Proteins and small molecules are commonly measured indirectly in diagnostics, through the use of antibodies (“immunodiagnostics”). Immunodiagnostic testing is the current “gold standard” for many diagnostic determinations. The application of RCAT™ in immunodiagnostics offers a significant opportunity for increasing the sensitivity of these tests.

More Sensitive Than Conventional Immunoassays
Protein detection by conventional immunoassay is relatively insensitive. Some recent approaches to molecular diagnostics use mRNA measurement as a surrogate for direct protein measurement, but changes in the concentration of an mRNA and its encoded protein are at times not proportional. In immuno-RCAT™, a unique DNA sequence tag is associated with a particular antibody using a covalent linkage. Antibodies bound to antigen are then measured by RCAT-based amplification of the associated DNA tag.

Each antibody-bound DNA tag is amplified and the resulting long DNA product remains bound to the antibody-antigen complex during the entire reaction. The amplified product can then be collapsed to a point source, permitting ultrasensitive localized detection capability (the technology has been demonstrated to detect single antibody-antigen complexes). Immuno-RCAT is readily adaptable to high-throughput surface array formats and simultaneous multi-analyte detection systems.