聚芳酰胺-多壁碳纳米管混合物固定漆酶电极的电化学行为

Poly Aryl Amide and Multiwalled Carbon Nanotube Composite Supported Laccase Electrode and Its Electrochemical Behavior

以聚芳酰胺-多壁碳纳米管混合物为载体,利用漆酶表面氨基与聚芳酰胺主链端羧基的共价偶联以及碳纳米管与漆酶间的疏水作用,构筑了具有较高稳定性和电催化活性的漆酶修饰电极.并对该固酶修饰电极的固酶量、酶活力、电化学行为及其电催化氧还原的性能进行了表征.对漆酶分子具有亲和力的聚芳酰胺芳环结构及聚芳酰胺端羧基与漆酶表面氨基的共价偶联避免了漆酶的脱落和变性.而碳纳米管与聚芳酰胺的混合使得该三维修饰电极具有良好的电子导电性,并成功地实现了漆酶的氧化还原活性位与电极之间的直接电荷转移,这一点可由在0.73和0.38V附近观察到漆酶的T1和T2(漆酶的T1,T2铜活性位的形式电位分别为0.78和0.39V(vsNHE))铜活性位的两对氧化还原峰确认.漆酶的担载量为56.0mg·g-1,具有电化学活性的漆酶占总担载漆酶量的68%.在pH=4.4磷酸盐缓冲溶液中,该修饰电极上氧气还原的起始电位为0.55V,其对氧气的米氏常数KM为55.8μmo·lL-1,对氧气的检测限为0.57μmo·lL-1.在4℃下保存两个月后能实现直接电荷转移的漆酶量仅下降了14%左右而氧还原超电势提高了约50mV.结果表明该修饰电极有望用作酶基生物燃料电池的阴极和电流型氧气传感器.

A novel strategy for the immobilization of laccase onto a glassy carbon electrode with high stability and electrocatalytic performance is presented. Laccase is attached to a matrix of mixed poly aryl amide （PAA） and multiwalled carbon nanotubes （MWCNTs） （denoted Lac/PAA-MWCNTs/GCE） by covalently bonding the surface amine group of laccase to the terminal carboxyl group of PAA and hydrophobic-hydrophobic interaction between MWCNTs and the laccase. The PAA backbone avoids the detachment and denaturing of the laccase, and the intermixed MWCNTs provide high electronic conductivity. The loading of laccase is 56.0 mg·g-1 and more than 68% shows electrochemical activity. The electrode delivers direct electron transfer between the redox center of the laccase and the electrode with two pairs of redox peaks at 0.73 and 0.38 V, which is close to the formal potential of the T1 and T2 Cu-sites （0.78 and 0.39 V （vs NHE））, respectively. The onset potential for O2 reduction reaction （ORR） is ca 0.55 V in a phosphate buffer solution （pH=4.4）. The Michaelis constant （KM） of the Lac/PAA-MWCNTs/GEs for O2 is 55.8 μmol·L-1 and the detection limit of oxygen reaches 0.57 μmol·L-1. After 2 months of storage at 4 ℃ the ORR activity of the Lac/PAA-MWCNTs/GC electrode retains ca 86% of its initial values and the peak potential of the ORR shifts negatively by ca 50 mV. Given the excellent catalytic performance towards ORR and its high stability this strategy will be widely applicable to the development of an enzyme-based cathode for biofuel cells and amperometric biosensors for oxygen.