Composite Hydrogel Based on Green Chlorella Polysaccharide–Selenium Nanoparticles for Simultaneous Wound Treatment and pH Monitoring

Once the skin was damaged, it lost the ability to prevent harmful bacteria from infiltrating into the tissues, leading to wound infection and even serious tissue damage. Although conventional therapies were effective in eradicating pathogenic bacteria, they could not promote the healing of damaged skin, which was easily affected by tissue adhesion and lacked the ability to maintain a moist wound environment. In this study, according to the principle of green chemistry, Chlorella extracellular polysaccharide–selenium nanoparticles (EPS-SeNPs) with high biological activity, high stability, and low toxicity were synthesized for the first time, which could be used to kill wound pathogens and relieve inflammation. EPS-SeNPs were combined with a wound dressing hydrogel, and the hydrogel was cross-linked by a Schiff base reaction between the biocompatible oxidized sodium alginate (OSA) and gelatin (Gel) to promote wound healing. At the same time, the pH fluctuation of the wound could be monitored by adding the acid–base indicator litmus to it by the solvent replacement method, thus indirectly predicting the healing process of the wound. The results of in vitro experiments showed that the composite hydrogel had strong antibacterial and anti-inflammatory abilities, which could inhibit the growth and reproduction of common pathogens. The experimental results showed that the antibacterial rate of the composite hydrogel could reach 99%, the ability to clear ABTS free radicals was 93.13%, and the ability to clear DPPH free radicals was 82.36%. In the in vivo experiment, SD rats were used to construct an infected wound model, and then wound healing experiments were conducted. The experimental results showed that the composite hydrogel could significantly accelerate the wound healing process, promote new epidermis formation and hair follicle growth, and reduce inflammatory response. This work may open up a way for the clinical management of infected wounds and the simultaneous monitoring of wound healing.