Enzyme-less electrochemical displacement heterogeneous immunosensor for diclofenac detection
2017
Nguyen, T.T.K. | Vu, T.T. | Anquetin, G. | Tran, H.V. | Reisberg, S. | Noël, V. | Mattana, G. | Nguyen, Q.V. | Dai Lam, Tran | Pham, M.C. | Piro, B.
We describe an electrochemical immunosensor based on functionalization of a working electrode by electrografting two functional diazonium salts. The first one is a molecular probe, diclofenac, coupled with an arylamine onto which a specific antibody is immobilized by affinity interactions; the second is a redox probe (a quinone) also coupled with an arylamine, able to transduce the hapten-antibody association into a change in electroactivity. The steric hindrance induced by the antibody leads to a current decrease upon binding of the antibody on the grafted molecular probe; conversely, when diclofenac is present in solution, a displacement equilibrium occurs between the target diffusing into the solution and the grafted probe. This leads to dissociation of the antibody from the electrode surface, event which is transduced into a current increase (“signal-on” detection). The detection limit is ca. 20 fM, corresponding to 6pgL⁻¹ diclofenac, which is competitive compared to other label-free immunosensors. We demonstrate that the sensor is selective and is able to quantify diclofenac in tap water.
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