Polyplexes chitosan

Koping-Hoggard, M., Varum, K. M., Issa, M., Danielsen, S., Christensen, B. E., Stokke, B. T. 2004. Improved chitosan-mediated gene delivery based on easily dissociated chitosan polyplexes of highly defined chitosan oligomers. GeneTher. 11 1441-1452. 

Danielsen, S., Strand, S., Davies, C.L., Stokke, B.T. Glycosaminoglycan destabilization of DNA—chitosan polyplexes for gene delivery depends on chitosan chain length and GAG properties. Biochim. Biophys. Acta 1721, 44-54 (2005)... 

Table 1 Parameters affecting transfection efficiency (TE) or silencing efficiency (SE) of chitosan polyplexes...

Exceedingly high stability constants of polymer-DNA complexes appear to be a major difficulty for intracellular release of DNA. It was reported that the ability of polymer-DNA complexes to escape the endolysosomal compartment could be correlated to the buffering capacity of the polycation in the pH range of 5-7 (Lu et al, 2008). More specifically, optimal transfection efficiency of chitosan polyplexes can be achieved between pH 6.8 and 7.0. Above pH 7.5, DNA was shown to dissociate from the complex, thus preventing cellular uptake and transfection efficiency. Below pH 6.5, cellular uptake was significant but transfection efficiency was low, possibly due to hindered endosomal release (Ishii et al, 2001 Sato et al., 2001 Mintzer Simanek, 2009). 

Abstract Carbohydrates have been investigated and developed as delivery vehicles for shuttling nucleic acids into cells. In this review, we present the state of the art in carbohydrate-based polymeric vehicles for nucleic acid delivery, with the focus on the recent successes in preclinical models, both in vitro and in vivo. Polymeric scaffolds based on the natural polysaccharides chitosan, hyaluronan, pullulan, dextran, and schizophyllan each have unique properties and potential for modification, and these results are discussed with the focus on facile synthetic routes and favorable performance in biological systems. Many of these carbohydrates have been used to develop alternative types of biomaterials for nucleic acid delivery to typical polyplexes, and these novel materials are discussed. Also presented are polymeric vehicles that incorporate copolymerized carbohydrates into polymer backbones based on polyethylenimine and polylysine and their effect on transfection and biocompatibility. Unique scaffolds, such as clusters and polymers based on cyclodextrin (CD), are also discussed, with the focus on recent successes in vivo and in the clinic. These results are presented with the emphasis on the role of carbohydrate and charge on transfection. Use of carbohydrates as molecular recognition ligands for cell-type specific dehvery is also briefly... 

Chitosan is generally considered nontoxic, with the rare reported toxicity explained by Koping-Hoggard et al. as a result of impurities [94]. In their study conducted with ultrapure chitosan, transfection efficiency of 293 cells was shown to be dependent on the polyplex stability, which in mm was dependent on the deacetylation degree of chitosan. A deacetylation degree of at least 65% was... 

The size of the polyplex depends not only on the chemical structure of chitosan but also on the ratio between chitosan and DNA used for polyplex formulation, the concentrations of polymers, and formulation technique. This is commonly described in terms of N/P ratio, the ratio of protonatable polymer amines to... 

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. 

Cationic polymers, such as poly(L-lysine) (PEL), polyethylenimine (PEI), chitosan, polyamidoamine (PAMAM) dendrimers, poly(2-dimethylamino) ethyl methacrylate, and polyphosphoesters, condense DNA to form compacted polyplexes. ° The size and the stability of polyplexes depend on the ratio of cations vs. anions, temperature, ionic strength, and the solvent. Stability of polyplexes can be enhanced by conjugating PEG to the polycations or by using PEG-containing block or graft polymers that form micelles. Small cationic peptides are also able to condense DNA, however, six-consecutive-cations is the minimal requirement to achieve this effectively. 

Varkouhi AK, Verheul RJ et al (2010) Gene silencing activity of siRNA polyplexes based on thiolated N, N, N-trimethylated chitosan. Bioconjug Chem 21 2339-2346... 

Thibault M, Nimesh S et al (2010) Intracellular trafficking and decondensation kinetics of chitosan-pDNA polyplexes. Mol Ther 18 1787-1795... 

Strand SP et al (2010) Molecular design of chitosan gene delivery systems with an optimized balance between polyplex stability and polyplex unpacking. Biomaterials 31(5) 975-987... 

In another interesting report, Jiang et al. showed the successful liver transfection after IP administration of galactosylated chitosan-graft-PEI (GC-g-PEI). Significant GFP expression was observed after IP administration of the polyplexes prepared from GC-g-PEI which was in agreement with the results of the successful in vivo biodistribution using Tc-GC-g-PEI by the same route of administration." Apart from successful DNA delivery by injectable carriers. 

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