Fluorescence polarization immunoassay

Fluorescence Polarization Anisotropy

Fluorescence Polarization Immunoassay

Fluorescence polarization immunoassay (FPIA) is a sensitive immunoassay technique used in clinical chemistry and pharmacology to measure the concentration of various analytes in biological samples. This method relies on the principle of fluorescence polarization, where the rotation of a fluorescently labeled molecule is inversely proportional to the size of the molecule it binds to.

Principle

In FPIA, a fluorescently labeled antigen or antibody is used as a probe to detect the presence of a specific analyte in a sample. When the probe binds to the target molecule, the rotational speed of the complex changes, leading to a change in the polarization of the emitted light. By measuring the polarization of the emitted light, the concentration of the analyte can be determined.

Procedure

The FPIA procedure involves incubating the sample with the fluorescent probe, allowing the formation of the antigen-antibody complex. The sample is then excited with polarized light, and the emitted light is measured at a right angle to the excitation light. The degree of polarization is calculated based on the intensity of the emitted light in the parallel and perpendicular orientations.

Applications

FPIA is commonly used in clinical laboratories for the quantification of various analytes, including hormones, drugs, and proteins. It is particularly useful in drug monitoring, therapeutic drug monitoring, and detection of biomarkers in diseases such as cancer and infectious diseases.

Advantages

One of the main advantages of FPIA is its high sensitivity and specificity, allowing for accurate quantification of analytes in complex biological samples. Additionally, FPIA is a rapid and cost-effective technique compared to other immunoassay methods.

Limitations

Despite its advantages, FPIA has some limitations, including the need for specialized equipment and expertise to perform the assay. Additionally, FPIA may be affected by factors such as sample matrix interference and non-specific binding, which can impact the accuracy of the results.

See also

• Immunoassay
• Fluorescence spectroscopy
• Clinical chemistry