Biomedical Engineering Reference
In-Depth Information
Figure 4-2
Schematic structure of different nanocarriers for
drug delivery in brain tumors.
morphology, and size. When injected intravenously, particles are cleared
rapidly from the circulation, predominantly by the liver and the spleen mac-
rophages [35]. Opsonization, which is surface deposition of blood opsonic
factors such as fibronectin, immunoglobulins, and complement proteins,
often aid particle recognition by these macrophages. Size and surface char-
acteristics of nanoparticles both play an important role in blood opsoniza-
tion processes and clearance kinetics. Larger particles (200 nm and above)
are more efficient at activating the human complement system and hence
are cleared faster from the blood by Kupffer cells. The binding of blood
proteins and opsonins to NPs differ considerably in amount and in pattern
depending on surface properties, such as the presence and type of functional
groups and surface charge density [35-36]. Indeed, precision surface engi-
neering with synthetic polymers can resolve aggregation and afford control
over nanoparticle interaction and their fate with biological systems. This
strategy suppresses macrophage recognition by an array of complex mecha-
nisms, which collectively achieve reduced protein adsorption and surface
