Non Biological Assay Components

In addition to the biological components of the assay system, there are also a range of reagents that will directly impact on the performance of the assay system. These include surfactants, blocking reagents, and buffers, which are typically used to condition the system to achieve the desired functional performance.

3.3.1. Surfactants

Surfactants are routinely used in DOA assays and contribute to assay performance in a number of ways. Surfactants typically used include both anionic and cationic groups. The effects of surfactants on immunoassay systems include sample conditioning to aid antigen epitope presentation and effects on antigen-antibody binding characteristics, which are key aspects that affect the performance of the system in terms of detection limit and in terms of controlling the rate of false-positive and/or -negative results (14).

Surfactants also play a key role in some of the physical aspects of the lateral-flow system. The flow of liquid through the system, the reconstitution of dried reagents, and the mixing of the assay reagents can all be affected by surfactant content. This in turn will affect the time to test result, the clarity of the test result, and other performance aspects. Additionally, depending on the choice of support membrane in the system (normally nitrocellulose), surfactant can be required to aid in membrane blocking. Typically, nonspecific binding of proteins or other components in the system to the membrane can be reduced or controlled by the use of surfactants, thereby avoiding or reducing potential false-positive or false-negative results.

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