A new approach for nitrite determination based on a HRP/catalase biosensor

In this paper, a new concept of enzyme inhibition-based biosensor involving a two enzyme system was developed. The latter displays a signal increase instead of a decrease in the presence of an inhibitor. HRP and catalase were thus separately entrapped into Layered Double Hydroxides (LDH), an anionic clay, as a host matrix. The inner layer was constituted of HRP electrically wired by [Zn2CrABTS] LDH and the outer layer contained catalase immobilized in [Zn3AlCl] LDH. Both enzymes catalyzed the decomposition of H2O2, HRP its reduction and catalase its breakdown into oxygen and water. Nitrite was selected as a specific inhibitor of catalase. In the presence of H2O2, the nitrite addition blocked the H2O2 consumption by catalase, inducing thus an increase in the amperometric signal of the H2O2 reduction at 0 V by the wired HRP. The optimum configuration of the bi-enzyme biosensor displayed in aerated aqueous solutions, a nitrite sensitivity of 102 μA M− 1· cm− 2 with a fast response time, the detective limit being 4 μM.