Highly sensitive nitrite biosensor based on the electrical wiring of nitrite reductase by [ZnCr-AQS] LDH

A biosensor for amperometric determination of nitrite was developed using cytochrome c nitrite reductase (ccNiR) from Desulfovibrio desulfuricans immobilized and electrically connected on a glassy carbon electrode by entrapment into redox active [ZnCr-AQS] layered double hydroxide containing anthraquinone-2-sulfonate (AQS). The transduction step corresponded to the electro-enzymatic reduction of nitrite by immobilized AQS molecules at −0.6 V. The biosensor showed a fast response to nitrite (5 s) with a linear range between 0.015 and 2.35 μM, a sensitivity of 1.8 A M−1 cm−2 and a detection limit of 4 nM. The apparent Michaelis–Menten constant (KMapp) was 7.5 μM.