Preparation And Performance Of Fiber-based Functional Composited Dressing

When the skin is damaged due to trauma,burns,skin ulcers,etc.,the normal physiological and barrier function of the skin is damaged to varying degrees,along with a series of problems,such as bacterial infection,increased metabolism,excessive moisture and protein Loss,endocrine and immune system dysfunction,etc.Therefore,in the wound healing,wound dressings are needed to replace the defective skin to protect the body from physical factors in the external environment and promote the wound healing.In addition,studies showed that 81%of patients feel different degrees of pain due to the adhesion between wound bed and the wound dressing,and the new epithelial tissue would also be damaged,which affecting healing process.Therefore,except for moisture maintaining and air permeability,promoting wound healing and preventing dressing adhesion are functions that need to be focused.Nanofiber membrane is a porous material with a three-dimensional network structure.It has advantages as wound dressing as followed:high specific surface area and porosity in favour of wound exudate absorption and gas exchange;size and morphology similar to the extracellular matrix;the drug carrier with slow release rate;fit well to the wound contour to prevent the invasion of external bacteria.Based on the above,a series of nanofibrous membranes with different functional types were designed and prepared in this dissertation,and the related properties for its dressing applications were studied.Finally,in view of the poor liquid absorption capacity per unit area of the prepared nanofibrous membrane,composited wound dressing is needed to expand the practical application with the animal experiment evaluted.The main research contents are as follows:Aimed at promoting wound healing,a nanofiber membrane that mimics the composition and structure of natural extracellular matrix was prepared.Using type I collagen from bovine tendon as the raw materials and mixture of HFIP and HAc as solvent,the dissolution,electrispinning and triple helix structure were system explored.The results showed a balance between spinnability and ratio of triple helix structure retented after optimized solvent spinning,with more than 60%of triple helix structure of collagen retained to ensure the good biological activity.Subsequently,the effect of methods and parameters used in the crosslining of collagen on the performance of nanofibrous membranes were explored.The Col/PEO nanofiber membranes prepared in this article were cross-linked with glutaraldehyde(GA)vapor and carbodiimide(EDC)and N-hydroxysuccinimide(NHS)in ethanol solution.The influence of the two cross-linking methods on the properties of nanofiber membranes was compared,and the difference in"cross-linking distance"were more fully and systematically verified,providing certain data and theoretical support for the cross-linking of collagen.The results show that the nanofiber membrane cross-linked by EDC/NHS ethanol solution can promote cell proliferation,and its mechanical curve is"J"-shaped,which is more in line with the tensile curve characteristics of the human body structure.At the same time,the swelling of the nanofibers under physiological condition is more“uniform”after crosslinked by EDC/NHS.Secondly,due to the possibility of bacterial growth of Col/PEO nanofibers and the improvement of drug resistance caused by antibiotic abuse,natural antibacterial agent chitosan is used to blend with collagen to endow certain antibacterial property.The research results show that the addition of chitosan will limit the reproduction of bacteria to varying degrees.When the chitosan content is higher than 60%,the composite nanofiber membrane has more than 90%resistance to E.coli and S.aureus.Also,the possible antibacterial mechanism of chitosan was analyzed.Furthermore,through the in vitro coagulation index(BCI)of nanofiber membranes with different chitosan content and SEM tests of post-coagulated samples,the difference in hemostasis mechanism between collagen and chitosan was analyzed,revealing the synergistic procoagulant effect in promoting blood clotting.Thirdly,for the function of preventing adhesion of wounds and dressings,nano-zinc oxide(ZnO)is used as an anti-adhesion material,due to the strong water absorption of nano-ZnO,it can absorb a certain amount of water molecules to form a"hydration layer",thereby reducing protein adsorption and cell adhesion to achieve anti-adhesion effects.PVDF/ZnO composite nanofiber membranes were prepared in this thesis.Also,the anti-adhension performance of the composite membranes were systematically studied and evaluated in vitro.The effect of nano-ZnO content on the performance of PVDF/ZnO nanofiber membranes was discussed.Two methods in vitro have been used to characterize the non-adhesion property of the wound dressings,namely cell adhesion and peel strength between wound dressings and the geltin.Through cell adhesion(including protein adhesion)and gelatin protein clot peeling force tests,the anti-adhesion mechanism of nano-ZnO was analyzed.The addition of nano-ZnO can significantly reduce protein adsorption,thereby reducing cell adhesion,and the gelatin protein clot peel test results show that the uniform distribution of nano-ZnO on the nanofiber membrane can significantly reduce the adhension of simulated wound leakage.Therefore,At the same time,the PVDF/ZnO composite nanofiber membrane designed and prepared by this institute has antibacterial properties against when the content of nano-ZnO is 5%.At the same time,the extract has no obvious cytotoxicity.It will not cause hemolysis.Finally,in view of the small liquid absorption per unit area of the nanofiber membrane,based on the principle of"ion exchange",the calcium alginate non-woven fabric is sprayed with Na⁺solution on the surface,and the Ca²⁺exchange is formed to form gel bonding points,thus forming a composite dressing.This provides a safe,non-toxic and effective way,and also enhances the practical performance of the nanofiber membrane as a dressing.The liquid absorption per unit area,water vapor transmission rate and blood coagulation performance of the dressing were tested before and after composited with calcium alginate nonwoven fabric.The performance difference shows that the composited dressing has better liquid absorption performance.Although the water vapor transmission rate is reduced to a certain extent,all composite dressings have excellent blood coagulation performance within a suitable range.Furthermore,the Col/CS/PEO and calcium alginate non-woven fabric composite dressing was used to perform full thickness wound woun healing experiment.With commercial collagen foam as the negative control and calcium alginate nonwoven as the blank control,the wound area,the histologic section and the expression of the three growth factors EGF,b FGF and TGF-?in the wound healing were characterized and evaluated.The results show that the wound healing rate of the composite functional dressing is significantly higher than that of the commercial control group.The composite dressing can effectively promote the expression of the above three growth factors in the early stage of wound healing,thereby promoting the proliferation of fibroblasts and epidermal cells and promoting wound healing to confirm the wound healig promotion and safety of the developed composited wound dressing.