactions, hydrogen bonding and covalent bonding so on. Among these interactions, Schiff base bond formed in covalent assembly not only has an advantage in stability, but also enables the assembled microcapsules with autofluorescence and pH-sensitivity. In this feature article, we will mainly describe the construction of biomimetic microcapsules through Schiff base mediated LbL assembly. The structures and properties of the assembled microcapsules are introduced and their application as drug carriers are highlighted.
... In this case, it was found that the electroactivity and catalytic activity of the proteins could be retained. We assembled Hb, GOD, and CAT onto the surface of manganese carbonate cores separately and cross-linked with GA [47, 48]. The amino groups in proteins were jointed with aldehyde groups in GA to form a Schiff's base bond. ...
... Template-based LbL assembly has provided a powerful strategy to construct biomimetic red blood cells. As a preliminary try, we prepared Hb-based microcapsules through covalent LbL technique by using a traditional cross-linker, GA [48]. After the Schiff's base reaction on the surface of solid MnCO 3 microparticles between the aldehyde groups of GA and free amino sites of Hb and the subsequent removal of templates , GA/Hb microcapsules could be obtained. ...
This chapter will introduce the recent development on the biocompatible and biogenic microcapsules assembled through layer-by-layer technique and their application in biomedicine. Usually, most of the microcapsules were composed of natural and modified lipids, proteins, polysaccharides, or other composites. When trapping some functional inorganic nanocrystallines such as magnetic nanoparticles, fluorescent quantum dots, and plasmonic nanoparticles, the microcapsules will change their physicochemical and biological properties and exhibit a great potential application in biomedicine. Herein, we will mainly summarize how the assembled microcapsules are applied in the drug delivery systems for cancer treatment and blood substitutes.
... C onfinement of biomolecules and biochemical reactions within membrane-bound microcompartments is a key step towards the construction of biomimetic microreactors that are capable of mimicking the rudimentary functionality of living cells 1,2 . Towards the localization of enzymatic elements, synthetic strategies primarily take advantage of spontaneous or directed amphiphile assembly in solution or at interface to produce microcompartments such as fatty acid vesicles 3 and liposomes 4,5 , polymersomes [6][7][8] , layer-by-layer capsules 9 , and proteinosomes 10,11 . Such bottom-up approaches offer plausible scenarios for the origin of life and have been utilized to demonstrate a diverse range of cell-mimicking functions including enzyme-mediated catalysis 12,13 , deoxyribonucleic acid (DNA) amplification 14 , and gene expression 15 . ...
Integrative colloidosomes with hierarchical structure and advanced function may serve as biomimetic microreactors to carry out catalytic reactions by compartmentalizing biological species within semipermeable membranes. Despite of recent progress in colloidosome design, integration of biological and inorganic components into tiered structures to tackle the remaining challenges of biocatalysis is highly demanded. Here, we report a rational design of three-tiered colloidosomes via the Pickering emulsion process. The microreactor consists of crosslinked amphiphilic silica-polymer hybrid nanoparticles as the semipermeable shell, an enzyme-incorporated catalytic sub-layer, and a partially-silicified adsorptive lumen. By leveraging confinement and enrichment effect, we demonstrate the acceleration of lipase-catalyzed ester hydrolysis within the microcompartment of organic-inorganic hybrid colloidosomes. The catalytic colloidosomes are further assembled into a closely packed column for enzymatic reactions in a continuous flow format with enhanced reaction rates. The three-tiered colloidosomes provide a reliable platform to integrate functional building blocks into a biomimetic compartmentalized microreactor with spatially controlled organization and high-performance functions.
... Although the structure of the globin chain allows heme to bind oxygen with minimal oxidation of ferrous to ferric iron, autoxidation is not entirely prevented; low concentrations (in human less than 2% of circulatory Hb) of methemoglobin are normally present in vivo. This methemoglobin can then react with the peroxides formed during the autoxidation process itself or elsewhere, Isoniazid ® metabolites, in the protein's vicinity; both the globin-bound radical and ferryl heme iron can cause tissue damage, by initiating lipid peroxidation reactions (Kanner & Harel, 1987;Newman et al., 1991;Jaffe & Hulquist, 1995 ;Rogers et al., 1995;Duan et al., 2007). ...
... Although the structure of the globin chain allows heme to bind oxygen with minimal oxidation of ferrous to ferric iron, autooxidation is not entirely prevented; low concentrations (less than 2% of circulatory Hb) of methemoglobin are normally present in vivo. Met-hemoglobin can then react with the peroxides formed during the auto-oxidation process itself or elsewhere, Isoniazid ® metabolites, in the protein's vicinity; both the globin-bound radical and ferryl heme iron can cause tissue damage, by initiating lipid peroxidation reactions [53][54][55][56][57]. Moreover, when Isoniazid ® -treated rats orally supplied with antioxidants, such as herbal extracts, they performed marked improvement in blood picture, this may be attributed to the antioxidant potential (directly by scavenging free radicals or indirectly by improving the enzymatic or non-enzymatic antioxidant systems of the rats tissues) that protects erythrocytes from the oxidative damages induced by toxic metabolites of INH. ...
soniazid® (INH), being the first line drug used as anti-tuberculosis drugs, is known to be associated with physiological deteriorations including hematological disturbances. The objective of this study was to explore the protective effect of rosemary and parsley aqueous extracts against INH-induced hematological disturbances. Adult rats (120-150g) were randomly divided into six groups (10 rats each): first group administrated with saline and served as control, second group ingested rosemary extract (440mg/kg/day), third group ingested parsley extract (250 mg/kg/day), fourth group received Isoniazid® (50mg/kg/day), fifth group received Isoniazid® and rosemary extract together, and sixth group received Isoniazid® in combination with parsley extract. After eight weeks, the results revealed that administration of either rosemary or parsley extract in combination with Isoniazid® ameliorated the Isoniazid®-induced hemato-deterioration; this was evidenced by the significant improvement of blood Hb, RBCs, HCt, blood indices, TLC, platelets and oxyhemoglobin (Hb-O2, functional Hb derivative) levels and met-Hbr activity coupled with a reduction in the level of nonfunctional Hb derivatives (met-Hb, Hb-CO and Hb-S), auto-oxidation rate of oxyhemoglobin and hemolysis of RBCs. In conclusion, both rosemary and parsley extract could play a beneficial role in prevention of Isoniazid®-induced hematological disturbances, consequently reducing both physiological and functional anemia. This effect could be through their anti-oxidative and anti-nitrosative voltage
(PDF) baset2018. Available from: https://www.researchgate.net/publication/353764668_baset2018 [accessed Sep 11 2021].
... It is a conjugated iron-protein compound in red blood cells and participates in the transportation of oxygen, carbon dioxide, and nitric oxide. 1 A deficiency of hemoglobin can result in various diseases, such as anemia, thalassemia, and so on. 2 Thus, to analyze Hb is of important significance for clinical diagnoses, and biomedical and proteomics research. ...
We describe a simple and effective strategy to construct molecular imprinting ratiometric fluorescence sensor (MIR sensor) for the visual detection of bovine hemoglobin (BHb) used as a model protein. The sensor was prepared by simply mixing the solution of green and red CdTe quantum dots (QDs), which were embedded in core–shell structured molecularly imprinted polymers and silica nanoparticles, respectively. The resultant hybrid MIR sensor can selectively bind with BHb and thus quench the fluorescence of the green QDs, while the red QDs wrapped with silica is insensitive to BHb with the fluorescence intensity unchanged. As a result, a continuous obvious fluorescence color change from green to red can be observed by naked eyes, with the detection limit of 9.6 nM. Moreover, the MIR sensor was successfully applied to determine BHb in bovine urine samples with satisfactory recoveries at three spiking levels ranging from 95.7–101.5%, indicating great potential application for detecting BHb in real samples. This strategy of using different fluorescence emission materials incorporated to construct a ratiometric fluorescence sensor is reasonable and convenient, which can be extended to the preparation of other ratiometric fluorescence systems for targeted analytes.
... Glutaraldehyde (GA) was successfully introduced to link the adjacent Hb layers by covalent bonding (Fig. 3a-c). Cyclic voltammetry and potential-controlled amperometric results confirm that hemoglobin microcapsules can retain their heme electroactivity after fabrication [42]. The direct electron transfer process from protein to the electrode surface was performed to detect the heme electrochemistry without using mediators or promoters. ...
In this review, we summarize the recent progress made in the fabrication of pure natural materials such as biogenic capsules. Unlike polyelectrolyte capsules, biogenic capsules are primarily prepared with pure natural components using layer-by-layer (LbL) assembly on sacrificial templates. These capsules have been developed as smart materials for guest molecule encapsulation and delivery in the last two decades. With the extreme demands on biodegradability and biocompatibility, biogenic capsules exhibit unique properties that can be integrated with special ligands or conjugated functional groups for the design of intelligent platforms, significantly enriching their functions and applications.
... In recently years, a series of Hb-based microcapsules for utilized as artificial oxygen carriers are successfully fabricated by LbL assembly in our group [42][43][44][45]. We have reported that Hb-based hollow microcapsules were prepared by the covalent LbL assembly of Hb and glutaraldehyde (GA) by using MnCO 3 templates (Fig. 1). ...
... The Schiff base itself is a powerful tool with applications in drug delivery, 143,145,146 bioreactor design, 147,148 biosensors, 149 protein microarrays, 150,151 preparation of nano 152 / microstructures, 153 etc. The imine possesses several unique properties which enable its widespread use including: (1) pH sensitivity, (2) autofluorescence, (3) formation under mild conditions without added reagents, (4) occurrence in both aqueous and organic solvents, and (5) reversibility (with the option of irreversibility through reductive amination). ...
The utility of metabolic synthons as the building blocks for new biomaterials is based on the early application and success of hydroxy acid based polyesters as degradable sutures and controlled drug delivery matrices. The sheer number of potential monomers derived from the metabolome (e.g., lactic acid, dihydroxyacetone, glycerol, fumarate) gives rise to almost limitless biomaterial structural possibilities, functionality, and performance characteristics, as well as opportunities for the synthesis of new polymers. This review describes recent advances in new chemistries, as well as the inventive use of traditional chemistries, toward the design and synthesis of new polymers. Specific polymeric biomaterials can be prepared for use in varied medical applications (e.g., drug delivery, tissue engineering, wound repair, etc.) through judicious selection of the monomer and backbone linkage.
... Γ-methyl-acryloyl trimethoxysilane (KH-570) can introduce methylacryloyl with alkenes into the surface of MMT, which makes it more accessible to proteins. The aldehyde group of glutaraldehyde (GA) has a Schiff base reaction with the amino group of protein to produce a carbon-nitrogen double bond [4] . This process can improve the stabilization of protein. ...
The existential state of protein in complexes directly affects the performance and applications of the composite materials. The interlayer space changes of montmorillonite in the protein / montmorillonite (MMT) composite were identified by X-ray diffraction (XRD). And the interaction between protein and MMT were analyzed by Fourier transform infrared spectrometry (FT-IR) and UV/vis spectrophotometry. The loading amount of bovine serum albumin (BSA) onto MMT was calculated from the TG data. The types of adsorption isotherm of BSA onto montmorillonite were analyzed. From the above analysis, it can be concluded that the structure of proteins in the montmorillonite interlayers has been changed, and the hydrogen bond and Van der Waals force between the BSA molecules and montmorillonite crystal layers are intensified. The α-helix content of BSA molecules reduces while random coil increases. The protein shows a state of being squashed.
... The process involves the step-wise deposition of species onto a core, which is subsequently removed to generate free-standing capsules [4]. The sequential formation of these capsules is based on the facile selection of sacrificial templates [5][6][7] and assembly components [7][8][9][10][11][12][13][14][15][16]. Various active compounds can be sequestered in to the capsule shell [17,18] and/or interior [19,20] for drug delivery and various other applications. ...
... In recent years, porous calcium carbonate (CaCO 3 ) particles have been widely applied as templates loading various biomaterials, such as proteins and drugs, due to their uniformity and monodispersity, easy preparation, controllable size from micrometer to nanometer, mild decomposition conditions, and especially its high loading capacity. In our previous work, [7] by templating porous CaCO 3 particles and covalent layer-by-layer (LbL) assembly technique, [8,9] the monodisperse additive-free Hb microspheres have been successfully fabricated, which have been considered as a potential blood substitute in the development of artificial oxygen carriers. In the present work, we have successfully assembled Hb microspheres as blood substitutes for the study of UO 2 2 + damage on the biofunction of blood cells. ...
The effect of radioactive UO22+ on the oxygen-transporting capability of hemoglobin-based oxygen carriers has been investigated in vitro. The hemoglobin (Hb) microspheres fabricated by the porous template covalent layer-by-layer (LbL) assembly were utilized as artificial oxygen carriers and blood substitutes. Magnetic nanoparticles of iron oxide (Fe3O4) were loaded in porous CaCO3 particles for magnetically assisted chemical separation (MACS). Through the adsorption spectrum of magnetic Hb microspheres after adsorbing UO22+, it was found that UO22+ was highly loaded in the magnetic Hb microspheres, and it shows that the presence of UO22+ in vivo destroys the structure and oxygen-transporting capability of Hb microspheres. In view of the high adsorption capacity of UO22+, the as-assembled magnetic Hb microspheres can be considered as a novel, highly effective adsorbent for removing metal toxins from radiation-contaminated bodies, or from nuclear-power reactor effluent before discharge into the environment.
... An efficient way to prepare uniformly sized protein-based particles or capsules is template-assisted layer-bylayer (LbL) assembly, by which sacrificial inorganic particle templates provide a uniform size of the resulting capsules. [24][25][26][27][28][29] In spite of the technical merits, nevertheless, the LbL assembly approach is experimentally laborious. In the technical approaches mentioned above, chemical cross-linking agents such as glutaraldehyde are often used to stabilize protein particles or capsules, but this is unfavorable for biomedical applications due to side effects and toxicity possibly caused by residual aldehyde. ...
We present a general strategy to nanoengineer protein‐based colloidal spheres (biomimetic protocells) as versatile delivery carriers with stimuli responsiveness by the electrostatic assembly of binary components (proteins and polypeptides) in association with intermolecular disulfide cross‐linking. The size of the colloidal spheres, ranging from nanoscale to microscale, is readily tuned through parameters like protein and polypeptide concentration, the ratio between both, pH, and so on. Moreover, such colloidal spheres show versatile encapsulation of various guest molecules including small organic molecules and biomacromolecules. The pH and redox dual‐responsiveness facilitates the rapid release of the payload in an acidic and reductant‐enriched ambient such as in lysosomes. Thus, nanoengineering of protein‐based biomimetic protocells opens a new alternative avenue for developing delivery vehicles with multifunctional properties towards a range of therapeutic and diagnostic applications. Versatile delivery carriers with dual‐stimuli responsiveness are fabricated by electrostatic assembly of binary components (proteins and polypeptides (poly‐L‐lysine, PLL); see figure) in association with intermolecular disulfide cross‐linking. The protein‐based delivery system may be used to load and transport a wide range of guest molecules from various small organic molecules to biomacromolecules, and thus opens a new alternative avenue for developing delivery vehicles with multifunctional properties towards a range of therapeutic and diagnostic applications.
The deposition of thin films plays a crucial role in surface engineering, tailoring structural modifications, and functionalization across diverse applications. Layer-by-layer self-assembly, a prominent thin-film deposition method, has witnessed substantial growth since its mid-20th-century inception, driven by the discovery of eligible materials and innovative assembly technologies. Of these materials, micro- and nanoscopic substrates have received far less interest than their macroscopic counterparts; however, this is changing. The catalogue of eligible materials, including nanoparticles, quantum dots, polymers, proteins, cells and liposomes, along with some well-established layer-by-layer technologies, have combined to unlock impactful applications in biomedicine, as well as other areas like food fortification, and water remediation. To access these fields, several well-established technologies have been used, including tangential flow filtration, fluidized bed, atomization, electrophoretic assembly, and dielectrophoresis. Despite the invention of these technologies, the field of particle layer-by-layer still requires further technological development to achieve a high-yield, automatable, and industrially ready process, a requirement for the diverse, reactionary field of biomedicine and high-throughput pharmaceutical industry. This review provides a background on layer-by-layer, focusing on how its constituent building blocks and bonding mechanisms enable unmatched versatility. The discussion then extends to established and recent technologies employed for coating micro- and nanoscopic matter, evaluating their drawbacks and advantages, and highlighting promising areas in microfluidic approaches, where one distinctly auspicious technology emerges, acoustofluidics. The review also explores the potential and demonstrated application of acoustofluidics in layer-by-layer technology, as well as analyzing existing acoustofluidic technologies beyond LbL coating in areas such as cell trapping, cell sorting, and multidimensional particle manipulation. Finally, the review concludes with future perspectives on layer-by-layer nanoparticle coating and the potential impact of integrating acoustofluidic methods.
The surface engineering of biomaterials is crucial for their successful (bio)integration by the body, i.e. the colonization by the tissue-specific cell, and the prevention of fibrosis and/or bacterial colonization. Performed at room temperature in an aqueous medium, the layer-by-layer (LbL) coating method is based on the alternating deposition of macromolecules. Versatile and simple, this method allows the functionalization of surfaces with proteins, which play a crucial role in several biological mechanisms. Possessing intrinsic properties (cell adhesion, antibacterial, degradable, etc.), protein-based LbL films represent a powerful tool to control bacterial and mammalian cell fate. In this article, after a general introduction to the LbL technique, we will focus on protein-based LbL films addressing different biomedical issues/domains, such as bacterial infection, blood contacting surfaces, mammalian cell adhesion, drug and gene delivery, and bone and neural tissue engineering. We do not consider biosensing applications or electrochemical aspects using specific proteins such as enzymes.
Bio‐macromolecule hemoglobin (Hb) is a kind of iron‐rich metalloprotein that abundant in erythrocytes with various physiological properties. Separating Hb from bio‐matrix with high efficacy is crucial to Hb application but quite challenging. In this study, a supermacroporous molecularly imprinted membrane (MIM) was prepared with high performance on recognizing bovine hemoglobin (BHb). By using the silk fibroin and calcium alginate as mechanical modifiers, the mechanical strength of the prepared membrane was significantly improved to at around 0.25 MPa, and the supermacroporous structure in MIM was also formed. The MIM adsorption capacity of BHb was as high as 121.8 mg g⁻¹ at the initial concentration of 0.5 mg mL⁻¹. The MIM separation factor of BHb from BHb/BSA mixtures was as high as 7.34, and the relative imprinting factor was at around 4.0. The prepared MIM demonstrated the superiority and the valuable application prospect on specific separation of BHb.
Proteins and peptides are attractive chemical building blocks to encapsulate and protect active substances thanks to their biocompatibility, biodegradability, low immunogenicity, and added functionality compared to synthetic polymers. This review provides a comprehensive overview of micro- and nanocapsules predominantly made of proteins—both natural and artificially produced—and peptides, detailing their different fabrication techniques and possible applications in various fields, including food technology and healthcare. Emphasis is given on the capability of proteins and peptides to assemble into capsular structures in the absence (e.g., protein cages and polypeptide-based coacervates) or presence of a template, as well as on the physical nature of the carriers core, i.e., gaseous, liquid, or solid.
One of the undeniable trends in modern bioengineering and nanotechnology is the use of various biomolecules, primarily of a polymeric nature, for the design and formulation of novel functional materials for controlled and targeted drug delivery, bioimaging and theranostics, tissue engineering, and other bioapplications. Biocompatibility, biodegradability, the possibility of replicating natural cellular microenvironments, and the minimal toxicity typical of biogenic polymers are features that have secured a growing interest in them as the building blocks for biomaterials of the fourth generation. Many recent studies showed the promise of the hard-templating approach for the fabrication of nano- and microparticles utilizing biopolymers. This review covers these studies, bringing together up-to-date knowledge on biopolymer-based multilayer capsules and beads, critically assessing the progress made in this field of research, and outlining the current challenges and perspectives of these architectures. According to the classification of the templates, the review sequentially considers biopolymer structures templated on non-porous particles, porous particles, and crystal drugs. Opportunities for the functionalization of biopolymer-based capsules to tailor them toward specific bioapplications is highlighted in a separate section.
In this paper, we propose a consistent mechanism of protein microcapsule formation upon ultrasound treatment. Aqueous suspensions of bovine serum albumin (BSA) microcapsules filled with toluene are prepared by use of high-intensity ultrasound following a reported method. Stabilization of the oil-in-water emulsion by the adsorption of the protein molecules at the interface of the emulsion droplets is accompanied by the creation of the cross-linked capsule shell due to formation of intermolecular disulfide bonds caused by highly reactive species like superoxide radicals generated sonochemically. The evidence for this mechanism, which until now remained elusive and was not proven properly, is presented based on experimental data from SDS-PAGE, Raman spectroscopy and dynamic light scattering.
Using the surface molecular imprinting technique, a thermo-sensitive molecularly imprinted fluorescent sensor was constructed for bovine hemoglobin (BHb) detection with the silanized carbon dots (CD@SiO2) as fluorescent signal, N-isopropylacrylamide as monomer sensitive to temperature, and BHb as template. The silanized carbon dots coated by the molecularly imprinted polymer (CD@SiO2@MIP) were characterized by high-resolution transmission electron microscopy, Fourier transform infrared spectroscopy, and fluorescence spectroscopy. Owing to the combination of the strong fluorescence sensitivity of CDs and the high selectivity of the molecular imprinting shell, the prepared sensor showed good recognition and detection performance to the target protein BHb, with a linear range of 0.31–1.55 μM and a detection limit of 1.55 μM. Furthermore, the sensor was utilized to detect the content of BHb in real urine with a recovery of 98.6–100.5%. The CD@SiO2@MIP sensors present a high potential for applications in the detection of BHb in biological systems.
Graphical abstract
A novel magnetic molecularly imprinted polymer only based on deep eutectic solvents (DESs-MMIP) was successfully synthesized. The DESs-MMIP was constructed by using 2-hydroxyethyl methacrylate/tetrabutylammonium chloride deep eutectic solvent (DES1) as functional monomer, arylamide/(3-acrylamidopropyl) trimethylammonium chloride deep eutectic solvent (DES2) as cross-linker and bovine hemoglobin (BHb) as template through surface imprinting technology. The obtained DESs-MMIP was characterized by transmission electron microscope, X-ray diffraction, fourier transform infrared spectrometry, thermal gravimetric analysis and vibrating sample magnetometer. Under the optimized conditions, the maximum adsorption capacity of DESs-MMIP on BHb was 229.54 mg g⁻¹ and the imprinting factor reached up to 21.89. The selective adsorption experiments indicated that compared with seven references, DESs-MMIP showed significant selectivity for BHb. The new-type DESs-MMIP exhibited higher adsorption capacity and imprinting factor on BHb than molecularly imprinted polymers constructed with traditional functional monomer and cross-linker in reported methods. The recognition of BHb by DESs-MMIP in calf blood samples demonstrated the practicality of the particles. The DESs-MMIP only based on deep eutectic solvents with excellent selectivity is expected to become an ideal candidate for selective recognition of BHb in complicated samples.
The ability of living organisms to perform structure, energy, and information‐related processes for molecular self‐assembly through compartmentalization and chemical transformation can possibly be mimicked via artificial cell models. Recent progress in the development of various types of functional microcompartmentalized ensembles that can imitate rudimentary aspects of living cells has refocused attention on the important question of how inanimate systems can transition into living matter. Hence, herein, the most recent advances in the construction of protein‐bounded microcompartments (proteinosomes), which have been exploited as a versatile synthetic chassis for integrating a wide range of functional components and biochemical machineries, are critically summarized. The techniques developed for fabricating various types of proteinosomes are discussed, focusing on the significance of how chemical information, substance transportation, enzymatic‐reaction‐based metabolism, and self‐organization can be integrated and recursively exploited in constructed ensembles. Therefore, proteinosomes capable of exhibiting gene‐directed protein synthesis, modulated membrane permeability, spatially confined membrane‐gated catalytic reaction, internalized cytoskeletal‐like matrix assembly, on‐demand compartmentalization, and predatory‐like chemical communication in artificial cell communities are specially highlighted. These developments are expected to bridge the gap between materials science and life science, and offer a theoretical foundation for developing life‐inspired assembled materials toward various applications.
Templated assembly techniques have been extensively used to develop various types of hemoglobin (Hb) loaded particles with improved performance. However, several instability issues must still be solved, including Hb exposure, enhanced Hb auto-oxidation, and the relatively weak binding of Hb to cross-linkers. Herein, to meet the stability requirements for novel hemoglobin-based oxygen carriers (HBOCs), hemoglobin-polydopamine particles (Hb-PDA) were fabricated using a mild process that combines the co-precipitation of Hb and an inorganic template with the spontaneous adhesion of PDA. The Hb-PDA showed uniform size distribution, chemical integrity of both Hb and PDA, high biocompatibility, and robust oxygen delivery. Our results demonstrated that the use of polydopamine as a biocompatible coating material reduced Hb leakage from the particles under both static and flow conditions, thus mitigating the toxicity associated with free Hb and strengthening the stability of Hb particles. In addition, Hb-PDA reduced HUVEC (Human Umbilical Vein Cells) oxidative injury and scavenged 85% of the available hydroxyl radicals, exhibiting its potential to act as an antioxidant for encapsulated Hb. Hb-PDA therefore shows significant promise as a cell-like structurally and functionally stable HBOCs.
What is the most favorite and original chemistry developed in your research group?
The most favorite and original chemistry developed in my research group is about the reconstitution of motor proteins in artificially designed and assembled units. It is based on the molecular assembly technique, but the method is different from the conventional approach. We have developed a Schiff base layer‐by‐layer assembly, which has been demonstrated to be particularly useful to assemble systems from biological molecules. With this strategy, we are able to artificially construct different types of large biological units with structures and functions of chloroplasts and mitochondria. Thus we can mimick biological activities similar to those of living system. We have spent nearly two decades to develop this method, which is now well accepted worldwide.
How do you get into this specific field? Could you please share some experiences with our readers?
I get into this specific field starting at the 200th Xiangshan conference on biomembrane in 2003. The topic of this meeting was about biological membranes. On this meeting, Prof. Fuyu Yang mentioned and introduced for the first time about the FoF1‐ATPase as a rotated motor protein. For their recognition of the hydrolysis mechanism on FoF1‐ATPas, three scientists, Paul D. Boyer, John E. Walker, Jens C. Skou had received the Nobel Price on Chemistry in 1997. When I attended the 2003 Xiangshan meeting, I heard for the first time about the structure and the function of this biological motor. I was fascinated and thought that this protein could be used to artificially assemble a more complicated system, in essence a simplified arrangement of the natural protein complex.
In 2004, I started to have one Ph.D student working on this topic. It cost us quite some time and effort to extract and purify this protein from plants. This biotechnology effort was hard work for us chemists. In the end，it took us almost three years to work this out and to finally produce sufficiently motor proteins including the linear motors, kinesins in adequate amount. Based on the proper characterization of FoF1‐ATPas, we finally managed to successfully reconstitute it into a biological membrane in a larger size as the first biomimetic system.
How do you supervise your students?
First of all, I give the students a lot of autonomy to select a certain topic within a general work frame. For them this is quite motivating, because they work on what they selected based on their own interests. Normally this approach works well. Only occasionally the direction of of his/her study has to be corrected directly by myself.
What is the most important personality for scientific research?
The most important personality for scientific research to me is the “persistence” and “patience” in face of the long duration and often frustrating challenges typically for scientific work.
What's your hobbies? What's your favorite book(s)?
I am particularly interested in Architecture and Painting. I also enjoy photography, films and classical music. My favorite books are Dream of the Red Chamber (红楼梦) and Les Miséables.
How do you keep balance between research and family?
I do take care of my family very much, especially the education of my two daughters. But I never put too much pressure on their studies. They study well and they also like sports, music, and films. They can play several different musical instruments. During the summer holidays, I often travel around with my family. I consider it as quite important to experience and recognize the world with social activities.
Who influences you mostly in your life?
My father and my brother. From my father I have learned the ability to solve various problems in daily life. My brother triggered my interest in science.
What is your favorite journal(s)?
No particular journals! But I do like those journals, which focus more on publishing original work.
Could you please give us some advices on improving Chinese Journal of Chemistry?
I am very pleased to accept CJC's interview. I do have the impression that this journal is getting better and better. It improves rapidly and is well recognized by our co‐workers. I personally also value it as an international journal in our research area. I am convinced that publishing on some featured topic or some featured articles will no doubt increase the influence of the journal.
Activities in the living organisms are propelled by protein‐style machines named molecular motors (or motor proteins). Molecular motors, such as myosin, kinesin, dynein, and ATPase, are abundant in living cells, and play crucial roles in the intracellular transportation and energy conversion. The vital functions and high‐efficient energy conversion of these molecular motors enable substantial researches on their reconstitution in vitro. In this review, we will summarize the recent progresses on the biomimetic assembly of biomolecular motors (FoF1‐ATPase and kinesin) and introduce the strategies used for the manipulation of their functions.
Proteins are considered as one of the most important highly reproducible and monodisperse building blocks with specific functions in life sciences and material science. Protein capsules and their hybrids composed of protein-polymer conjugates have been intensively explored in drug delivery, catalysis and mimicking cell functions. Herein, we presented a facile, universal and efficient method to fabricate the diverse protein capsules, independent on the molecular weight (Mw), isoelectric points (IEP), wettability, amino acid sequence and functional domains of enumerated proteins. The protein capsules were well characterized by various techniques. Furthermore, their ability to store the original protein functionality was demonstrated, which was mainly embodied in their enzyme responsiveness and good biocompatibility in vitro and in vivo. We believe that these protein capsules have multiple potential applications such as in drug delivery, tissue engineering, catalysis and other application fields.
Stimulated response molecularly imprinted polymers (MIPs) have attracted wide attention not only because of their intriguing response to external stimuli, but also due to the desired molecular recognition ability. Herein, a novel dual responsive proteins MIPs with both photonic and magnetic stimuli has been developed by surface imprinting polymerization, where double bonds modified Fe 3 O 4 nanoparticles, a water-soluble azobenzene containing 4-[(4-methacryloyloxy)phenylazo]benzenesulfonic acid and bovine hemoglobin (BHb) were used as magnetic core, photoswitchable functional monomer and template protein, respectively. The resultant MIPs possessed a typical spherical structure with a relative rough imprinted layer of 15 nm thickness. Moreover, the MIPs had good binding behavior toward BHb with fast binding kinetics, high adsorption capacity and satisfactory selectivity. The MIPs were proved to be well photo-controlled toward the template protein BHb under the alternating irradiation of 365 and 440 nm: 31.4% BHb was released from the MIPs at 365 nm and 67.2% BHb was bound into the MIPs at 440 nm. As a result, the MIPs were successfully applied to specifically extract template protein from actual biological sample. As a consequence, combining photocontrolled release and uptake, rapidly magnetic separation and specific recognition, the resultant MIPs with photonic and magnetic dual responsive abilities show significant advantages in the enrichment of trace protein in biological samples.
Covalent layer-by-layer (LbL) assembly is a powerful method used to construct functional ultrathin films that enables nanoscopic structural precision, componential diversity, and flexible design. Compared with conventional LbL films built using multiple noncovalent interactions, LbL films prepared using covalent crosslinking offer the following distinctive characteristics: (i) enhanced film endurance or rigidity; (ii) improved componential diversity when uncharged species or small molecules are stably built into the films by forming covalent bonds; and (iii) increased structural diversity when covalent crosslinking is employed in componential, spacial, or temporal (labile bonds) selective manners. In this review, we document the chemical methods used to build covalent LbL films as well as the film properties and applications achievable using various film design strategies. We expect to translate the achievement in the discipline of chemistry (film-building methods) into readily available techniques for materials engineers and thus provide diverse functional material design protocols to address the energy, biomedical, and environmental challenges faced by the entire scientific community.
Nanoarchitectonics has begun to extend to many are as such as nanostructured materials, hybrid materials, energy and environmental sciences, biomedical applications, fabrication methodologies, and particularly in supramolecular assemblies. This chapter focuses on the biomedical applications of organic ultrathin film, especially in carriers. The concept of nanoarchitectonics as a new paradigm shift from nanotechnology is proposed for the future development of nanotechnology. The sacrificial templates are then decomposed until the desired number of layers is formed, and the hollow multilayer container nanoarchitectonics is obtained. In particular, layer-by-layer (LbL) assembly methods make it possible to construct functional ultrathin film nanoarchitectonics quickly and efficiently. Nanomaterials of organic ultrathin film will open up new possibilities for personalized medical therapy for patients in the near future. Three representative strategies for ultrathin film fabrication would be the self-assembled monolayer (SAM) method; Langmuir-Blodgett (LB) technique, and LbL assembly.
Utilizing colloidal particles for the assembly of the shell of nano- and microcapsules holds great promise for the tailor-made design of new functional materials. Increasing research efforts are devoted to the synthesis of such colloidal capsules, by which the integration of modular building blocks with distinct physical, chemical, or morphological characteristics in a capsule's shell can result in novel properties, not present in previous encapsulation structures. This review will provide a comprehensive overview of the synthesis strategies and the progress made so far of bringing nano- and microcapsules with shells of densely packed colloidal particles closer to application in fields such as chemical engineering, materials science, or pharmaceutical and life science. The synthesis routes are categorized into the four major themes for colloidal capsule formation, i.e. the Pickering-emulsion based formation of colloidal capsules, the colloidal particle deposition on (sacrificial) templates, the amphiphilicity driven self-assembly of nanoparticle vesicles from polymer-grafted colloids, and the closely related field of nanoparticle membrane-loading of liposomes and polymersomes. The varying fields of colloidal capsule research are then further categorized and discussed for micro- and nano-scaled structures. Finally, a special section is dedicated to colloidal capsules for biological applications, as a diverse range of reports from this field aim at pharmaceutical agent encapsulation, targeted drug-delivery, and theranostics.
Hollow micro-/nano-particles from biopolymers are very promising for various applications due to their unique physical and chemical properties. This chapter is devoted to the progress made in recent years in the fabrication and applications of hollow micro-/nano-particles from biopolymers. This chapter will first highlight the various fabrication methods, including template method, emulsion method and self-assembly method. Fundamental aspects of these formation processes and their effects on the particle properties are also discussed in this chapter. Then various applications in drug delivery, tissue engineering and wastewater treatment will be introduced.
After 20 years, the layer-by-layer (LbL) assembly of nanoscale films has become a widely accepted method in academic and industrial research approaching an impact similar to that of a name reaction in organic chemistry. The field has grown so large that it has become impossible to compile a complete review on this topic. We, therefore, prefer to highlight some of the essential facts in a comprehensive way. This development was because the LbL method is robust and offers an unprecedented choice of components (small molecules, macromolecules, proteins, DNAs, fibrils, clay minerals, latex particles, nanoparticles, living cells, etc.) in combination with an unprecedented choice of surfaces (any size, any shape, different materials, including flat surfaces, foils, fibers, colloids, and nanoparticles) for the fabrication of thin films even with real applications on the market and new prospects on the horizon ('soft matter devices' and 'living multilayers').
IntroductionF0F1-ATPase – A Rotary Molecular MotorReconstitution of F0F1-ATPase in Cellular Mimic StructuresConclusions and PerspectivesReferences
IntroductionLayer-by-layer Assembly of Polyelectrolyte Multilayer MicrocapsulesBiointerfacing Polyelectrolyte Microcapsules – A Multifunctional Cargo SystemApplication of Biomimetic MicrocapsulesConclusions and PerspectivesReferences
Safe and effective artificial oxygen carriers are the subject of great interest due to the problems of traditional blood transfusion and enormous demand in clinical use. In view of its unique oxygen-transport ability and normal metabolic pathways, hemoglobin is regarded as an ideal oxygen-carrying unit. With advances in nano-biotechnology, hemoglobin assemblies as artificial oxygen carriers achieve great development. Here, recent progress on hemoglobin-based oxygen carriers is highlighted in view of two aspects: acellular hemoglobin-based oxygen carriers and cellular hemoglobin-based oxygen carriers. These novel oxygen carriers exhibit advantages over traditional carriers and will greatly promote research on reliable and feasible oxygen carriers.
Layer-by-layer (LBL) assembly of polymers and polymers/small molecules on colloidal particles forms core-shell particles, which produce hollow microcapsules with a layered structure after core removal. This article reviews the recent progress in driving forces for fabricating the LBL microcapsules, intelligent stimuli-responsivity and loading and release properties. The manipulation of the electrostatic and hydrogen bonded microcapsules by chemical crosslinking in terms of their structures and properties is first presented. Then the microcapsules based on new driving forces, i.e. covalent interaction, base pair and host-guest interaction, are introduced. The microcapsules thus obtained are responsive to pH, temperature, charge, light, electricity, magnetic field and chemical compounds. The typical loading and release properties and techniques established so far, such as direct encapsulation by the multilayers, pre-adsorption or pre-incorporation into the templates and charge controlled deposition, are discussed subsequently. Finally, aiming at the target delivery of the microcapsules and functional capsule devices, the methods for arraying the microcapsules on the substrates based on the electrostatic interaction and bioconjugation are described.
Due to the extraordinarily high theoretical capacity of sulfur (1675 mAh g−1), the lithium–sulfur (Li–S) battery has been considered a promising candidate for future high-energy battery applications. Li–S batteries, however, have suffered from limited cycle lives, mainly due to the formation of soluble polysulfides, which prevent the practical application of this attractive technology. The encapsulation of sulfur with various conductive materials has addressed this issue to some extent. Nevertheless, most approaches still present partial encapsulation of sulfur and moreover require a large quantity of conductive material (typically, >30 wt%), making the use of sulfur less desirable from the viewpoint of capacity. Here, we address these chronic issues of Li–S cells by developing a graphene oxide-sulfur composite with a thin crosslinked polyaniline (PANI) layer. Graphene oxide nanosheets with large surface area, high conductivity and a uniform conductive PANI layer, which are synthesized by a layer-by-layer method, have a synergetic interaction with a large portion of the sulfur in the active material. Furthermore, a simple crosslinking process efficiently prevents polysulfide dissolution, resulting in unprecedented electrochemical performance, even with a high sulfur content (∼75%): a high capacity retention of ∼80% is observed, in addition to 97.53% of the average Coulombic efficiency being retained after 500 cycles. The performance we demonstrate represents an advance in the field of lithium–sulfur batteries for applications such as power tools.
Biologically inspired materials and structures with tailored biological, physical, and chemical properties provide an indispensable platform to actively modulate and protect cell function in hostile and synthetic environments (e.g., devices or matrices). Herein, recent innovations are discussed in cell surface engineering methods based on bulk hydrogels, microgels, and ultrathin capsules derived from inorganic, polymeric, biomolecular, or nanoparticle materials applicable to various protective and interaction mediating applications. These biomimetic cell coatings can dramatically increase cell viability and stability in a hostile environment and expand their applicability for demanding biomedical, biotechnology, and bioelectronics applications. Some of the most recent studies of traditional inorganic and organic gels, polymeric and biomolecular microgels, and ultrathin conformal soft shells from polymers and proteins are also discussed. Proper selection of chemical composition and assembly conditions has potential to dramatically enhance viability of encapsulated cells by increasing their mechanical stability, masking the cell surface from immunological agents, increasing mechanical stability, and providing chemical resistance to aggressive environments. Some recent examples of such robust and viable protected cells for biotechnology and bioelectronics are presented.
The effects of surface modification on montmorillonite (MMT) were illustrated in order to produce the composite material with premium properties. MMT was treated with two coupling agents: glutaraldehyde (GA) and γ-methacryloxy-propyl-trimethoxy silane (KH570). The effects of different coupling agents on MMT and protein interaction were investigated by XRD, FT-IR, TGA, UV-Vis, etc. The results of structure characterization indicated that KH570 modification could change the surface crystal structure of MMT. However, GA reacted with amino groups of Bovine serum albumin (BSA) and the ordered layer structures of MMT were not completely destroyed. Coupling agents could greatly increase the amounts of BSA intercalated and the effect of KH570 is better than that of GA. And, the optimum concentrations of KH570 and GA were 2% and 6%, respectively. The rate of weight loss increased by about 12% after MMT was pretreated with coupling agents. The possible reason is that coupling agent treatment makes the structure of MMT more accessible to protein absorption and helps to stabilize the protein structure. Moreover, the presence of coupling agents can reduce the direct chemical interaction between BSA and MMT, which results in increasing protein desorption.
Researchers specifically provide information about covalent molecular assembly with the layer-by-layer (LbL) method through Schiff base interactions, including properties and advantages of Schiff base interactions, the micro- and nanostructures fabricated through Schiff base interactions, and the biomedical applications of the products fabricated through Schiff base interactions. Schiff base interactions are preferred as in situ Schiff base formation avoids the extra post-treatment processes to improve the stability of the multilayer and Schiff base reactions can be conducted both in aqueous and in organic solutions. This allows for incorporating materials that only dissolve or only can be used in nonaqueous solutions.
Polyelectrolyte microcapsules loaded with fluorescent dyes have been proposed as biosensors to monitor local pH and ionic strength for diagnostic purposes. In the case of charged microcapsules, however, the local electric field can cause deviations of ion densities inside the cavities, potentially resulting in misdiagnosis of some diseases. Using nonlinear Poisson-Boltzmann theory, we systematically investigate these deviations induced by charged microcapsules. Our results show that the microcapsule charge density, as well as the capsule and salt concentrations, contribute to deviations of local ion concentrations and pH. Our findings are relevant for applications of polyelectrolyte microcapsules with encapsulated ion-sensitive dyes as biosensors.
This article presents an overview of the different types of intermolecular interactions behind the fabrication of multilayer assemblies using the layer-by-layer (LbL) assembly approach. It comments on the potential impact of each type of intermolecular interaction and materials assembled through them on the development of advanced functional systems or devices for several emerging applications. The discussion begins with a brief overview of the most commonly used bottom-up methods to modify surfaces and fabricate functional multilayer thin films, with a special focus on their main advantages and disadvantages.
Poly(carboxylic acid) hydrogel films and hollow capsules undergo reversible size changes in response to variations in pH and/or
ionic strength. The films and capsules were obtained from hydrogenbonded poly-N-vinylpyrrolidone/poly(carboxylic acid) layer-by-layer
films by chemical crosslinking of the polyacid, followed by pH-induced removal of poly-N-vinylpyrrolidone. Surface-attached hydrogel films present attractive matrices for reversible pH-stimulated loading and/or
controlled release of large amounts of synthetic or natural macromolecules including proteins. By varying acidity of poly(carboxylic
acids), the hydrogel swelling and the corresponding values of pH for encapsulation/release of functional molecules could be
tuned in a wide range from pH 5 to 10. In addition, the capsules are capable of entrapping macromolecules by “locking” the
capsule wall with an electrostatically associating polycation, followed by the release of the encapsulated macromolecules
at high salt concentrations.
Liposomes and polymerosomes generally represent two most widely used carriers for encapsulating compounds, in particular drugs for delivery. While these are well established carriers, recent applications in biomedicine and food industry have necessitated the use of proteins as robust carriers that are stable under extreme acidic and basic conditions, have practically no toxicity and are able to withstand high shear force. This review highlights the different methods for using proteins as encapsulating materials and lists some biomedical applications of the microcapsules. The advantages and limitations in the capsules from the different preparation routes are enumerated.
Polymer multilayered hollow microspheres prepared by layer-by-layer (LbL) self-assembly attract more and more interest due to their unique application, especially as drug delivery system (DDS). Unfortunately, the multilayered hollow microspheres assembled via weak linkages could fuse and/or aggregate in high ionic strength media or strong acidic or basic media. This severely restricts the practical applications of the multilayered hollow microspheres as DDS in human physiological medium. In the present work, the progress in stabilization of the multilayered hollow microspheres is reviewed, with emphasis on the assembling process and their crosslinking mechanism.
In the past decade, mesoporous silica nanoparticles (MSNs) as nanocarriers have showed much potential in advanced nanomaterials due to their large surface area and pore volume. Especially, more and more MSNs based nanodevices have been designed as efficient drug delivery systems (DDSs) or biosensors. In this paper, lipid, protein and poly(NIPAM) coated MSNs are reviewed from the preparation, properties and their potential application. We also introduce the preparative methods including physical adsorption, covalent binding and self-assembly on the MSNs' surfaces. Furthermore, the interaction between the aimed cells and these molecular modified MSNs is discussed. We also demonstrate their typical applications, such as photodynamic therapy, bioimaging, controlled release and selective recognition in biomedical field.
This review covers the experimental data on the preparation and characterization of protein microparticles with controlled stability that are formed by layer-by-layer adsorption of oppositely charged macromolecules. Variants of using proteins as adsorbed polyelectrolyes, methods of incorporating proteins into matrixes (aggregates and microspheres) for further deposition of biopolyelectrolytes, and immobilization of proteins in preformed multilayered polyelectrolyte particles due to a change in the permeability of their shells are considered. Special attention is given to biocompatible and biodegradable microparticles characterized by depot functions, that is, the ability to reliably protect biologically active compounds from aggregative media of the body and to quantitatively release protein preparations (hormones, enzymes, and peptides) into solution when a certain acidity of solution is attained. This feature is especially important for designing peroral means of protein delivery.
A comparative study of polyelectrolyte microcapsules templated on melamine formaldehyde (MF) and manganese carbonate (MnCO 3 ) particles was performed using confocal Raman microscopy, scanning electron microscopy and by force measurements with an atomic force microscope. There is no significant difference between the properties of the shells templated on the MF and completely decomposable carbonate particles. In the case of capsules filled with polystyrene sulfonate (PSS), the MF oligomers formed a network complex with the polymer which resulted in a gel‐like structure in the interior. The existence of such a structure was proved by characteristic MF and PSS bands in Raman spectra, the bulky morphology of the dried capsules and much stiffer resistance to applied force as compared with PSS‐filled capsules templated on carbonate particles.
SEM images of PSS‐loaded PAH/PSS capsules assembled on the on the MF template core.
magnified image SEM images of PSS‐loaded PAH/PSS capsules assembled on the on the MF template core.
We report the preparation, characterization, and mechanical properties of DNA/poly(allylamine hydrochloride) (PAH) multilayer microcapsules. The DNA/PAH multilayers were first constructed on a planar support to examine their layer-by-layer buildup. Surface plasmon resonance spectroscopy (SPR) showed a nonlinear growth of the assembly upon each bilayer deposited independently on a concentration of salt. A weak increase in the film thickness with the DNA concentration was, however, detected. A post-treatment of the multilayers in the salt solutions has shown a thinning of the film. The optimal conditions of the planar film growth were used to deposit the same multilayers on the surface of colloidal templates and to study their roughness and morphology with the atomic force microscope (AFM) imaging. When an outer layer is formed by DNA, we observe large domains of oriented parallel DNA loops, while an outer layer formed by PAH shows highly porous morphology. The dissolution of colloidal templates led to a formation of highly porous DNA/PAH microcapsules. We probe their mechanical properties by measuring force-deformation curves with the AFM-related setup. The experiment suggests that the DNA/PAH capsules are softer than capsules made from the flexible polyelectrolytes studied before. The softening is due to both higher permeability and smaller Young's modulus of the shell material. The Young's modulus of the DNA/PAH shells increases after post-treatment in salt solutions of relatively low concentration.
Composite capsules containing low molecular weight species together with charged macromolecules were prepared both in aqueous and organic solution. Dyes were used as building blocks to quantify the adsorption.
Multilayer films of organic compounds on solid surfaces have been studied for more than 60 years because they allow fabrication
of multicomposite molecular assemblies of tailored architecture. However, both the Langmuir-Blodgett technique and chemisorption
from solution can be used only with certain classes of molecules. An alternative approach—fabrication of multilayers by consecutive
adsorption of polyanions and polycations—is far more general and has been extended to other materials such as proteins or
colloids. Because polymers are typically flexible molecules, the resulting superlattice architectures are somewhat fuzzy structures,
but the absence of crystallinity in these films is expected to be beneficial for many potential applications.
Stable weak polyelectrolyte microcapsules were prepared by assembly of branched poly(ethylenimine) (PEI) and sodium poly(acrylic acid) (PAA) followed by glutaraldehyde (GA) cross-linking. By assembly of the building blocks onto polystyrene (PS) latex particles, the variation of the zeta-potentials of the multilayers before and after cross-linking was measured as a function of pH. Charge reversal was observed for all multilayers regardless of their outmost layer composition and cross-linking during a change of pH. The phenomenon is explained by the penetration of the underlying layer. The cross-linked capsules could maintain their macroscopic topology at extreme low or high pH, while reorganizing their microstructure to enable selective permeation or rejection of macromolecules at lower (< pH 4) and higher pH (> pH 6), respectively. Using this property, dextran with a molecular weight of 2000 kDa was successfully encapsulated. Thus, it is possible to produce capsules that are at the same time pH responsive as well as stable over a large pH range.
Polyanion/polycation multilayers floating at the air/water interface were prepared by consecutive adsorption of polyelectrolyte layers onto a Langmuir monolayer from aqueous polyelectrolyte subphase solutions. With the positively charged Langmuir monolayer headgroups of the lipid dimethyldioctadecylammonium bromide, the layer sequence starts with the negatively charged polyelectrolyte polystyrene sulfonate. With the negatively charged monolayer dimyristoylphosphatidic acid, it starts with the positively charged polyallylamine. Equally charged monolayer headgroups and polyelectrolytes do not bind to each other. Consecutive subphase exchange cycles of polyelectrolyte solutions with alternating charges and pure solvent in between lead to the formation of floating multilayers consisting of an alternating polyelectrolyte sequence. Ellipsometric measurements show that the thickness (adsorbed amount per unit area) of the multilayer film at the air/water interface grows in proportion to the number of adsorbed polyelectrolyte layers. The thickness of individual layers increases with increasing polyelectrolyte and/or ion subphase concentration, respectively. The floating multilayers can be deposited as a sequence of layers of monomeric lipid and polyelectrolytes (hetero-superlattices) onto solid substrates via Langmuir−Blodgett transfer. UV-absorbance studies corroborate the quantitative interpretation of the ellipsometric data in terms of the polymer concentration in the layers, the individual layer thicknesses, and the adsorbed amounts per unit area.
The stability of hollow microcapsules against environmental alterations such as pH, osmotic pressure, and temperature is a critical issue for practical applications. It is demonstrated here that multilayer capsules assembled from poly(allylamine hydrochloride) (PAH) and sodium poly(styrene sulfonate) (PSS) can be considerably stabilized by cross-linking of only the PAH component with glutaraldehyde (GA). Formation of a Schiff base between the aldehyde and the amine groups was evidenced by UV−vis spectroscopy. After cross-linking by 2% GA for 2 h, an apparently thicker capsule wall was obtained with higher folds, and no alteration of the macroscopic topology of the capsules was observed after incubation in 0.1 M NaOH for 24 h. The cross-linking significantly improved the mechanical strength of the capsules to resist osmotic pressure induced invagination. Consequently, both the critical pressure and the elasticity modulus (680 MPa) of the capsule wall were doubled compared with that of the control. The cross-linking also greatly lowered the permeability of the capsule wall, as evidenced by confocal laser scanning microscopy and fluorescence recovery after photobleaching. Quantitative analysis revealed that the permeation coefficient for dextran (Mw 250 kD) was reduced by a factor of 3 after cross-linking.
Optimization of the technological parameters affecting the mechanical properties and permeability of capsules is essential to produce capsules with improved properties for cell immobilization. In the present paper, the effect of different parameters on the technological properties of alginate/Ca2+/oligochitosan capsules has been investigated. The correct adjustment of the alginate concentration in the polymer matrix and the oligochitosan molar mass, concentration and coating time, have been found to be key parameters in obtaining porous and mechanically stable alginate/Ca2+/oligochitosan capsules. Results showed that an increase in the coating time and concentration of the alginate generated more stable capsules with a reduced membrane cut-off. Furthermore, we have established some correlations between capsule properties and the effectiveness of chitosan binding within the capsule's membrane. Data addressed herein could be a valid tool to fabricate optimized alginate/Ca2+/oligochitosan capsules with a potential for use in cell immobilization technology. Copyright © 2006 Society of Chemical Industry
Exact control of the film thickness of polyelectrolyte shells (a transmission electron microscopy image is shown) is achieved by colloid-templated consecutive adsorption of polyanions and polycations followed by decomposition of the templating core. Possible areas of application for these shells range from the pharmaceutical, food, cosmetic, and paint industries to catalysis and microcrystallization.
The influence of thermal treatment on the permeability of polyelectrolyte multilayer capsules is studied via confocal fluorescence microscopy of individual microcapsules. For the specific most frequently used example, capsules made of poly(styrenesulfonic acid) and poly(allylamine hydrochloride), the penetration of fluorescein is shown to be reduced by 3 orders of magnitude on heating at 80 degreesC. The data show that holes formed during preparation may be annealed in a predictable way.
Three-dimensional confocal laser scanning microscopy (CLSM) was used as an essential investigation method to obtain information about the formation and morphological characteristics of nanocapsules. Nanocapsules are built by layer-by-layer deposition of alternatively charged polyelectrolytes on templates forming nanostructured hollow shells. CLSM is unique in allowing for monitoring of the core dissolution process in real time and for studying nanocapsule functioning in hydrated conditions within a three-dimensional and temporal framework. Since we are also interested in the identification of other possible templates, we briefly report on the use of yeast cells as biocolloidal cores monitored by means of two-photon microscopy. Here we focus our attention on the use of CdCO(3) crystals as template candidates for the preparation of stable capsules. Both cubic and spherical CdCO(3) cores have been produced. Cubic cores exhibit higher monodispersity and smaller size compared to spherical ones. Capsules templated on these cores have a higher surface-to-volume ratio that is valuable for applications related to drug delivery, functional properties of the shells and adsorption of proteins, and other biologically relevant molecules. Microsc. Res. Tech. 59:536-541, 2002.
Phospholipid vesicles on polyelectrolyte multilayer shells can be stabilized against ethanol by coating a single cationic polyelectrolyte. Confocal laser scanning microscopy (CLSM) proved that the lipids were stabilized by cationic polyelectrolytes and the permeability to small hydrophilic dyes was decreased. Measurements of fluorescence recovery after photo-bleaching (FRAP) with individual capsules enable quantification of release profiles.
The formation of microcapsules by layer-by-layer (LBL) self assembly and polypeptides was described. Polypeptide layers were crosslinked by oxidation, forming disulfide bond locked capsules. The concentration of DMSO was incremented and counting repeated until all capsules have disintegrated. The reversibility of disulfide bond formation was found to be advantageous for microparticle diassembly and drug delivery, as the intracellular environment is reducing.
A layer-by-layer deposition strategy for preparing protein nanotubes within the pores of a nanopore alumina template membrane is described. This method entails alternately exposing the template membrane to a solution of the desired protein and then to a solution of glutaraldehyde, which acts as cross-linking agent to hold the protein layers together. The number of layers of protein that make up the nanotube walls can be controlled at will by varying the number of alternate protein/glutaraldehyde cycles. After the desired number of layers have been deposited on the pore walls, the alumina template can be dissolved to liberate the protein nanotubes. We show here that glucose oxidase nanotubes prepared in this way catalyze glucose oxidation and that hemoglobin nanotubes retain their heme electroactivity. Furthermore, for the glucose oxidase nanotubes, the enzymatic activity increases with the nanotube wall thickness.
The permeability of lipid and protein microcapsules fabricated by alternating adsorption of human serum albumin (HSA) and L-alpha-dimyristoylphosphatidic acid (DMPA) on a template and subsequent removal of the core is studied as a function of pH value and supplementary layers. The capsules were permeable for macromolecules (FITC-labeled dextran, M(w) 40 kDa) at pH < 4.8 and impermeable at pH > 7.4. The assembly of supplementary DMPA bilayers rendered the capsules impermeable for small hydrophilic molecules such as 6-carboxyfluorescein (6-CF). Hence DMPA/HSA capsules can be resealed after fabrication by supplementary layers. This provides the opportunity of applying such biomimetic membrane capsules as drug carriers or model systems to study biological processes at membranes.
Negatively charged heme protein hemoglobin (Hb) or myoglobin (Mb) at pH 9.0 and positively charged poly(diallyldimethylammonium) (PDDA) were alternately adsorbed on the surface of CaCO(3) nanoparticles, forming core-shell CaCO(3)-[PDDA/(protein/PDDA)(m)] ([protein-m]) nanoclusters. Oppositely charged [protein-m] and poly(styrenesulfonate) (PSS) were then assembled layer by layer on various solid substrates, forming {[protein-m]/PSS}(n) films. In the meantime, ordinary layer-by-layer films of heme proteins with CaCO(3) nanoparticles ({protein/CaCO(3)}(n)) were also grown on solid surfaces. Transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) spectroscopy, quartz crystal microbalance (QCM), and cyclic voltammetry (CV) were used to characterize the nanoclusters and monitor the growth of the two types of films. Both kinds of protein films assembled on pyrolytic graphite (PG) electrodes exhibited well-defined, nearly reversible CV reduction-oxidation peaks, characteristic of heme Fe(III)/Fe(II) redox couples, and were used to catalyze the electrochemical reduction of hydrogen peroxide. The {[protein-m]/PSS}(n) films demonstrate distinct advantages over the {protein/CaCO(3)}(n) films due to their larger fraction of electroactive proteins, higher catalytic efficiency, and better thermostability. The penetration experiments of the electroactive probe into these films indicate that the {[protein-m]/PSS}(n) nanocluster films possess more pores or channels than the simple {protein/CaCO(3)}(n) films, which may be beneficial to counterion transport in the charge-hopping mechanism and helpful for the diffusion of catalysis substrates into the films. In addition, the electrochemical and biocatalytic activity of protein nanocluster films can be tailored by controlling the number of bilayers assembled on the nanoparticle cores (m) as well as the film thickness or the number of nanocluster layers on the electrodes (n).
(A) Typical fluorescence bleaching and recovery curve of (GA/Hb) 5 capsules. (B) CLSM images for the experimental process of photo-bleaching and recovery
- Fig
Fig. 6. (A) Typical fluorescence bleaching and recovery curve of (GA/Hb) 5 capsules. (B) CLSM images for the experimental process of photo-bleaching
and recovery.