Self-powered anti-interference photoelectrochemical immunosensor based on Au/ZIS/CIS heterojunction photocathode with zwitterionic peptide anchoring

Accurate detection of important biomarkers with ultra-low levels in complex biological matrix is one of the frontier scientific issues because of possible signal interference of potential reductive agents and protein molecules. Herein, a self-powered anti-interference photoelectrochemical (PEC) immunosensor was explored for sensitive and specific detection of model target of cardiac troponin I (cTnI). Specifically, a novel ternary heterojunction served as the photocathode to offer a remarkable current output and a zwitterionic peptide was introduced to build a robust antifouling biointerface. CuInS2 (CIS) film with porous network nanostructure was first prepared and then modified in order with ZnIn2S4 (ZIS) nanocrystals and Au nanoparticles to fabricate the Au/ZIS/CIS heterojunction photocathode. After capture cTnI antibody (Ab) was immobilized, the zwitterionic peptide KAEAKAEAPPPPC was then anchored to compete the immunosensor. The elaborated PEC immunosensor exhibited high sensitivity for target cTnI antigen (Ag) detection, with good anti-interference against reductive agents and nonspecific proteins. This integration strategy of heterojunction photocathode with zwitterionic peptide provides a new sight to develop advanced PEC immunosensors applying in practical biosamples.