Bioactivity and toxicity studies of amphotericin B incorporated in liquid crystals.

The main objective of the present work was to evaluate the bioactivity and safety of amphotericin B-liquid crystal mixtures (AmB-LC). The effects of liquid crystal (LC) materials and AmB-LC ratios on bioactivity and toxicity to respiratory cell lines were investigated. The formation of AmB-LC mixtures did not change the physical properties of LC when the AmB loading was not more than a 1:3 mole ratio (25%). The exposure of respiratory cell lines to LC did not generate any toxicity (2.5-80 µg/mL). The inhibitory activity of AmB in all liquid crystal formulations (cholesteryl palmityl carbonate: CPC, dicholesteryl carbonate: DCC and sodium cholesteryl carbonate: SCC) on fungi was significantly enhanced when compared to that of the same amount of pure AmB. However, their toxicity to respiratory related cells and red blood cells was significantly decreased. This could be a huge advantage in clinical applications as there is more possibility for dose adjustments. The exposure of small airway epithelial cells (SAEC) and alveolar macrophages (AMs NR8383) to liquid crystals had no significant detrimental effects at doses of between 2.5 and 80 µg/mL (viability was always over 80%). The production of toxic cytokines and inflammatory mediators, including tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1ß) and nitric oxide (NO), after treatment with AmB in liquid crystals at concentrations of between 2 and 32 µg/mL was significantly reduced by about a 1000-fold compared to that generated by lipopolysaccharide (LPS).

Physicochemical properties and antifungal activity of amphotericin B incorporated in cholesteryl carbonate esters.

The antifungal activity of amphotericin B (AmB) incorporated in three cholesteryl carbonate esters (CCEs), sodium cholesteryl carbonate, cholesteryl palmityl carbonate, and dicholesteryl carbonate, was examined to assess their potential for use in a dry powder aerosol. Formulations containing dissolved AmB were stable for 6 months. The particle size varied inversely with liquid crystalline content with observed mass median aerodynamic diameters ranging from 4 to 8 µ m. This was consistent with the visual appearance of the liquid crystals as being low density and free flowing at room temperature. When dispersed in water, the presence of the CCE reduced the rate and extent of AmB release, consistent with the estimated liquid crystal/water partition coefficient. Nevertheless, the rate of AmB release was always sufficient to kill the fungus as established with bioactivity studies. AmB formulated with CCE as a dry powder appears to be promising for use in treating lung fungal infections.

Interaction of Amphotericin B with cholesteryl palmityl carbonate ester.

A cholesteryl carbonate ester was prepared and evaluated as a possible thermotropic liquid crystal excipient for dry powder inhalers. Cholesteryl palmityl carbonate (CPC) was synthesized, and the phase behavior was characterized by differential scanning calorimetry, transmission electron microscopy, polarized light microscope, small angle X-ray diffraction, and solid-state nuclear magnetic resonance spectroscopy. Amphotericin B (AmB) was incorporated into CPC at various mole% (7.7, 14.3, 25, 33.3, and 50) using a solvent evaporation method. The amount of AmB loaded into liquid crystal was limited. The mixture of AmB in liquid crystal did not produce a new complex; rather, the addition of AmB affected the orientational order and the motional aspects of liquid crystal molecules.