Detecting in the Dark

Abstract

Many of the assays produced in the diagnostics field today take advantage of molecular labeling. Are you a coach who wants to know if your player is taking a performance-enhancing drug? A doctor interested in the disease status of your patient? Or, a TSA official wondering if there are explosives in a bag? Label it! But as diseases, drugs, and other threats evade our detection systems, researchers are not consigning themselves to label-based techniques. Labeling a molecule can interfere with its reactivity. “When you get into proteins and glycoproteins, it becomes more difficult to make label material,” says Dr. Larry Bowers, Chief Science Officer for the US Anti-Doping Agency (USADA).3 “Label-free biosensing is clearly very important.” The community is listening and has put its energy into the field of label-free diagnostic methods to improve the sensitivity and quality of detection. We discuss a recent advance in optical transduction that capitalizes on plasmons and man-made nanomaterials, which can come together to create a sensitivity so improved that “we can potentially see the binding of a single molecule,” says Andrei Kabashin, CNRS Research Director at Aix-Marseille University and lead researcher on the work. Kabashin and his colleagues reported recently in Nature Materials that label-free optical transduction technology has “at its core” surface plasmon resonance (SPR) (1). In SPR, scientists monitor the refractive index to observe the binding of a ligand to its receptor in real time. A newer offspring of SPR, localized plasmon resonance (LPR), in which SPR occurs in nanostructures, is full of potential—from detecting low molecular weight …