A catechol-chitosan-based adhesive and injectable hydrogel resistant to oxidation and compatible with cell therapy

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Tissue Engineering

Background:

• Injectable hydrogels require tissue adhesion for cell therapy retention and host-cell communication.
• Catechol grafting enhances polymer adhesion but can cause cytotoxicity due to oxidation in alkaline environments.
• Existing catechol-grafted chitosan (cat-CH) hydrogels face limitations in adhesion and cell encapsulation due to rapid oxidation.

Purpose of the Study:

• To improve the cytocompatibility and reduce oxidation of catechol-grafted chitosan hydrogels.
• To develop injectable hydrogels with enhanced adhesive properties for cell therapy applications.
• To investigate the potential of dihydroxybenzoic acid (DHBA) for stabilizing catechol-grafted chitosan.

Main Methods:

• Chitosan was grafted with dihydroxybenzoic acid (DHBA) to create dhba-CH, a more oxidation-resistant alternative to hydrocaffeic acid-grafted chitosan (hca-CH).
• Thermosensitive injectable hydrogels were fabricated by combining dhba-CH with sodium bicarbonate and phosphate buffer.
• Oxidation levels, mechanical properties, gelation time, and cell encapsulation efficiency (L929 fibroblasts) were evaluated.

Main Results:

• DHBA-grafted chitosan (dhba-CH) exhibited significantly slower and lesser oxidation compared to hca-CH.
• The fabricated dhba-CH hydrogels demonstrated enhanced mechanical properties, rapid gelation, and reduced oxidation.
• High adhesion to inorganic substrates was observed, and L929 fibroblast encapsulation maintained high viability (≥90% after 24 hours).

Conclusions:

• DHBA grafting effectively limits oxidation and improves the cytocompatibility of chitosan-based hydrogels.
• DHBA-CH hydrogels are promising for minimally invasive cell therapies requiring strong tissue adhesion.
• These hydrogels overcome previous limitations, enabling successful cell encapsulation and high cell viability.