1 Biologics, Department of Pharmacy, Faculty of Health and Medical Sciences, Københavns Universitet2 Pharmaceutical Design and Drug Delivery, Department of Pharmacy, Faculty of Health and Medical Sciences, Københavns Universitet3 Drug Research Academy A, Drug Research Academy, Faculty of Pharmaceutical Sciences, Københavns Universitet4 unknown5 Drug Research Academy A, Drug Research Academy, Faculty of Pharmaceutical Sciences, Københavns Universitet6 Pharmaceutical Design and Drug Delivery, Department of Pharmacy, Faculty of Health and Medical Sciences, Københavns Universitet7 Biologics, Department of Pharmacy, Faculty of Health and Medical Sciences, Københavns Universitet
Understanding the delivery dynamics of nucleic acid nanocarriers is fundamental to improve their design for therapeutic applications. We investigated the carrier structure-function relationship of lipid-polymer hybrid nanoparticles (LPNs) consisting of poly(dl-lactic-co-glycolic acid) (PLGA) nanocarriers modified with the cationic lipid dioleoyltrimethyl-ammoniumpropane (DOTAP). A library of siRNA-loaded LPNs was prepared by systematically varying the nitrogen-to-phosphate (N/P) ratio. Atomic force microscopy (AFM) and cryo-transmission electron microscopy (cryo-TEM) combined with small angle X-ray scattering (SAXS) and confocal laser scanning microscopy (CLSM) studies suggested that the siRNA-loaded LPNs are characterized by a core-shell structure consisting of a PLGA matrix core coated with lamellar DOTAP structures with siRNA localized both in the core and in the shell. Release studies in buffer and serum-containing medium combined with in vitro gene silencing and quantification of intracellular siRNA suggested that this self-assembling core-shell structure influences the siRNA release kinetics and the delivery dynamics. A main delivery mechanism appears to be mediated via the release of transfection-competent siRNA-DOTAP lipoplexes from the LPNs. Based on these results, we suggest a model for the nanostructural characteristics of the LPNs, in which the siRNA is organized in lamellar superficial assemblies and/or as complexes entrapped in the polymeric matrix.
Journal of Controlled Release, 2015, Vol 201, p. 22-31