Selective Colorimetric Detection of Polynucleotides Based on the Distance-Dependent Optical Properties of Gold Nanoparticles*
Robert Elghanian, James J. Storhoff, Robert C. Mucic, Robert L. Letsinger, Chad A. Mirkin
Abstract
A highly selective, colorimetric polynucleotide detection method based on mercaptoalkyloligonucleotide-modified gold nanoparticle probes is reported. Sequence-specific methods for detecting polynucleotides are critical to the diagnosis of genetic and pathogenic diseases. The use of mercaptoalkyloligonucleotide-modified Au nano-particles in any sensing scheme requires that they exhibit long-term stability in the presence of high-molecular-weight DNA and in solutions that span a wide range of electrolyte concentration. The high degree of discrimination in these systems may be attributed to two features. Alignment of two relatively short (15 nucleotide) probe oligonucleotides on the target is required for a positive signal. A mismatch in either segment is more destabilizing than a mismatch for a single, longer probe with the same target. As in the spectrophotometric analyses, the colorimetric signal depends on the formation or dissociation of a polymeric network of Au nanoparticles held together by multiple structurally similar tethers, which results in the narrowing of the temperature range observed for the transition.