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Marc Suñé-Pou,1–3 Silvia Prieto-Sánchez,2 Younes El Yousfi,2 Sofía Boyero-Corral,2 Anna Nardi-Ricart,1 Isaac Nofrerias-Roig,1 Pilar Pérez-Lozano,1,3 Encarna García-Montoya,1,3 Montserrat Miñarro-Carmona,1,3 Josep Ramón Ticó,1,3 Josep Mª Suñé-Negre,1,3 Cristina Hernández-Munain,4 Carlos Suñé2 1Service of Development of Medicines (SDM), Faculty of Pharmacy, University of Barcelona, Barcelona, Spain; 2Department of Molecular Biology, Institute of Parasitology and Biomedicine “López-Neyra” (IPBLN-CSIC), Granada, Spain; 3Pharmacotherapy, Pharmacogenetics and Pharmaceutical Technology Research Group, IDIBELL-UB, Duran i Reynals Hospital, Hospitalet de Llobregat, Barcelona, Spain; 4Department of Cell Biology and Immunology, Institute of Parasitology and Biomedicine “López-Neyra” (IPBLN-CSIC), Granada, Spain Background: Cationic solid lipid nanoparticles (SLNs) have been given considerable attention for therapeutic nucleic acid delivery owing to their advantages over viral and other nanoparticle delivery systems. However, poor delivery efficiency and complex formulations hinder the clinical translation of SLNs. Aim: The aim of this study was to formulate and characterize SLNs incorporating the cholesterol derivative cholesteryl oleate to produce SLN–nucleic acid complexes with reduced cytotoxicity and more efficient cellular uptake. Methods: Five cholesteryl oleate-containing formulations were prepared. Laser diffraction and laser Doppler microelectrophoresis were used to evaluate particle size and zeta potential, respectively. Nanoparticle morphology was analyzed using electron microscopy. Cytotoxicity and cellular uptake of lipoplexes were evaluated using flow cytometry and fluorescence microscopy. The gene inhibition capacity of the lipoplexes was assessed using siRNAs to block constitutive luciferase expression. Results: We obtained nanoparticles with a mean diameter of approximately 150–200 nm in size and zeta potential values of 25–40 mV. SLN formulations with intermediate concentrations of cholesteryl oleate exhibited good stability and spherical structures with no aggregation. No cell toxicity of any reference SLN was observed. Finally, cellular uptake experiments with DNA- and RNA-SLNs were performed to select one reference with superior transient transfection efficiency that significantly decreased gene activity upon siRNA complexation. Conclusion: The results indicate that cholesteryl oleate-loaded SLNs are a safe and effective platform for nonviral nucleic acid delivery. Keywords: cationic solid lipid nanoparticles, SLNs, cholesteryl oleate, plasmid DNA, siRNA, transfection, cytotoxicity, uptake

Non-viral delivery using cationic solid lipid nanoparticles (SLNs) represents a useful strategy to introduce large DNA and RNA molecules to target cells. A careful selection of components and their amounts is critical to improve transfection efficiency. In this work, a selected and optimized formulation of SLNs was used to efficiently transfect circular DNA and linear RNA molecules into cells. We characterized the main physicochemical characteristics and binding capabilities of these SLNs and show that they deliver DNA and RNA molecules into cells where they display full bioactivity at nontoxic concentrations using fluorescence- and luminescence-based methodologies. Hence, we established a novel and simple SLN formulation as a powerful tool for future therapeutic use. [ABSTRACT FROM AUTHOR]