Despite several advantages of non-viral vectors over viral vectors in gene therapy, few clinical trials have investigated non-viral systems. A major reason for the suboptimal performance of non-viral gene approaches is their low transfection efficiency especially in vivo. Extensive investigations into the major limiting factors during the cellular trafficking processes have provided spectra of tools anticipated to circumvent the extracellular and intracellular obstacles in successful use of non-viral systems. Polymeric vectors demonstrate great flexibility in their design and functionalization. Biodegradable or non-degradable polycations are often used as DNA condensing vectors and modifying a few functional groups helps targeting and trafficking into the nucleus. However, current approaches are not truly well-defined because the modified polycations are electrostatically and randomly complexed with anionic genes. A poorly defined vector preparation with a few functionalities and inadequate exposure of the functional groups at the right places are primarily responsible for low efficiency. A novel approach proposed in this application is to accommodate all functionalities (as many as needed) for gene trafficking from an injection site to the nucleus, which include shielding the positively charged surface in the blood stream, cell targeting ligands, endosomolytic agents, controlled release of DNA from polyplex, nuclear pore dilation and nuclear import. All these functionalities will be incorporated into nanoscaled assemblies constructed by a layer-by-layer method, resulting in triple layered gene vectors;the core, mantle, and the shell layers. More importantly the nanoconstruct is expected to expose the functional groups at the place required in the intracellular compartments in a well defined manner and each layer will be peeled-off after serving its due role, leaving minimal components for nuclear import of the incorporated gene. This unique assembly approach assures high potential for pharmaceutical gene formulations for future translational studies. The long term goal will be accomplished in four specific aims: first three aims for core layer, mantle layer and shell layer respectively. Each layer will be customized for target cells;proliferating and non-proliferating cells, endosomal pH, and ligand receptor. The fourth specific aim will test and prove the proposed concept in vivo.
Despite several advantages of non-viral vectors over viral owns in gene therapy, particularly in reproducible production of pharmaceutical formulations, most clinical trials for gene therapy employed viral systems. This application is for development of polymeric gene carriers based on a new design concept, which is anticipated to present a high potential for a translational study, for acceptable transfection efficiency in vivo and have minimal toxicity. The novel and unique design principle will accommodate all functionalities required for effective gene transfection and these functionalities will be exposed in the appropriate intracellular compartments where needed the most in a well-defined fashion. The nano-sized gene carrier will be constructed from pharmaceutically-friendly polymers.
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