Effect of ionic strength on the interaction of AuNPs with calf spleen DNA

Gold nanoparticles (AuNPs) are well-known biomedical and biotechnological applications because of their interesting properties. They easily cross the cell membranes and interact with intracellular materials. This study was designed to investigate the interaction of calf spleen DNA with AuNPs at a molar ratio of 2:1 in an aqueous solution with different ionic strengths (10, 50, and 100%). AuNPs and AuNPs/DNA complex were characterized by different techniques such as UV/Vis spectrophotometry, transmission electron microscopy (TEM), dynamic light scattering (DLS), and Fourier transform IR spectrophotometry. The results revealed that the maximum absorption ( λ max ) of AuNPs synthesis was observed at 520 nm, and the average particle size was about 13 nm. In addition to a negative zeta potential (− 37 mV), the interaction of AuNPs with DNA was confirmed by melting point and TEM. The melting point that reflects the DNA became unstable in the presence of AuNPs, and the melting temperature decreased by about 3–5 °C with different ionic strength. Additionally, the TEM image of AuNPs/DNA complex obviously illustrated the location of AuNPs on the DNA groove. Finally, these results clearly indicate the attachment of AuNPs with DNA.