Miltefosine-loaded lipid nanoparticles: Improving miltefosine stability and reducing its hemolytic potential toward erythtocytes and its cytotoxic effect on macrophages.

The toxic effects of miltefosine on the epithelial cells of the gastrointestinal tract and its hemolytic action on erythrocytes have limited its use as an antileishmanial agent. As part of our search for new strategies to overcome the side effects of miltefosine during the treatment of leishmaniasis, we have developed stable miltefosine-loaded lipid nanoparticles in an attempt to reduce the toxic effects of the drug. We have evaluated lipid nanoparticles containing varying amounts of miltefosine and cholesterol, prepared by sonication, in terms of their physicochemical properties, preliminary stability, hemolytic potential toward erythrocytes, and cytotoxicity to macrophages and to promastigote and amastigote forms of Leishmania (L.) chagasi. Miltefosine loading into lipid nanoparticles was 100% for low drug concentrations (7.0 to 20.0mg/mL). Particle size decreased from 143nm (control) to between 43 and 69nm. From fluorescence studies, it was observed that the presence of miltefosine and cholesterol (below 103µM) promoted ordering effects in the phospholipid region of the nanoparticles. The formulation containing 15mg/mL miltefosine was stable for at least six months at 4°C and in simulated gastrointestinal fluids, and did not promote epithelial gastrointestinal irritability in Balb/C mice. When loaded into lipid nanoparticles, the hemolytic potential of miltefosine and its cytotoxicity to macrophages diminished, while its antiparasitic activity remained unaltered. The results suggested that miltefosine-loaded lipid nanoparticles may be promising for the treatment of leishmaniasis and might be suitable for oral and parenteral use.

Miltefosine and BODIPY-labeled alkylphosphocholine with leishmanicidal activity: Aggregation properties and interaction with model membranes.

Miltefosine (hexadecylphosphocholine, MT) afforded successful oral treatment against human visceral and cutaneous leishmaniasis. Knowledge of MT aggregation in aqueous solutions and of its interaction with lipid membranes is important to understand pharmacokinetics, bioavailability and antiparasitic effects. Methods based on surface tension and fluorescence spectroscopy gave the value of 50µM for critical micelle concentration (CMC) in buffered water solution, and the value is influenced by salt content. Interaction between MT and lipid vesicles was monitored by fluorescence and the drug promotes only minor changes in the surface of the vesicles. At MT concentration below CMC, modifications in probe fluorescence are due to disordering effects promoted by the drug in the bilayer. Above the CMC, MT promoted large modifications in the vesicles as a whole, resulting in mixed aggregates containing lipids, drug and probe. Effects are less evident above thermal phase transition when the bilayer is in less ordered state.

Comparison between cucurbiturils and ß-cyclodextrin interactions with cholesterol molecules present in Langmuir monolayers used as a biomembrane model.

Specific surface techniques can probe the interaction of cholesterol (Chol) with substances that are able to host and/or sequester this biomolecule, provided that the additives are properly assembled at the interface. Reports on inclusion complexes of Chol with ß-cyclodextrins exist in the literature. Here we compare the interaction of ß-cyclodextrin and cucurbiturils with Chol present in Langmuir phospholipid (dipalmitoylphosphatidylcholine, DPPC) monolayers, used as a biomembrane model. Cucurbiturils, CB[n], comprise macrocyclic host molecules consisting of n glycoluril units. Classic surface pressure curves, dilatational surface viscoelasticity measurements, and fluorescence emission spectra and images obtained by time-resolved fluorescence of the corresponding Langmuir-Blodgett films have shown that homologues with 5 and 6 glycoluril units, CB[5] and CB[6], do not form inclusion complexes. Higher-order homologues, such as CB[7], are likely to complex with Chol with changes in the minimum molecular areas recorded for DPPC/Chol monolayers, the fluorescence decay lifetimes, and the dilatational surface viscosities of the monolayers generated in the presence of these molecules. Moreover, we proof the removal of cholesterol from the biomimetic interface in the presence of CB[7] by means of fluorescence spectra from the subphase support of monolayers containing fluorescent-labeled Chol.