Scientists from the University of California, Davis and Texas A&M recently collaborated on research into whether certain metal oxide nanoparticles may cause inflammation in the type of cells that line the human circulatory system.  The authors theorized that certain types of metal oxide nanoparticles might be taken up by endothelial cells and cause endothelium inflammation, which in turn has been shown to play a central role in atherosclerosis.  The scientists’ in vitro experiment exposed human aortic endothelial cells to three types of metal oxide nanoparticles — iron oxide, yttrium oxide, and zinc oxide — under a wide range of concentrations and for exposure times ranging between 1 to 8 hours.  The study found that while all three types of nanoparticles were taken up into the cells, only two caused an inflammatory response.  Yttrium oxide and zinc oxide impacted inflammatory markers in the cells, while zinc oxide did not.  Interestingly, the scientists believe that the size and surface area of the nanoparticles were not responsible for the amount of inflammatory response observed.   The smallest nanoparticles with the largest surface area — iron oxide — caused no inflammatory response, while the largest particles with the smallest surface area — zinc oxide — caused the greatest inflammatory response in the study.  The scientists cautioned that no broad conclusions should be drawn from their research, and that both in vitro testing simulating actual blood flow conditions and in vivos tests are necessary.

A. Gojova, et al., "Induction of Inflammation in Vascular Endothelial Cells by Metal Oxide Nanoparticles: Effects of Particle Composition," Environmental Health Perspectives, Vol. 115, No. 3 (March 2007).