负载锌离子的复合水凝胶对糖尿病小鼠全层皮肤缺损感染创面的作用及机制

OBJECTIVE: To investigate the effects and mechanisms of zinc ion-loaded composite hydrogel (hereinafter referred to as the zinc-containing hydrogel) on infected full-thickness skin defect wounds in diabetic mice. METHODS: This study was an experimental study. A poly (glycerol sebacate)-co-poly(ethylene glycol)-g-catechol prepolymer/quaternized-chitosan hydrogel (hereinafter referred to as the simple hydrogel) and a solid-state zinc-containing hydrogel with porous and good adhesion by adding zinc ions to the simple hydrogel were prepared. The release rate of zinc ions from the zinc-containing hydrogel after immersion in phosphate buffer solution (PBS) for 14 days was calculated. The concentration of methicillin-resistant Staphylococcus aureus (MRSA) cultured for 2 hours with the simple hydrogel, zinc-containing hydrogel, and PBS was measured. The scavenging ability of the simple hydrogel, zinc-containing hydrogel, and PBS for 1, 1-diphenyl-2-picrylhydrazyl radical 2, 2-diphenyl-1-(2, 4, 6-trinitrophenyl) hydrazyl (DPPH) was detected using microplate reader to reflect the ability of oxygen free radical removal. The length of vessels formed by human umbilical vein endothelial cells (HUVECs) cultured for 24 hours with the simple hydrogel, zinc-containing hydrogel, and PBS was measured. The cell viability of L929 cells cultured for 24 hours with the simple hydrogel, zinc-containing hydrogel, and PBS was detected using the cell counting kit-8. The mouse red blood cell suspension was divided into blank control group treated with PBS, simple hydrogel group, zinc-containing hydrogel group, and Triton X-100 group treated with corresponding solution. Hemolysis was detected using microplate reader after 2 hours of treatment, and the hemolysis rate was calculated. All experiments had a sample size of 3. Twenty-one C57BL/6J mice aged 6-8 weeks were taken, and a full-thickness skin defect wound was prepared in the symmetrical position on the back spine and infected with MRSA. Mice were divided into blank control group treated with PBS, simple hydrogel group, and zinc-containing hydrogel group treated with the corresponding hydrogel. Three days after injury, bacterial concentration in the wounds were measured in all groups of mice (n=4). On day 0 (immediately), 3, 7, and 14 after injury, the wound infection status of mice was generally observed and the wound healing rate was calculated (n=5). Hematoxylin-eosin staining and Masson staining were used to detect new epithelium and collagen formation in the wounds of mice on day 14 after injury. Immunofluorescence staining was used to detect neovascularization and distribution of M2 macrophages in the wounds of mice. RESULTS: After immersion for 14 days, the release rate of zinc ions of the zinc-containing hydrogel was (70.5±4.6)%. Compared with the zinc-containing hydrogel, the bacterial concentration was significantly increased after 2 hours of culture with PBS and the simple hydrogel (P < 0.05). The DPPH scavenging rate of the zinc-containing hydrogel was significantly higher than that of PBS and the simple hydrogel (with P values all < 0.05). The length of vessels formed by HUVECs cultured for 24 hours with the zinc-containing hydrogel was significantly longer than that cultured with PBS (P < 0.05). Compared with PBS and the simple hydrogel, the cell viability of L929 cells cultured for 24 hours with the zinc-containing hydrogel was significantly higher (P < 0.05). After 2 hours of incubation, compared with that in Triton X-100 group, the hemolysis rate of red blood cells in blank control, simple hydrogel, and zinc-containing hydrogel groups was significantly reduced (P < 0.05); and the hemolysis rate of red blood cells in the latter three groups was similar (P > 0.05). On day 3 after injury, the bacterial concentration in the wounds of mice in zinc-containing hydrogel group was significantly lower than that in blank control and simple hydrogel groups (with P values all < 0.05). From day 3 to day 14 after injury, the wounds of mice in all the three groups were gradually healing, and on day 14 after injury, the wounds of mice in the zinc-containing hydrogel group were basically healed. On day 7 after injury, the wound healing rate of mice in zinc-containing hydrogel group was (72.4±8.4)%, which was significantly higher than that of blank control and simple hydrogel groups, being (31.6±6.7)% and (44.7±5.4)%, respectively(with P values all < 0.05). On day 14 after injury, the wound healing rate of mice in zinc-containing hydrogel group was (92.7±4.3)%, which was significantly higher than (73.5±7.4)% in blank control group (P < 0.05). On day 14 after injury, compared with that in blank control and simple hydrogel groups, the newly formed epidermis in mice wound of zinc-containing hydrogel group was longer and thicker, with more collagen deposition, and a more abundant distribution of new vessels and M2 macrophages. CONCLUSIONS: The zinc-containing hydrogel exhibits good biocompatibility, oxygen free radical scavenging capacity, and antimicrobial effects both in vitro and in vivo, as well as angiogenic promotion capability. It can provide sustained release of zinc ions to promote re-epithelialization and collagen synthesis, thus enhancing the healing of infected full-thickness skin defect wounds in diabetic mice.