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

Abstract

A novel highly sensitive electrochemical carboxymethylcellulose–gelatin–TiO2–superoxide dismutase biosensor for the determination of O2•− was developed. The biosensor exhibits high analytical performance with a wide linear range (1.5nM to 2mM), low detection limit (1.5nM), high sensitivity and low response time (1.8s). The electron transfer of superoxide dismutase was first accomplished at the carboxymethylcellulose–gelatin–Pt and carboxymethylcellulose–gelatin–TiO2–Pt surface. The electron transfer between superoxide dismutase and the carboxymethylcellulose–gelatin–Pt wihout Fe(CN)64−/3− and carboxymethylcellulose–gelatin–Pt, carboxymethylcellulose–gelatin–TiO2–Pt with Fe(CN)64−/3− is quasireversible with a formal potential of 200mV, 207mV, and 200mV vs Ag|AgCl respectively. The anodic (ksa) and cathodic (ksc) electron transfer rate constants and the anodic (αa) and cathodic (αc) transfer coefficients were evaluated: ksa=6.15s−1, αa=0.79, and ksc=1.48s−1αc=0.19 for carboxymethylcellulose–superoxide dismutase without Fe(CN)64−/3−, ksa=6.77s−1, αa=0.87, and ksc=1s−1αc=0.13 for carboxymethylcellulose–superoxide dismutase with Fe(CN)64−/3−, ksa=6.85s−1, αa=0.88, and ksc=0.76s−1αc=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 TiO2 nanoparticles tend to act like nanoscale electrodes.