壳聚糖-g-N-羧甲基-二(2-苯并咪唑)-1,2-乙二醇和纳米金溶胶复合物固定漆酶修饰玻碳电极的直接电化学

Direct Electrochemistry of Glassy Carbon Electrode Modified by Complex of Nanogold Sol and Chitosang-N-Carboxymethyl-Bi(2-Benzoimidazole)1,2-Ethandiol with Laccase Entrapped

制备了壳聚糖-g-N-羧甲基-二(2-苯并咪唑)-1,2-乙二醇(CTS-g-N-CBBIE),将其与纯化的纳米金溶胶(NGS)共混得到CTS-g-N-CBBIE-NGS复合物。以此复合物作为固酶载体固定云芝漆酶,固酶量大(31.10 mg/g),固酶比活力高(1.43 U/mg);此固酶复合物修饰的玻碳电极在无氧磷酸盐-柠檬酸盐缓冲溶液(pH=5.0)中可以实现无中介酶-电极直接电子迁移(一对准可逆氧化还原峰式电位576 mV(vs.Ag/AgCl)对应于漆酶活性中心T1位的氧化还原),电子迁移速率常数为228.3 s-1。当氧气浓度较小时,这种固酶修饰电极对氧气还原具有一定的生物电催化性能(空气饱和缓冲溶液中氧还原峰电位约为320 mV(vs.Ag/AgCl))。当氧气浓度增高后,氧还原反应受到抑制;但这种漆酶修饰电极对pH较为敏感,且稳定性和重复使用性欠佳。

Chitosan-g-N-carboxymethyl-bi （2-benzoimidazole） -1,2-ethandiol （CTS-g-N-CBBIE） was synthesized through grafting on the side chain of chitosan with 2-bromoacetic acid, chitosan, bi （2-benzoimidazole）-1,2- ethandiol, chloroauric acid and sodium citrate as raw materials. Compsosite of CTS-g-N-CBBIE-NGS was obtained by means of intermixing purified nanogold sol （NGS） and CTS-g-N-CBBIE. The composite was adopted to act as the carrier of immobilized laccase from Trametes versicolor mainly by means of physical entrapment. The laccase-entrapped CTS-g-N-CBBIE-NGS composite with superiority of high laccase-loading （31.10 mg/g） and specific activity of immobilized enzyme （1.43 U/mg） was used to modify the glassy carbon electrode（GCE）. Results from experiments conducted on this laccase modified glassy carbon electrode showed mediatorless direct electron transfer occurred between active site of laccase and laccase modified electrode in deaerated phosphate-citrate buffer solution （pH = 5.0 ） （formal potential of quasi-reversible redox peaks corresponding to the T1 site copper ion in the laccase ： 576 mV （ vs. AgCl/Ag） ）. Rate constant of electron transfer：228.3 s-1 was derived from relationship of separation of redox peaks and logarithm of scan rates. Laccase-entrapped matrix modified GCE also displayed bioelectrocatalytic effect on oxygen reduction reaction to some extent under low oxygen concentration （peak potential of laccase modified GCE for oxygen reduction reaction in air-saturated buffer solution at ca. 320 mV （vs. AgCl/Ag））. Oxygen reduction reaction was depressed when oxygen concentration increased. This laccase modified electrode was sensitive to variation of pH and its inferiority originated from undesirable usability and long-term stability. It is essential for higher bioelectrocatalytic function on oxygen reduction reaction of laccse modified electrode that constituent of composite to immobilize enzyme which was used to modify electrode must be optimized.