Solid-phase immunoassays

Solid-phase quantitative immunoassays are some of the most commonly used diagnostic tests for both soluble antigen composition and the assessment of cellular functions. These immunoassays (e.g., ELISA, ELISPOT) provide a highly sensitive means to measure the presence of antigen in defined and homogeneous samples such as purified proteins in buffer, as well as in undefined heterogenous biological samples such as cell lysates, tissue culture supernatants, blood, and other clinical samples. The sensitivity of these assays can enable (under optimal conditions) detection of protein concentrations in the picogram range. A recent modification of the basic ELISA immunoassay takes advantage of the phenomenon of grating-coupled surface plasmon resonance (GCSPR) to provide a label-free real-time variant of this solid-phase immunoassay. Using GCSPR, similar assessments of antigen-antibody interactions can be done with smaller sample sizes and in a microarray format that enables the simultaneous measurement of large numbers of antibody/antigen interactions on the same sensor chip. These measurements allow for a highly refined and sensitive determination of the effects that toxins can have on biological systems, and they can be applied to a variety of immune and non-immune protein, cell, and tissue evaluations.