Selective Colorimetric Detection of Polynucleotides Based on the Distance-Dependent Optical Properties of Gold Nanoparticles*
This chapter reports a highly selective, colorimetric polynucleotide detection method based on mercaptoalkyloligonucleotide-modified gold nanoparticle probes. Sequence-specific methods for detecting polynucleotides are critical to the diagnosis of genetic and pathogenic diseases. Most detection systems make use of the hybridization of an immobilized target polynucleotide with oligo- or polynucleotide probes containing covalently linked reporter groups. The chapter reports a highly selective colorimetric detection technology for polynucleotides. First, mercaptoalkyloligonucleotide-modified gold nanoparticles are used as reporter groups rather than radioactive atoms or organic substituents. Second, hybridization results not only in the binding of an oligonucleotide probe to the target sequence, but also in the formation of an extended polymeric network in which the reporter units are interlocked by multiple, short duplex segments. Third, the signal for hybridization is governed by the optical properties of the nanoparticles, which depend in part on their spacing within the polymeric aggregate.