(618a) Hydrophobically Modified Chitosan Coated Liposomes for Gene Delivery

Non-viral gene delivery is not as effective as viral gene delivery when it comes to transfection efficiency. The highly studied complexes of DNA with cationic polymers and cationic liposomes have major obstacles of inflammatory toxicity, aggregation and rapid clearance from the blood stream. Encapsulating DNA within neutral liposomes has been comparatively less studied than other strategies of gene delivery. Liposomes are known to effectively deliver cargo and they can be coated with some polymers such as polyethylene glycol (PEG) which can enhance their blood circulation half-life and circumvent the problem of aggregation. The concern with PEG coated liposomes is that the covalently attached PEG to the lipid extends inside the aqueous core of the liposomes, which physically hinders the cargo of liposomes. Thus, to encapsulate condensed DNA complexes which are around 100nm in size, larger liposomes are required which are not efficiently taken up by cells. Employing a different polymer for coating liposomes such as hydrophobically modified chitosan (HMC) which coats only the outside of liposomes allows one to encapsulate bigger complexes in small liposomes. HMC has alkyl groups covalently attached to the chitosan backbone which insert themselves in the bilayer of liposomes and at the right concentrations, coat liposomes effectively. Chitosan being a slightly cationic polymer at neutral pH helps the liposomes from aggregation and increases the blood residence time of the liposomes like PEG. Plasmid DNA was condensed in a core using cationic chitosan and polyethyleneimine (PEI) and then encapsulated inside liposomes by using the thin film hydration method. The effect of different molecular weights and concentration ratios of the chitosan on the DNA condensation was evaluated using dynamic light scattering and transmission electron microscopy analysis. Then these various complexes were evaluated for their in vitro transfection. Further in vivo studies are necessary but nonetheless delivering DNA using coated liposomes can be an effective approach as the major difficulties of toxicity, aggregation and rapid clearance can be avoided. This work was supported by the National Science Foundation.