FIGURE 2.

Passive and active targeting of NPs to cancer cells. Targeting of NPs enhance therapeutic efficiency and reduce systemic toxicity. Passive targeting of NPs is mainly achieved by the enhanced permeability and retention (EPR) effect, which exploits the increased vascular permeability and weakened lymphatic drainage of cancer cells and enables NPs to target cancer cells passively. Active targeting is achieved by the interaction between ligands and receptors. The receptors on cancer cells include transferrin receptors, folate receptors, glycoprotein (such as lectin), and epidermal growth factor receptor (EGFR).