The effect of titanium dioxide nanoparticles on pulmonary surfactant function and ultrastructure

Abstract

Background: Pulmonary surfactant reduces surface tension and is present at the air-liquid interface in the alveoli where inhaled nanoparticles preferentially deposit. We investigated the effect of titanium dioxide (TiO2) nanosized particles (NSP) and microsized particles (MSP) on biophysical surfactant function after direct particle contact and after surface area cycling in vitro. In addition, TiO2effects on surfactant ultrastructure were visualized.Methods: A natural porcine surfactant preparation was incubated with increasing concentrations (50-500 μg/ml) of TiO2NSP or MSP, respectively. Biophysical surfactant function was measured in a pulsating bubble surfactometer before and after surface area cycling. Furthermore, surfactant ultrastructure was evaluated with a transmission electron microscope.Results: TiO2NSP, but not MSP, induced a surfactant dysfunction. For TiO2NSP, adsorption surface tension (γads) increased in a dose-dependent manner from 28.2 ± 2.3 mN/m to 33.2 ± 2.3 mN/m (p < 0.01), and surface tension at minimum bubble size (γmin) slightly increased from 4.8 ± 0.5 mN/m up to 8.4 ± 1.3 mN/m (p < 0.01) at high TiO2NSP concentrations. Presence of NSP during surface area cycling caused large and significant increases in both γads(63.6 ± 0.4 mN/m) and γmin(21.1 ± 0.4 mN/m). Interestingly, TiO2NSP induced aberrations in the surfactant ultrastructure. Lamellar body like structures were deformed and decreased in size. In addition, unilamellar vesicles were formed. Particle aggregates were found between single lamellae.Conclusion: TiO2nanosized particles can alter the structure and function of pulmonary surfactant. Particle size and surface area respectively play a critical role for the biophysical surfactant response in the lung. © 2009 Schleh et al; licensee BioMed Central Ltd.