FIGURE 2.

Schematic representation of active and passive targeting mechanisms. Active targeting is based on the presence of antibodies on the surface of the NP. In passive targeting, NPs mainly diffuse through leaky blood vessels and accumulate in the tumor tissue due to the EPR effect, while active targeting promotes the accumulation of NPs in the immediate vicinity of tumor cells. Formation of an antibody-antigen complex on the surface of cancer cells greatly facilitates endocytosis of the nanoparticles.