| 초록 |
Current application of nanotechnology to biomedical application mostly intends one way effect like DDS(Drug Delivery System) where the function of nano machine is set to work uni-directionally onto biological organism and subsidiary reaction from organism is unwelcome. However, since the average size of cells is 10 m, micro to nano particles have the competing size with innercellular organs, which gives rise to the potential possibility to interact with cells. The usual and most influential factor of materials to biological organism is chemical effect by ionic dissolution. Whether it is nutrition or toxicity, this effect is dominant and with the decrease of size, therefore the increase of specific surface area (=surface area/volume) leads to the increase of reactivity and enhancement of functions. This effect is strong, easy to recognize but the origin is material without any relation to living organism and the function occurring in nanosizing is essentially the same as in macro and regarded as extrapolation from macro. When particle size becomes smaller than 10 m, it induces phagocytosis to cells and inflammation to tissue whatever material it is. This physical size effect occurs nonspecifically to materials and dependent only on size. The origin is biointeraction between particles and biological organism (cells). Its cytotoxicity is very weak, therefore negligible. However since it induces bioreaction, it leads to the conversion of functions different from those of materials in macro through biological process, such as bone substitutional in nano apatite from non-bone substitional in macro apatite, cell adhesive in carbon nanotubes from non-cell adhesive of macro graphite. Nano-structure induces nano-level reaction of cells. Below 200 nm, particles become less stimulative and the recognition by body defense system becomes weaker. They may invade directly into the internal body through the respiratory or digestive system and diffuse inside the whole body. Thus nanoparticles are essentially bi-directionally reactive between particles and biology, and have the biointeractive nature. [F.Watari et al.: Material nanosizing effect on living organism, J.Roy.Soc.Interface 6, S371-388, 2009] |
