An intelligent controlled release hydrogel with photothermal effect for the treatment of bone defects

To solve the difficulty of natural healing in patients with severe bone defects, and the challenges of insufficient autologous bone graft material and large incisions in conventional surgery, we were designed an intelligent co-regulated hydrogel system with NIR response. The goal is to be able to prevent inflammation and bacterial adhesion, thereby promoting repair and development of the bone defect area. The hydrogel system consisted of hyaluronic acid, carboxymethyl chitosan and Pht-loaded PDA-encapsulated ZIF-8 NPs (Pht@ZIF-8@PDA) by Schiff base reaction. Compared to high-temperature photothermal therapy (PTT), which destroyed surrounding healthy cells, the present study was based on a new strategy of mild photothermal therapy (42.5 ± 1.2 °C) and leaded to a better promotion of osteogenesis. NIR activated the photothermal properties of PDA in scaffolds, intelligently released Pht and Zn 2+ , inhibited Escherichia coli and Staphylococcus aureus (inhibition rate ≥ 96 %), and promoted bone regeneration in the rat model. Meanwhile, it could promote bone regeneration by upregulating osteogenic factors and stimulating the expression of proteins related to BMP/SMAD signaling pathway. The research highlights the potential applications of synergistically modulated hydrogels, which opens up a new application path for this material in bone tissue engineering, regenerative medicine, and other related fields.