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Nanoparticles have specific optical and electric properties. Concerns about the biological effects of these nanoparticles being produced for use in industrial products have arisen since epidemiologic data have shown a correlation between airborne nanoparticles. There is a need for tests that simulate human exposure to nanoparticles to observe their health effects experimentally. Hubbs et al. reviewed that surface area to mass ratio increases as the size of particulates decreases, and the toxicity of particulates often but always, correlates with surface area more than mass.(Toxicologic pathology, 39: 301-324,2011) In this study, we evaluated the pulmonary effect of nano-titanium dioxide and various particles in relation with surface area.
Methods
We used various titanium dioxide particles(P90,P25 and amorphous: 102, 53.8, 110 m2/g, BET surface area respectively), and nickel oxide (88.2 m2/g, BET surface area), and crystalline silica(15.6 m2/g, BET surface area) in this study. Each material was suspended in 0.4 mL distilled water or saline. Each material suspension at the dose of 1mg per rat was intratracheally instilled once to male Wistar rats. At 3days, 1month, and 6 months after instillation, the left lung was clamped and 50 ml of bronchoalveolar lavage fluid (BALF) was collected from the right lung. The number of inflammatory cells in the collected BALF was determined by an automatic cell counter and the neutrophil fraction was counted from the cytospin sample stained by Diff-Quik kit.
Results
In titanium dioxide instillation group, the total cell numbers in BALF showed amorphous>P90>P25 at 3 days after instillation, however, at 1month P25>amorphous>P90. Nickel oxide and crystalline silica have an smaller surface area but the effect (total cell numbers in BALF at 3 days and 1 month) were greater than titanium dioxide.
Discussion
Surface area may be a significant factor for toxicity of nanoparticles.