Wound Microenvironment-Responsive Hydrogel With Efficient Angiogenesis For Promoting Diabetic Wound Healing

Diabetic wounds such as diabetic foot ulcers are one kind of typical chronic wounds.Such non-healing wounds cost great harm to the patients.Diabetic wounds are caused by the accumulation of different factors.The continuous inflammatory in the wound microenvironment produces a large amount of reactive oxygen species(ROS)thus the highly expressed ROS can damage normal cells and tissues.Meanwhile,the high glucose environment of the wound also causes harm to wound healing.Matrix metalloproteinases have huge impact on necrotic tissue removal,formation of new blood vessels and remodeling of collagen tissue.However,the high expression of matrix metalloproteinase-9(MMP-9)in diabetic wounds delays wound healing.In addition,the reduced angiogenesis in diabetic wounds and the damaged vascular function will make it difficult to transport the oxygen and nutrients needed in the healing process,thereby delaying wound healing.Therefore,in this paper,we have prepared a diabetic microenvironmental responsive-hydrogel,combining it with a drug delivery system based on gelatin microspheres.Through promoting angiogenesis,this hydrogel dressing can accelerate diabetic wound healing.Firstly,quaternized chitosan(QCS)was synthesized.Then 3-carboxy-4fluorophenylboronic acid was grafted to the side chain of QCS to prepare quaternized chitosan with phenylboronic acid groups(QCSF).The dynamic borate bond was formed between the phenylboronic acid group on the side chain of QCSF and the hydroxyl group on polyvinyl alcohol(PVA).Combined with a drug delivery system based on cross-linked gelatin microspheres,the drug-loaded hydrogel DFO@G-QCSFP was prepared.In vitro response experiment proved that DFO@G-QCSFP hydrogel could respond to p H changes and high glucose environment.ROS removal experiment proved that DFO@G-QCSFP could effectively reduce the amount of ROS.In vitro drug release experiment suggested that the drug delivery system based on gelatin microspheres could achieve controlled release of DFO by the ability of responding to MMP-9.In the in vitro cell experiment,the impacts of different concentrations of DFO on the promotion of cell proliferation and angiogenesis were investigated,and the optimal concentration of DFO in the in vitro experiment was proved as 3 μM.At the same time,in vitro cell experiments also proved that the drug-loaded microspheres DFO@GMs and the drug-loaded hydrogel DFO@G-QCSFP have good biocompatibility after incubating with the cells for different periods of time.Full-thickness skin wounds of diabetic SD rats were established.The ability of DFO@GQCSFP hydrogel to promote wound healing was investigated.The residual wound area was only 5.1% on the 10 th day after treatment.Furthermore,H&E staining and Masson staining confirmed that DFO@G-QCSFP had the highest healing efficiency.Immunohistochemical analysis suggested that DFO@G-QCSFP could effectively promote the angiogenesis.In addition,the ability of DFO@G-QCSFP on reducing the expression of MMP-9 and promoting cell proliferation also provided a positive effect on wound healing.