Aliphatic Bis-Diazirines for Photochemical Crosslinking of Aqueous Hydrogels

In various biomedical applications, crosslinking of biomaterial networks with high spatiotemporal control is of key importance. In this context, diazirine photo-crosslinkers, like trifluoromethyl aryl diazirines, have evolved as radical-free, highly-efficient go-to agents. However, aryl derivatives face solubility issues in aqueous environments, which limit loading and crosslinking density. We thus set out to synthesize and investigate aliphatic bis-diazirines as highly-soluble alternatives. The improved water solubility of the agents was systematically analyzed through HPLC studies and their responsiveness to light was confirmed through in-operando-UV-Vis absorption and IR spectroscopy. Comparative swelling and rheological analyses of gelatin gels with different amounts of crosslinker dopants reflected the positive impact of higher loading propensity due to improved aqueous solubility of the biomaterial. While CryoSEM provided additional structural information on the gels, cytotoxicity studies of the crosslinkers on cells showed their benign nature, even at comparably high concentrations. Taken together, these data suggest that aliphatic bis-diazirines are suitable for use as a molecular platform for light-responsive additives in the field of biomaterial engineering.