Poly(lactic acid)-poly(ethylene glycol) nanoparticles as new carriers for the delivery of plasmid DNA

The purpose of the present work was to produce and characterize poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) nanoparticles (size lower than 300 n m) containing a high loading of plasmid DNA in a free form or co-encapsulat ed with either poly(vinyl alcohol) (PVA) or poly(vinylpyrrolidone) (PVP). T he plasmid alone or with PVA or PVP was encapsulated by two different techn iques: an optimized w/o/w emulsion-solvent evaporation technique as well as by a new w/o emulsion-solvent diffusion technique. Particle size, xi poten tial, plasmid DNA loading and in vitro release were determined for the thre e plasmid-loaded formulations. The influence of the initial plasmid loading s (5, 10, 20 mug plasmid DNA/mg PLA-PEG) on those parameters was also inves tigated. The plasmid loaded into the nanoparticles and released in vitro wa s quantified by fluorimetry and the different molecular forms were identifi ed by gel electrophoresis. PLA-PEG nanoparticles containing plasmid DNA in a free form or co-encapsulated with PVA or PVP were obtained in the range s ize of 150-300 urn and with a negative potential, both parameters being aff ected by the preparation technique. Encapsulation efficiencies were high ir respective of the presence of PVA or PVP (60-90%) and were slightly affecte d by the preparation technique and by the initial loading. The final plasmi d DNA loading in the nanoparticles was up to 10-12 mug plasmid DNA/mg polym er. Plasmid DNA release kinetics varied depending on the plasmid incorporat ion technique: nanoparticles prepared by the w/o diffusion technique releas ed their content rapidly whereas those obtained by the w/o/w showed an init ial burst followed by a slow release for at least 28 days. No significant i nfluence of the plasmid DNA loading and of the co-encapsulation of PVP or P VA on the in vitro release rate was observed. In all cases the conversion o f the supercoiled form to the open circular and linear forms was detected. In conclusion, plasmid DNA can be very efficiently encapsulated, either in a free form or in combination with PVP and PVA, into PLA-PEG nanoparticles. Additionally, depending on the processing conditions, these nanoparticles release plasmid DNA either very rapidly or in a controlled manner. (C) 2001 Published by Elsevier Science B.V.