Nanoparticle transport pathways into tumors

Two transport pathways (interendothelial and transendothelial routes) have long been proposed for entry of nanoparticles from the blood circulation into solid tumors. We examine and discuss available evidence supporting interendothelial and transendothelial transport processes and suggest new avenues for reevaluating these pathways. Understanding of integrative mechanisms controlling nanoparticle extravasation into tumors is important for improving engineering and performance of anti-cancer nanopharmaceuticals.