<title>Molecular analysis of biomarkers for earlier cancer detection</title>

Abstract

Single-molecule phosphorescence immunoassay microscopy was developed and applied for high-throughput screening of tumor markers at the single-molecule (SM) level with no need of separation processes. The screening of individual analyte in a mixture was based upon distinguished diffusion images of single molecules associated with its size and mass. As a working example, several molecular forms of serum prostate- specific antigens (PSA) were labeled with Ru(bpy)32+-NHS-ester and labeled PSA-free and PSA-complex were distinguished based upon their SM diffusion images using this SM microscopy. The bound and unbound PSA-free with its monoclonal antibody (MAB) were also detected using this SM microscopy. A novel solution-phase quantitative electro chemiluminescence (ECL) immunoassay was developed to measure affinity constants of PSA with its antibody and diffusion coefficients of labeled PSA. The ECL immunoassay was able to detect PSA at 1.7 pg/mL. Diffusion of labeled PSA-free and PSA-complex measured by ECL and SM microscopy was consistent demonstrating that distinguished SM diffusion images could be used to screen multiple analytes in a complex mixture. This also implied the possibility of real- time monitoring of kinetics of binding reactions using such SM microscopy.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.