Lung surface is the first line of contact between inhaled carbon nanomaterials, CNMs, and the organism, so this is the place where pulmonary health effects begin. The paper analyzes the influence of several CNMs (single-and multi-walled nanotubes with various surface area: 90-1,280 m 2 /g and aspect ratio: 8-3,750) on the surface-active properties of the lung surfactant, LS, model (Survanta). Effects of CNM concentration (0.1-1 mg/ml) and surface oscillation rate were determined using the oscillating drop method at simulated breathing conditions (2-10 s per cycle, 37 °C). Based on the values of apparent elasticity and viscosity of the interfacial region, new parameters: S ε and S μ were proposed to evaluate potential effect of particles on the LS at various breathing rates. Some of tested CNMs (e.g., COOH-functionalized short nanotubes) significantly influenced the surfactant dynamics, while the other had weaker effects even at high particle concentration. Analysis of changes in S ε and S μ provides a new way to evaluate of a possible disturbance of the basic functions of LS. The results show that the expected pulmonary effects caused by inhaled CNMs at variable breathing rate depend not only on particle concentration (inhaled dose) but also on their size, structure and surface properties. Carbon nanomaterials, CNMs, are used (or can be formed as by-products) in many applications, which can be associated with an unintentional release of nanometric dust to the air 1-7. The aerosol generated in this way is respirable (inhalable) and easily penetrates to the alveolar region of the respiratory system 8,9. A substantial number of inhaled nanoparticles that are deposited in this region can promote direct interactions with the organism 10-12. The first surface met by inhaled particles in the pulmonary region is a thin layer of alveolar liquid on the top of lung epithelium. This layer contains the mixture of specific compounds of the lung surfactant, LS-the structure, which plays a vital role in the physiological functions of the respiratory system 13. It has been recognized that LS is sensitive to inhaled materials 9,14-16 , and the resulting impairment of LS composition and/or properties may contribute to serious health problems, including the acute lung injury and respiratory distress. Accordingly, the analysis of LS properties in the presence of external factors such as micro/nanoparticles or chemicals, can give a preliminary information regarding the possible respiratory health problems that may follow inhalation of these agents 17-20. Because of the high surface-to-volume ratio, inhaled nanoparticles present a particular threat for health even when their deposited mass is not high 21. As shown by the recent studies 22,23 , effect of different nanomaterials on LS system may be highly specific and depend on several particle properties, such as the specific surface area, SSA or degree of hydrophobicity. Particle dose (concentration) is another essential factor in predicting lung toxicity 24. Therefore, the current stu...
