骨髓基质干细胞在IKVAV多肽纳米纤维凝胶表面增殖、黏附及向神经细胞诱导分化的研究

目的研究骨髓基质干细胞（BMSCs）与IKVAV多肽纳米纤维凝胶复合的细胞假体应用于脊髓损伤治疗的可行性。方法合成IKVAV多肽两亲性分子，进行自组装，用透射电镜检测。将IKVAV多肽纳米纤维凝胶与BMSCs复合培养，采用倒置显微镜下观察、Calcein—AM／PI染色、CCK-8法、免疫荧光双标法，检测IKVAV多肽对BMSCs增殖、黏附及向神经细胞方向诱导分化的影响。结果IKVAV多肽可成功自组装成纳米纤维凝胶，其与BMSCs复合培养细胞生长良好，活细胞数达90％以上，IKVAV多肽对BMSCs增殖没有影响，可促进BMSCs的黏附，并在诱导BMSCs向神经细胞分化过程中提高神经元分化比例。结论BMSCs在IKVAV多肽纳米纤维凝胶材料表面可良好的增殖及黏附，并可提高其向神经细胞分化过程中神经元的分化比例。     

Controlled Release of the Indomethacin Microencapsulation Based on Layer-by-layer Assembly by Polyelectrolyte Multilayers

Indomethacin has been encapsulated with polyelectrolyte multilayers for controlled release. Gelatin and alginate were alternatively deposited on indomethacin microcrystals. The released amount of indomethacin from coated microcrystals in pH6. 8 phosphate buffer solution （PBS） was measured with a UV spectrophometer. The polyelectrolyte multilayer capsule thickness was proved to control the release rate. The effects of osmotic pressure existed during the release process of indomethacin from microcapsules coated by （gelatin/alginate） 4.     

Self-assembly of short peptides to form hydrogels: Design of building blocks,physical properties and technological applications

Hydrogels are unique supramolecular solid-like assemblies composed mainly of water molecules that are held by molecular networks. Physical hydrogels that are formed by a set of non-covalent interactions to establish a well-ordered scaffold devoid of any chemical cross-linking are especially intriguing for various biotechnological and medical applications. Peptides are particularly interesting building blocks of physical gels because of the role of polypeptides as structural elements in biological systems, the extensive ability for their chemical and biological decoration and functionalization, and the facile synthesis of natural and modified peptides. This review describes the assembly and properties of physical hydrogels that have been formed by the self-association of very simple peptide building blocks. Natural short peptides, as short as dipeptides, can form ordered gel assemblies. Moreover, in the case of N-terminal protection, even a protected amino acid can serve as an efficient hydrogelator. Further elucidation of hydrogelators’ assembly, as well as the characterization of their physical properties, can guide the rational design of building blocks for a desired application. The possible mechanism of self-assembly is discussed in line with the chemical nature of the short peptides. Different methods have been used to induce hydrogel assembly, which may significantly affect the mechanical characteristics of the resulting gels. Here, special emphasis is given to methods that allow either spatial control of hydrogel formation or modulation of physical properties of the gel. Finally, the parameters that influence hydrogelation are described, and insights for their design are provided.     

Introducing a combinatorial DNA-toolbox platform constituting defined protein-based biohybrid-materials

The access to defined protein-based material systems is a major challenge in bionanotechnology and regenerative medicine. Exact control over sequence composition and modification is an important requirement for the intentional design of structure and function. Herein structural- and matrix proteins provide a great potential, but their large repetitive sequences pose a major challenge in their assembly. Here we introduce an integrative “one-vector-toolbox-platform” (OVTP) approach which is fast, efficient and reliable. The OVTP allows for the assembly, multimerization, intentional arrangement and direct translation of defined molecular DNA-tecton libraries, in combination with the selective functionalization of the yielded protein-tecton libraries. The diversity of the generated tectons ranges from elastine-, resilin, silk- to epitope sequence elements. OVTP comprises the expandability of modular biohybrid-materials via the assembly of defined multi-block domain genes and genetically encoded unnatural amino acids (UAA) for site-selective chemical modification. Thus, allowing for the modular combination of the protein-tecton library components and their functional expansion with chemical libraries via UAA functional groups with bioorthogonal reactivity. OVTP enables access to multitudes of defined protein-based biohybrid-materials for self-assembled superstructures such as nanoreactors and nanobiomaterials, e.g. for approaches in biotechnology and individualized regenerative medicine.     

Facile route to versatile nanoplatforms for drug delivery by one-pot self-assembly

There is still unmet demand for developing powerful approaches to produce polymeric nanoplatforms with versatile functions and broad applications, which are essential for the successful bench-to-bedside translation of polymeric nanotherapeutics developed in the laboratory. We have discovered a facile, convenient, cost-effective and easily scalable one-pot strategy to assemble various lipophilic therapeutics bearing carboxyl groups into nanomedicines, through which highly effective cargo loading and nanoparticle formation can be achieved simultaneously. Besides dramatically improving water solubility, the assembled nanopharmaceuticals showed significantly higher bioavailability and much better therapeutic activity. These one-pot assemblies may also serve as nanocontainers to effectively accommodate other highly hydrophobic drugs such as paclitaxel (PTX). PTX nanomedicines thus formulated display strikingly enhanced in vitro antitumor activity and can reverse the multidrug resistance of tumor cells to PTX therapy. The special surface chemistry offers these assembled entities the additional capability of efficiently packaging and efficaciously transfecting plasmid DNA, with a transfection efficiency markedly higher than that of commonly used positive controls. Consequently, this one-pot assembly approach provides a facile route to multifunctional nanoplatforms for simultaneous delivery of multiple therapeutics with improved therapeutic significance.     

The promotion of functional urinary bladder regeneration using anti-inflammatory nanofibers

Current attempts at tissue regeneration utilizing synthetic and decellularized biologic-based materials have typically been met in part by innate immune responses in the form of a robust inflammatory reaction at the site of implantation or grafting. This can ultimately lead to tissue fibrosis with direct negative impact on tissue growth, development, and function. In order to temper the innate inflammatory response, anti-inflammatory signals were incorporated through display on self-assembling peptide nanofibers to promote tissue healing and subsequent graft compliance throughout the regenerative process. Utilizing an established urinary bladder augmentation model, the highly pro-inflammatory biologic scaffold (decellularized small intestinal submucosa) was treated with anti-inflammatory peptide amphiphiles (AIF-PAs) or control peptide amphiphiles and used for augmentation. Significant regenerative advantages of the AIF-PAs were observed including potent angiogenic responses, limited tissue collagen accumulation, and the modulation of macrophage and neutrophil responses in regenerated bladder tissue. Upon further characterization, a reduction in the levels of M2 macrophages was observed, but not in M1 macrophages in control groups, while treatment groups exhibited decreased levels of M1 macrophages and stabilized levels of M2 macrophages. Pro-inflammatory cytokine production was decreased while anti-inflammatory cytokines were up-regulated in treatment groups. This resulted in far fewer incidences of tissue granuloma and bladder stone formation. Finally, functional urinary bladder testing revealed greater bladder compliance and similar capacities in groups treated with AIF-PAs. Data demonstrate that AIF-PAs can alleviate galvanic innate immune responses and provide a highly conducive regenerative milieu that may be applicable in a variety of clinical settings.     

Maximizing gene delivery efficiencies of cationic helical polypeptides via balanced membrane penetration and cellular targeting

The application of non-viral gene delivery vectors is often accompanied with the poor correlation between transfection efficiency and the safety profiles of vectors. Vectors with high transfection efficiencies often suffer from high toxicities, making it unlikely to improve their efficiencies by increasing the DNA dosage. In the current study, we developed a ternary complex system which consisted of a highly membrane-active cationic helical polypeptide (PVBLG-8), a low-toxic, membrane-inactive cationic helical polypeptide (PVBLG-7) capable of mediating mannose receptor targeting, and DNA. The PVBLG-7 moiety notably enhanced the cellular uptake and transfection efficiency of PVBLG-8 in a variety of mannose receptor-expressing cell types (HeLa, COS-7, and Raw 264.7), while it did not compromise the membrane permeability of PVBLG-8 or bring additional cytotoxicities. Because of the simplicity and adjustability of the self-assembly approach, optimal formulations of the ternary complexes with a proper balance between membrane activity and targeting capability were easily identified in each specific cell type. The optimal ternary complexes displayed desired cell tolerability and markedly outperformed the PVBLG-8/DNA binary complexes as well as commercial reagent Lipofectamine™ 2000 in terms of transfection efficiency. This study therefore provides an effective and facile strategy to overcome the efficiency-toxicity poor correlation of non-viral vectors, which contributes insights into the design strategy of effective and safe non-viral gene delivery vectors.     

Matrix metalloproteinase 2-sensitive multifunctional polymeric micelles for tumor-specific co-delivery of siRNA and hydrophobic drugs

Co-delivery of hydrophilic siRNA and hydrophobic drugs is one of the major challenges for nanomaterial-based medicine. Here, we present a simple but multifunctional micellar platform constructed by a matrix metalloproteinase 2 (MMP2)-sensitive copolymer (PEG-pp-PEI-PE) via self-assembly for tumor-targeted siRNA and drug co-delivery. The micellar nanocarrier possesses several key features for siRNA and drug delivery, including (i) excellent stability; (ii) efficient siRNA condensation by PEI; (iii) hydrophobic drug solubilization in the lipid “core”; (iv) passive tumor targeting via the enhanced permeability and retention (EPR) effect; (v) tumor targeting triggered by the up-regulated tumoral MMP2; and (vi) enhanced cell internalization after MMP2-activated exposure of the previously hidden PEI. These cooperative functions ensure the improved tumor targetability, enhanced tumor cell internalization, and synergistic antitumor activity of co-loaded siRNA and drug.     

Self-assembly LiFePO4/polyaniline composite cathode materials with inorganic acids as dopants for lithium-ion batteries

Carbon-coated LiFePO₄ (C-LFP) composites incorporated with electrochemically-active conducting polymer polyaniline (PANI) are fabricated via a self-assembly process. Inorganic acids HCl, H₂SO₄ and H₃PO₄ are used as dopants for PANI. The C-LFP/PANI composites are characterized by thermogravimetric analysis, scanning electron microscopy, electrochemical impedance spectroscopy, Raman spectra and four-probe resistivity measurements. Our results show that a remarkable improvement in capacity and rate capability can be achieved in the C-LFP/PANI composite cathodes doped with HCl and H₃PO₄. The C-LFP/PANI-HCl composite exhibits the best electrochemical performance, which gives a ca. 15% capacity enhancement at 0.2 C and 40% enhancement at 5 C compared to the parent C-LFP. The mechanism for the enhancement has been discussed.     

Self-assembly of and charge transfer at N-docosyl-N′-methyl viologen on electrode surfaces

Self-assembled molecular films were formed on the electrode surfaces of glassy carbon (GC), platinum (Pt), gold, silver and indium–tin oxide in aqueous electrolyte solutions of N-docosyl-N′-methyl viologen (C₂₂VC₁). The temperature dependence of voltammetric responses showed a higher stability with higher surface coverage and with a Pt than a GC surface. Charge transfer reactions of the solution redox species of Ru(NH₃)₆³⁺ and Fe(CN)₆^4? at the irreversibly self-assembled C₂₂VC₁ ∣ GC interface were found to take place by an interplay of direct penetration of solution species through the self-assembled molecular layer of C₂₂VC₁ and of cross reaction between solution and surface bound redox agents.