Preparation Of Composite Hydrogels Based On Polyvinyl Alcohol And Its Application In Medical Dressings

Every year,thousands of patients around the world suffer from burns,scald and skin damage caused by accidents.These accidents normally accompany with infection,disability and even death.Therefore,different medical dressings have been developed to deal with injuries.However,traditional medical dressings(such as gauze)have some defects in protecting wounds and promoting wound recovery.Single hydrogel dressings also have some shortcomings such as poor mechanical properties and inability to resist microorganisms.The hydrogels based on polyvinyl alcohol(PVA)has good biocompatibility,non-toxicity and can provide a moist recovery environment for the wound.And the composite hydrogels can obtain good comprehensive properties by adding other materials to solve these problems.Under this background,the new composite hydrogels with non-toxic,antibacterial,good mechanical properties and ideal water vapor transmission rate(WVTR)were prepared by using PVA and other materials in this paper.The research of this paper can be divided into the following three parts:1.Polyvinyl alcohol/chitosan-cerium(PVA/Cs-Ce)composite hydrogels were prepared by cyclic freeze-thaw method and characterized by infrared spectroscopy(FTIR),X-ray diffraction(XRD)and scanning electron microscope(SEM).In addition,the effects of chitosan-cerium(Cs-Ce)complexes with different contents on the mechanical properties,WVTR,swelling ratio and thermal stability were also investigated.The SEM images indicated that the composite hydrogels had a good three-dimensional pore structure.Compared with the pure PVA hydrogel,the composite hydrogels showed better swelling property by adding Cs-Ce complexes.The elongation at break of the composite hydrogel with a ratio of 5:3(PVA:CS-Ce,solution volume ratio)was the highest value of 567%.In the bacteriostatic circle experiment,PVA/Cs-Ce composite hydrogels exhibited a pronounced inhibitory effect against two bacteria(Staphylococcus aureus and Escherichia coli).2.PVA/CNF composite hydrogels were prepared by using PVA as the main material and adding nano-cellulose(CNF,cellulose nanofibers).The micro-morphology of CNF and composite hydrogels was observed.Its composition and structure were analyzed by infrared spectrometer(FTIR)and X-ray diffraction(XRD).The gel fraction,water content,mechanical properties,swelling ratio,WVTR and thermal stability of the composite hydrogels were tested.The results showed that PVA/CNF composite hydrogels had good pore characteristics and mechanical properties.And the WVTR of hydrogels decreased obviously with the addition of CNF.The four composite hydrogels with CNF were in the ideal WVTR range(2000-2500g/m~2·day).3.On the basis of the above research,PVA/Cs-Ce/CNF composite hydrogels were prepared and analyzed by changing the ratio of raw materials and the number of freeze-thaw cycles.The structure and thermal stability of composite hydrogels were analyzed by scanning electron microscope(SEM),X-ray diffraction(XRD)and thermogravimetric(TG).Based on the requirements of medical dressings,its physical and chemical properties,including gel fraction,water content,WVTR,swelling ratio and mechanical properties,were tested and analyzed.Its stickiness,including shear bond strength,adhesive strength and skin following,were tested and analyzed.And its biomedical aspects,including cytotoxicity and antibacterial ability,were tested and analyzed.The results showed that the three-dimensional structure of PVA/Cs-Ce/CNF composite hydrogels was good.Different CNF ratio had great influence on the WVTR of hydrogels.And different freeze-thaw cycles had great influence on the cross-linking degree of hydrogel.Among them,the two hydrogels with 1:7.5%:0.5%(PVA:Cs-Ce:CNF,mass ratio)(numbered A0.5,3 freeze-thaw cycles)and 1:7.5%:1%(PVA:Cs-Ce:CNF,mass ratio)(numbered A1,3 freeze-thaw cycles)showed good comprehensive properties.The tensile strength of A0.5 and A1 were 132.6 Kpa and 130.1 Kpa,respectively.And the elongation at break of them were more than 400%.WVTR of them were in the ideal range and they had good skin stickiness.The results of cytotoxicity showed that they were non-toxic.And they had an obvious inhibitory effect on Escherichia coli and Staphylococcus aureus.