N-Heterocyclic Carbene–Graphene Nanotransistor Based on Covalent Bond for Ultrastable Biosensors

Fatal pathogenic organisms have been detected by various point-of-care tests (PoCTs) in clinical samples. PoCTs based on portable electrical devices are able to detect organisms in simple and rapid method. Although electrical PoCT devices show ultra sensitivity when detecting pathogens in standard samples, their industrialization has been limited due to low reproducibility, sensitivity, and specificity, resulting from nonspecific binding issues by media. In this research, a perpendicular N-heterocyclic carbene self-assembled monolayer (NHC-SAM) conjugated on graphene micropattern field-effect transistors (NGMFETs) is first demonstrated for monitoring pathogens. Two single bonds of NHCSAM on GM are investigated via density functional theory (DFT) and surface analyses. Bioreceptors are conjugated on the side gate-modulated NGMFET for ultra-stable on-site detection. The side-gated BNGMFETs system displayed remarkable performance in the detection of the following: i) SARS-CoV-2 spike protein S1 (limit of detection (LOD): ≈10 pg mL⁻¹) in CTM, ii) O. tsutsugamushi Ab (LOD: ≈1 pg mL⁻¹), and iii) E. coli (LOD: 10° CFU mL⁻¹) in serum. Compared to commercial methodology, the platform presents 10² times higher LODs towards those pathogens in clinical samples with higher reproducibility. Based on these results, side-gated BNGMFETs can be utilized as universal PoCT during pandemics.