Aggregation of gold nanoparticles and DNA damage by atomic force microscopy

Abstract

The plasmid DNA binding and cleavage activities with gold nanoparticles (Au-NPs) were investigated by the integrated tools of UV-vis spectroscopy, atomic force microscopy (AFM), and DNA electrophoresis. The results showed that the absorbance of Au-NPs decreased at 520 nm and a new absorption peak at 570 nm was found, as the DNA concentration increased, which indicated the particle aggregation. AFM experiments showed that DNA-induced particle aggregation originated from the strong interactions between DNA and Au-NPs, that is, the adsorption of DNA onto the Au-NPs surface would result in particle aggregation. After a short period of time, the Au-NPs were easier to aggregate in the presence of the higher concentration of DNA. At the early stage of incubation, the DNA double helix conformation was substantially changed by particles. The electrophoresis manifested the absorption and damage appeared on the native DNA molecules. With a longer treating time, the molecules were broken into fragments. The DNA damage was deemed to be a gradual process. The nonspecific interactions between DNA and Au-NPs resulted in the binding of DNA to the Au-NPs surface. Consequently, not only Au-NPs were aggregated but also DNA was damaged.

Keywords

plasmid DNA / gold nanoparticles / damage / aggregation / AFM

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