Fig. 5: Electrochemical detection of Vit-D and analytical characterization of the platform sensitivity, specificity, and reproducibility.

a Schematic illustration representing the Vit-D biosensor's electrochemical detection strategy. b Differential pulse voltammetry (DPV) scans of the Vit-D sensor at different concentrations (0, 0.1, 1, 10, 100, and 500 ng mL⁻¹) of Vit-D in 5 mM [Fe(CN)₆]^3-/4- in 1X PBS solution. c Calibration curve (log of normalized current versus log of Vit-D concentration) of the Vit-D biosensor. Error bars indicate the standard error of the mean for N ≥ 6 data points collected from two or three individual biosensors with three DPV scans acquired per concentration. d Interference or specificity test of the Vit-D sensor in the presence of non-target analytes: glucose (7 mM), Vit-C (1 mM), Vit-B₁₂ (300 pg mL⁻¹ or 2.2 zM), miR-141 (10 fM) and Vit-D (25(OH)D₃), (10 ng mL⁻¹ or 0.0265 µM) in 5 mM [Fe(CN)₆]^3-/4- in 1X PBS solution (**** indicates p < 0.0001). eData was collected from one sensor per analyte type (with three DPV scans per sensor) and signalswere compared to that from the target Bit-D, normalized to 100%. e Reproducibility test of the Vit-D sensors which were all incubated with the same concentration of target Vit-D (10 ng mL⁻¹) tested with 5 mM [Fe(CN)₆]^3-/4- in 1X PBS solution. Signals from Sensors 2-5 were compared to the signal from Sensor 1, normalized to 100%.