Simply constructed chitosan nanocarriers with precise spatiotemporal control for efficient intracellular drug delivery.

A novel intelligent nanocarrier with pH and redox sensitivities was developed based on Carboxymethyl-chitosan (CMCS) and thioglycolic acid conjugated chitosan (TCS) to provide precise spatiotemporal control for efficient intracellular delivery. Doxorubicin (DOX) loaded nanocarriers (DOX/CMCS-TCS NPs) were simply prepared by ionic gelation and then oxidation crosslink. The nanocarriers exhibited decent stability at pH 7.4 for up to 3days and underwent aggregation under acidic pH (5.5) due to protonation of the carboxyl groups on CMCS. The TCS skeleton was stable at pH 5.5 (mimic endo/lysosomes) but disintegrated in the presence of 10mM glutathione (GSH) at pH 7.4 (mimic cytosol). In vitro DOX release from DOX/CMCS-TCS NPs was enhanced at pH 5.5 compared with physiological condition, with 64.2% and 31.6% DOX released in 2h, respectively. While 85.2% of DOX was released within 2h as treated with 10mM GSH, suggesting the release was closely associated with structural disintegration of nanocarriers. The maximum release of DOX was obtained at 10mM GSH and pH 5.5 with 92.3% of DOX released in 5h. Confocal laser scanning microscopy observation indicated that DOX/CMCS-TCS NPs efficiently escaped from endo/lysosomes within 1h incubation with MCF-7 cells and gave the best performance in delivering DOX into nucleus in 2h. Anticancer activity assay revealed that DOX/CMCS-TCS NPs had comparable or even better inhibition of cell viability at high drug concentrations than free DOX, with the IC of 0.6μg/mL following 48h incubation. In summary, the simply constructed DOX/CMCS-TCS NPs could not only respond to intracellular delivery temporally, they also achieve rapid release spatially in nucleus, which provide a precise spatiotemporal control of drug delivery for cancer therapy.