Zwitterionic peptide-grafted S-CNQDs/Cu2O photocathode for reliable photoelectrochemical detection of cardiac troponin I.

BACKGROUND

Reliable detection of cardiac troponin I (cTnI) in complex biological fluids is essential for early diagnosis of cardiovascular diseases. However, biofouling from nonspecific protein adsorption and interference from redox-active small species at the electrode interface often cause signal instability and compromised analytical accuracy in photoelectrochemical (PEC) sensing. Therefore, developing PEC platforms capable of mitigating biofouling and molecular interference remains challenging.

RESULTS

Herein, a zwitterionic peptide-grafted photocathode was constructed for accurate PEC detection of cTnI in human serum. The photocathode was prepared by integrating S-doped carbon nitride quantum dots (S-CNQDs) with Cu2O nanowires to form an S-CNQDs/Cu2O heterostructure, which served as an efficient signal transducer for subsequent peptide functionalization. The resulting heterostructure exhibited enhanced photocurrent and inherent resistance to interference from reductive small molecules, ensuring stable signal output. The covalently grafted zwitterionic peptide effectively suppressed nonspecific protein adsorption, thereby improving the interfacial anti-fouling performance. In combination with the specific recognition of the immobilized peptide probe, the PEC biosensor enabled sensitive, selective, and interference-resistant detection of cTnI. This interfacial peptide engineering strategy provides a promising platform for reliable PEC bioanalysis in complex biological environments.