Microenvironment-responsive Bletilla polysaccharide hydrogel with photothermal antibacterial and macrophage polarization-regulating properties for diabetic wound healing

The healing of diabetic wounds (DW) is challenging due to the complex microenvironment, manifesting severe bacterial infections, persistent inflammation, and excessive oxidative stress. Therefore, overcoming these impediments to restore the wound microenvironment to a normal state is critical points and challenges in the development of effective DW dressings. Herein, a B/TF hydrogel was developed in our study using Bletilla striata polysaccharide (BSP), borax, and the tannic acid/ferric iron (TA/Fe3+) complex. The crosslinking of the hydrogel constructed by dynamic borate bonds not only impart remarkable physical properties to the hydrogel, but also exhibited responsive release of BSP and TA/Fe3+ complex to pH and glucose levels. Incorporating the TA/Fe3+ complex provided notable near-infrared (NIR) photothermal properties to the hydrogel, thereby demonstrating significant photothermal antibacterial activity and antioxidant capability. Additionally, the B/TF hydrogel effectively regulated the transformation of macrophages from the pro-inflammatory M1 phenotype to the antiinflammatory M2 phenotype. Animal experiments have also effectively confirmed that the treatment with B/ TF hydrogel combined with NIR radiation promoted the regeneration of skin tissue in DW. In summary, the developed multifunctional B/TF hydrogel showed advantages and met clinical requirements for treating DW.