Redox probe-free electrochemical immunosensor utilizing electropolymerized melamine on reduced graphene oxide for the point-of-care diagnosis of gastric cancer

Pepsinogen I (PG I) is a biomarker that plays a crucial role in the diagnosis of gastric cancer. The development of biosensor to monitor PG I overexpression in serum is crucial for early gastric cancer diagnosis, offering a less invasive alternative to the costly and uncomfortable gastroscopy procedure. This study presents a cost-efficient, scalable and disposable label-free biosensing strategy for detecting PG I, utilizing a redox-active polymelamine electrodeposited on a reduced graphene oxide screen-printed electrode surface (PM-rGO/SPE). Under optimized conditions, the conducting polymer PM was deposited on the rGO/SPE via a potentiodynamic method. The structural and morphological features of PM-rGO/SPE were analyzed with the assistance of Raman and Scanning Electron Microscopy analysis. Specific monoclonal anti-PG I antibodies were immobilized on the in situ prepared redox-active layer via EDC/NHS chemistry to develop a novel electrochemical immunosensor. Unlike the traditional immunosensing strategies which utilizes external redox probe solution for measuring the signal, the developed configuration allowed for redox-probe free monitoring of current changes of the redox active PM resulting from the formation of the immunocomplex on the electrode surface. Utilizing this method, PG I detection spanned a clinically relevant concentration range of 0.01–200 ng/mL, with a low limit of detection at 9.1 pg/mL. The electrochemical immunosensor demonstrated specificity against other biomarkers such as PDCD1, ErBb2, and CD28 with negligible interference. The immunosensor exhibited excellent recovery capabilities for PG I detection in serum samples. These findings underscore the potential of the PM-rGO/SPE immunosensor as a point-of-care diagnostic tool for gastric cancer.