The scanometric assay was first introduced by the Mirkin group in a 2000 Science paper. In a typical assay, a DNA target is captured by a DNA strand complementary to one portion of it that is attached to the surface of a chip. This target is then sandwiched by a spherical nucleic acid (SNA)-gold nanoparticle conjugate bearing DNA strands also complementary to a portion of the target. This assay is capable of distinguishing single-base mismatches with enhanced selectivity compared to that observed for fluorophore-labeled probes of the same sequence. Furthermore, when silver staining is used for signal amplification, the overall sensitivity of the scanometric assay is orders of magnitude higher than that of an assay based on the analogous fluorophore-labeled probe. Since 2000, the Mirkin group has developed versions of this system for a wide variety of nucleic acid signatures associated with genetic, bacterial, and viral diseases. In addition, they have developed related assays for mercury ion, prostate cancer markers (protein and miRNA-based), and duplex and triplex DNA binders. This technology forms the basis for the Luminex Verigene System, which was originally commercialized by Nanosphere, a company founded in the late 1990s by Mirkin. Today, there are millions of tests run every year at the point-of-care based upon this technology.
Middle: Schematic of the scanometric assay for the detection of a target nucleic acid strand using spherical nucleic acid (SNA) probes and silver staining. Taken from Anal. Chem. 2009, 81, 9183 and J. Am. Chem. Soc., 2012, 134, 1376.
Far Right: Image of the Verigene system, originally commercialized by Nanosphere and now a major revenue stream for Luminex (https://www.luminexcorp.com/the-verigene-system/).