Aptasensing Nucleocapsid Protein on Nanodiamond Assembled Gold Interdigitated Electrodes for Impedimetric SARS-CoV-2 Infectious Disease Assessment

In an aim of developing portable biosensor for SARS-CoV-2 pandemic, which facilitates the point-of-care apta-sensing, a strategy using 10 mu m gap-sized gold interdigitated electrode (AuIDE) is presented. The silane-modified AuIDE surface was deposited with similar to 20 nm diamond and enhanced the detection of SARS-CoV-2 nucleocapsid protein (NCP). The characteristics of chemically modified diamond were evidenced by structural analyses, revealing the cubic crystalline nature at (220) and (111) planes as observed by XRD. XPS analysis denotes a strong interaction of carbon element, composed similar to 95% as seen in EDS analysis. The C-C, C=C, C=O, C=N functional groups were well-refuted from XPS spectra of carbon and oxygen elements in diamond. The inter-relation between elements through FTIR analysis indicates major intrinsic bondings at 2687-2031 cm(-1). The aptasensing was evaluated through electrochemical impedance spectroscopy measurements, using NCP spiked human serum. With a good selectivity the lower detection limit was evidenced as 0.389 fM, at a linear detection range from 1 fM to 100 pM. The stability, and reusability of the aptasensor were demonstrated, showing similar to 30% and-33% loss of active state, respectively, after similar to 11 days. The detection of NCP was evaluated by comparing anti-NCP aptamer and antibody as the bioprobes. The determination coefficients of R-2 = 0.9759 and R-2 = 0.9772 were obtained for aptamer- and antibody-based sensing, respectively. Moreover, the genuine interaction of NCP aptamer and protein was validated by enzyme linked apta-sorbent assay. The aptasensing strategy proposed with AuIDE/diamond enhanced sensing platform is highly recommended for early diagnosis of SARS-CoV-2 infection.