Self-crosslinked hydrogel with delivery carrier obtained by incorporation of oxidized alginate microspheres into gelatin matrix

A novel self-crosslinked hydrogel with a delivery carrier was prepared by incorporating 0.5, 1, and 4% (w/v) oxidized alginate di-aldehyde microspheres (Ad_s) into a 5% (w/v) gelatin matrix. The Ad_s have a two-fold function. Namely, they act as delivery vehicles and promote the self-crosslinking of the hybrid hydrogel. Both light and scanning electron microscopy confirmed a homogenous distribution of the Ad_s in the gelatin matrix. In contrast to the unmodified alginate microspheres, clustering and sedimentation could be avoided. Furthermore, their incorporation improved the mechanical properties and the thermal stability of the thermosensitive gelatin. Crosslinking was completed after 213 min at 37 °C. The addition of 1% (w/w) borax shortened the crosslinking process to 59.5 min. The crosslinking time could be further reduced to 20 min by performing the Schiff base reaction at an elevated temperature of 45 °C.