Non-Viral Nucleic Acid Delivery

Peptoids have also shown great utility in their ability to complex with and deliver nucleic acids to cells, a critical step toward the development of antisense drugs, DNA vaccines, or gene-based therapeutics. Most non-viral nucleic acid delivery systems are based on cationic molecules that can form complexes with the polyan-... 

Since the first reports on magnetically enhanced nucleic acid delivery in the year 2000 (1,2), magnetofection has become a well-established method and has been predominantly used for in vitro applications. It has been shown to potentiate viral (3, 4) and non-viral nucleic acid delivery, including plasmids or small constructs such as antisense oligonucleotides, and synthetic siRNA and PCR products (5-10). The nucleic acids can be directly associated with magnetic nanoparticles in... 

DDS systems may be ascribed to more than one type, e.g. nanoparticles or microspheres coated with multilayer films. Cationic polymers are extensively used in nucleic acid delivety and the respective delivery systems may also be considered as DDSs. However, since non-viral nucleic acid delivery with a great potential in gene therapy has become such an intensively studied area, it is out of the scope of the present chapter. 

Finally, Ruthardt andBraeuchle summarize recent findings, describing transfection pathways of non-viral gene carriers by single particle tracking approaches. This approach allows the detailed identification of potential hurdles for efficient nucleic acid delivery from a single cell viewpoint. 

RNAi technology has obvious therapeutic potential as an antisense agent, and initial therapeutic targets of RNAi include viral infection, neurological diseases and cancer therapy. The synthesis of dsRNA displaying the desired nucleotide sequence is straightforward. However, as in the case of additional nucleic-acid-based therapeutic approaches, major technical hurdles remain to be overcome before RNAi becomes a therapeutic reality. Naked unmodified siRNAs for example display a serum half-life of less than 1 min, due to serum nuclease degradation. Approaches to improve the RNAi pharmacokinetic profile include chemical modification of the nucleotide backbone, to render it nuclease resistant, and the use of viral or non-viral vectors, to achieve safe product delivery to cells. As such, the jury remains out in terms of the development and approval of RNAi-based medicines, in the short to medium term at least. 

As previously discussed, the protection of pDNA against degrading enzymes is a critical parameter for a non-viral carrier. Such ability is needed for the polyplex to protect the nucleic acid for an extended period of time in the blood while the polyplex circulates and distributes. Research conducted in 1999 by Richardson and coworkers [101] to study the ability of chitosan to protect against DNase degradation revealed that incubation of polyplexes prepared at NIP ratio of 3/1 in the presence of DNase I (8 U, 1 h incubation) protected pDNA from degradation. Other studies of chitosans as gene delivery vehicles confirm that the NIP ratio has to be at least 3/1 to 5/1 in order to provide a sufficient protective effect against DNases. 

Key Words Transfection Non-viral DNA delivery RNA delivery siRNA delivery Nucleic acid transfer Knockdown Reporter assay. 

One reason can be found in their main characteristics, such as a well-defined size and structure, flexibility, monodispersity and multivalent molecular surface. In particular, cationic dendritic systems have been studied as non-viral delivery carriers of nucleic acids such as oligonucleotides, siRNA, mRNA or DNA and as antimicrobial systems. 

As non-viral delivery vectors of nucleic acids, dendrimers have shown to be able to form stable dendriplexes by electrostatic interaction with nucleic acids these dendriplexes in general are biocompatible over a wide concentrations range, protect the nucleic material from attack of serum proteins or nucleases and are able to internalize these nucleic acids in a large number of cell-lines and primary cell cultures with great efficiency. 

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