Redox-Responsive Nanocapsules for Intracellular Protein Delivery
Proteins play a crucial role in life, taking part in all vital processes in the body. Intracellular protein delivery holds enormous promise for biological and medical applications, including cancer therapy, vaccination, regenerative medicine, treatment for loss-of-function genetic diseases and imaging. Engineering vehicles for escorting therapeutic proteins into specific cells in a controlled release fashion has thus generated considerable interest. The development of such therapeutics to selectively target tumor has also been a major research focus in cancer nanotechnology. A novel strategy using polymeric redox-responsive nanocapsules for intracellular protein delivery is described, in which through in situ interfacial polymerization, the target therapeutic protein is noncovalently encapsulated into a biocompatible polymeric shell interconnected by disulfide-containing crosslinkers. The dissociation of the polymeric shell under reducing conditions and the subsequent release of protein were confirmed using cell-free assays in the presence of glutathione. Several therapeutic proteins with different properties, both cytosolic and nuclear, were successfully delivered using the platform. The nanocapsules were demonstrated to be efficiently internalized into mammalian cells through interactions between charge or targeting ligand, and to release the protein in the reducing cytosol in active forms. Using such redox-responsive nanocapsule as a vehicle, pro-apoptotic protein caspase 3 was delivered to induce apoptosis in a variety of human cancer cell lines, including HeLa, MCF-7 and U-87 MG. Tumor-selective killer apoptin was delivered into different breast cancer cell lines as well, which led to rapid resurrection of apoptosis in breast cancer cell lines and shrinkage of xenograft mice models. Tumor suppressor p53 protein, the most commonly mutated protein, was also delivered selectively into tumor cells for apoptosis induction, through targeted redox-responsive nanocapsules. The delivery methodology is general, effective and nontoxic towards healthy cells. This work facilitate the development of new tools for tumorgenesis and drug resistance studies, as well as expanding current therapeutic target pool to many other tumor suppressor proteins for cancer treatment.