“The small size of nanoparticles allows them to enter cells and cell organelles to a greater extent than larger particles (depending also on surface chemistry and charge); inside cells, nanoparticles can damage mitochondrial membranes, cause oxidative stress, and increase cell death.”1
1. P. Schulte, C. Geraci, R. Zumwalde, M. Hoover, and E. Kuempel, “Occupational Risk Management of Engineered Nanoparticles,” Journal of Occupational and Environment Hygiene 5(4)239-249 (April 2008) .