Amine-reactive crosslinking enhances type 0 collagen hydrogel properties for regenerative medicine.

Introduction: Collagen is extensively utilised in regenerative medicine due to its highly desirable properties. However, collagen is typically derived from mammalian sources, which poses several limitations, including high cost, potential risk of immunogenicity and transmission of infectious diseases, and ethical and religious constraints. Jellyfish-sourced type 0 collagen represents a safer and more environmentally sustainable alternative collagen source. Methods: Thus, we investigated the potential of jellyfish collagen-based hydrogels, obtained from Rhizostoma pulmo (R. pulmo) jellyfish, to be utilised in regenerative medicine. A variety of R. pulmo collagen hydrogels (RpCol hydrogels) were formed by adding a range of chemical crosslinking agents and their physicochemical and biological properties were characterised to assess their suitability for regenerative medicine applications. Results and Discussion: The characteristic chemical composition of RpCol was confirmed by Fourier-transform infrared spectroscopy (FTIR), and the degradation kinetics, morphological, and rheological properties of RpCol hydrogels were shown to be adaptable through the addition of specific chemical crosslinking agents. The endotoxin levels of RpCol were below the Food and Drug Administration (FDA) limit for medical devices, thus allowing the potential use of RpCol in vivo. 8-arm polyethylene glycol succinimidyl carboxyl methyl ester (PEG-SCM)-crosslinked RpCol hydrogels preserved the viability and induced a significant increase in the metabolic activity of immortalised human mesenchymal stem/stromal cells (TERT-hMSCs), therefore demonstrating their potential to be utilised in a wide range of regenerative medicine applications.

Effective Endotoxin Removal from Chitosan That Preserves Chemical Structure and Improves Compatibility with Immune Cells.

Chitosan is one of the most researched biopolymers for healthcare applications, however, being a naturally derived polymer, it is susceptible to endotoxin contamination, which elicits pro-inflammatory responses, skewing chitosan's performance and leading to inaccurate conclusions. It is therefore critical that endotoxins are quantified and removed for in vivo use. Here, heat and mild NaOH treatment are investigated as facile endotoxin removal methods from chitosan. Both treatments effectively removed endotoxin to below the FDA limit for medical devices (<0.5 EU/mL). However, in co-culture with peripheral blood mononuclear cells (PBMCs), only NaOH-treated chitosan prevented TNF-α production. While endotoxin removal is the principal task, the preservation of chitosan's structure is vital for the synthesis and lysozyme degradation of chitosan-based hydrogels. The chemical properties of NaOH-treated chitosan (by FTIR-ATR) were significantly similar to its native composition, whereas the heat-treated chitosan evidenced macroscopic chemical and physical changes associated with the Maillard reaction, deeming this treatment unsuitable for further applications. Degradation studies conducted with lysozyme demonstrated that the degradation rates of native and NaOH-treated chitosan-genipin hydrogels were similar. In vitro co-culture studies showed that NaOH hydrogels did not negatively affect the cell viability of monocyte-derived dendritic cells (moDCs), nor induce phenotypical maturation or pro-inflammatory cytokine release.