Label-free photoelectrochemical immunosensor for amyloid β-protein detection based on SnO₂/CdCO₃/CdS synthesized by...

In this study, we propose a SnO₂/CdCO₃/CdS-based label-free photoelectrochemical (PEC) immunosensor for the sensitive quantification of amyloid β-protein (Aβ) which plays a critical role in the early diagnosis of Alzheimer's disease. Under specific pH conditions, SnO₂/CdCO₃/CdS was first designed and successfully synthesized with simple one-pot method. The synthesis of SnO₂/CdCO₃/CdS circumvents the trouble of traditional composite materials to be gradually compounded, saving a lot of time and energy. The synthesis mechanism of SnO₂/CdCO₃/CdS nanocomposite was also deeply explored. Moreover, thanks to the matched energy levels of its three components, SnO₂/CdCO₃/CdS nanocomposite exhibited enhanced photocurrent intensity, which is dozens of times bigger than any of its components, thus making it an excellent photoactive matrix for PEC immunosensor. Under optimal conditions, the as-constructed PEC immunosensor manifested a broad linear range (0.1 pg mL^-1 to 100 ng mL^-1) with a low detection limit (LOD, 0.05 pg mL^-1, S/N = 3). High selectivity, coupled with good stability, allowed the developed PEC immunosensor to be applied in the clinical detection of Aβ or other biomarkers in human serum.