This invention relates to assaying a liquid mixture for a particular biologically active component.
The component may be present only in minute quantities in a complex mixture such as blood or urine, which may also contain molecules of similar structure to the component of interest.
In one method for determining the concentration of such a component (for example, the method disclosed in Lane et al., J. Electroanal. Chem. 95: 117-122 (1979)), a voltage sweep is applied between a reference electrode and a working electrode to oxidize or reduce the component. The resulting current, which flows between the working electrode and a counter electrode, is measured as an indication of the concentration of the component in the liquid mixture.
In another method, disclosed in Yamamoto et al., J. Immuno. Methods 22: 309-317 (1978), the presence of an antigen component is determined by immobilizing on the working electrode antibodies which are binding partners to the antigen component, and allowing the antigen component molecules to bind to the antibodies to form a charged layer. The presence of the charged layer is detected as an indication of the presence of the antigen component.
In a third method, disclosed in Aizawa et al. Anal. Biochem. 94: 22-28 (1979), the concentration of an antigen component is measured by a series of steps which include adding to the liquid mixture an additional amount of the antigen component labeled with an enzyme, allowing both the labeled and non labeled antigens to compete for antibody binding sites, providing a substance which is acted upon by the enzyme associated with the bound labeled antigens to cause the release of a reporter substance, and measuring the reporter substance as an indication of concentration.