Sandwich Assay Manufacturing
The sandwich-based immunoassay provides greater assay sensitivity and semi-quantitative capability, but requires a larger analyte with multiple antibody binding sites, such as LH, hCG, H. pylori, PSA, TNI and HIV. The target molecule is first bound by a nanogold-conjugated primary monoclonal antibody which is then captured by a secondary antibody embedded in the membrane to form a visible test, or T-line. All excess, unbound primary antibody flows past the T-line to be captured by a third antibody specific to the primary antibody, thus forming a visible control, or C-line. In the sandwich assay, a visible T-line represents a positive result for the analyte in question.
Competitive Assay Manufacturing
ALFA offers device manufacturing for competitive immunoassays using a traditional lateral flow approach, or with our innovative Driven Flow™.
Competitive assays are particularly useful for analytes that are too small to contain multiple antibody binding sites such as traditional pharmaceuticals and illicit drugs-of-abuse. During the competitive assay test process, the sample migrates to the testing area of the membrane by capillary action, mobilizing all antibody conjugates to a region containing immobilized drug antigen. In the absence of the drug or if the drug concentration is below the cutoff limit in the sample, the colored antibody conjugates are captured by the immobilized drug antigen in the test region, giving a burgundy-colored band, or T-line. However, if the target drug is present in the sample at sufficient concentration, it will compete for these limited antibody binding sites, preventing the formation of the burgundy T-line. The control line (C-line) serves as internal quality.