Preparation and physicochemical characterizations of solid lipid nanoparticles containing DOTAP$^®$ for DNA delivery


Abstract: The aim of this study was to prepare and evaluate stable cationic solid lipid nanoparticles (SLNs) as colloidal carriers for gene therapy. SLNs were mainly composed of three different biocompatible and biodegradable matrix lipids called tripalmitin, glyceryl dibehenate, and triglyceride, all containing the cationic lipid $N$-(1-(2,3-dioleoyloxy)propyl)-$N,N,N$-trimethylammonium (DOTAP$^®$). Each of these SLNs were divided into three parts and characterized by applying different processes: Part I was autoclaved (121 $^{\circ}$C, 15 min), Part II was lyophilized (5 mbar, --50 $^{\circ}$C), and Part III was kept in its intact form. These parts were stored at 4 $^{\circ}$C, 25 $^{\circ}$C (room temp.), and 40 $^{\circ}$C for short-term stability tests. The formulations were tested physically regarding the particle size and zeta potential. pUC18 plasmid DNA was used as the genetic material. Zeta potentials of all SLNs and pDNA-SLN complexes were determined to be highly positive (between +28.90 and +59.39). Crystallization processes of lipid matrices were characterized by X-ray diffractometry and differential scanning calorimetry. pDNA binding ability of SLNs and the stability of pDNA-SLN complexes with DNase I enzyme were also determined by gel electrophoresis. It was determined that all formulations became positively charged with DOTAP$^®$. They were able to bind DNA and were partially protective against enzyme degradation. Although additional studies are necessary, this study reveals the promising potential of this gene delivery system for gene therapy.

Keywords: Cationic solid lipid nanoparticles, DOTAP$^®$, plasmid DNA, gene delivery, colloidal carriers, preparation, characterization, stability, SLN

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