With the fast development of cell therapy, there has been a shift toward the development of injectable hydrogels as cell carriers that can overcome current limitations in cell therapy. However, the hydrogels are prone to damage during use, inducing cell apoptosis. Therefore, this study was carried out to develop an injectable and self-healing hydrogel based on chondroitin sulfate multiple aldehyde (CSMA) and N-succinyl-chitosan (SC). By varying the CSMA to SC ratio, the hydrogel stiffness, water content, and kinetics of gelation could be controlled. Gelation readily occurred at physiological conditions, predominantly due to a Schiff base reaction between the aldehyde groups on CSMA and amino groups on SC. Meanwhile, because of the dynamic equilibrium of Schiff base linkage, the hydrogel was found to be self-healing. Cells encapsulated in the hydrogel remained viable and metabolically active. In addition, the hydrogel produced minimal inflammatory response when injected subcutaneously in a rat model and showed biodegradability in vivo. This work establishes an injectable and self-healing hydrogel derived from carbohydrates with potential applications as a cell carrier and in tissue engineering.

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Covalent functionalization of azide-modified SiO(2) with well-defined, alkyne-terminated poly(N-isopropylacrylamide) was accomplished by the Cu(I)-catalyzed [3 + 2] Huisgen cycloaddition. The alkyne-terminated RAFT chain transfer agent was first synthesized, and then the alkyne-terminated thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) with different molecular weights were synthesized by the RAFT of NIPAM monomer. The polymerization kinetics and the evolution of number-average molecular weights (M(n)), and polydispersities (M(w)/M(n)), with monomer conversions were investigated. A copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) "grafting to" method was used to attach thermoresponsive polymers onto the exterior surface of SiO(2) nanoparticles which produced relatively high grafting density. The as-synthesized hybrid nanoparticles showed thermoresponsive behavior and were characterized by FTIR, XPS, TGA, DLS, and TEM, etc.

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