Multilayered construction of glucose oxidase and silica nanoparticles on Au electrodes based on layer-by-layer covalent attachment

A feasible approach to construct multilayer films of aminated silica nanoparticles/glucose oxidase (ASNPs/GOx) on the Au electrode surface using a glutaraldehyde as a covalent attachment cross-linker is described. The covalent attachment processes were followed and confirmed by electrochemical impedance spectroscopy (EIS), which demonstrated that the ASNPs/GOx multilayer films are formed in a progressive and uniform manner. The gold electrodes modified with the ASNPs/GOx multilayer films were studied by cyclic voltammetry (CV) and showed excellent electrocatalytical response to the oxidation of glucose when ferrocenemethanol was used as an artificial redox mediator. From the analysis of voltammetric signals, the coverage of active enzyme on the electrode was estimated, which showed a linear relationship with the number of ASNPs/GOx bilayers. This suggests that the analytical performance such as sensitivity, detection limit is tunable by controlling the number of attached bilayers. The linear response range of the biosensor constructed with four bilayers of ASNPs/GOx to the concentration of glucose can extend at least to 8 mm and reached 95% of the steady-state current in less than 4 s with the sensitivity of 5.11 μA/mm cm2 and the detection limit of 9 μm. In addition, the sensor exhibited good stability and long-term life.