An scFv‐Based Impedimetric Immunosensor Using SPCE/AuNP for RBD of SARS‐CoV‐2 Detection

Abstract

A single‐chain variable fragment (scFv) is an antibody fragment composed of VH and VL linked by a hydrophilic linker that can be designed according to the shape of the target molecule and synthesized in prokaryotic or eukaryotic cells via biotechnology engineering. This study developed an electrochemical immunosensor that detects the RBD of SARS‐CoV‐2 using a screen‐printed carbon electrode modified with gold nanoparticles, and scFv as a bioreceptor. Electrochemical impedance spectroscopy was employed to measure specific interactions of antigens with antibodies. The developed immunosensor had a limit of detection and a quantification limit of 4.86 ng mL−1 and 16.20 ng mL−1, respectively. The immunosensor was stable at room temperature for up to 30 days’ storage. The immunosensor was assessed at biosafety level 3 using 33 nasopharyngeal swab specimens (clinical samples); the pieces of data were compared with quantitative Reverse Transcriptase‐PCR. The agreement of the data, the low detection limit achieved, the rapid analysis (30 min), the miniaturization, and the portability of the instrument combined with the easiness to use has the potential to become Point of Care (POC) for diagnosing the COVID‐19 disease.

Hydroxyapatite-Gold Modified Screen-Printed Carbon Electrode for Selective SARS-CoV-2 Antibody Immunosensor

“…The stability of the immunosensor must be high for detecting anti-SARS-CoV-2 IgG and the sensitivity decreases during storage. 54 Various storage conditions affect immunosensor stability, such as time, temperature, exposure to light and particles, air humidity, and the addition of stabilizer solutions. In this study, all storage conditions were evaluated for 7 days using a fractional factorial design experiment to determine the main effect of the factors (Figures S9a and S9b).…”

Nanoparticles in Electrochemical Immunosensors – A Concept and Perspective

“…Therefore, this approach has been gradually replaced with the so-called "scFv" (single chain variable fragments) that is directly obtained by genetic engineering, thus avoiding protein manipulation. In this regard, Fadhilah et al [182] (Figure 8) obtained thiolated scFv by adding a cysteine gene in the protein-coding, to allow their direct immobilization on gold NPs via S-Au formation. The EIS immunosensor was able to detect SARS-CoV-2 Spike RBD with a LOD of 4.86 ng mL À 1 without using any labeling.…”

CeO2@NH2 functionalized electrodes for the rapid detection of SARS-CoV-2 spike receptor binding domain

“…2 The Spike RBD plays a role in the formation of an immune response of the host cells, therefore it is widely used as a biomarker for the detection of SARS-CoV-2 in the immunochemistry-based methods. 3–5…”

“…2 The Spike RBD plays a role in the formation of an immune response of the host cells, therefore it is widely used as a biomarker for the detection of SARS-CoV-2 in the immunochemistry-based methods. [3][4][5] The gold standard method for SARS-CoV-2 detection is realtime reverse transcriptase PCR (rtRT-PCR/qPCR), using a specic probe to detect several target genes. 4,[6][7][8] The main limitations of this method are; time-consuming, requires expensive equipment and reagents, as well as trained laboratory personnel.…”