The schematic illustration of the mechanisms of SWCNT to induce cell damage. Based on the studies of Yang et al. . SWCNTs interact with the mitochondria electron transmission chains (ETC) (by binding to ETC?) after they enter into mitochondria (1); The interaction of SWCNTs with ETC blocks the transmission of electrons, which results in the increase of the leaking of free electrons from ETC (2); The leaked free electrons form free radicals H2O2 or reactive oxygen species (ROS) (3); The free radicals or ROS attack the membrane system of mitochondria through peroxidation (4); Then the free radicals or ROS diffuse through the damaged mitochondrial membrane to lysosomes to destroy the membrane of the lysosomes (5); The injured lysosomes release digestive enzymes, leading to the damage or death of the whole cells. On the other hand, the blocking of ETC makes mitochondria incapable of producing ATP (7), which results in the depletion of energy for the living activities of the cells, also leading to the damage or death of the whole cells (8).