Extended Data Fig. 1: Development of a highly sensitive LFA for picomolar detection of sweat cortisol.
a, Schematic illustration of AuNF synthesis chemistry. b, Measurement of zeta potential for AuNF incubated for 1 h with varying concentrations of anti-cortisol antibody. n = 3. c-f, Demonstration of chronosampled LFA with increasing cortisol concentrations: 0 (c), 1 (d), 10 (d) and 100 ng/mL (f). Scale bar, 5 mm. g, An optical image of an LFA strip at a cortisol concentration of 1000 ng/mL. Scale bar, 5 mm. h, Adjustment of artificial sweat and real sweat to pH 6.5 using phosphate buffer within the sample pads. Measured color (a*, black) and pH values (red) are shown. n = 3. i, pH titration curve for artificial sweat (pH 4.3) using 1 M sodium phosphate buffer (pH 6.5). n = 1. j, Evaluation of different working buffer concentrations (1:1 ratio of BSA to Tween 20) for LFA sensitivity. n = 3. k, Performance comparison of different working buffer types (Trixton, Tw20, 10G and PVP) for AuNF transport through the NC membrane. Scale bar, 10 mm. l, Effect of varying BSA-CTS concentrations (from 1 mg/mL to 0.125 mg/mL) on the visual appearances of the test lines. Scale bar, 2 mm. m, Effect of BSA-CTS dilution factors (4X and 8X), and anti-cortisol antibody dilution factors (6X and 8X) on the control/test line ratios at cortisol concentrations of 0, 1, and 100 ng/mL. n = 3. Data are presented as mean values ± SD (n = 3 technical replicates).
