Using PbS–Au heterodimers as signal quencher for the sensitive photoelectrochemical immunoassay of amyloid β-protein

Abstract

By using PbS–Au heterodimers as the signal quencher, TiO2/BiOI as matrix, a novel sandwich-type photoeletrochemical (PEC) biosensor for sensitive determination of amyloid β-protein (Aβ, ∼4 KDa) was developed. BiOI was attached to the surface of TiO2 and formed a heterogeneous structure (p-n junction), which enlarged the light harvest range and enhanced the electron transfer rate of TiO2. In order to quench the PEC signal, PbS–Au heterodimers were used as the labels to combine with Aβ. Owing to the competitively light energy harvesting and electron donor consuming effect of PbS–Au heterodimers, less light energy and electron donor arrived at TiO2/BiOI. In addition, Au directly contacted with PbS could enhance the electron seperation and transfer rate, and lead to improved competitiveness consumption of the electron donor. PbS–Au integrated with secondary antibodies formed PbS–Au-Ab2 bioconjugate, which would further obstruct the electron transfer and impede the interreaction between electron donor and photoelectrode surfaces. Owing to the unique PbS–Au heterodimer structure and the quenching effect of PbS–Au-Ab2 bioconjugate, the fabricated immunosensor for Aβ detection exhibited good stability, high sensitivity, and a low detection limit of 0.028 pg/mL (S/N = 3).