Figure 2.

Quick cortisol assay based on immunochromatography and gold nanoparticles. (A) The strip consists of a drop site and a reading window. Plasma (100 μL) is placed in the well over the immunochromatographic paper strip. (B) Plasma applied to the drip site reacts with Colloidal Gold Labeled Anti-Cortisol Antibody (Ab·Gold). Cortisol (antigen: Ag) is present in the test line, and anti-mouse antibody is present in the control line. If plasma contains a sufficient amount of cortisol, the Ag-Ab·Gold complex is formed. Then, the complex migrates toward the reading window, and the complex is caught by the anti-mouse antibody. (C) Excess Ab·Gold and/or “Ag-Ab·Gol” complex migrates to the control line where anti-mouse IgG is impregnated. These molecules are bound by anti-mouse IgG at the control line. If the plasma cortisol level is high, only one magenta line appears, with no apparent test line. (D) If the cortisol content in the plasma is insufficient and/or is not present, two magenta lines appear at the test and control lines.