Capacitive biosensor based on vertically paired electrodes for the detection of SARS-CoV-2

Abstract

Vertically paired electrodes (VPEs) with multiple electrode pairs were developed for the enhancement of capacitive measurements by optimizing the electrode gap and number of electrode pairs. The electrode was fabricated using a conductive polymer layer of PEDOT:PSS instead of Ag and Pt metal electrodes to increase the VPE fabrication yield because the PEDOT:PSS layer could be effectively etched using a reactive dry etching process. In this study, sensitivity enhancement was realized by decreasing the electrode gap and increasing the number of VPE electrode pairs. Such an increase in sensitivity according to the electrode gap and the number of electrode pairs was estimated using a model analyte for an immunoassay. Additionally, a computer simulation was performed using VPEs with different electrode gaps and numbers of VPE electrode pairs. Finally, VPEs with multiple electrode pairs were applied for SARS-CoV-2 nucleoprotein (NP) detection. The capacitive biosensor based on the VPE with immobilized anti-SARS-CoV-2 NP was applied for the specific detection of SARS-CoV-2 in viral cultures. Using viral cultures of SARS-CoV-2, SARS-CoV, MERS-CoV, and CoV-strain 229E, the limit of detection (LOD) was estimated to satisfy the cutoff value (dilution factor of 1/800) for the medical diagnosis of COVID-19, and the assay results from the capacitive biosensor were compared with commercial rapid kit based on a lateral flow immunoassay.

Carbon electrode obtained via pyrolysis of plasma-deposited parylene-C for electrochemical immunoassays

“…Thermal deposition was performed using a conventional parylene deposition system obtained from Kisco (Osaka, Japan). [4][5][6][7][8] Deposition was conducted in three steps: (1) evaporation of the parylene-C dimer at 160 °C, (2) decomposition of the parylene-C precursor to reactive free radicals (monomers) at 650 °C, and (3) polymerization of the free radicals at ambient temperature. The entire process was performed under a vacuum of 5.3 Pa (40 mTorr), and the film thickness was controlled by the initial amount of parylene-C dimer used.…”

“…For the preparation of a standard curve the positive samples are frequently used as standard samples by serial dilution. 6,20…”

“…Initially, k app was estimated for the pyrolyzed parylene-C electrode, which was prepared using parylene-C obtained via thermal and plasma deposition. k app in the redox reaction of ferricyanide (d[Fe(CN) 6 4− ]/dt = k app •[Fe(CN) 6 3− ]) was estimated using the Nicholson method, 52,53 wherein the separation between the cathodic and anodic peak potentials was estimated according to the scan rates. 54 Additionally, k app is calculated using the peak potential separation between the cathodic and anodic peaks in the cyclic voltammograms at different scan rates:…”

“…[1][2][3] Various types of parylene dimers, with different functional groups attached to their benzene rings, are used, such as parylene-C bearing a chloride, parylene A bearing a primary amine, and parylene H bearing a formyl group. [4][5][6] Because deposition is conducted in the gas phase, the deposited parylene film exhibits a highly homogeneous thickness, even if the substrate exhibits a very complicated 3D structure. 7,8 Parylene-C, in particular, is widely used in various applications due to its physi-cal and chemical properties, such as transparency and high electric isolation and resistances to organic solvents.…”

Assembling Vertical Nanogap Arrays with Nanoentities for Highly Sensitive Electrical Biosensing

“…A vertical nanogap device, on the other hand, did not require advanced nanopatterning techniques to precisely control the gap distance. The size of nanogaps formed between the top and bottom electrodes was readily determined by the thickness of the dielectric spacer layer in between. − However, the vertical nanogap device had complexity in structural design and fabrication processes and showed a higher level of leakage current due to larger areas of overlap between the electrodes. Moreover, bioreceptor functionalization, analyte binding, and washing steps took much longer since biochemical molecules had limited access to the nanogaps, only through the narrow side openings close to the substrate.…”