Fig. 5.
Cell and particle interactions. Toxicological effects of nanomaterials can be simplified into eight events as shown in the illustration above but limiting the interaction between a nanoparticle and a cell to eight events is an over simplification and the details of actual phenomena that are happening at the interfaces are very difficult to analyze and understand. (1) Reactive oxygen species products such as superoxide (•O2-) and hydroxyl radical (•OH) whether it is inside or outside can be key factors in nanostructured materials toxicological effects (Nel et al., 2006). Cell membrane integrity leading to cell survivability will be affected by ROS produced by a nanoparticle smaller than a cell (red particle) as shown. (2) Event 2 represents the situation where a nanoparticle is internalized and then creates ROS products (Nel et al., 2006). (3) Particle dissolution affecting cellular function after nanoparticle internalization is event 3 (Borm et al., 2006). (4) Event 4 represents any mechanical damage to sub-cellular units such as the lysosome, endoplasmic reticulum, and nucleus (Yamamoto et al., 2004). (5) Different functional groups and surface electronic structures arising from different nanostructured materials will determine the level of interaction between the nanoparticles and their surroundings which is represented by event 5 (Karakoti et al., 2006; Kostarelos et al., 2007). (6) Overall size of the particle can play an important role as represented by event 6 since large particles can potentially induce permanent damage to the cell membrane while small particles can pass through the membrane and do harm inside cell (Yoshida et al., 2003). (7) Non-spherical particles, on the other hand, might have a different biological response compared to the spherical nanoparticles which is shown as event 7 (Geng et al., 2007). (8) Event 8 represents dissolution characteristics of the nanomaterials outside the cell which can affect the cell in various ways (event 8) (Borm et al., 2006).