A signal-off sandwich photoelectrochemical immunosensor using TiO2 coupled with CdS as the photoactive matrix and copper (II) ion as inhibitor

摘要

In this work, a novel sandwich photoelectrochemical (PEC) biosensor was developed based on a signal-off strategy using TiO2 coupled with CdS quantum dots (QDs) as the photoactive matrix and copper (II) ion (Cu2+) as inhibitor. TiO2/CdS modified indium tin oxide (ITO) electrode was employed for primary antibody (Ab(1)) immobilization and the subsequent sandwich-type antibody-antigen (Ab-Ag) affinity interactions. Flower-like copper oxide (CuO) was used as labels of secondary antibody (Ab(2)) and immobilized on the modified electrode via specific affinity interactions between Ab(2) and Ag. Cu-2 was released by dissolving CuO with HCl, and then reacted with CdS to form CuxS (x = 1, 2), which would create new energy levels for electron-hole recombination and resulted in a decrease of the photocurrent. CuO, as the labels of Ab(2), was first applied in PEC biosensor based on the signal-off strategy of the Cu2+ for CdS. Greatly enhanced sensitivity was achieved through the coupling of CdS QDs with TiO2. Besides, the introduction of polythiophene (PT-Cl) on the surface of TiO2 made the PEC signal more stable. Under 405 nm irradiation at 0.1 V. the PEC biosensor for H-IgG determination exhibited a linear range from 0.1 pg mL(-1) to 100 ng mL(-1) with a low detection limit of 0.03 pg mL(-1). The proposed biosensor showed high sensitivity, stability and selectivity, which opens up a new promising signal-off PEC platform for future bioassay. (C) 2014 Elsevier B.V. All rights reserved.