ABSTRACT
Acknowledgments .........................................................................................................................154
References .....................................................................................................................................155
The concept of membrane includes two differing interfacial entities in biology: tissue barriers such
as the mucus barrier for the inner or luminal tissue lining of the airways on the one hand, and cell
layers, the cell membrane itself, lipid air-water films, and lipid bilayers, as biophysical models for
the cell interfacial layers on the other hand. The tissue membrane lining the airways forms a barrier
that protects the underlying tissue layers. However, increasing scientific evidence has demon-
strated, for instance, that nanoparticles cannot only cross easily tissue membranes, they also can
pass subsequently into secondary organs by crossing cell boundaries, including the outer cellular
membranes as well as internal cellular membranes like the nuclear membrane and membranes of
organelles. These organelles encompass structural and functional units including mitochondria,
endoplasmic reticulum, the Golgi apparatus, lysosomes, and others. Cellular membranes are
composed of phospholipids, glycolipids, and numerous membrane proteins.
