A novel carboxymethylcellulose-gelatin-titanium dioxide-superoxide dismutase biosensor; electrochemical properties of carboxymethylcellulose-gelatin-titanium dioxide-superoxide dismutase

摘要

A novel highly sensitive electrochemical carboxymethylcellulose-gelatin-TiO_2-superoxide dismutase biosensor for the determination of O_2?~? was developed. The biosensor exhibits high analytical performance with a wide linear range (1.5 nM to 2 mM), low detection limit (1.5 nM), high sensitivity and low response time (1.8 s). The electron transfer of superoxide dismutase was first accomplished at the carboxymethylcellulose-gelatin-Pt and carboxymethylcellulose-gelatin-TiO_2-Pt surface. The electron transfer between superoxide dismutase and the carboxymethylcellulose-gelatin-Pt wihout Fe(CN)_6~(4?/3?) and carboxymethylcellulose-gelatin-Pt, carboxymethylcellulose-gelatin-TiO_2-Pt with Fe(CN)_6~(4?/3?) is quasireversible with a formal potential of 200 mV, 207 mV, and 200 mVvs Ag|AgCl respectively. The anodic (ks_a) and cathodic (ks_c) electron transfer rate constants and the anodic (α_a) and cathodic (α_c) transfer coefficients were evaluated: ks_a=6.15 s~(-1), α_a=0.79, and ks_c=1.48 s~(-1) α_c=0.19 for carboxymethylcellulose-superoxide dismutase without Fe(CN)_6~(4?/3?), ks_a=6.77 s~(-1),α_a=0.87, and ks_c=1 s~(-1) α_c=0.13 for carboxymethylcellulose-superoxide dismutase with Fe(CN)_6 ~(4?/3?), ks_a=6.85 s~(-1), α_a=0.88, and ks_c=0.76 s~(-1) α_c=0.1 carboxymethylcellulose-gelatin-TiO2-superoxide dismutase. The electron transfer rate between superoxide dismutase and the Pt electrode is remarkably enhanced due to immobilizing superoxide dismutase in carboxymethylcellulose-gelatin and TiO_2 nanoparticles tend to act like nanoscale electrodes.