Digital detection of biomarkers assisted by nanoparticles: application to diagnostics.

Single-molecule detection and counting is the new frontier in biomarker analysis. Here, we report on recent techniques for the digital detection of biomolecules for clinical application. First we highlight methods based on the immunocapture of proteins onto microparticles, followed by isolation of individual particles in microenvironments so that a sufficient signal is acquired for each binding event to make a binary decision, thus dramatically enhancing the signal:noise ratio. Various approaches are categorized based on the method used for particle confinement in an isolated microenvironment. We go on to describe methods for the detection of individual biological nanoparticles as well as the digital detection of proteins by artificial nanoparticle labels. The discussion of the methods emphasizes the practical considerations and their clinical applicability.