Ni(OH)2 versus Ni/Al layered double hydroxides as matrices to immobilize glucose oxidase

Ni hydroxide and Ni/Al layered double hydroxide (LDH) were electrochemically deposited on Pt electrodes in the presence of glucose oxidase in the electrolytic solution, in order to verify if the performances of the two biosensors were dependent on the Ni content of the inorganic matrix used to entrap the enzyme. The comparative study was conducted by recording the current response due to the oxidation of H₂O₂, produced enzymatically after glucose additions, at +0.45 V versus SCE, pH 7.0 and T = 25 °C.A higher sensitivity and a narrower linearity range were observed for nickel hydroxide based biosensor (up to 5 mM against 15 mM exhibited when LDH was the immobilizing matrix). These results suggested that the amount of the enzyme entrapped on the electrode surface was higher when the matrix was Ni(OH)₂ and they were confirmed by EQCM measurements. On the contrary, the selectivity displayed by the two biosensors in the presence of interfering compounds, such as acetaminophen, citric, uric and ascorbic acids, was almost the same.