A hybrid hydrogel constructed using drug loaded mesoporous silica and multiple response copolymer as an intelligent dressing for wound healing of diabetic foot ulcers.

Traditional wound dressings have poor mechanical properties and a single function, which cannot achieve rapid healing of diabetic wounds in a unique physiological microenvironment. In order to develop multifunctional hydrogel dressings with appropriate biological activity to accelerate wound healing and obtain better clinical therapeutic effects, herein we report a hybrid system based on drug loaded mesoporous silica and injectable polymer hydrogels mixed with hypoglycemic drug metformin (Met) as a dressing for diabetic wounds. Firstly, a copolymer with the phenylboronic acid group in the side group, poly(acrylamide--dimethylaminopropylacrylamide--methacrylamidophenylboronic acid) (abbreviated as PB), was prepared. PB was mixed with polyvinyl alcohol (PVA) to obtain an injectable hydrogel (named PP) with pH/glucose dual responsiveness, which was formed through the combination of the phenylborate group of PB and -diol of PVA. In another reaction, polydopamine-modified mesoporous silica nanoparticles (MSN@PDA) were prepared and used to adsorb antibiotic tetracycline hydrochloride (TH) to obtain drug-loaded MSN@PDA-TH nanoparticles. Subsequently, the hybrid hydrogel dressing (abbreviated as PP/MSN@PDA-TH/Met) was obtained by mixing PB, PVA, Met and MSN@PDA-TH. The self-healing, rheological and adhesive properties of the hybrid hydrogel were characterized. The results show that the hydrogel dressing has good physical properties. Met and TH were released in different pH media and glucose environments. The results show that the hydrogel dressing has dual responsiveness towards pH and glucose, and can continuously release metformin and tetracycline, which is conducive to accelerating wound healing. The antimicrobial activity, ROS clearance ability and biocompatibility of the hydrogel dressing were evaluated. The results indicate that the hydrogel dressing was multifunctional. Finally, a full-thickness wound repair model of diabetic mice induced by streptozotocin (STZ) was established. The hybrid hydrogel dressing was applied to the wound surface of mice. The wound healing testing on diabetic mice confirmed that the wound covered with the hybrid hydrogel dressing was completely healed with the formation of the new skin and hair within 9 days to 12 days. Histological analysis indicates that, compared to the PBS control, the hydrogel dressing did not cause significant inflammation in the wound, and a large number of blood vessels, glands and hair follicles appeared. This study provides a good strategy for multi-drug synergistic treatment of diabetic foot ulcers.