Preparation And Antibacterial Activity Of Polyvinyl Alcohol/chitosan Hydrogel Induced By Lignin Nanoparticles

Polyvinyl alcohol/chitosan(PVA/Ch)mixture gel has been used in controlled release of drugs,tissue engineering and new materials engineering due to its low toxicity and good biocompatibility.Lignin is a kind of natural polymer with abundant resources.Nanoscale lignin particles(LNP)have been proved to have inherent antibacterial and antioxidant properties.In this thesis,a series of PVA/Ch hydrogels containing LNPs were synthesized through freeze-thaw cycling method.The effect of different contents of LNPs on the microstructure of the mixture hydrogel was investigated.The effects of swelling properties,thermodynamic properties,and antibacterial properties of the mixture hydrogels were also studied,which provides a strong basis for the development of new types of nano-biomaterials.The detail of the studies are as follows:1.Three kinds of PVA/Ch hydrogels were prepared by freeze-thaw cycle method in which the ratios of polyvinyl alcohol and chitosan are 3:7,5:5,and 7:3.The swelling properties of the composite gel were tested and the effect of freeze-thaw cycle times on the swelling rate of composite gels was studied.Results shown that the PVA/Ch hydrogels have formed interpenetrating network structures and have better swelling performance,which lays a foundation for the application in the field of biomedicine.The swelling rate of the PVA / Ch cross-cutting network decreases while the PVA content gradually decreases with the increase of the freeze-thaw cycles.In terms of overall performance,the best freeze-thaw cycles is 3 times.2.PVA/Ch hydrogels containing 1 wt% and 3 wt% of LNPs were successfully prepared by applying a freezing-thaw procedure.It was observed that the hydrogels show better uniformity and higher porosity(pores with diameters about 10-20μm)in the presence of LNPs,which facilitated the accessibility of water into the amorphous regions of the hydrogels.The results demonstrated that hydrogels with 1 wt% of LNPs could efficiently enhance both the thermal and mechanical properties of PVA/Ch hydrogels due to the strong interactions between PVA/Ch and LNPs while in the case of3 wt% LNPs the PVA/Ch-LNPs interactions were limited by some agglomerates.The swelling studies reveal that the strong interactions between PVA/Ch molecules and LNPs prevent the PVA molecules from dissolving into the water and promoting the crosslinking effect.Moreover,LNPs which served as release agents in synergism with Ch in the PVA/Ch were proved to be efficient in terms of antioxidative response.3.Antibacterial activity tests shown that chitosan and LNPs components in the hydrogels were both effective against E.coli and S.aureus bacteria strain.The increased concentration of LNPs in PVA/Ch/3LNP blend reduced bacterial viability.It suggested that PVA/Ch hydrogels incorporating LNPs have application prospects in biomedical and packaging sectors.