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

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).