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A biosensing platform based on horseradish peroxidase immobilized onto chitosan-wrapped single-walled carbon nanotubes
Authors:Huijun Jiang  Chong Du  Zhiqing Zou  Xiaowei Li  Daniel L Akins  Hui Yang
Institution:(1) Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai, 200050, People’s Republic of China;(2) School of Pharmacy, Nanjing Medical University, Nanjing, 210029, People’s Republic of China;(3) CASI and Department of Chemistry, The City College of The City University of New York, New York, NY 10031, USA
Abstract:One-step, diameter-selective dispersion of single-walled carbon nanotubes (SWCNTs) has been accomplished through noncovalent complexation of the nanotubes with a water-soluble, biocompatible polymer chitosan at room temperature. Such chitosan-wrapped individual SWCNTs can be used for the immobilization of horseradish peroxidase (HRP) and be used to construct an electrode for direct bioelectrochemical sensing without an electron mediator. The direct electron transfer between HRP and the electrode surface was observed with a formal potential of approximately −0.35 V (vs. saturated calomel electrode) in phosphate buffer solution and the calculated heterogeneous electron transfer rate constant is approximately 23.5 s−1. Experimental results indicate that the immobilized HRP retains its catalytic activity for the reduction of nitric oxide. Such an HRP–SWCNT–chitosan-based biosensor exhibited a rapid response time of less than 6 s and a good linear detection range for nitrite concentration, from 25 to 300 μM with a detection limit of 3 μM. The apparent Michaelis–Menten constant (K m) and the maximum electrode sensitivity (imax/K m) are found to be 7.0 mM and 0.16 μA mM−1, respectively. Both the unique electrical properties of SWCNTs and biocompatibility of chitosan enable the construction of an excellent biosensing platform for improved electrocatalysis of HRP, allowing, specifically, the detection of trace levels of nitric oxide.
Keywords:Single-walled carbon nanotubes  Horseradish peroxidase  Chitosan  Direct electrochemistry  Biosensor
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