Cfsp001700

The sample application pad (17 mm × 30 cm) was made from cellulose fiber (CFSP001700, Millipore) and was soaked with a buffer (pH 8.0) containing 0.25% Triton X-100, 0.05 M Tris–HCl, and 0.15 mmol L⁻¹ NaCl. Then the pad was dried at room temperature and stored in desiccators at 4 °C. Test and control zones on the nitrocellulose membrane (25 mm × 30 cm) were prepared by dispensing polyclonal goat anti-R-IgG antibody (test zone, 1.2 mg mL⁻¹) and mouse anti goat IgG secondary antibody (control zone, 200 μg mL⁻¹) solutions, respectively. The distance between test and control zone was 3 mm. The membrane was dried at room temperature for 1 h and stored at 4 °C. Finally, all of the parts were assembled on a plastic adhesive backing layer (typically an inert plastic, e.g., polyester) using the Clamshell Laminator. Each part overlapped 2 mm to ensure the solution migrating through the strip during the assay. Strip with a 3 mm width were cut by using the Guillotin cutting module CM 4000 cut module.

Glass fibers (GFCP000800), cellulose fiber sample pads (CFSP001700), laminated cards (HF000MC100) and nitrocellulose membranes (HFB24004) were provided by Millipore (Bedford, MA). Polyvinylpyrrolidone (PVP K30) was obtained from Fluka (www.fluka.org). Na₃PO₄ 12H₂O, HAuCl₄, trisodium citrate, sucrose, Tween 20, Triton X-100, phosphate buffer saline (PBS, pH 7.4, 0.01 mol L⁻¹ NaH₂PO₄ and Na₂HPO₄ containing 0.9% NaCl), silver nitrate (AgNO₃), hexamethylenetetramine (HTM, C₆H₁₂N₄), ascorbic acid, bovine serum albumin (BSA), human serum albumin (HSA) and casein (from bovine milk) were purchased from Sigma-Aldrich (www.sigmaaldrich.com). Rabbit IgG, Polyclonal goat anti-rabbit immunoglobulin G (IgG) antibody, mouse anti goat immunoglobulin G secondary antibody and human IgM were purchased from Thermo Scientific (www.thermofisher.com).