Freeze-Dried Targeted Mannosylated Selenium-Loaded Nanoliposomes: Development and Evaluation

The aim of this investigation was to develop and evaluate freeze-dried mannosylated liposomes for the targeted delivery of selenium. Dipalmitoylphosphatidylcholine, distearoylphosphatidylglycerol, and cholesterol were dissolved in a chloroform and methanol mixture and allowed to form a thin film within a rotatory evaporator. This thin film was hydrated with a sodium selenite (5.8 mu M) solution to form multilamellar vesicles and homogenized under high pressure to yield unilamellar nanoliposomes. Se-loaded nanoliposomes were mannosylated by 0.1% w/v mannosamine (Man-Lip-Se) prior to being lyophilized. Mannosamine concentration was optimized with cellular uptake studies in M receptor expressing cells. Non-lyophilized and lyophilized Man-Lip-Se were characterized for size, zeta potential, and entrapment efficiency. The influence of liposomal composition on the characteristics of Man-Lip-Se were evaluated using acidic and basic medium for 24 h. Thermal analysis and powder X-ray diffraction were used to determine the interaction of components within the Man-Lip-Se. The size, zeta potential and entrapment efficiency of the optimum Man-Lip-Se were observed to be 158 +/- 28.9 nm, 33.21 +/- 0.89 mV, and 77.27 +/- 2.34%, respectively. An in vitro Se release of 70-75% up to 24 h in PBS pH 6.8 and <8% Se release in acidic media (0.1 N HCl) in 1 h was observed. The Man-Lip-Se were found to withstand gastric-like environments and showed sustained release. Stable freeze-dried Man-Lip-Se were successfully formulated with a size of <200 nm, similar to 75% entrapment, and achieved controlled release of Se with stability under acidic media, which may be of importance in the targeted delivery of Se to the immune system.