Tunable stabilization of gold nanoparticles in aqueous solutions by mononucleotides.

Gold nanoparticles are one of the popular nanomaterials, widely used in biosensor applications as well as nanostructure construction. An essential attribute of these gold nanoparticles (Au-nps) is their stabilization against salt-induced aggregation. In this work, utilization of deoxyribonucleotides (dNTPs) as a tunable surface-stabilization agent for Au-nps was investigated. It was found that surfaces of Au-nps are covered by a layer of dNTPs after an adequate incubation with dNTPs solutions. Electrostatic repulsion among dNTP-coated Au-nps could prevent aggregation of Au-nps at a high salt concentration. The strength of dNTP-based protection can be manipulated by changing preparation protocols (e.g., incubation temperature, ionic strength, and ratio of Au-nps to dNTPs). Four different types of dNTPs exhibit different binding affinity to Au-nps and thus various stabilization efficiency in the order of dATP > dCTP > dGTP approximately dTTP. Moreover, this salt-induced aggregation can be reinitiated by the increase of solution temperature, which leads to a partial removal of the protective dNTP layer on Au-nps. The advantage of thermally tunable aggregation/dispersion of Au-nps mediated by dNTP adsorption offers a useful approach for the preparation of biomolecule (oligonucleotides and oligopeptides) modified nanoparticles in applications of bioassay and nanobiotechnology.