Water-based synthesis of dextran-methacrylate and its use to design hydrogels for biomedical applications

• A catalyst-free water-based synthesis of dextran-methacrylate was developed. • The reaction was rapid (1 h), efficient (≈90 % yield) and required pH control. • Polymer degrees of substitution up to 62% were achieved. • Solid-state photo-crosslinking resulted in dextran-based hydrogels. • Biocompatible hydrogels displayed high mechanical strength. Polysaccharide-based hydrogels are desirable for biomedical applications owing to their biocompatibility and physicochemical tunability. The chemical modification of polysaccharides with photo-sensitive groups, such as methacrylates is a common method to obtain new hydrogel materials. This study introduces a non-toxic water-based method to effectively functionalize dextran with methacrylate groups. The methacrylation reaction with methacrylic anhydride in water in the presence of NaOH was rapid and efficient (85 %−92 % yield), permitting degrees of substitution (DS) up to 62 % within 60 min. An unconventional solid-state photo-crosslinking method was employed to form chemically crosslinked dextran-based hydrogels with LAP (lithium phenyl-2,4,6-trimethylbenzoylphosphinate) as the photoinitiator. By varying the polymer formulations (DS, polymer mass, LAP concentration), a wide range of hydrogels were obtained with various swelling ratios (40–250 %) and release kinetics of model drug and protein biomolecules. Compression modulus values ranged from 32 ± 1 to 342 ± 10 MPa (dry state) and 87 to 8500 kPa (swollen state). Cytotoxicity experiments indicated good biocompatibility for the crosslinked dextran hydrogels. The green synthesis protocols and obtained dextran-based hydrogels with high mechanical strength open up perspectives for applications from tissue engineering to the design of medical devices such as microneedles.