Development of glucose biosensor using ferrocene containing carbon nanotubes modified glassy carbon electrode

The works presented solve of leakage of ferrocene (Fc) which is a mediator in glucose biosensor from the biosensor, making the performance of the biosensor poorly. This work presented two immobilization methods of ferrocene onto the biosensor 1) ferrocene immobilized onto the NH2-functionalized multiwall carbon nanotubes and 2) ferrocene immobilized onto chitosan. This work consists of two methods for the construction of novel amperometric glucose biosensors. The first method is based onglucose oxidase (GOx) entrapped on composite of ferrocene covalently bound onto the NH2-functionalized multiwall carbon nanotubes (CNTs-NH2-Fc) and ferrocene bound chitosan (CS-Fc) to prevent ferrocene leakage from the matrix and retain its activity as an electron mediator before being coated on a glassy carbon (GC) electrode. The developed glucose biosensor (GC/CNTs-NH2-Fc/CS-Fc/GOx) was applied in a flow injection analysis system for amperometric detection of glucose using a solution of 0.1 M phosphate buffer (pH 7.0) as a carrier and applying a potential of 0.3 V. The proposed glucose biosensor exhibits linear calibration over the range of 2-80 mM of glucose with a slope of 5.0 nA/nM and a correlation coefficient of 0.997. The limit of detection, based on a signal-to-noise ratio (S/N=3) of three, was 1.86 mM. The developed biosensor also provides good precision (% RSD=3.6) for glucose signal (10 mM, n=10) with rapid sample throughput (42 samples/h). The second method, the biosensor was developed based on ferrocene (Fe) covalently bound onto the NH2-functionalized multiwall carbon nanotubes (CNTs-NH2) to prevent ferrocene leakage from the matrix and retain its activity as an electron mediator. Glucose oxidase (GOx) was immobilized to ferrocene-modified NH2-functionalized mutiwalled carbon nanotubes and bovine serum albumin (CNTs-NH2-Fc -BSA) composite film by using glutaraldehyde (Glu) before being coated on a glassy carbon (GC) electrode. The developed glucose biosensor (GC/CNTs-NH2-Fc-BSA-GOx) was applied in a flow injection analysis system for amperometric detection of glucose using solution of 0.1 M phosphate buffer (pH 7.0) as a carrier and applying a potential of 0.6 V. The proposed glucose biosensor exhibits linear calibration over the range of 2-16 mM of glucose with a slope of 323 nA/nM and a correlation coefficient of 0.999. The limit of detection, based on a signal-to-noise ratio (S/N=3) of three, was 0.65 mM. The developed biosensor also provides good precision (%RSD=1.9) for glucose signal (2 mM, n=7) with rapid sample throughput (72 samples/h). Both fabrication methods of amperometric glucose biosensors exhibited good reproducibility, sensitivity, selectivity, stability, fast response time and ease of preparation and low cost.