Increasing stiffness and thermal response behavior of collagen/metal nanoparticle composite hydrogels fabricated...

Metal nanoparticle/hydrogel composites have attracted attention in the fields of materials science and applied chemistry. In this study, collagen/transition-metal nanoparticle (Col-TMNP) hydrogels are fabricated through radiochemical reduction on collagen-transition metal (Col-TM) gels, which we previously reported. ⁶⁰Co γ-ray irradiation of Col-Au and Col-Pt gels enables the uniform formation of metal nanoparticles within the collagen matrix, eliminating the need for chemical reducing agents. This method applies to a wide range of materials, regardless of their morphology or shape, and enables the synthesis of metal nanoparticles in a non-flowable gel state, which is difficult to achieve using solution-phase chemical reduction. The thus formed Col-AuNP and Col-PtNP gels exhibit enhanced elasticity compared to pristine Col-TM gels due to the formation of a cross-linking network structure by radiation-induced covalent bonds. Furthermore, the photothermal properties of Col-TMNP gels were examined using a Yb:YAG green laser (515 nm), showing a reversible photothermal response.