Glutathione-Responsive Gemini Polymeric Micelles as Controlled Drug Carriers

Gemini poly(ethylene glycol)-cystine-poly(s-butyl cysteine) ((PEG)(2)-Cyt-(PBC)(2)) with a cystine disulfide bond as a spacer was prepared via oxidation of the cysteine group of monomeric poly(ethylene glycol)-cysteine-poly(s-butyl cysteine) (PEG-Cys-PBC) in solution, which is specifically cleavable in intracellular compartments. Due to its amphiphilic nature, (PEG)(2)-Cyt-(PBC)(2) formed micelles under aqueous conditions; the average diameter of the micelles was 26.9 nm. The critical micelle concentration (CMC) of the polymer was 15.8 mg/L. The loading content of the chosen model drug, indomethacine (IMC), was much higher for gemini micelles than that for monomeric micelles. The (PEG)(2)-Cyt-(PBC)(2) micelles released 75% of the loaded IMC within 72 h under 10 mM glutathione (GSH), whereas 36% of the loaded IMC was released from the micelles in the absence of GSH. An in vitro cytotoxicity experiment revealed that PTX-loaded gemini micelles showed toxicity to A549 cells with increasing GSH concentrations. Microscopic observation of gemini micelles demonstrated that the micelles containing a disulfide bond could effectively deliver the drug into A549 cells. These results suggest the potential of disulfide-based gemini polymeric micelles as controlled drug delivery carriers.