Direct single-molecule imaging for diagnostic and blood screening assays
Qiaoqiao Ruan, Patrick J. Macdonald, Kerry M. Swift, Sergey Y. Tetin
Abstract
Significance Direct imaging and counting single molecules captured on magnetic microparticles enables diagnostic assays with ultrahigh sensitivities and wide linear detection ranges. The method offers simple assay protocols, short incubation times, minimal reagent consumption, and does not require enzymatic signal amplification. The ratiometric readout, linking the signal and binding area, eliminates the need for strict control over the number of microparticles. Direct imaging provides the sensitivity, flexibility, and simplicity required by rigorous clinical standards. Other benefits of the technique include a seamless transition between digital and analog data analysis modes, scalability, basic consumables, and the reliability to achieve robust implementation in high-throughput automated instruments. HDIA is a versatile tool that can easily be adopted for all receptor–ligand binding assays.