Studies On Sol-Gel Based Glucose Biosensors And Carbon Nanotube-Modified Electrodes

Objective: To develop a new design of amperometric glucose biosensors based on the enzyme immobilization onto an electrochemically platinized carbon paste matrix modified with sol-gel, and examine the unique electroanalytical performance of the prepared biosensor.To fabricate the multi-wall carbon nanotube (MWCNT) modified electrode and study the electrochemical behaviors of nifedipine (NIF) and Sudan I and their determinations at the MWCNT modified electrode.Methods: The new amperometric glucose biosensor was prepared by immobilizing the glucose oxidase (GOD) onto the electrochemically platinized carbon paste followed by modification with silicon sol-gel. Amperometric detection was conducted to examine the electrochemical responses of glucose substrate at the developed glucose biosensor.A combination of three commonly used voltammetric techniques, namely cyclic voltammetry (CV), differential pulse voltammetry (DPV) and linear sweep voltammetry (LSV) was employed to determine the electrochemical behaviors of NIF and Sudan I at the MWCNT modified electrode, thus developing a new electroanalytical method for the analytes.Results: The unique voltammetric profile was shown for the developed glucose biosensor, suggesting that it allowed ameperometric detection with a reduction mode at low potentials around 0V. Cathodic currents were induced upon successive additions of glucose at the operating potential of 0V (vs. Ag/AgCl), presenting a well defined linearity for the concentration dependence. The biosensor also showed good selectivity due to the elimination of interferences from endogenous species and long-term stability in that about 90% of original activity was retained following 45-day storage of the biosensor.The reduction peak current of NIF was enhanced significantly at the MWCNT modified glassy carbon electrode (GCE), in contrast to that at the bare GCE. Under the optimized experimental conditions, the reduction peak current varied linearly with the concentration of NIF over the range from 7.5×10-8 to 2.5×10-5 mol·L-1 with a detection limit of 2.5×10-8 mol·L-1. The relative standard deviation (RSD) for 1.0×10-6 mol·L-1 NIF is approximately 4.6% (n=10).Sudan I yielded a well-defined and sensitive reduction peak at the MWCNT modified electrode in 0.1 mol·L-1 phosphate buffer solution (PBS, pH 7.0). Under the optimized experimental conditions, the reduction peak current varied linearly with the concentration of Sudan I over the range from 6.0×10-7 to 7.5×10-5 mol·L-1 with a detection limit of 2.0×10-7 mol·L-1. RSD for 2.0×10-5 mol·L-1 Sudan I is approximately 4.8% (n=10).Conclusion: Our developed glucose biosensor can be used for monitoring the glucose concentration in biological fluids and other applications in biotechnological areas.The MWCNT modified GCE exhibits catalytic activity to the reduction of NIF and Sudan I. The proposed method is simple, rapid and sensitive, and can be used for the determination of NIF in pharmaceutical formulations and Sudan I in chili powder.