We evaluated the in vitro
influences of two types of ultrafine titanium dioxide differing in surface treatment and ultrafine zinc oxide on the area rate and length of tubule-like structures using a human angiogenesis kit. In addition, the influences of titanium and zinc oxide ions were evaluated. A comparison of influences on tubule-like structures between the two surface treatment methods of ultrafine titanium dioxide showed only slight influences of surface treatment providing water-repellency. Using ultrafine zinc oxide, no tubule-like structure formation was observed. The area rate of tubule-like structures was 84.0% for titanium ions and 78.3% for zinc ions at a concentration of 2.5 ppm, but this rapidly decreased with an increase in the ion concentration. These results may differ from those obtained in the nanoparticle dispersion state. It is possible that in vivo
biological influences also differ between aggregation and dispersion states. Further studies based on the in vivo
dispersion state are necessary.
Key words: titanium dioxide, zinc oxide, ultrafine, tubule-like structure, human angiogenesis kit