A Comparative Study of DNA Loading on the Positive and Negative Surface Charge Gold Nanoparticles

Due to their unique properties, functionalized GNPs provide a high potential for solving many problems, such as diagnosis and treatment of genetic diseases using nanotechnology. Depending on the purpose of each experiment, a particular interaction of DNA and nanoparticle is desirable that can be achieved by changing various parameters. The purpose of this study was to investigate the effect of gold nanoparticles surface charge on the conjugation process and the type of DNA interactions, as well as increasing the loading of DNA on the surface of gold nanoparticles.

Two types of 30nm gold nanoparticles with positive and negative charge were synthesized. Gold nanoparticles were functionalized with three different concentrations of DNA. Bioconjugation was investigated using UV-Vis and fluorescence spectroscopy. Quantification of the DNA loading on each nanoparticle surface was done using two methods by fluorescence assay.

The SPR spectrum of nanoparticles confirmed the binding of DNA to the surface of nanoparticles and also illustrates the level of DNA loading to the surface of the nanoparticle, as well as the effect of the surface charge of nanoparticles on the bioconjugation process. The fluorescence assay showed a higher loading of DNA in CTAB-stabilized nanoparticles and more non-specific than citrate-stabilized nanoparticles.

Depending on the surface charge of GNPs, DNA loading on the surface of GNPs occurs with different affinities. Based on the purpose of the study, citrate stabilized GNPs and high concentration of DNA was appropriate to achieve this goal.