Enhanced permeability and retention effect: A key facilitator for solid tumor targeting by nanoparticles

Exploring the enhanced permeability and retention (EPR) effect through therapeutic nanoparticles has been a subject of considerable interest in tumor biology. This passive targeting based phenomenon exploits the leaky blood vasculature and the defective lymphatic drainage system of the heterogeneous tumor microenvironment resulting in enhanced preferential accumulation of the nanoparticles within the tumor tissues. This article reviews the fundamental studies to assess how the EPR effect plays an essential role in passive targeting. Further, it summarizes various therapeutic modalities of nanoformulation including chemo-photodynamic therapy, intravascular drug release, and photothermal immunotherapy to combat cancer using enhanced EPR effect in neoplasia region.