A NOVEL GLUCOSE BIOSENSOR BASED ON SILVER NANOPARTICLE (AgNP) STABILIZED WITH SODIUM TRIPOLYPHOSPHATE (NaTPP) CROSS-LINKED CHITOSAN: DIRECT ELECTRON TRANSFER AND ELECTROCATALYTIC ACTIVITY

Abstract

Abstract The development of non-enzymatic glucose biosensor has been the concern of many researchers mainly because enzymes based sensor despite having excellent sensitivity and selectivity, has the limitations such as poor stability, complicated enzyme immobilization, critical operating conditions such as optimum temperature and reproducibility, which hinder the sensor properties. The prevalence of renal problem globally justifies the need for the development of non-enzymatic glucose biosensor that can effectively and accurately detect glucose in any medium which can be very effective to the detection and treatment of diabetes mellitus. This study has developed a biocompatible non-enzymatic glucose biosensor, Direct electron transfer and electro-catalytic activity of non-enzymatic glucose biosensor based on silver nanoparticle (AgNPs) stabilized with sodium tripolyphosphate (NaTPP) cross-linked chitosan was studied. Silver nanoparticle was prepared and characterized by Fourier transform Infra-red spectroscopy (FTIR), X-ray diffractometry (XRD) and Scanning electron microscopy (SEM). The electro-catalytic activity of the synthesised AgNPs was investigated through potentiometric and amperometric techniques. The crystalline size of the AgNPs was revealed with XRD. The cubic face-centered structure of the synthesised silver nanoparticle was confirmed. This was supported by the observed sharp four diffraction peaks with peaks intense appearing at 2θ = 38.09°, 44.15°, 64.67°, and 77.54°. However, the SEM micrograph of the synthesised AgNPs revealed the spherical shape of AgNPs with a non-uniform granular shape attributed to bio-mediated ionic gelation process. The surface of the synthesised AgNPs has a spherical shape and slightly elongated with a big tendency to aggregate and form larger particle clusters. Whereas, FTIR spectra of AgNPs gave peaks at 1054 – 1645 cm-1 suggesting the presence of phosphonate linkages between ammonium, -NH3+ of chitosan and –PO32- moieties of NaTPP during cross linking process. The electro-catalytic oxidation of glucose at the electrode surface was examined and the mechanism involved in glucose oxidation was revealed. The silver nanoparticle modified glassy carbon electrode (AgNPGCE) showed a better electrochemical response towards glucose. This glucose sensor shows high sensitivity at +0.54 V. A low detection limit of 1.22 M taken the confident level to be 3, and wide linear range of 2 to 24 M with a correlation coefficient of 0.9987 were obtained. The calculated parameters revealed that AgNPs has shown better overall electrochemical performance with a response which is better than enzymatic biosensor. The fabricated AgNPs sensor shows comparable sensitivity (98%) of the initial value after it was kept in air for 8 days, demonstrating the very good sensitivity and durability of the glucose sensing. The good adhesion towards electrode and structural stability of AgNPs could be ascribed to long-term stability of AgNPs sensor. Based on these results, the AgNPGCE is a promising glucose biosensor candidate for excellent determination of glucose level in any medium.