Biodistribution of gold nanoparticles and gene expression changes in the liver and spleen after intravenous administration in rats.

Biodistribution of gold nanoparticles (AuNPs) in more than 25 organs were examined on 1 day, 1 week, 1 month and 2 months after a single intravenous (i.v.) injection in rats. Au was rapidly and consistently accumulated in liver (49.4+/-50.4-72.2+/-40.5 ng/g) and spleen (8.4+/-5.0-9.5+/-6.4 ng/g) throughout the entire timeframe of the study (2 months). Significant accumulation of Au in kidney (up to 5.5+/-2.5 ng/g) and testis (up to 0.6+/-0.1 ng/g) occurred from 1 month post-injection when Au level in urine and feces decreased. Significant increase of Au in blood occurred 2 months after injection, coincident with the delayed accumulation in kidney. Au accumulation in lungs was found at 1 day post-injection but decreased within a week. No accumulation of Au was found in the brain. Microarray results of liver and spleen point to significant effects on genes related to detoxification, lipid metabolism, cell cycle, defense response, and circadian rhythm. These results demonstrate that significant biodistribution of Au occurs in the body over 2 months after a single i.v. injection of AuNPs, accompanied by gene expression changes in target organs.