明胶-壳聚糖共混材料的酪氨酸酶修饰研究

Preparation of Tyrosinase-modified Gelatin-chitosan Blend Material

开展了明胶-壳聚糖共混材料的酪氨酸酶修饰研究,该材料是一种全部由天然高分子构建及修饰的生物材料,即采用蛋白质与生物多糖作为本体材料,采用生物酶作为修饰剂。流变性能测试和凝胶形成实验表明,酪氨酸酶能够催化明胶与壳聚糖进行反应,并使明胶与壳聚糖共混溶液形成凝胶;拉伸测试结果显示,经过酪氨酸酶修饰的明胶-壳聚糖生物材料的拉伸强度比未修饰材料提高了50.22%。此外,与纯明胶材料相比,该生物材料显示出了更好的细菌抑制作用,其对大肠杆菌和金黄色葡萄球菌的抑制率分别提高了40.56%和31.13%。

An enzymatic modification method was used for preparing the conjugated gelatin-chitosan biomaterial which wholly consists of biopolymers,that is,gelatin and chitosan blend was employed as the protein and polysaccharide matrix,and tyrosinase was employed as the enzymatic modifier.Tyrosinase can catalyze the oxidation of tyrosine residues of gelatin in the presence of oxygen to generate o-quinone residues.The o-quinone residues can react with the nucleophilic—NH2 groups of chitosan to form covalent junctions between gelatin and chitosan.Rheological measurements and vial inversion tests both confirm that the gel formation and the covalent junctions of gelatin and chitosan blend can be triggered by tyrosinase.The tensile tests show that the tensile strength of enzymatically modified gelatin-chitosan film increases by 50.22%compared to unmodified gelatin/chitosan film.Owing to the formation of covalent junctions,the enzymatically modified gelatin-chitosan film has better stability in aqueous medium,even in an acidic medium at a moderately high temperature.In addition,compared with unmodified gelatin,the tyrosinase-modified gelatin-chitosan shows a better inhibitory effect on bacteria and the inhibition rate of Escherichia coli and Staphylococcus aureus increased by 40.56%and 31.13%,respectively.