Figure 4.

Dose-response curve for detecting rIL-6 spiked into healthy human serum using the vertical-flow paper-based assay. (A) The membrane-type used is Amersham 0.2 µm with two layers. Two replicates were obtained at each concentration. The top left of the membrane represents the test zone. (B) Colorimetric intensity values were calculated using ImageJ. The 3 × σ + negative mean line indicates the summation of the mean intensity of non-spiked healthy serum samples (0 pg/mL) and 3X its standard deviation (σ). The concentration above this line marks the LoD, which is 3.2 pg/mL. The dose-response curve demonstrated a reportable range from 3.2 pg/mL to 10,000 pg/mL of rIL-6 in ten-fold diluted serum.