Dopamine enhances the mechanical and biological properties of enzyme-induced mineralized hydrogels

Abstract

Bio-inspired approaches to increasing the mechanical properties of hydrogels, such as enzyme-induced mineralization, have attracted great interest recently, but the biological properties also need to be improved at the same time. In this study, we systematically compared the mechanical properties and biological properties of sulfosuccinimidyl 6-(4′-azido-2′-nitrophenylamino) hexanoate (Sulfo-SANPAH) and dopamine biofunctionalized acrylamide hydrogels in the presence and absence of alkaline phosphatase (ALP)-induced mineralization. The results showed that enzyme-induced mineralization is an effective approach to improving the mechanical properties of acrylamide hydrogel and dopamine biofunctionalization can further significantly improve both the biological properties and the mechanical properties. The dynamic thermomechanical analysis (DMA) results indicated that the dopamine biofunctionalized mineralized acrylamide hydrogel (AAm–ALP–Dopa) had the highest storage modulus of 2688 ± 122 kPa, more than nine times of that of the pristine hydrogels. In addition, the AAm–ALP–Dopa sample exhibited the highest breaking stress, as well as the highest elongation rate. The surprising synergistic effect of dopamine biofunctionalization and enzyme biomineralization in improving the mechanical properties was likely due to the self-polymerization of dopamine within the hydrogel, which led to the formation of a more complicated network and strengthening of junctions within the network. The cellular responses also indicated that the cells on the dopamine biofunctionalized hydrogels had the best cell adhesion and spreading. Our results provide an effective approach to preparing dopamine biofunctionalized mineralized hydrogels with excellent mechanical properties and biocompatibility, which demonstrated considerable potential in biomedical applications.