Size-dependent in vitro cytotoxicity assay of gold nanoparticles

Gold nanoparticles (AuNps) may serve as a promising model to address the size-dependent biological response of cell lines. Their size can be controlled with great precision during chemical synthesis. AuNps have potential applications in drug delivery, cancer diagnosis, and therapy, in the food industry, and for environmental remediation. However, some of the recent literature contains conflicting data regarding the cytotoxicity of gold nanoparticles. Against this background, a systematic study of water soluble gold nanoparticles stabilized by citrate ranging in size from 3nm to 45nm were synthesized. The cytotoxicity of these particles were tested by employing the (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide reduction assay), the neutral red cellular uptake assay, and lactate dehydrogenase release assay. Noticeable differences in the cytotoxic effects depending on the assay, and the nanoparticle size have been found. Citrate stabilized gold nanoparticles with sizes of 3nm, 8nm, and 30nm were more sensitive to the cell lines and caused gradual cell death within 24h at higher concentrations. This results in IC50 values ranging from 57 to 78gmL1 depending on the particle size, and cell line combinations. In contrast, AuNps with diameters of 5nm, 6nm, 10nm, 17nm, and 45nm were nontoxic up to three to four fold higher concentrations, and at long-term exposure.