Schematic representation of different routes followed by nanoparticles in cancer therapy. (1) In transcellular route, the drug carrying nanoparticle injected into the bloodstream passes through the endothelial cell and reaches as the cancer site. (2) Whereas in paracellular route, the nanoparticle passes through the inter-endothelial cell spaces and known as active targeting. These nanoparticles induce leakiness by widening the gap between the endothelial cells and enhance the cancer cell targeting also known as naoEL effect. (3) Passive targeting is the classical and common phenomenon where the nanoparticle transverse through the leaky vasculature by EPR effect to the site of cancer cells.