Fig. 7: Standard calibration curve for the detection of anti-SARS-CoV-2 antibodies obtained using label-free non-Faradaic EIS biosensor and comparison of its performance with other biosensors.
From: Label-free impedimetric immunosensor for point-of-care detection of COVID-19 antibodies
Standard calibration curve for the detection of anti-SARS-CoV-2 immunoglobulin (IgG, IgA, IgM), which were experimentally determined in duplicate (n = 2) using different concentrations of WHO IS (NIBSC 20/136) antibody solutions. Linear fit (solid line) to the experimental data points (filled squares) yielded a straight line, ΔZRel% = 2.1178 log [BAU/mL] + 3.7173 with R2 = 0.9979, indicating that the highest concentration used, i.e., 100 BAU/mL still lied within the linear region of the impedance response (ΔZRel % = ΔZ/Zbgr × 100) to antibody concentration. The dotted line represents the LOD determined fromthe impedance response ΔZRel% of the negative serum sample with no anti-SARS-CoV-2 immunoglobulin. For ease of representation, the bindingantibody unit BAU/mL is used to express the concentration of all immunoglobulins (IgG, IgA, IgM), and according to WHO/NIBSC both (IU/mL and BAU/mL) units are numerically identical. All EIS measurements were conducted in 0.001× PBS at pH 6.5.
