The effect of the degree of chitosan deacetylation on the efficiency of gene transfection.

Chitosans with various degrees of deacetylation were synthesized by acetylation with acetic anhydride. These chitosans were evaluated for efficacy of nanoparticle formation, DNA binding efficiency, morphology, and in vitro and in vivo gene transfection efficiency. DNA binding efficacy was reduced as degree of deacetylation was decreased, therefore requiring an increased +/-ratio to effect complete DNA complexation. For chitosan with a molecular weight of 390 kDa, the +/-ratio to achieve complete DNA complexation for degrees of deacetylation of 90%, 70% and 62% was 3.3:1, 5.0:1, and 9.0:1, respectively. The size and morphology of these nanoparticle formulations were not significantly different. The decreased degree of deacetylation results in a decrease in overall luciferase expression levels in HEK293, HeLa, and SW756 cells due to particle destabilization in the presence of serum proteins. However, intramuscular luciferase expression levels increased with decreasing deacetylation over the time points tested. Degree of chitosan deacetylation is an important factor in chitosan-DNA nanoparticle formulation as it affects DNA binding, release and gene transfection efficiency in vitro and in vivo.