Quantitative detection in the attomole range for immunochromatographic tests by means of a flatbed scanner.
This work describes the use of the combination of carbon black as an antibody label, a membrane-based immunochromatographic device, and a flatbed scanner as a quantitative test system. The scanner detected 0.4-345 ng carbon black/mm(2) on a nitrocellulose membrane (0.2-170 amol carbon black/mm(2)) with an imprecision (coefficient of variation, CV) lower than 2% for the carbon black determination and a detection limit of 0.04 ng carbon black/mm(2) (0.02 amol/mm(2)). The detection ability was compared to that obtained with alkaline phosphatase (ALP) using a substrate yielding a chemiluminescent signal (0.02 amol ALP/well), beta-galactosidase using a substrate yielding a fluorescent signal (0.3 amol beta-galactosidase/well), and horseradish peroxidase (HRP) using a substrate yielding a colored signal (5 amol HRP/microtiter well). The carbon black immunochromatographic test for immunoglobulin E (IgE) showed a detection limit of 0.13 pM IgE (0.01 kU/L) after a testing time of 10 min. The scanner detection imprecision for the IgE determination was 0.6% CV in the range 1-10 kU IgE/L when 2.3 mm(2) was used for detection and 1% CV when 0.19 mm(2) was used. A flatbed scanner is an inexpensive instrument with multiple uses, which now also includes the sensitive evaluation of immunoassays.
Lönnberg
M
M
Center for Surface Biotechnology, Uppsala, S-751 23, Sweden. maria.lonnberg@pharmacia.com
Carlsson
J
J
D000327:Adsorption; D000469:Alkaline Phosphatase / Q000276:immunology / Q000378:metabolism; D002244:Carbon / Q000378:metabolism*; D002846:Chromatography, Affinity / Q000295:instrumentation / Q000379:methods*; D003124:Colorimetry; D001330:Electronic Data Processing / Q000295:instrumentation* / Q000379:methods*; D005453:Fluorescence; D006735:Horseradish Peroxidase / Q000276:immunology / Q000378:metabolism; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods*; D007124:Immunoenzyme Techniques / Q000379:methods; D007073:Immunoglobulin E / Q000032:analysis / Q000276:immunology; D008163:Luminescent Measurements; D008970:Molecular Weight; D011485:Protein Binding; D012680:Sensitivity and Specificity; D013194:Staining and Labeling; D001616:beta-Galactosidase / Q000276:immunology / Q000378:metabolism
D007073:Immunoglobulin E; D002244:Carbon; D006735:Horseradish Peroxidase; D000469:Alkaline Phosphatase; D001616:beta-Galactosidase