An assessment of the suitability of using streptavidin coated microspheres on the test line of a lateral flow immunoassay with a hydrophilic membrane

Lateral flow immunoassays provide quick, qualitative detection of biomolecules. They are designed to be easy to use, cheap and suitable for applications away from the laboratory. Most lateral flow assays detect a single analyte and use two analyte specific antibodies. One antibody is labelled, and physically separated from the other, which is bound to the test line of a hydrophobic membrane. When a liquid sample is applied, the sample and labelled antibodies flow towards the capture antibodies on the test line. If the analyte is present in the sample, a sandwich assay forms on the test line, giving a visual signal to indicate the presence of the analyte. This research investigated using Streptavidin coated microspheres on the test line of a hydrophilic membrane and a mobile, analyte specific, biotinylated capture antibody upstream of the test line. A hydrophilic membrane material reduced the number of materials required, compared to a traditional design and the Streptavidin provided a method for designing a multi-analyte assay with an analyte independent test line. The mobile biotinylated capture antibody and Streptavidin based test line gave variable results. Only one in four of the target assays developed could detect the analyte used (Rotavirus antigen) and only at higher concentrations, compared to traditional lateral flow designs. Better results were achieved by pre-incubating the biotinylated capture antibody with the Streptavidin microspheres, although it was unable to match the sensitivity of the traditional lateral flow assays. Furthermore, traditional lateral flow designs produced obvious results within ten minutes, while hydrophilic membrane based assays, with Streptavidin test lines, took approximately sixty minutes to produce less distinct signals. Experiments were performed to reduce the time taken to generate signals, but no significant improvement was achieved. Further work should investigate the antibodies, buffers, choice of label, alternative test line capture methods and membrane materials.