  We report on the interaction of pulmonary surfactant composed of
phospholipids and proteins with nanometric alumina (Al2O3) in the context of
lung exposure and nanotoxicity. We study the bulk properties of
phospholipid/nanoparticle dispersions and determine the nature of their
interactions. The clinical surfactant Curosurf, both native and extruded, and a
protein-free surfactant are investigated. The phase behavior of mixed
surfactant/particle dispersions was determined by optical and electron
microscopy, light scattering and zeta potential measurements. It exhibits broad
similarities with that of strongly interacting nanosystems such as polymers,
proteins or particles, and supports the hypothesis of electrostatic
complexation. At a critical stoichiometry, micron sized aggregates arising from
the association between oppositely charged vesicles and nanoparticles are
formed. Contrary to the models of lipoprotein corona or of particle wrapping,
our work shows that vesicles maintain their structural integrity and trap the
particles at their surfaces. The agglomeration of particles in surfactant phase
is a phenomenon of importance since it could change the interactions of the
particles with lung cells.
