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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. (C) 2016 Elsevier B.V. All rights reserved., This work was supported by grants from the Spanish Ministry of Economy and Competitiveness (grant number BFU2014-54660-R) and the Andalusian Government (Excellence Project BIO-2515/2012) to C.S. and from the Spanish Ministry of Economy and Competitiveness (grant number BFU2013-44660-R) and the Andalusian Government (Excellence Project CTS-6587) to C.H.M. Support from the European Region Development Fund (ERDF [FEDER]), is also acknowledged.

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., We are grateful to many colleagues for their helpful suggestions, critical discussions, and comments. We thank Jose Alcami and Mayte Coiras (National Microbiology Center, Majadahonda, Madrid, Spain) for the TZM-bl cells. This work was supported by grants from the Spanish Ministry of Economy and Competitiveness (grant number BFU2014-54660-R) and the Andalusian Government (Excellence Project BIO-2515/2012) to CS and from the Spanish Ministry of Economy and Competitiveness (grant number BFU2016-79699-P) to CHM. Support from the European Region Development Fund (ERDF [FEDER]) is also acknowledged. MSP was supported by a fellowship from the Spanish Ministry of Education (FPU Program [Training Program for Academic Staff]).

Cationic solid lipid nanoparticles (SLNs) have recently been suggested for non-viral gene delivery as a promising alternative to the liposomes. The aim of this study was to investigate the possibility to obtain re-dispersible cationic SLNs after a freeze-drying process in the absence of lyo- and/or cryoprotectors. The physical-chemical characteristics of cationic SLNs and their ability to bind gene material were investigated before and after the freeze-drying. To perform this study three samples of cationic SLNs, based on stearic acid, Compritol or cetylpalmitate, were prepared and characterized by PCS (photon correlation spectroscopy) and AFM (atomic force microscopy). The results indicated that solely the re-dispersed sample of stearic acid (SLN-SA) became very similar in terms of size and morphology to the fresh prepared sample, although it displayed a sensible reduction of the zeta potential (from 39.2 to 23.3 mV). By both the DSC (differential scanning calorimetry) and the ESCA (electron spectroscopy for chemical analysis) determinations, the reduction of the zeta potential was ascribed to the loss of the cationic lipids from the particle surface due to the rearrangement of the stearic acid lattice after the freeze-drying. Finally, the gel electrophoresis analysis demonstrated that SLN-SA re-suspended in PBS are unable to complex the DNA, while the SLN-SA re-dispersed in water displayed the same ability to bind DNA as the fresh prepared sample. We can conclude that cationic SLNs, based on stearic acid, retain the ability to complex DNA even after the freeze-drying in the absence of lyo- or cryoprotectors; thus, the powder form of this sample represents an attractive candidate to be investigated as in vivo DNA vector formulation.