Redox-triggered activation of nanocarriers for mitochondria-targeting cancer chemotherapy.

The importance of mitochondrial delivery of an anticancer drug to cancer cells has been recognized to improve therapeutic efficacy. The introduction of lipophilic cations, such as triphenylphosphonium (TPP), onto the surface of nanocarriers was utilized to target mitochondria via strong electrostatic interactions between positively charged TPP and the negatively charged mitochondrial membrane. However, the highly positive charge nature of TPP leads to rapid clearance from the blood, decrease of circulation lifetime, and nonspecific targeting of mitochondria of cells. Here, we report a strategy for improving the anticancer efficacy of paclitaxel via redox triggered intracellular activation of mitochondria-targeting. The lipid-polymer hybrid nanoparticles (LPNPs) are composed of poly(d,l-lactide-co-glycolide) (PLGA), a TPP-containing amphiphilic polymer (C18-PEG2000-TPP) and a reduction-responsive amphiphilic polymer (DLPE-S-S-mPEG4000). The charges of TPP in LPNPs were almost completely shielded by surface coating of a PEG4000 layer, ensuring high tumor accumulation. After uptake by cancer cells, the surface charges of LPNPs were recovered due to the detachment of PEG4000 under intracellular reductive conditions, resulting in rapid and precise localization in mitochondria. This kind of simple, easy and practicable mitochondria-targeting nanoplatform showed high anticancer activity, and the activatable strategy is valuable for developing a variety of nanocarriers for application in the delivery of other drugs.