Fabrication and Cell Responsive Behavior of Macroporous PLLA/Gelatin Composite Scaffold with Hierarchical Micro-Nano Pore Structure

The role of Gel-Ppy-modified nerve conduit on the repair of sciatic nerve defect in rat model

The serious clinical challenge of peripheral nerve injury (PNI) is nerve regeneration. Nerve conduit represents a promising strategy to contribute to nerve regeneration by bridging injured nerve gaps. However, due to a unique microenvironment of nerve tissue, autologous nerves have not been substituted by nerve conduit. Nerve regeneration after nerve conduit implantation depends on many factors, such as conductivity and biocompatibility. Therefore, Gelatin (Gel) with biocompatibility and polypyrrole (Ppy) with conductivity is highly concerned. In this paper, Gel-Ppy modified nerve conduit was fabricated with great biocompatibility and conductivity to evaluate its properties of enhancing nerve regeneration in vivo and in vitro. The proliferation of Schwann cells on Gel-Ppy modified nerve conduit was remarkably increased. Consistent with in vitro results, the Gel-Ppy nerve conduit could contribute to the regeneration of Schwann cell in vivo. The axon diameters and myelin sheath thickness were also enhanced, resulting in the amelioration of muscle atrophy, nerve conduction, and motor function recovery. To explain this interesting phenomenon, western blot results indicated that the Gel-Ppy conduit facilitated nerve regeneration via upregulating the Rap1 pathway to induce neurite outgrowth. Therefore, the above results demonstrated that Gel-Ppy modified nerve conduit could provide an acceptable microenvironment for nerve regeneration and be popularized as a novel therapeutic strategy of PNI.

Adipose-derived mesenchymal stem cell-loaded β-chitin nanofiber hydrogel promote wound healing in rats

Because of stem cells are limited by the low efficiency of their cell homing and survival in vivo, cell delivery systems and scaffolds have attracted a great deal of attention for stem cells' successful clinical practice. β-chitin nanofibers (β-ChNF) were prepared from squid pens in this study. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy proved that β-ChNFs with the diameter of 5 to 10 nm were prepared. β-ChNF dispersion became gelled upon the addition of cell culture medium. Cell culture experiments showed that β-ChNFs exhibited negligible cytotoxicity towards ADSCs and L929 cells, and it was found that more exosomes were secreted by the globular ADSCs grown in the β-ChNF hydrogel. The vivo experiments of rats showed that the ADSCs-loaded β-ChNF hydrogel could directly cover the wound surface and significantly accelerate the wound healing and promote the generation of epithelization, granulation tissue and collagen. In addition, the ADSCs-loaded β-ChNF hydrogel clearly regulated the expressions of VEGFR, α-SMA, collagen I and collagen III. Finally, we showed that ADSCs-loaded β-ChNF hydrogel activated the TGFβ/smad signaling. The neutralization of TGFβ markedly reduced Smad phosphorylation and the expressions of TIMP1, VEGFR and α-SMA. Taken together, these findings suggest that ADSCs-loaded β-ChNF hydrogel promises for treating wounds that are challenge to heal via conventional methods. Graphical abstract.

Recent Advances in Three-Dimensional Stem Cell Culture Systems and Applications

Cell culture is one of the most core and fundamental techniques employed in the fields of biology and medicine. At present, although the two-dimensional cell culture method is commonly used in vitro, it is quite different from the cell growth microenvironment in vivo. In recent years, the limitations of two-dimensional culture and the advantages of three-dimensional culture have increasingly attracted more and more attentions. Compared to two-dimensional culture, three-dimensional culture system is better to realistically simulate the local microenvironment of cells, promote the exchange of information among cells and the extracellular matrix (ECM), and retain the original biological characteristics of stem cells. In this review, we first present three-dimensional cell culture methods from two aspects: a scaffold-free culture system and a scaffold-based culture system. The culture method and cell characterizations will be summarized. Then the application of three-dimensional cell culture system is further explored, such as in the fields of drug screening, organoids and assembloids. Finally, the directions for future research of three-dimensional cell culture are stated briefly.

Biological Characterization of Polymeric Matrix and Graphene Oxide Biocomposites Filaments for Biomedical Implant Applications: A Preliminary Report

Carbon nanostructures application, such as graphene (Gr) and graphene oxide (GO), provides suitable efforts for new material acquirement in biomedical areas. By aiming to combine the unique physicochemical properties of GO to Poly L-lactic acid (PLLA), PLLA-GO filaments were produced and characterized by X-ray diffraction (XRD). The in vivo biocompatibility of these nanocomposites was performed by subcutaneous and intramuscular implantation in adult Wistar rats. Evaluation of the implantation inflammatory response (21 days) and mesenchymal stem cells (MSCs) with PLLA-GO took place in culture for 7 days. Through XRD, new crystallographic planes were formed by mixing GO with PLLA (PLLA-GO). Using macroscopic analysis, GO implanted in the subcutaneous region showed particles' organization, forming a structure similar to a ribbon, without tissue invasion. Histologically, no tissue architecture changes were observed, and PLLA-GO cell adhesion was demonstrated by scanning electron microscopy (SEM). Finally, PLLA-GO nanocomposites showed promising results due to the in vivo biocompatibility test, which demonstrated effective integration and absence of inflammation after 21 days of implantation. These results indicate the future use of PLLA-GO nanocomposites as a new effort for tissue engineering (TE) application, although further analysis is required to evaluate their proliferative capacity and viability.

Characterizations and interfacial reinforcement mechanisms of multicomponent biopolymer based scaffold

It is difficult for a single component biopolymer to meet the requirements of scaffold at present. The development of multicomponent biopolymer based scaffold provides an effective method to solve the issue based on the advantages of each kind of the biomaterials. However, the compatibility between different components might be very poor due to the difficulties in forming strong interfacial bonding, and thereby significantly degrading the integrated mechanical properties of the scaffold. In recent years, interface phase introduction, surface modification and in situ growth have been the major strategies for enhancing interfacial bonding. This article presents a comprehensive overview on the research in the area of constructing multicomponent biopolymer based scaffold and reinforcing their interfacial properties, and more importantly, the interfacial bonding mechanisms are systematically summarized. Detailly, interface phase introduction can build a bridge between biopolymer and other components to form strong interface bonding with the two phases under the action of interface phase. Surface modification can graft organic molecules or polymers containing functional groups onto other components to crosslink with biopolymer. In situ growth can directly in situ synthesize other components with the action of nucleating agent serving as an adherent platform for the nucleation and growth of other components to biopolymer surface by chemical bonding. In addition, the mechanical properties (including strength and modulus) and biological properties (including bioactivity, cytocompatibility and biosensing in vitro, and tissue compatibility, bone regeneration capacity in vivo) of multicomponent biopolymer based scaffold after interfacial reinforcing are also reviewed and discussed. Finally, suggestions for further research are given with highlighting the need for specific investigations to assess the interface formation, structure, properties, and more in vivo studies of scaffold before applications.

Gelatin-polysaccharide composite scaffolds for 3D cell culture and tissue engineering: Towards natural therapeutics

Gelatin is a promising material as scaffold with therapeutic and regenerative characteristics due to its chemical similarities to the extracellular matrix (ECM) in the native tissues, biocompatibility, biodegradability, low antigenicity, cost-effectiveness, abundance, and accessible functional groups that allow facile chemical modifications with other biomaterials or biomolecules. Despite the advantages of gelatin, poor mechanical properties, sensitivity to enzymatic degradation, high viscosity, and reduced solubility in concentrated aqueous media have limited its applications and encouraged the development of gelatin-based composite hydrogels. The drawbacks of gelatin may be surmounted by synergistically combining it with a wide range of polysaccharides. The addition of polysaccharides to gelatin is advantageous in mimicking the ECM, which largely contains proteoglycans or glycoproteins. Moreover, gelatin-polysaccharide biomaterials benefit from mechanical resilience, high stability, low thermal expansion, improved hydrophilicity, biocompatibility, antimicrobial and anti-inflammatory properties, and wound healing potential. Here, we discuss how combining gelatin and polysaccharides provides a promising approach for developing superior therapeutic biomaterials. We review gelatin-polysaccharides scaffolds and their applications in cell culture and tissue engineering, providing an outlook for the future of this family of biomaterials as advanced natural therapeutics.

Porcine skin gelatin-silver nanocomposites: synthesis, characterisation, cell cytotoxicity, and antibacterial properties

Silver nanoparticles (AgNPs) were synthesised with hydrothermal autoclaving technique by using AgNO₃ salt (silver precursor) at different concentrations (0.01, 0.1, 0.55, 1.1, 5.5, and 11 mM) and porcine skin (1% (w/v) ) gelatin polymeric matrix (reducing and stabiliser agent). The reaction was performed in an autoclave at 103 kPa and 121°C and the hydrothermal autoclaving exposure time and AgNO₃ molar concentration were varied at a constant porcine skin gelatin concentration. The as-prepared AgNPs were characterised by UV-visible spectroscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. The antibacterial properties of AgNPs were tested against gram-positive and gram-negative bacteria. Furthermore, 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide and 2,2-diphenyl-1-picrylhydrazyl assays were used to test whether the synthesised AgNPs can be potentially applied in cancer therapy or used as an antioxidant. This approach is a promising simple route for synthesising AgNPs with a smaller average particle 10 nm diameter. Furthermore, AgNPs exhibited a good cytotoxicity activity, reducing the viability of the liver cancer cell line HepG2 with a moderate IC₅₀; they also showed a low-to-fair antioxidant activity. In addition, AgNPs had a remarkable preferential antibacterial activity against gram-positive bacteria than gram-negative bacteria. Therefore, these fabricated AgNPs can be used as an antibacterial agent in curative and preventive health care.

Powering tyrosol antioxidant capacity and osteogenic activity by biocatalytic polymerization

Oxidative polymerization of tyrosol afforded a mixture of oligomers (OligoTyr) which proved to be more active than tyrosol as antioxidant and as stimulator of alkaline phosphatase (ALP) activity when loaded into polylactic acid (PLA) scaffolds.