Dispersions based on noble metal nanoparticles-DNA conjugates.

Many biomolecules have specific binding properties in the nanostructure formation; they are attractive materials for nanotechnology. One such promising construction material for growing a well-defined nanostructure is deoxyribonucleic acid, due to its π-electron hydrophobic core and predictable recognition attributed to the specificity of Watson-Crick base-pairing. Hydrogen bonding provides the specificity behind the matching of complementary pairs of single-stranded (ss) DNA to hybridize into a double strand (ds) of helical DNA. The double-helical structure of DNA is determined by a subtle balance of noncovalent interactions among the DNA building blocks. The most prominent role is played by the interactions between the DNA bases, where two binding motifs can be recognized: planar hydrogen bonding and vertical stacking. DNA-based nanotechnology has generated interest in a number of applications due to the specificity, programmability, and reproducibility of DNA interaction with noble metal nanoparticles. 5' and 3' thiol moieties are used to prepare composite DNAs, DNA-gold nanoparticle conjugates and nanostructures with a variety of nanoparticle-based DNA assays. Particularly, color changes induced by the association of nanometer-sized gold particles provide a basis of a simple yet highly selective method for detecting specific biological reactions between anchored ligand molecules and receptor molecules in the milieu. Colloidal noble metal nanoparticles, in particular, have found application in a variety of assay formats in which analyte binding is coupled to particle adsorption. The extreme sensitivity of the bandwidth, the peak height, and the position of the absorption (or scattering) maximum of surface plasmon resonance spectra to environmental changes have prompted the development of approaches directly monitor the DNA hybridization. The same features that make DNA an effective molecule for the storage of genetic information also render it useful as an engineering material for the construction of smart objects at the nanometer scale because of its ability to self organize into desired structures via the specific hybridization of complementary sequences. Biocompatibility between gold nanomaterials and biological scaffolding is crucial to the development of smart biomaterials. These DNA/metal colloids are interesting for their fundamental properties as well as for applications in nanomaterials science and nanobiotechnology.