Point-of-Care Applicability of Graphene-Based Field Effect Transistors upon Modification with a Pyrene-Tagged Antifouling Copolymer: Application for cTnI Sensing in Blood

Field-effect transistors (FETs) are an integrated part of various electronic products and play an irreplaceable role in modern-day bioelectronics and biosensors. The electronic performance of FET-based sensors is intrinsically correlated with the choice of the sensing layer, with graphene being one of the most widely employed active semiconductor materials through which charge carriers (i.e., electrons or holes) propagate upon bioreceptor–analyte interactions. One of the challenges remaining before widespread practical applications of graphene-based FET (gFET) is linked to its direct operation in blood, as the complex protein environment matrix causes significant issues. Here, we propose a sensitive and rapid detection of cardiac troponin I (cTnI) in unprocessed blood samples by integrating pyrene-tagged antifouling copolymer thin films onto the graphene channel. By leveraging the unique properties of the zwitterionic copolymer composed of N-(2-hydroxypropyl) methacrylamide (HPMAA) and carboxy betaine methacrylamide (CBMAA) in the form of a pyrene-tagged poly[HPMAA-co-CBMAA], we demonstrate excellent signal stability in whole blood, along with the potential for sensitive cTnI sensing in high ionic strength media (1× PBS) upon immobilization of DNA aptamers onto the copolymer network. With a limit of detection of 0.6 ± 0.1 pg mL–1 and a limit of quantification of 1.8 ± 0.3 pg mL–1, the sensor operates well within the clinically relevant cTnI range, demonstrating a significant step forward for cardiovascular biomarker monitoring in physiologically relevant conditions.