An anti-fouling photoelectrochemical immunosensor based on zwitterionic peptide and Z-scheme PEDOT/ZnIn2S4 heterojunction for highly sensitive detection of Aβ40

Amyloid-beta peptide (Aβ) is considered a promising biomarker for the diagnosis of Alzheimer’s disease (AD). Herein, we developed an anti-fouling photoelectrochemical (PEC) immunosensor for sensitive Aβ40 detection based on Z-scheme heterojunction poly (3,4-ethylenedioxythiophene) (PEDOT)/ZnIn₂S₄ and zwitterionic peptide. Due to the excellent electrical conductivity of PEDOT, the Z-scheme PEDOT/ZnIn₂S₄ heterojunction exhibited a high photocurrent response, which can promote the separation and transfer of photogenerated electron/hole pairs. The zwitterionic peptide with hydrophilicity and electrical neutrality was used as a blocking agent to reduce nonspecific adsorption. The proposed PEC immunosensor showed outstanding performance for Aβ40 with high selectivity, stability, wide liner range (from 10 pg mL⁻¹ to 5 ng mL⁻¹), and a low detection limit (4.7 pg mL⁻¹). Moreover, the integration strategy of heterojunction with zwitterionic peptide provides a promising way for protein detection in practical applications.