BackgroundPulmonary surfactant reduces surface tension and resembles the air−liquid interface in the alveoli where inhaled nanoparticles preferentially deposit. We investigated the effect of titanium dioxide (TiO2) nanoparticles (NP) and microparticles (MP) on biophysical surfactant function after direct particle contact and after surface area cycling in vitro. In addition, TiO2 NP effects on surfactant ultrastructure were visualized. Methods A porcine surfactant preparation (1.5 mg/ml) was incubated with increasing concentrations (0−500 µg/ml) of TiO2 NP or MP. Biophysical surfactant function was measured in a pulsating bubble surfactometer before and after surface area cycling, which was done at 37°C for 8 hours (0.43 Hz). Furthermore, surfactant ultrastructure was evaluated with a transmission electron microscope.
ResultsTiO2 NP but not MP induced a slight surfactant dysfunction. Adsorption surface tension (γads) dose dependently increased from 27.9 ± 4.4 mN/m to 32.5 ± 8.3 mN/m. Surface tension at minimum bubble size only slightly increased from 4.9 ± 1.9 mN/m up to 8.1 ± 4.5 mN/m at high TiO2 concentrations. Presence of NP during surface area cycling markedly increased γads up to 63.6 ± 1.0 mN/m. Surface tension at minimum bubble size increased dramatically to 21.1 ± 0.7 mN/m. Interestingly, TiO2 NP induced aberrations in the surfactant ultrastructure. Lamellar body like structures were decreased in size and deformed. Unilamellar vesicles were induced. In addition, TiO2 particle aggregates were found between single lamellae. Conclusion TiO2 nanoparticles can alter the structure and function of pulmonary surfactant. This abstract is funded by: DFG SFB 587/B8 and Fraunhofer ITEM. Am J Respir Crit Care Med 179;2009:A5255 Internet address: www.atsjournals.org Online Abstracts Issue
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