Anti-interference Photoelectrochemical Immunosensing of Staphylococcal Enterotoxin A Using a Dendritic Peptide Tetramer-Modified HsGDY/Cu ₂ O Photocathode

Staphylococcal enterotoxin A (SEA) is a major foodborne pathogen toxin capable of causing severe food poisoning even at nanogram levels. However, as widely reported, accurate quantification of SEA in complex food matrices remains challenging due to matrix effects from coexisting proteins, lipids, carbohydrates, and reducing small molecules. Herein, we report an innovative anti-interference photoelectrochemical (PEC) immunosensing platform constructed from a hydrogen-substituted graphdiyne (HsGDY)/Cu₂O photocathode further functionalized with a dendritic peptide tetramer (DPT) bearing four terminal peptide chains. The HsGDY layer, with its extended π-conjugated framework and porous structure, stabilizes the Cu₂O component and broadens light absorption, thereby enhancing charge separation and photocurrent generation. Meanwhile, DPT forms a multivalent interfacial layer that suppresses nonspecific adsorption, minimizing matrix interference and ensuring high specificity. SEA antibodies immobilized on the HsGDY/Cu₂O photocathode mediate highly specific antigen recognition. The HsGDY-enhanced photocurrent, combined with the DPT-mediated suppression of nonspecific adsorption, yields exceptional sensitivity, selectivity, and interference tolerance. The platform exhibits a wide linear range of 0.05-5000 ng/mL and a low detection limit of 18.63 pg/mL. This strategy offers a general approach for developing high-performance, anti-interference PEC immunosensors applicable to food safety monitoring, clinical diagnostics, and environmental analysis.