Fig 1.

A. Passive targeting of liposomes. (1) Selective accumulation of liposomes through leaky vasculature surrounding the tumors. (2) Size-dependent retention of liposomes in the tumor tissue. Drugs alone can diffuse back to the bloodstream, reducing drug concentration in the targeted site, while drug-loaded liposomes stay concentrated in the targeted site due to its particle size. B. Active targeting strategies. Targeting peptides grafted at the surface of liposomes bind to receptors (over)expressed by (1) cancer cells or (2) angiogenic endothelial cells (adapted with permission from [15]).