Preparation Of Composite Materials Based On Quaternary Ammonium Chitosan And Research In Their Biological Properties

Chitosan,as the only natural alkaline polysaccharide with positive charge,has been widely used in biomedical engineering,food and industrial fields due to its excellent antibacterial activity,biocompatibility and biodegradability.However,chitosan with poor solubility,making it difficult to be directly used in various industrial fields.In this paper,chitosan was used as raw material to prepare chitosan-based composites with different solubility,and its biological properties were investigated.Firstly,chitosan was modified by N-substitution method in this paper.By grafting 2,3-epoxypropyl trimethylammonium chloride onto the molecular chain of chitosan,infrared spectrum analysis and solubility in water proved that the quaternary ammonium salt chitosan was successfully prepared and its solubility in water was improved significantly.The optimum concentration ratio of gelatin and water-soluble chitosan in the composite was obtained as 5:1.The surface morphology of the composites was observed by Atomic Force Microscope(AFM).T-4 viscometer was used to measure the viscosity of composite materials,the viscosity showed the highest at the best concentration,at the same proportion,the compound exhibited the best preservation effect of fresh cherries at 24?,the gloss and hardness in seven days remain the same,the o utter skin also had no obvious shrinkage and moldy phenomenon even at the 16th day,which demonstrated the quaternary ammonium of water-soluble chitosan had nice moisture retention and was suitable for storage;In addition,at the same ratio,turbidimetric method was used to detect the highest inhibition rate of the composite against Escherichia coli and Staphylococcus aureus(57%and 93%,respectively),but the inhibition effect was different for different species.In comparison,the composite could inhibit the growth of gram-positive bacteria more effectively.Secondly,on the basis of water-soluble chitosan,difluoromethane sulfoimide lithium was added in this research to complete ion exchange,and the product was characterized by nuclear magnetic hydrogen spectrum.It was proved that alcohol-soluble chitosan was prepared through Energy Dispersion Spectrum(EDS),and solubility in methanol showed that its favorable solubility in some organic reagents,such as absolute ethyl alcohol and dimethyl sulfoxide.By screening the concentration ratio of tannic acid and alcohol soluble chitosan composite material,it was found that when the mass ratio of tannic acid and alcohol soluble chitosan composite material was 1:3,its comprehensive performance was the best,and the tablet counting method showed the best inhibitory effect on Staphylococcus aureus,up to 75%.The results of scanning electron microscopy(SEM)showed that when the mass ratio of tannic acid to alcohol soluble chitosan was 1:3,the dense micropore structure appeared,which significantly increased the specific surface area of the material.In addition,hemolysis test results showed that hemolysis was generally lower(<5%),and the hemolysis of the composites containing chitosan all reached the national standard.Thermogravimetric analyzer was used to analyze the thermal stability of the composites.It was found that the thermal stability of the composites decreased with the increase of tannic acid content.