Figure 2.

Characterization and calibration of RAPID 1.0

(A) Schematic representation of the RAPID diagnostic process.

(B and C) (B) Cyclic voltammetry and (C) Nyquist plots (inset shows the zoomed region of the curve with the semi-arc) of all functionalization steps showing progressively increased resistivity between the bare electrode (in black) and the four modification steps: addition of glutaraldehyde (in red), functionalization of ACE2 (in blue), addition of the blocking agent bovine serum albumin (in green), and addition of the Nafion permselective membrane (in purple).

(D) Nyquist plots for different SP concentrations ranging from 100 fg mL⁻¹ to 100 ng mL⁻¹ with 10-fold increments in neat saliva from a healthy donor (negative result by qRT-PCR). The inset shows the linearized correlation between normalized R_CT values and the concentration of SP exposed to the electrode.

(E) Nyquist plots for titered inactivated virus solutions at concentrations ranging from 10¹ to 10⁶ PFU mL⁻¹ with 10-fold increments. The upper left inset shows the linearized correlation between the normalized R_CT values and the concentration of inactivated virus in solution. The lower right inset shows a zoomed region of the curve with the Nyquist plots' semi-arc (R_CT). The analytical curves presented in (D) and (E) were based on triplicate measurements. All data were recorded using the eChip version of RAPID.