From processing byproduct to functional biomaterial: Tunable oxidized Tremella fuciformis stem polysaccharide hydrogels for skin tissue repair

The stem of Tremella fuciformis , an abundant byproduct of edible mushroom processing, is typically discarded despite containing higher levels of crude polysaccharide than the fruiting body. To valorize this agricultural residue, a series of polysaccharide-based hydrogels was fabricated via Schiff base crosslinking between carboxymethyl chitosan (CMCS) and oxidized T. fuciformis stem polysaccharide (OTP) with tunable aldehyde contents. The oxidation degree of OTP critically influenced the crosslinking density, thereby modulating the gelation kinetics, microstructure, rheological properties, and swelling behavior. Specifically, increasing the polysaccharide oxidation degree from 17.30 ± 1.66% to 32.85 ± 1.47% and subsequently to 40.75 ± 1.96% progressively shortened the gelation time from 12 min to 3 min and decreased the pore size from 219.2 ± 12.50 μm to 93.16 ± 16.60 μm. Concurrently, the storage modulus increased from 49 Pa to 388 Pa, and the CMOT3 hydrogel achieved the highest equilibrium swelling rate of 99.6%. All hydrogel formulations exhibited excellent cytocompatibility. In a full-thickness skin defect model, the optimally crosslinked CMOT3 hydrogel significantly accelerated wound closure, which was associated with reduced pro-inflammatory cytokine levels, elevated VEGF expression, and improved collagen organization. These findings suggest that the T. fuciformis stem polysaccharide-based hydrogel effectively promotes skin tissue repair, highlighting its potential as a sustainable functional biomaterial derived from agricultural byproducts.