Epifluorescent single-molecule counting with Streptavidin-Phycoerythrin conjugates

Single-molecule methods, specifically single-molecule counting, convey high sensitivity in research applications. However, single-molecule counting experiments require specialized equipment or consumables to perform. We demonstrate the utility of using bright Streptavidin-Phycoerythrin (SA-PE) conjugates and an epifluorescence microscope, for single-molecule counting applications. In this work, we show that we can visualize single-molecules on glass surfaces, perform single-molecule diagnostic assays on magnetic microparticles, and image individual foci on cell surfaces. This approach is simple and effective for researchers interested in single-molecule counting.