Preparation And Antibacterial Property Of Photocurable ε-poly-l-lysine Hydrogel

As a natural antimicrobial polypeptide,epsilon-poly-l-lysine(EPL)can be converted into human essential amino acids and has broad-spectrum antibacterial property against both bacteria and fungi,therefore,EPL has been widely used in the food industry and biomedical domain.One of the hotspots in current research is transforming EPL into hydrogel.However,the application of EPL is limited by its lack of the ability of gel forming and poor mechanical strength.In view of the above problems,there is important significance to transform EPL into hydrogel and improve the mechanical property.In this work,a photocurable antibacterial hydrogel based on EPL was fabricated by grafting photosensitive groups onto EPL and complexing with tannic acid,which can be applied to antimicrobial dressing and tissue engineering.Firstly,the glycidyl methacrylate(GMA)was grafted onto EPL by one-step reaction,and then the modified EPLMA hydrogel material was obtained after dialysis and freeze-drying.The results of UV-Vis absorption spectra,~1H NMR spectra and FTIR spectra showed that the glycidyl methacrylate was successfully grafted onto EPL.The degree of substitution(DS)of EPLMA was obtained by calculating the integral area ratio of each functional group on the ~1H NMR spectrum,and DS was positively correlated with the ratio of reactants,reaching the maximum of 49.7%.The experimental results of EPLMA hydrogel show that with the increase of DS or concentration,the cross-linking network inside the hydrogel was denser,the swelling property was reduced,and the mechanical property was more stable.However,the antimicrobial experiment results of hydrogel indicated that the antimicrobial performance of EPLMA would be greatly weakened by grafting photosensitive groups.It has been widely accepted that the sterilizing effectiveness of EPL depends greatly on the protonated amino group of the side chain,and it decreased when the amino group was consumed during graft modification.In order to solve this problem,EPLMA hydrogel was used in combination with tannic acid(TA)to improve the antibacterial activity.TA,as a kind of natural polyphenol existing in plants and fruits,has been widely used as a crosslinking agent due to its abundant hydroxyl group.In addition,the additional bioactive functions such as antimicrobial,anti-inflammatory and antioxidant properties are endowed by the TA as an additive for the hydrogel.The EPLMA-TA hydrogel material was obtained by dipping EPLMA hydrogel into TA solution.It was proved that TA was successfully complexed into the hydrogel by structure characterization.With the increase of TA concentration,the mechanical property of the composite hydrogel was further improved,the compression modulus of EPLMA-TA hydrogels treated with 30wt%TA solution was 670 KPa.The results showed that 94.6%of Escherichia coli(E.coli)and 95.3%of Staphylococcus aureus(S.aureus)were killed by the EPLMA-TA hydrogel.The study on the biocompatibility of EPLMA-TA hydrogel showed that endothelial cells could proliferate and spread on the surface of hydrogel.Compared with the control group,the cell survival rate reached more than 80%,which proved that EPLMA-TA hydrogel had excellent biocompatibility.In summary,the photocurable antibacterial hydrogel material was successfully prepared by grafting photosensitive groups onto EPL and finally complexing with TA,which realized the light response efficiency,mechanical property and precise control of antibacterial property.The EPLMA-TA composite hydrogel can effectively inhibit bacterial infection,which has greatly expanded the application scope of EPL in biomedical field,especially in antimicrobial dressings.