Single-molecule detection

Developing technologies and methods are allowing practical access to single-molecule detection (SMD), manipulation, and analysis. New optical detectors and imaging devices permit rapid high-sensitivity and low-noise capture of optical signatures from individual molecules. Chemically selective optical labels such as fluorophores or nanoscale scattering objects enhance the optical signature of selected molecules and enable their recognition in a complex mixture. Micro- and nanofluidic systems are advancing technological capabilities that can couple optical analysis to small volumes of fluid and also select and separate molecules of interest. Nanoscale structuring and optical methods combined with fluid handling are being integrated into lab-on-a-chip tools for radically new approaches to analytical chemistry or biomolecular study. These tools are being directed toward ultrasensitive detection and identification of molecules, even if rare in number or rate of occurrence. Future generations of DNA sequencing and gene expression may utilize single-molecule analysis (Eid et al. 2009). SMD methods provide direct visualization of mRNA dynamics within live Escherichia coli cells (Golding and Cox 2004; Golding et al. 2005), allowing access to study the rich biodiversity present within a given species of an animal or organism. This attention to biomolecule individuality and uniqueness enables studies and discoveries previously obscured in ensemble measurements.