Microencapsulation of (deoxythymidine)₂₀–DOTAP complexes in stealth liposomes optimized by Taguchi design

Abstract

Stealth liposomes encapsulating oligonucleotides are considered as promising non-viral gene delivery carriers; however, general preparation procedures are not capable to encapsulate nucleic acids (NAs) efficiently. In this study, the lyophobic complexes of deoxythymidine₂₀ oligonucleotide (dT₂₀) and DOTAP were used instead of free dT₂₀ for nano-encapsulation process by reverse phase evaporation method. Regarding the various factors that can potentially affect the liposome characteristics, Taguchi design was applied to analyze the simultaneous effects of factors comprising PEG-lipid (%), dT₂₀/total lipid molar ratio, cholesterol (Chol%) and organic-to-aqueous phase ratio (o/w) at three levels. The response variables, hydrodynamic diameter, loading efficiency (LE%) and capacity (LC%), were studied by dynamic light scattering and ethidium bromide exclusion assay, respectively. The optimum condition described by minimum particle size as well as high LE% and LC% was obtained at 5% PEG-lipid, dT₂₀/total lipid of 7, 20% Chol and o/w of 3 with an average size of 84 nm, LE% = 83.4% and LC% = 11.6%. Moreover, stability assessments in presence of heparin sulfate revealed the noticeable resistance, unlike DOTAP/dT₂₀ lipoplexes, to premature release of NA. Transmission electron microscopy confirmed formation of discrete and circular vesicles encapsulating dT₂₀.

• Microencapsulation
• oligonucleotide
• reverse phase evaporation
• stealth liposome
• Taguchi orthogonal array

Declaration of interest

The authors confirm that there is no conflict of interest. The study was a part of Ms. Shirin Tavakoli thesis that supported financially by the SUMS grant from Shiraz University of Medical Sciences.