Diagnostics of SARS-CoV-2 infection using electrical impedance spectroscopy with an immunosensor to detect the spike protein

• Published in: Talanta (Oxford) 2022-03, Vol.239, p.123076-123076, Article 123076
• Main Authors: Soares, Juliana C., Soares, Andrey C., Angelim, Monara Kaelle S.C., Proença-Modena, Jose Luiz, Moraes-Vieira, Pedro M., Mattoso, Luiz H.C., Oliveira Jr, Osvaldo N.
• Format: Article
• Language: English
• Subjects: Biosensing Techniques; COVID-19; Dielectric Spectroscopy; Humans; Immunoassay; Immunosensors; Impedance spectroscopy; Information visualization; SARS-CoV-2; Spike Glycoprotein, Coronavirus; Spike protein
• ISSN: 0039-9140; 1873-3573
• DOI: 10.1016/j.talanta.2021.123076

Mass testing for the diagnostics of COVID-19 has been hampered in many countries owing to the high cost of the methodologies to detect genetic material of SARS-CoV-2. In this paper, we report on a low-cost immunosensor capable of detecting the spike protein of SARS-CoV-2, including in samples of inactivated virus. Detection is performed with electrical impedance spectroscopy using an immunosensor that contains a monolayer film of carboxymethyl chitosan as matrix, coated with an active layer of antibodies specific to the spike protein. In addition to a low limit of detection of 0.179 fg/mL within an almost linear behavior from 10−20 g/mL to 10−14 g/mL, the immunosensor was highly selective. For the samples with the spike protein could be distinguished in multidimensional projection plots from samples with other biomarkers and analytes that could be interfering species for healthy and infected patients. The excellent analytical performance of the immunosensors was validated with the distinction between control samples and those containing inactivated SARS-CoV-2 at different concentrations. The mechanism behind the immunosensor performance is the specific antibody-protein interaction, as confirmed with the changes induced in C–H stretching and protein bands in polarization-modulated infrared reflection absorption spectra (PM-IRRAS). Because impedance spectroscopy measurements can be made with low-cost portable instruments, the immunosensor proposed here can be applied in point-of-care diagnostics for mass testing even in places with limited resources. [Display omitted] •Low-cost immunosensors to detect the spike protein of SARS-CoV-2 virus.•Limit of detection of 0.179 fg/mL for SARS-CoV-2 spike protein using electrical impedance spectroscopy.•Tests can be made with portable instruments for point-of-care diagnostics.•The immunosensors were selective for the spike protein, without interference from other biomarkers.