We report the changes in the electrical properties of the lipid-protein film of pulmonary surfactant produced by excess cholesterol. Pulmonary surfactant (PS) is a complex lipid-protein mixture that forms a molecular film at the interface of the lung's epithelia. The defined molecular arrangement of the lipids and proteins of the surfactant film gives rise to the locally highly variable electrical surface potential of the interface, which becomes considerably altered in the presence of cholesterol. With frequency modulation Kelvin probe force microscopy (FM-KPFM) and force measurements, complemented by theoretical analysis, we showed that excess cholesterol significantly changes the electric field around a PS film because of the presence of nanometer-sized electrostatic domains and affects the electrostatic interaction of an AFM probe with a PS film. These changes in the local electrical field would greatly alter the interaction of the surfactant film with charged species and would immediately impact the manner in which inhaled (often charged) airborne nanoparticles and fibers might interact with the lung interface.
A new technique, that involves the plasma processing of frozen hydrocarbons by a pulsed laser generated graphitic plasma, is presented. Polymer‐like hydrogenated amorphous carbon (a‐C:H) thin films were created by allowing the plasma generated during the fs‐pulsed laser ablation of a highly oriented pyrolytic graphite target in high vacuum, to impact on solid layers of n‐hexane (CH3(CH2)4CH3) at 77 K. This technique results in the formation of thin films whose morphology and properties are shown to depend on the plasma processing time tp. Polymer‐like a‐C:H with residual hexane incorporated into the carbon matrix and exhibiting a unique dendritic surface morphology was formed after short processing times. Following longer processing times, these dendritic structures are destroyed resulting in thin films having similar spectral properties to those of conventional a‐C:H. The composition of the plasma was studied using time of flight mass spectrometer (TOF‐MS) and the surface morphology of the synthesized thin films was examined by atomic force microscopy (AFM). A variety of analytic techniques including photoluminescence (PS), UV–Vis absorption, surface enhanced Raman (SERS), and Fourier transform infrared (FTIR) spectroscopy have been used to characterize the structure and composition of these materials.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.