Effects of different nitrocellulose materials on the detection of printed human IgG. Panel A: Various amounts of human IgG (1.2, 0.6, 0.3, 0.15 and 0.075 ng /spot) were printed on Whatman Protran BA-85 (0.1, 0.2 or 0.45 μm porosity) or Amersham Hybond-C (0.45 μm porosity) membrane using PBS + 20% glycerol as printing buffer. Printed IgG was visualised in spot-ELISA and signals quantified by determining the pixel intensities of digitized spots. Each line on graph represents the analyses results of IgG printed on a specific nitrocellulose (see Panel A for details). Each data point consists of measurements of five spots on five different strips (N = 25 per data point). X-axis: human IgG amount per spot. Y-axis: Staining intensity defined as the mean pixel intensity measured on a 0–255 grey scale. Panel B: R2 and CV% (Coefficient of variation) range for each tested nitrocellulose membrane type.