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Schlagwörter:
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Zusammenfassung:
Adhesion and engulfment by the membrane are key steps in the endocytosis and exocytosis of nanoparticles by cells, which are the main pathways for transport in and out of the cell. An understanding of particle engulfment is thus essential for many applications such as biomedical imaging and drug delivery, as well as studies of nanotoxicity and viral infection. The engulfment process is governed by a competition between particle-membrane adhesion and membrane bending, and can take place not only in living cells, but also spontaneously in simple model systems consisting of lipid or polymer vesicles in contact with nano- or micron-sized particles. In this chapter, we will present the main theoretical tools and results needed to describe the engulfment of particles by vesicles or ceslls. The particles may have uniform or Janus-like (patchy) surfaces with varying adhesiveness. The membrane may have complex properties, such as nonzero bilayer asymmetry or a non-uniform curvature along its surface. Depending on the local curvature and the asymmetry of the membrane, particles may remain free, or get partially or completely engulfed. In the presence of non-uniform curvature, particles may also experience curvature-induced forces towards regions of lower or higher membrane curvature. Lastly, we also include the possibility of adhesion-induced segregation of membrane components, as in the case of clathrin-mediated endocytosis, and show that the nonmonotonic size-dependence of nanoparticle endocytosis observed in experiments can be explained in this way.
