S-Scheme Porphyrin Covalent Organic Framework Heterojunction for Boosted Photoelectrochemical Immunoassays in Myocardial Infarction Diagnosis.

Cardiac troponin I (cTnI) is an extremely sensitive biomarker for early indication of acute myocardial infarction (AMI). However, it still remains a tough challenge for many newly developed cTnI biosensors to achieve superior sensing performance including high sensitivity, rapid detection, and resistance to interference in clinical serum samples. Herein, a novel photocathodic immunosensor toward cTnI sensing has been successfully developed by designing a unique S-scheme heterojunction based on the porphyrin-based covalent organic frameworks (p-COFs) and p-type silicon nanowire arrays (p-SiNWs). In the novel heterojunction, the p-SiNWs are employed as the photocathode platform to acquire a strong photocurrent response. The in situ-grown p-COFs can accelerate the spatial migration rate of charge carriers by forming proper band alignment with the p-SiNWs. The crystalline π-conjugated network of p-COFs with abundant amino groups also promotes the electron transfer and anti-cTnI immobilizing process. The developed photocathodic immunosensor demonstrates a broad detection range of 5 pg/mL-10 ng/mL and a low limit of detection (LOD) of 1.36 pg/mL in clinical serum samples. Besides, the PEC sensor owns several advantages including good stability and superior anti-interference ability. By comparing our results with that of the commercial ELISA method, the relative deviations range from 0.06 to 0.18% ( n = 3), and the recovery rates range from 95.4 to 109.5%. This work displays a novel strategy to design efficient and stable PEC sensing platforms for cTnI detection in real-life serums and provides guidance in future clinical diagnosis.