Engineering dual-crosslinked oxidized carrageenan–chitosan semi-IPN hydrogels with adjustable mechanical and biological performances for soft tissue applications

This study aims to develop a semi-interpenetrating network (semi-IPN) hydrogel composed of oxidized kappa-carrageenan (OKC) and methacrylated quaternary chitosan (MQC), engineered through dual Schiff base crosslinking and ionic interactions. Moreover, by tuning the oxidation degree of carrageenan (low, medium, and high), the structural, mechanical, and rheological behaviors of the resulting hydrogels are optimized to mimic the characteristics of native skin tissue. Results reveal that increasing oxidation degree enhances the equilibrium swelling ratio by 1387 ± 115% and the degradation rate (55 ± 1% after 7 days at pH 6.2). Moreover, the mechanical performances of semi-IPN hydrogels are significantly tunable, depending on the oxidation rate of carrageenan. Remarkably, the medium-oxidized hydrogel (MQC/OKC-M, 70% oxidation) reveals a superior compressive modulus of 3.1 ± 0.3 kPa, strength of 9.8 ± 0.1 kPa, and excellent elastic recovery (95–100%), closely matching the soft-tissue properties. Additionally, MQC/OKC hydrogels demonstrate excellent cytocompatibility, supporting cell viability and spreading, particularly at higher oxidation degrees. Overall, the MQC/OKC-M hydrogel, combining tunable mechanical performance, controlled degradation, tunable swelling, and biocompatibility, emerges as a promising scaffold for soft tissue engineering applications.