Study On The Effect Of Electric Field Coupled Negative Pressure Integrated Treatment System Based On Triboelectric Nanogenerator To Promote Wound Healing

Background:Wound healing is a dynamic and orderly biological process that includes hemostasis,inflammation,proliferation,and remodeling phases.Abnormalities in any of these stages may lead to prolonged wound healing or even chronic refractory wounds.However,current wound treatment strategies are often limited to interventions at a single point or stage,and there is a lack of comprehensive treatment strategies that can integrate the different stages of wound healing mechanisms.Negative pressure wound therapy（NPWT）has become the most widely used technique for the treatment of acute and chronic wounds because of its effectiveness in draining wound exudate,reducing the risk of infection,maintaining a good wound microenvironment,and promoting granulation formation.Although NPWT can provide good wound conditions for reepithelialization including epidermal cell proliferation and migration by promoting granulation formation,it does not directly induce or drive the directed migration of epidermal cells,which is known to be the rate-limiting step of wound re-epithelialization.Therefore,the study of new comprehensive therapeutic strategies is of obvious importance for the development of new clinical techniques to promote wound repair.Electric fields（EF）is an important signal to guide epidermal cells to migrate to the wound and promote wound repair.The in vitro cell wound healing model proved that the EF played a more critical role in guiding the directional migration of epidermal cells than other coexisting signals.It has been known that endogenous EF failure may be an important cause of chronic wound refractory.Therefore,by applying exogenous EF to enhance wound EF and accelerate the directional migration of epidermal cells from the wound edge to the wound center,it is expected to achieve active intervention in the process of wound re-epithelialization.Studies have shown that the directional flow of ions in the wound edge tissue is the material basis for the formation of endogenous EF in the wound.There are a variety of ion channels and ion pumps in tissue cells,which play a key role in transporting nutrients,metabolizing waste,maintaining water balance and regulating the formation and stability of cell transmembrane potential.After skin injury,blood and exudate flow out of the wound,helping to mediate wound healing and prevent wound dryness.This exudate has complex components and contains a variety of cytokines,ions,etc.It is an important component of the wound microenvironment.NPWT exerts anti-infective and granulation-promoting effects mainly by draining wound exudate and exerting mechanical force on tissue.We speculate that the continuous drainage of wound exudate by NPWT may lead to electrolyte loss in the wound,affect the ion flow at the wound edge,and ultimately weaken the endogenous EF of the wound.Based on the above inferences,exogenous EF treatment is expected to make up for the limitations of NPWT and accelerate wound healing by reshaping wound EF to achieve organic synergy with NPWT.However,although traditional direct current can effectively induce the directional migration of epidermal cells,its electrical side effects including electrothermal and electrolytic effects are obvious,which limits its application in wound treatment.In addition,traditional DC treatment equipment also has problems such as complex equipment lines and low biosafety.However,if a power supply system integrated with NPWT can be constructed,it can not only achieve the organic synergy of the therapeutic effects of the two,but also be convenient to use and more in line with clinical needs.Triboelectric nanogenerator（TENG）is a new type of force-electric conversion device invented by Wang Zhonglin,a foreign academician of the Chinese Academy of Sciences in2012,and has developed rapidly in recent years.It can collect weak mechanical energy and convert it into periodic electrical pulses.The principle is that two materials（friction layer）triboelectric,and produce electrostatic induction,and finally through the electrode layer to generate electrical output.TENG has the characteristics of controllable parameters,light design and high safety.Since its inception,it has been widely used in the research and preparation of various self-powered biosensors.More importantly,the output electricity of TENG has the characteristics of high voltage and low current,which is consistent with the characteristics that the wound EF depends on voltage rather than current.Therefore,TENG-based self-powered devices undoubtedly provide a practical solution for wound EF treatment.In view of the above research ideas,this study designed an electro-generative dressing（EGD）with TENG as the self-powered power supply,the flexible porous conductive dressing developed by the research group as the electrode,and the polyurethane（PU）foam dressing in NPWT as the main scaffold,and combined with the Negative Pressure Control Device（NCD）.An electric field coupled negative pressure integrated treatment system（ECNITS）based on the combination of TENG and NPWT was constructed for wound treatment.Purpose:Based on the deep understanding of wound healing mechanism,combined with TENG and NPWT technology,this project constructs an electric field coupling negative pressure integrated treatment system based on triboelectric nanogenerator with dressing self-powered characteristics,and discusses its healing effect,in order to provide theoretical and practical basis for the development of new wound repair technology with clinical transformation prospects.Contents and methods:1.Based on the TENG,an electric field coupled negative pressure integrated treatment system with self-powered dressing is constructed.A TENG with high safety,small size and certain flexibility was constructed by using vertical contact-separation mode,and its electrical output performance was tested.TPFS-Ag NWs-PU flexible conductive dressing was prepared by the previous method of the research group.EGD was constructed with TENG as the power supply,TPFS-Ag NWs-PU flexible conductive dressing as the conductive electrode,and ordinary PU foam dressing as the main body and support of the dressing.By connecting with the negative pressure control device,an electric field coupling negative pressure integrated treatment system with self-powered dressing was constructed.The electrical signal output characteristics of the integrated treatment system in different intermittent negative pressure modes were detected,and the parameters suitable for both negative pressure treatment and electric field treatment were selected.2.The biological safety and in vitro cell biological effects of the output electricity of the ECNITS.Using a combination of electrical theory to calculate thermal effects and in vitro cell model experiments to evaluate the biosafety of the output EF of the ECNITS;using an in vitro cell model of EF to study the effect of the output EF of the ECNITS on the migration of keratinocytes and the polarization of macrophages in vitro under the working mode.3.Study the effect and mechanism of ECNITS on wound healing in vivo.The full-thickness skin defect wound model of Bama miniature pig was constructed to observe the healing effect of electric field coupling negative pressure integrated treatment system.The possible healing mechanism of the treatment system was studied from the aspects of wound inflammation,angiogenesis,epidermal cell proliferation and migration,collagen type and distribution.Results:1.Successful preparation of TENG:Al and PTFE were used as the friction layer,Al and Cu were used as the electrode layer,and the vertical contact TENG was successfully prepared.The constructed TENG has good flexibility and outputs an AC electrical signal with a peak voltage of 60 V and a peak current of 1μA under motor drive.2.Successful preparation of TPFS-Ag NWs-PU conductive dressing:TPFS-Ag NWs-PU conductive dressing with good flexibility,conductivity and biocompatibility was successfully prepared by high pressure spraying of silver nanowires（Ag NWs）using PU foam dressing as substrate.When the TPFS-Ag NWs-PU conductive dressing is compressed by 80%,its resistance value is only 6.6Ω,and the conductivity is almost unaffected after the solution is contaminated.The TPFS-Ag NWs-PU conductive dressing has the same flexibility and 3D spatial structure as the PU foam dressing,and the biosafety level is 1.3.Successful construction of ECNITS with excellent biosafety:ECNITS was successfully constructed using TENG,TPFS-Ag NWs-PU conductive dressing,PU foam dressing,negative pressure device and other components.In the intermittent negative pressure mode（pump-in and pump-out time ratio:3/1）,ECNITS generates a DC pulse current with a peak voltage of 4V and a peak current of only 28 n A.The output electricity of ECNITS has excellent biosafety,and its theoretical heat production is 1.5542×10^-11J,which is only one trillionth of the traditional DC power supply.4.In vitro experiments:The output electric field of ECNITS significantly induced the electrotaxis of keratinocytes（|cos（θ）|=0.85±0.02）,and its mechanism was related to the activation of PI3K/AKT pathway and MAPK/ERK pathway,and the reduction of intercellular adhesion（E-cadherin）;at the same time,it may promote the polarization of macrophages to M2 type.5.In vivo experiments:（1）The exogenous EF output by ECNITS significantly enhanced the wound EF weakened by NPWT,and increased the wound EF intensity from 40 m V/mm to 197 m V/mm,thus playing an important role in reshaping the endogenous electric field of the wound.（2）ECNITS significantly promoted wound healing and re-epithelialization.On the 6th day after injury,the wound healing area of EGD group was 53.48%,which was 1.93 times of NPWT treatment group（27.74%）and 7.35 times of blank group（7.28%）.The average length of new epidermis in EGD group was 2724μm,which was significantly higher than that in NPWT group（775μm）and blank group（686μm）.On the 12 th day after injury,the wound healing area of EGD group was 90.37%,which was significantly higher than that of NPWT treatment group（72.52%）and blank group（55.21%）.The length of new epidermis in EGD group was 4982μm,which was 1.76 times that of NPWT group and 1.80times that of blank group.（3）ECNITS significantly inhibited wound inflammation,promoted wound neovascularization and keratinocyte proliferation,and reduced the adhesion between keratinocytes.On the third day after injury,the density of macrophages in the wound of EGD group was only 4/0.01mm²,the density of neutrophils was only 14/0.01mm²,and the density of lymphocytes was only 32/0.01mm²,which was much lower than that of NPWT group and blank group.On the 6th day after injury,the expression of PCNA in EGD group was 46.54%higher than that in NPWT group and 86.10%higher than that blank group,and the expression of E-cadherin was 57.85%lower than that in NPWT group and28.31%lower than that in blank group.On the 12 th day after injury,the expression of PCNA in the EGD group was 46.17%higher than that in the NPWT group and 94.50%higher than that in the blank group,and the expression of E-cadherin was 80.99%lower than that in the NPWT group and 44.71%lower than that in the blank group.（4）ECNITS significantly improved the quality of wound healing.On the 28 th day after injury,the scar area of the EGD group was only 51.90%of the NPWT group and29.58%of the blank group,respectively,and the VSS score was only 3;the average thickness of the new epidermis in the EGD group was 183μm,which was significantly higher than that in the NPWT group（90μm）and the blank group（45μm）,and the density of rete pegs was significantly higher than that in the NPWT group and the blank group.Compared with the NPWT group and the blank control group,the collagen fibers in the dermis of the EGD group were closely arranged in parallel,and the number of type I collagen fibers increased significantly.Conclusion:1.Through the organic integration of TENG and NPWT,ECNITS with both electric field and negative pressure therapy was successfully developed.2.ECNITS converts the mechanical deformation generated by NPWT（intermittent mode）into a safe and stable pulsed direct current,thereby enhancing and reshaping the wound EF.3.ECNITS inhibits wound inflammation and makes the wound enter the proliferative phase earlier;promote proliferation of angiogenesis,epidermal migration and proliferation,accelerate re-epithelialization;which in turn improves wound healing quality,promotes new epidermal maturation and orderly collagen arrangement,and reduces scar formation.ECNITS combines negative pressure and electric field in a non-invasive way,which has a good prospect in wound treatment.