Figure 4.

The figure shows passive (enhanced permeability and retention (EPR) effect) (a) and active tumor targeting (b) of nanoparticles (NPs) for targeted drug delivery. Tumors have disorganized and leaky vasculature with a higher number of pores facilitating the movement of NPs from the vasculature and their accumulation in the tumor environment. Moreover, active targeting makes use of targeting ligands that are attached to NPs and bind specifically to cell surface receptors of tumor cells.