ABSTRACT
Figure 6.1 Illustration of the main routes by which NP may access the body. The organization of this chapter is according to the different aspects of the interaction of NPs with biological components and/or systems that NPs encounter sequentially along their life cycle in biological environments (Fig. 6.2). The lung is considered by far the most important portal of entry for NPs into the human body. As illustrated in Fig. 6.2, therefore the interactions of NPs with the surfactant layers of the alveolar tract is the first point of contact. As opposed to larger particles, which are mainly deposited at the walls of the upper airways, nanoparticles are unique in that they follow the air-flow all the way down to the alveoli. After penetration through the lung epithelial cell system they are exposed to body fluids including proteins. As will be shown below, the interactions of NPs with proteins to establish a protein
corona are an integral part of existence of all NPs in any biological environment. The step following protein corona formation is the entry of NPs into cells or even the cell nucleus. The cell membrane (plasma membrane) forms an effective selective barrier between the cytosol and the extracellular environment. It maintains a selectively permeable interface to ions and organic molecules and controls traffic through a variety of active and passive routes that allow the exchange with substances varying in size, shape, charge and chemical composition.
