Major progress in tumor accumulation and penetration of nanomedicine

Nanomedicine has great potential in cancer therapy, but the complex tumor microenvironment greatly prevents nanomedicine from being effectively delivered into tumor in vivo. It has been widely accepted that the encapsulated drugs in the nanoparticles have to go through five major cascading steps, including blood circulation, accumulation in tumor, penetration into the depth of tumor tissue, internalization by tumor cells and then intracellular drug release, before they can exert the anti-tumor efficacy. Among the five steps, drug accumulation in tumor and penetration in the depth of tumor have been the two major issues undermines the antitumor efficacy of nanomedicine. This paper summarizes the new major progress in improving the tumor accumulation and penetration of nanomedicine, especially the technologies that appeared or developed in the last five years.