Disease Biomarker Detection Using Fluorescence Polarization Assays: Principles and Clinical Applications.

Modern clinical diagnostics require highly sensitive, rapid, and technologically simple methods for quantitatively determining biomarkers directly at the patient's bedside. Fluorescence polarization (FP) meets these criteria, as it enables the homogeneous recording of an analytical signal based on changes in the rotational diffusion of a fluorescently labeled ligand upon binding to a target, without separation or washing steps. This comprehensive narrative review analyzes the literature over the past 10-15 years devoted to the use of FP analysis for detecting biomarkers of socially significant diseases. The fundamental principles of the method and modern analysis formats are discussed-from classical fluorescence polarization immunoassay (FPIA) with antibodies to aptamer sensors, DNAzyme-based systems, and reagent-free biosensors such as Quenchbody. Particular attention is paid to new approaches to signal amplification, including those using nanoparticles, protein aggregation, and isothermal amplification of nucleic acids. The main part of the review is devoted to practical applications of FP: diagnostics of infectious diseases (brucellosis, tuberculosis, and viral infections) demonstrating sensitivity at the level of traditional ELISA; liquid biopsy in oncology, including the detection of extracellular vesicles using aptamer FP platforms; therapeutic drug monitoring of antibiotics in whole blood on portable paper media; and the identification of biomarkers for metabolic and ophthalmological disorders. Prospects for integrating polarization detection with CRISPR/Cas systems, microfluidics, and smartphone-compatible readers are discussed, paving the way to the creation of a new generation of inexpensive devices for personalized medicine.