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Yongping Luo, Guoqi Hu, Zhen Wang, Chunyuan Liu, Yang Tian
Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092, China
Abstract
A biomimetic sensor for superoxide ion (O2−) has been developed by immobilization of the synthesized Mn–TPAA (TPAA = tris[2–[N–(2–pyridylmethyl) amino] ethyl] amine) on TiO2 nanoneedles surface, with high sensitivity and selectivity, and long-term stability. Direct electron transfer of Mn–TPAA has been realized with a formal redox potential (E0’) falling in the range of the E0’ values of the redox couples O2/O2− and O2−/H2O2. Meanwhile, Mn–TPAA immobilized on the TiO2 films shows an excellent biomimetic catalytic activity like superoxide dismutase (SOD) toward O2− by thermodynamically mediating both the oxidation of O2− to O2 and the reduction of O2− to H2O2. Thus, the present biomimetic sensor for O2− not only possesses high selectivity at a lower working potential of 0 V vs. Ag|AgCl, but also exhibits a fast amperometric response to O2− within 6 s and a good linear response over a wide range of concentration from 10−7 M to 10−4 M. By utilizing the facile, inexpensive and reliable fabrication strategy and the excellent electro-active of biomimetic SOD, we have realized the real–time monitoring of O2− concentration released from living cells and further investigated the relationship between the concentration changes of O2− and intracelluar Ca2+, which may gain additional insights on the reactive oxygen species (ROS) signal transduction and other physiological and pathological events. The sensing platform should hold a great potential for the construction of selective and long-term stable biosensors based on a wide variety of biomimetic enzymes.
