Interaction of soot derived multi-carbon nanoparticles with lung surfactants and their possible internalization inside alveolar cavity.

A systematic investigation of interaction of multi-carbon nanoparticles, obtained from soot, with dipalmitoyl phosphatidylcholine (DPPC), a clinical pulmonary phospholipid surfactant, sold under trade name "Survanta", was undertaken to establish a model for internalization of these nanoparticles inside alveolar cavity. In vitro experiments were carried out to establish the phospholipid assisted dispersion mechanism of carbon nanoclusters (size approximately 150 nm, zeta potential approximately -15 mV) in water. Results obtained from an array of experimental methods, like dynamic laser light scattering, electrophoresis, UV-absorption spectroscopy, surface tension studies and transmission electron microscopy, revealed that the carbon nanoparticles interacted with DPPC predominantly via hydrophobic interactions. Selective surface adsorption of DPPC molecules on nanoparticle surface was found to be strongly dependent on the concentration of the phospholipid. DPPC, a gemini surfactant, formed a rigid monolayer around the carbon nanocluster even at nanomolar concentration and provided excellent stability to the dispersion. Based on the experimental data it is proposed that the free-energy gain involved in the hydrophobic interactions will facilitate the internalization of these nanoparticles on the inner wall of the alveolar cavity.