RESUMO
A novel oxidase enzyme sensor was fabricated based on the chemisorption of highly active glucose oxidase (GOx) on gold nanoparticles that were adsorbed on a polytyramine layer (AuNPs/Pty). The GOx/AuNPs/Pty assembly was coated on a Prussian blue (PB)-modified screen-printed carbon electrode (SPCE) to produce the GOx/AuNPs/Pty/PB/SPCE biosensor. The amperometric glucose biosensor response was measured at -0.10 V using a Ag pseudo-reference electrode through the reduction current of the PB mediator in a flow injection analysis system. Under optimised experimental conditions, the developed biosensor displayed linearity over the 1.0 µM-1.0 mM glucose concentration range and a limit of detection of 1.0 µM (S/N ≥ 3). A low value for the Michaelis constant of 0.21 mM indicated that the immobilised GOx had high affinity for glucose. The developed biosensor exhibited excellent operational stability over 374 injections, long-term stability over 3 weeks, good reproducibility (relative standard deviations = 1.9%-4.3%) and high selectivity. The results obtained analysing glucose in blood plasma samples were satisfactory when compared with the corresponding results recorded implementing the standard hexokinase-spectrophotometric method (P > 0.05).
