[Performance of phenylboronic acid-modified GelMA hydrogel loaded with copper-doped cerium oxide nanozyme and its effect on healing of infected burn wounds in mice].

Abstract

Objective: To explore the performance of phenylboronic acid-modified gelatin methacryloyl (GelMA) hydrogel loaded with copper-doped cerium oxide nanozyme (hereinafter referred to as composite hydrogel) and its effects on healing of infected burn wounds in mice. Methods: This study was an experimental study including group design and repeated measures design. The phenylboronic acid-modified GelMA hydrogel (hereinafter referred to as simple hydrogel) with a three-dimensional loose porous network structure was prepared. The copper-doped cerium oxide nanozyme with a uniform spherical structure was prepared by a hydrothermal method. The copper-doped cerium oxide nanozyme with a final mass concentration of 100 μg/mL, which had no obvious effect on the viability of human umbilical vein endothelial cells and possessed high superoxide dismutase-like and catalase-like activities, was screened out and added into the simple hydrogel to prepare the composite hydrogel. After the composite hydrogels were soaked in phosphate buffer saline (PBS) or hydrogen peroxide solution for 24, 48, and 72 h, the release percentages of copper-doped cerium oxide nanozymes in the composite hydrogel were calculated, with a sample size of 3. Thirty 8-week-old male BALB/c mice were taken to establish a burn wound infection model by creating symmetrical burn wounds on both sides of the spine, and then dropping methicillin-resistant Staphylococcus aureus (MRSA) bacterial suspension to the wounds. According to the random number table method (the same grouping method below), the mice were divided into control group, simple hydrogel group, and composite hydrogel group, with 10 mice in each group (20 wounds). No drug intervention was administered to the wounds of mice in control group, the simple hydrogel and composite hydrogel were dropped on the wounds of mice in simple hydrogel group and composite hydrogel group, respectively. At post injury day (PID) 3, 7, and 14, the residual wound area was measured and the percentage of residual wound area was calculated. At PID 3, the MRSA concentration in the wound was measured using the plate counting method. At PID 5, the wound blood perfusion volume was evaluated by a laser speckle blood flow imaging system. Another six 8-week-old male BALB/c mice were taken and divided into PBS group and composite hydrogel implantation group, with 3 mice in each group, and PBS was subcutaneously injected and composite hydrogels were subcutaneously implanted into the center of the mice's backs, respectively. At 14 d after treatment, abdominal whole blood of mice was collected, then the blood routine test indexes and blood biochemical test indexes were detected. Results: After immersion in PBS or hydrogen peroxide solution for 24, 48, and 72 h, respectively, the overall differences in the release percentages of copper-doped cerium oxide nanozymes in the composite hydrogel were statistically significant (with F values of 30.29 and 65.16, respectively, P<0.05). At PID 3, 7, and 14, compared with those in control group, the percentages of residual wound area of mice in simple hydrogel group and composite hydrogel group were all significantly reduced (P<0.05); the percentages of residual wound area of mice in composite hydrogel group were significantly lower than those in simple hydrogel group (P<0.05). At PID 3, compared with that in control group, the MRSA concentrations in the wounds of mice in simple hydrogel group and composite hydrogel group were both significantly decreased (P<0.05); the MRSA concentration in the wounds of mice in composite hydrogel group was significantly lower than that in simple hydrogel group (P<0.05). At PID 5, compared with (221±25) perfusion units in control group, the wound blood perfusion volumes of mice in simple hydrogel group and composite hydrogel group ((313±53) and (535±104) perfusion units, respectively) were both significantly increased (P<0.05); the wound blood perfusion volume of mice in composite hydrogel group was significantly higher than that in simple hydrogel group (P<0.05). At 14 d after treatment, the blood routine test indexes and blood biochemical test indexes of mice in composite hydrogel implantation group and PBS group were all maintained within normal physiological ranges, with no statistically significant differences between the two groups (P>0.05). Conclusions: The composite hydrogel possesses good biocompatibility, reactive oxygen species responsiveness, and excellent antibacterial properties. It can accelerate wound healing by eliminating MRSA from the infected burn wounds in mice at early stage and promoting blood flow recovery.