Among non-viral vectors, chitosan and chitosan derivatives have been developed in
vitro and in vivo for DNA and siRNA delivery systems because of their cationic charge,
biodegradability and biocompatibility, as well as their mucoadhesive and permeability-enhancing
properties. However, the transfection efficiency of chitosan is too low for clinical
application. Studies indicated that the transfection efficiency depends on a series
of chitosan-based formulation parameters, such as the Mw of chitosan, its degree of
deacetylation, the charge ratio of chitosan to DNA/siRNA (N/P ratio), the chitosan
salt form used, the DNA/siRNA concentration, pH, serum, additives, preparation techniques
of chitosan/nucleic acid particles and routes of administration. In this paper, chitosan-based
formulations for the delivery of DNA and siRNA were reviewed to facilitate the process
of chitosan vector development for clinical application. In addition to formulation
optimization, chitosan structure modification or additive incorporation is an effective
way to improve the stability of the polyplex in biological fluids, enhance targeted
cell delivery and facilitate endo-lysosomal release of the complex. In summary, the
transfection efficiency of chitosan-based delivery systems can be adjusted by changing
formulation-related parameters.
2009 Elsevier B.V. All rights reserved.