Effect of Gold Nanoparticle Aggregation on the Kinetic Aspect of AuNPs/DNA Interactions

Since successful therapy for curing cancer and others genetic diseases requires the transport of DNA into the cell by delivery vehicles, the understanding of the factors that control the complexation and condensation of the DNA is a key problem. During the last decade, researchers have developed some uses of nanoparticles-DNA systems, the majority of these studies dealing with NPs, which are covalently bound to the DNA. However, the kinetic aspect of AuNPs/DNA system by non-covalent interactions is less explored. Moreover, the role of high salt concentrations in these studies is of great interest due to the majority of nanoparticles have a great tendency to aggregate upon exposure to biological medium, significantly alter the uptake extent, rate, and mechanism of AuNPs/DNA interaction. As a contribution to this field, we have studied kinetics aspects of the binding of small tiopronin gold nanoparticles, AuNPs, to double stranded DNA in at high salt concentration by using the stopped-flow technique. The kinetic curves are biexponential and reveal the presence of two kinetic steps. Moreover, AFM studies reveal AuNPs aggregation in the presence of high salt content, while the same particle are well-dispersed in water. A two-step series mechanism reaction scheme was proposed. According to the reaction scheme, the formation of an intermediate complex formed by aggregated gold nanoparticles and DNA precedes the rate-determining step of the reaction.