Photo-cross-linked Hydrogels for Cartilage and Osteochondral Repair

Biomedical potentials of alginate via physical, chemical, and biological modifications

Alginate is a linear polysaccharide with a modifiable structure and abundant functional groups, offers immense potential for tailoring diverse alginate-based materials to meet the demands of biomedical applications. Given the advancements in modification techniques, it is significant to analyze and summarize the modification of alginate by physical, chemical and biological methods. These approaches provide plentiful information on the preparation, characterization and application of alginate-based materials. Physical modification generally involves blending and physical crosslinking, while chemical modification relies on chemical reactions, mainly including acylation, sulfation, phosphorylation, carbodiimide coupling, nucleophilic substitution, graft copolymerization, terminal modification, and degradation. Chemical modified alginate contains chemically crosslinked alginate, grafted alginate and oligo-alginate. Biological modification associated with various enzymes to realize the hydrolysis or grafting. These diverse modifications hold great promise in fully harnessing the potential of alginate for its burgeoning biomedical applications in the future. In summary, this review provides a comprehensive discussion and summary of different modification methods applied to improve the properties of alginate while expanding its biomedical potentials.

An Anti-Oxidative Bioink for Cartilage Tissue Engineering Applications

Since chondrocytes are highly vulnerable to oxidative stress, an anti-oxidative bioink combined with 3D bioprinting may facilitate its applications in cartilage tissue engineering. We developed an anti-oxidative bioink with methacrylate-modified rutin (RTMA) as an additional bioactive component and glycidyl methacrylate silk fibroin as a biomaterial component. Bioink containing 0% RTMA was used as the control sample. Compared with hydrogel samples produced with the control bioink, solidified anti-oxidative bioinks displayed a similar porous microstructure, which is suitable for cell adhesion and migration, and the transportation of nutrients and wastes. Among photo-cured samples prepared with anti-oxidative bioinks and the control bioink, the sample containing 1 mg/mL of RTMA (RTMA-1) showed good degradation, promising mechanical properties, and the best cytocompatibility, and it was selected for further investigation. Based on the results of 3D bioprinting tests, the RTMA-1 bioink exhibited good printability and high shape fidelity. The results demonstrated that RTMA-1 reduced intracellular oxidative stress in encapsulated chondrocytes under H2O2 stimulation, which results from upregulation of COLII and AGG and downregulation of MMP13 and MMP1. By using in vitro and in vivo tests, our data suggest that the RTMA-1 bioink significantly enhanced the regeneration and maturation of cartilage tissue compared to the control bioink, indicating that this anti-oxidative bioink can be used for 3D bioprinting and cartilage tissue engineering applications in the future.