Drug release kinetics analysis of CURE

Given that Cu2+ could be reduced by GSH, NanoCURE might be disassembled by high levels of GSH in tumor cells, thus effectively releasing the loaded BTZ and LOx. To verify this, the drug release behavior was investigated. The CURE nanoparticles (1 mg/mL) were encapsulated in dialysis bags with a molecular weight of 3000 and then incubated with the following solution: (1) phosphate buffer saline (PBS); (2) PBS + 0.5 mM GSH; (3) PBS (pH = 5.5); (4) PBS (pH = 5.5) + 0.5 mM GSH. After incubation at 37℃ 200 rpm, the dialysate was collected at indicated time points (0 h, 0.5 h, 1 h, 2 h, 4 h, 8 h, 12 h and 24 h) and analyzed the released BTZ level by HPLC. BTZ could be released efficaciously in PBS (pH 7.4) containing 10 mM GSH or a pH 5.5 solution. However, only a few released BTZ were observed. Moreover, in a pH 5.0 solution containing 10 mM GSH, CURE could completely dissociate and quickly release most of the loaded BTZ. These results suggested that NanoCURE possessed excellent GSH and pH dual-responsive performance and could be specifically activated within the tumor microenvironment.