Selective Colorimetric Detection of Viral DNA Sequence of Hepatitis C Virus Genotype-4 Genetic Material Using Gold Nanoparticles

Simple, fast, economical and selective colorimetric polynucleotide detection based on mercaptoalkyloligonucleotide-modified gold nanoparticle probes which align in a "head-to-tail" fashion onto a target polynucleotide has been investigated. In this nanoparticle-based detection system, of DNA sequence, gold nanoparticles of ∼13 nm diameter, capped with 5/-(alkanethiol) oligonucleotide, were used to detect a 21-base oligonucleotide target. The oligonucleotide target has been selected as the genetic material of HCV, strain 4, which is much common in Egypt. Hybridization of the target with the probes results in the formation of an extending polymeric gold nanoparticles/polynucleotide aggregates, which trigger a red to pinkish/purple color change in solution. The color change is due to the change in the interparticle distance of gold nanoparticles upon hybridization which result in a red shift in the surface plasmon resonance of gold nanoparticles. Hybridization was facilitated by freezing and thawing of the solution. The unoptimized system can detect about 60 picomole of the oligonucleotide target in question.