Dual crosslinked alginate hydrogels by riboflavin as photoinitiator.

Photodegradation behavior of riboflavin (RF) as photoinitiator and photosensitizer was investigated. When the visible light was irradiated to RF, the radical activation and decomposition of RF was induced by reactive oxygen species (ROS) that has formed by dissolved oxygen. One of its photoproducts, lumichrome (LC), was a reduced form of RF, which lost its color when photodegraded. Photodegradation mechanisms of RF and its photoproducts by light irradiation were investigated using structural quantitative analysis derived from UV-Vis spectra. It was found that RF provided photocrosslinking reaction to make alginate-based hydrogels. For this investigation, alginate derivative with tyramine moiety was prepared by EDC/NHS chemistry and it used to induce photocrosslinking, which might serve to reinforce the unstable ionic crosslinking in the physiological environment of alginate hydrogel. The structural stability of single-crosslinked (ionically or covalently crosslinked) or dual-crosslinked (ionically and covalently crosslinked) alginate-based hydrogels were compared using rheometer, texture analyzer and SEM.