Effects of micro/nano particle size on cell function and morphology

The cytotoxicity of micro/nano particles in Ti, TiO and carbon nanotube was investigated by in vitro biochemical analyses using human neutrophils. The particles smaller and larger than the neutrophils were used to determine the relationship between cell and particle size with respect to cytotoxicity. As the particle size decreased, the cell survival rate was decreased and, with the good corresponding relation to this, the value of lactate dehydrogenase (LDH), which is the indication of cell disruption, was increased. The release of superoxide anion showed the increasing tendency. Proinflammatory cytokines were detected distinctly for 3 mum or smaller particles and very little in more than 10 mum, which is closely related to the phagocytosis by neutrophils. ICP elemental analysis showed that the dissolution from Ti particles was below detection limit. Micro and nano particles stimulated the cell reactions according to the results of the human neutrophil functional tests. As the particle size was smaller, the inflammation was pronounced. The fine particles less than 3 mum caused distinctly the inflammation in the surrounding tissue. All these results indicated that the cytotoxicity was induced due to the physical size effect of particles, which is different from the ionic dissolution effect. The clinical phenomenon confirmed the result obtained in vitro cell tests. The neutrophils stimulated by fine particles may cause the inflammatory cascade and harm the surrounding tissue.