A novel horseradish peroxidase biosensor towards the detection of dopamine: a voltammetric study.

A polymerized film of glycine (Gly) was prepared on the surface of carbon paste electrode (CPE) through the cyclic voltammetry (CV) technique. A novel biosensor for the determination of dopamine (DA) has been constructed based on horseradish peroxidase (HRP) and multiwalled carbon nanotubes (MWCNTs) immobilizing on Poly (Gly)/CPE through silica sol-gel (SiSG) entrapment. CV measurements were employed in order to understand the feasibility of poly (Gly) as an electron carrier between the immobilized peroxidase and the surface of CPE. By using differential pulse voltammetry (DPV) the calibration curves of DA was obtained in the range of 15-865 μM. The limit of detection (LOD) and limit of quantification (LOQ) of DA was found to be 6×10⁻⁷ M and 2×10⁻⁶ M respectively. The apparent Michaelis-Menten constant (Km(app)) was found to be 0.5 mM and illustrated that the good biological activity of the fixed enzyme. Electrochemical impedance spectroscopy (EIS) results confirmed the rapid electron transfer and also the immobilization of enzyme on the electrode surface. The biosensor showed high sensitivity, selectivity and reproducibility. This method has been used to determine DA in the presence of various interferences and in clinical preparations.