Stimuli-responsive charge-reversal nano drug delivery system: The promising targeted carriers for tumor therapy.

The stimuli-responsive charge-reversal nano drug delivery system (CRNDDS) for the treatment of tumors has attracted much attention as an effective drug delivery system. The charge-reversal nanocarriers are either uncharged or negatively charged under normal physiological environment; however, they acquire positive charged in tumor tissue microenvironment. The process of charge reversal from negative-to-positive results in not only quick drug release in acidic environment but also enhance the cellular uptake of drug through electrostatic absorptive endocytosis resulting in improvement of cancer therapeutic outcome. In this review, we discuss the recent advances in the study of charge-reversal nanocarriers that could control the distribution of drugs in response to specific stimuli, such as pH, reduced glutathione (GSH) concentration, enzyme concentration, light and thermal stimulation. The applications of CRNDDS in the tumor treatment was also analyzed and summarized.