Dicationic gemini nanoparticle design for gene therapy

Abstract

Gene therapy is a medical technique whereby genetic defects can be repaired by inserting a normal or functional gene to replace or correct a faulty gene or repress an overexpressing gene. Hence, gene therapy can be used for the treatment of a wide range of diseases, such as cancer, viral infections, and dermatological diseases [1–4]. However, the therapeutic benefits from nucleic acid-based therapy are still unsatisfactory. Introducing nucleic acids into blood or topical application on the skin or mucosal surfaces encounters many barriers that alter their cellular biodistribution and intracellular bioavailability. Following administration, they rapidly degrade in biological fluids by extracellular nucleases before they can reach the surface of the target cells. This definitely influences their activity and interactionwith the cells, compromising the therapeutic outcome of nucleic acids. In addition, nucleic acids have very limited cellular uptake because of their hydrophilic nature and high molecular weight. A small fraction that can be taken up by the cells is usually internalized into vesicles (i.e., endosomes), which convert later into lysosomes. Accumulation and subsequent digestion of the nucleic acids inside the lysosomes preclude them from reaching their cytoplasmic or nuclear targets and is an important barrier to their efficacy. In addition, the nuclear membrane is an additional barrier for the efficient translocation of the plasmid DNA (pDNA) into the nucleus (Figure 23.1). The successful transfection with pDNA or other small nucleic acids (e.g., antisense oligonucleotides, short interfering RNA)must include packaging the DNA/RNA in a delivery system that can compact the nucleic acids and facilitate their transfer through the cell membrane. Many strategies have been investigated to increase the intracellular bioavailability of nucleic acids [5,6]. These delivery systems consist of two types: viral and nonviral. The former have been used in a majority of gene therapy clinical trials, but there is concern and evidence that their use can elicit a strong immune response [7–9]. Due to these events, emphasis over the past decade has begun to shift to the development of nonviral delivery systems. These delivery systems have significant advantages over viral systems, because they are safer to use and easier to prepare and can transfer larger-sized plasmids into cells. However, in order for nonviral delivery systems to be useful in gene therapy, they must have higher transfection efficiencies than have been realized to date. The focus of our research group over the last decade has been to design cationic nonviral systems that improve the efficiency of the gene delivery process.