Poly(d,l-lactic acid) and chitosan complexes: interactions with plasmid DNA

The use of sub-micrometric particles for DNA delivery is an extensively investigated approach to increase the efficiency of genetic vaccines. New particulate DNA carriers were prepared by surface modification of pre-formed poly(d,l-lactic acid) (PLA) particles with various chitosans. The investigation of their abilities to bind DNA showed that this type of biodegradable carriers could interact with DNA in acidic or neutral media, despite the net negative charge of the carrier, in the latter case. At pH 7, hydrogen bonding could be responsible for the binding of DNA but, since 8 M urea did not completely suppress them, hydrophobic interactions should be considered as well. Neither the degree of acetylation (DA) of chitosan nor its molecular weight impacted the ability at binding DNA. The release of plasmid DNA on storing in various buffers increased with the pH of the storing medium, but the percent of DNA released was never higher than 60.