Self-powered Enzyme-linked Microneedle Patch For Tissue Defect Repair

Objective:In this study,the transdermal drug delivery technology of microneedles was combined with the enzyme cascade biofuel cells to design and prepare a new type of self-produced electroenzymatic cascade microneedle patch.The morphology,electrical conductivity,mechanical properties,antibacterial properties and biocompatibility of the compounds were tested.Then,the rat model of diabetic wound and sciatic nerve injury was treated to study the application of the self-powered enzyme-linked microneedle patch in promoting diabetic wound healing and sciatic nerve repair.Method:(1)Preparation and characterization of self-powered enzyme-linked microneedle patch: The MNs consists of a substrate with excellent electroconductivity,an anode array and a cathode array.The substrate was prepared by polydopamine modification(DA)modified polypyrrole(PPy)-polyvinyl alcohol(PVA)(-hyaluronic acid(HA))(DPP(H))gel,which had good electrical conductivity;anode loaded with ZIF-8 fixed GOx(ZG nanoparticles);cathode array loaded with ZIF-8 fixed HRP(ZH nanoparticles).The morphology,electrical conductivity,mechanical properties,antibacterial properties and biocompatibility were tested.(2)Establishment of an animal model of diabetic wound and evaluation of the effect of promoting wound healing: After the successful establishment of a rat model of type I diabetes mellitus by intraperitoneal injection of STZ.Two equal 1×1cm square full-thickness wounds were prepared on both sides of the spine of diabetic rats.The constructed animal models were divided into 6 groups with 6 animals in each group.The wounds of 5 groups were treated with Blank-MNs patch,ZIF-MNs patch,ZG-MNs patch,ZH-MNs patch and ZGH-MNs patch,respectively.The diabetic wound rats were sacrificed at 7,14 and 21 days,respectively.For further immunohistochemical staining to evaluate the efficacy of diabetic wound healing,the skin tissue at the wound site was taken for fixation.(3)Establishment of animal model of sciatic nerve injury and evaluation of the effect of promoting sciatic nerve repair: A 5 mm segment was removed from the middle sciatic nerve trunk of rats to construct an animal model of sciatic nerve injury,and the rats were divided into 7 groups with 6 animals in each group.In 6 groups,blanch-Mn patch,ZIF-MN patch,ZG-MN patch,ZH-MN patch,ZGH-MN patch and rat autogenous nerve were placed on the free end of the injured nerve to replace the missing nerve.The injured sciatic nerve in the remaining group was not repaired.The rats in each group were sacrificed after 6 and 12 weeks of treatment,and the nerve tissue at the repair site was obtained for immunohistochemical staining to evaluate the repair effect of the injured sciatic nerve.Results:(1)Preparation and characterization of the self-powered enzyme-linked microneedle patch: It was observed by scanning electron microscopy(SEM)that the needle bodies of self-powered enzyme-linked microneedle array were uniformly and orderly arranged on the bottom plate,and each needle body was conical with an interval of 300μm.The bottom diameter of each needle was 200μm,and the height was 600μm.In addition,it is also proved that self-powered enzyme-linked microneedle patch has good electrical conductivity,mechanical properties,biocompatibility and antibacterial properties.(2)Establishment of an animal model of diabetic wound and evaluation of the effect of promoting wound healing: Detailed analysis of wound healing area at day 7,14 and 21 showed that,compared with other treatment groups and Blank control group,ZGH-MNs group had complete wound healing and smooth surface similar to normal skin tissue structure after 21 days of treatment.At the same time,the above results were further verified by wound tissue H&E staining,Masson staining,TGF-β,CD31 and MMP-9 immunohistochemical results.(3)The establishment of an animal model of sciatic nerve injury and the evaluation of the effect of promoting sciatic nerve repair: The recovery of gastrocnemius innervated by repaired sciatic nerve was observed after 6 and 12 weeks of treatment,and the results showed that the gastrocnemius atrophy was more obvious in the Control group at 12 weeks.In contrast,the experimental group recovered from atrophy,in which the muscle recovery of ZGH-MN was relatively better than that of the Autograft group,indicating that ZGH-MN had the best repair effect on sciatic nerve.Then,the results of H&E staining,TB staining,LFB staining,immunofluorescence staining of nerve filament marker NF200 and Schwann cell specific marker S-100β,and CD31 immunohistochemical staining of the repaired sciatic nerve tissue proved that the ZGH-MN catheter could significantly promote the regeneration of muscles,blood vessels and nerve fibers innervated by the sciatic nerve.Furthermore,it has good repair effect on sciatic nerve injury.Conclusion:The results of this study show that: the self-powered enzyme-linked microneedle patch,designed and prepared based on the combination of microneedle and enzyme biofuel cell technology,can use glucose in organisms as fuel to generate micro current,and then through bioelectric stimulation can effectively realize the effective repair of diabetic wounds and sciatic nerve defects,indicating that the microneedle has a broad application prospect in the field of clinical repair of tissue defects.