g-C 3 N 4 /ZnO Nanocomposite-modified disposable paper carbon electrode for label-free electrochemical immunodetection of lung cancer biomarker CYFRA21-1

Previous studies have validated that the cytokeratin 19 fragment antigen 21-1 (CYFRA 21-1) is an effective biomarker in NSCLC (Non-small cell lung cancer). Cyfra21-1 is the most important biomarker for NSCLC, as its elevated levels strongly correlate with tumor progression, metastasis and an unfavorable prognosis. Early detection of Cyfra21-1 improves lung cancer diagnosis, monitors treatment efficacy and enhances the patient’s chances of survival. However, many reported CYFRA21-1 sensing platforms rely on costly nanomaterials, noble metals, or complex signal amplification strategies, limiting their practical application in point-of-care diagnostics. In this study, a simple, inexpensive approach that avoids the use of noble metals and complex signal amplification technology is developed for an electrochemical immunosensor to sensitively and selectively detect the biomarker CYFRA21-1. The fabrication of the immunosensor involved electrode modification using nanocomposites, the anti-CYFRA21-1 antibody immobilization and BSA blockage for highly selective detection. Under the optimized conditions, the current value changes proportionally to the logarithm of the CYFRA21-1 concentration at 0.1-100 ng/mL (R2=0.998) with a very low detection limit of 0.0281 ng/mL. A potential method for the creation of portable electrochemical devices for quick CYFRA21-1 detection and upcoming point-of-care diagnostic applications is the suggested inexpensive, disposable, and label-free sensing platform.