Evaluation of asymmetric liposomal nanoparticles for encapsulation of polynucleotides.

Conventional lipid bilayer liposomes have similar inner and outer leaflet compositions; asymmetric liposomes have different lipid leaflet compositions. The goal of this work is to place cationic lipids in the inner leaflet to encapsulate negatively charged polynucleotides and to place neutral/anionic lipids on the outer leaflet to decrease nonspecific cellular uptake/toxicity. Inverse emulsion particles have been developed with a single lipid leaflet of cationic and neutral lipids surrounding an aqueous core containing a negatively charged 21-mer DNA oligo. The particles are accelerated through an oil-water interface, entrapping a second neutral lipid to form oligo encapsulated unilamellar liposome nanoparticles. Inverse emulsion particles can be consistently produced to encapsulate an aqueous environment containing negatively charged oligo. The efficiency of encapsulated liposome formation is low and depends on the hydrocarbon used as the oil phase. Dodecane, mineral oil, and squalene were tested, and squalene, a branched hydrocarbon, yielded the highest efficiency.