Preparation And Antibacterial Properties Of Wter-Soluble Curdlan Quaternary Ammonium Salt And Its Gel

Diseases caused by microbial infections have caused great harm to human health.Moreover,the resistance of microorganisms to antibiotics is gradually increasing,which makes the prevention and treatment of related diseases increasingly difficult.Therefore,it is an urgent and meaningful research topic to develop highly effective and safe non-antibiotic antimicrobial materials.In this thesis,the two kinds of water-soluble quaternized curdlan,Cur-NH-Bet and Cur-Lys-Bet,have been synthesized by amidation and cycloaddition form the main raw materials of lysine and betaine.Then,the structure and thermal stability of the compounds were determined by means of ¹H-NMR,¹³C-NMR,FT-IR,GPC,XRD,SEM and TGA.Moreover,the analysis concluded that the modification did not change the basic skeleton structure of curdlan,and only part of the crystallinity was destroyed.The symmetry and thermal stability of curdlan's derivatives are slightly reduced and can be completely dissolved in water.At the same time,the toxicity of Cur-NH-Bet and Cur-Lys-Bet to HEK293T cells was tested by MTT assay.The result showed that the cytotoxicities of Cur-NH-Bet and Cur-Lys-Bet were significantly lower than that of the unquaternized aminated curdlan.Finally,we tested the bactericidal properties of Cur-NH-Bet and Cur-Lys-Bet by plate counting method systematically.It was concluded that the minimum bactericidal rates of Cur-NH-Bet and Cur-Lys-Bet for S.aureus were 100%and 97.83%at a bacterial concentration of 10⁵ CFU/mL,while the highest bactericidal rate for E.coli was only99.8%and 95.5%.Obviously,the bactericidal effect of Cur-Lys-Bet is significantly higher than that of Cur-NH-Bet,which has better bactericidal effect on S.aureus than E.coil.In addition,the gels of Cur-Lys-Bet-Alg and Cur-NH-Bet-Alg with antibacterial activity were obtained by crosslinking method with glutaraldehyde.Cur-Lys-Bet-Alg has a bactericidal rate of 100%for S.aureus and E.coil,when the concentration of the bacterium was 10⁵ CFU/mL;the highest bactericidal rate of Cur-NH-Bet-Alg for S.aureus and E.coil was only 86.37%and 89.00%.In summary,the two novel and effective antibacterial compounds of quaternary ammonium salts curdlan were obtained in the thesis,which provides a useful reference for the development of non-antibiotic antibacterial materials,and the research results is important for the development of safe and efficient new antibacterial agents.