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, iii and to release the protein in the reducing cytosol in active forms. Using such redoxresponsive 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.iv The Dissertation of Muxun Zhao is approved.
This study reports a general method of labeling enveloped viruses with semiconductor quantum dots (QDs) for use in single virus trafficking studies. Retroviruses, including human immunodeficiency virus (HIV), could be successfully tagged with QDs through the membrane incorporation of a short acceptor peptide (AP) that is susceptible to site-specific biotinylation and attachment of streptavidin-conjugated QDs. It was found that this AP tag-based QD labeling had little effect on the viral infectivity and allowed for the study of the kinetics of the internalization of the recombinant lentivirus enveloped with vesicular stomatitis virus glycoprotein (VSVG) into the early endosomes. It also allows for the live cell imaging of the trafficking of labeled virus to the Rab5(+) endosomal compartments. This study further demonstrated by direct visualization of QD-labeled virus that VSVG-pseudotyped lentivirus enters cells independent of clatherin- and caveolin-pathways, while the entry of VSVG-pseudotyped retrovirus occurs via the clathrin pathway. The studies monitoring HIV particles using QD-labeling showed that we could detect single virions on the surface of target cells expressing either CD4/CCR5 or DC-SIGN. Further internalization studies of QD-HIV evidently showed that the clathrin pathway is the major route for DC-SIGN-mediated uptake of viruses. Taken together, our data demonstrate the potential of this QD-labeling for visualizing the dynamic interactions between viruses and target cell structures.
Target proteins can be functionally encapsulated using a cocoon-like polymeric nanocapsule formed by interfacial polymerization. The nanocapsule is cross-linked by peptides that can be proteolyzed by proteases upon which the protein cargo is released. The protease-mediated degradation process can be controlled in a spatiotemporal fashion through modification of the peptide cross-linker with photolabile moieties. We demonstrate the utility of this approach through the cytoplasmic delivery of the apoptosis inducing caspase-3 to cancer cells.
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