Advances in the tumor microenvironment-responsive smart drug delivery nanosystem

With the rapid development of nanotechnology and in-depth understanding of tumor microenvironment, stimuli-responsive smart drug delivery nanosystem based on tumor microenvironment(TME)has received extensive attention. TME-responsive smart delivery nanosystem can transport antitumor drug in circulation stably, after arriving in tumor tissue or targeted cells, the structure of nanocarriers changes under the stimuli of TME. Improved drug concentrations in targeted site significantly increase the antitumor efficiency and reduce the side effects of drugs. The stimulating factors in the TME include pH, redox potential, enzyme, reactive oxygen species(ROS), adenosine-5′-triphosphate(ATP)and so on. This review mainly gives a comprehensive overview in the latest research and new development in TME-responsive smart drug delivery nanosystems for efficient tumor therapy, mainly based on pH response type, enzyme response, reduction response, ROS response, and ATP response smart drug delivery nanosystems. Moreover, research directions in the future are pointed out in this review.