RESUMO
The objective of this study is to develop a completely natural material based photo-initiation system for fabricating biologically compatible hydrogels, that is, free of any synthetic materials like conventional synthetic photo-initiators. The resulting biodegradable hydrogels would be completely free of conventional toxic synthetic substances. Dextran-based precursor was used as a model system for this study. The natural material based photo-initiation system used riboflavin (vitamin B2) as photo-initiator and L-arginine as a coinitiator. Dextran-methacrylate precursor was prepared to introduce photosensitive unsaturated moieties into dextran for subsequent photo-induced gel formation. Riboflavin alone could not initiate the photo-crosslinking reaction of the dextran methacrylate solution upon UV irradiation. L-arginine, which can act as an electron donor in the photo-initiation process, was used as a coinitiator. The optimum gel formulation conditions in terms of the concentrations of riboflavin and L-arginine as well as different pH media were extensively investigated. The dextran-methacrylate hydrogels were formed well and fast at low riboflavin concentration range (0.2-1 wt %), and L-arginine promoted the photo-initiation at all concentrations. The gelation was promoted most in the neutral pH and the least in the alkaline pH. The turbidity of the dextran-methacrylate hydrogel precursor solution affected the polymerization because UV penetration was significantly hindered as the opacity of the solution increased. The swelling property and structural visualization of the prepared hydrogels were also investigated.
