Abstract
Nanoparticles can be used for cancer diagnosis and treatment, however, their delivery to tumors is challenging. One of the main problems is the lack of understanding of the storage mechanisms of nanoparticles in solid tumors. To solve this problem, two mechanisms of producing nanoparticles to solid tumors and their effect on nanoparticles for cancer applications have been investigated. One of these proposed mechanisms is the effect of permeation and retention (EPR), which states that nanoparticles are inefficient to tumors through endothelial tissue gaps. To solve this problem, an alternative mechanism called the active transport and maintenance effect (ATR) has also been proposed; which suggests the entry, retention and active exit of nanoparticles as the basic mechanisms of nanoparticle production in solid tumors. This mechanism can improve the production of nanoparticles to tumors and increase the efficiency of cancer treatment. This article provides an overview that the mechanisms of delivery of nanoparticles to solid tumors are critical for the advancement of nanomedicine in determining ways to cure cancer.