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Miltefosine an alkylphosphocholine analogue, is the only drug taken orally for the treatment of leishmaniasis-a parasitic disease caused by sandflies. Although it is believed that Miltefosine exerts its activity by acting at the lipid membrane, detailed understanding of the interaction of this drug with eukaryotic membranes is still lacking. Herein, we exploit microcavity pore suspended lipid bilayers (MSLBs) as a biomimetic platform in combination with a highly sensitive label-free electrochemical impedance spectroscopy (EIS) technique to gain biophysical insight into the interaction of Miltefosine with host cell membrane as a function of lipid membranes composition. Four membrane compositions with increasing complexity were evaluated; DOPC, DOPC:Chol (75:25), domain forming DOPC:SM:Chol (40:40:20) and mammalian plasma membrane (MPM) mimetic DOPC:DOPE:Chol:SM:DOPS (32:25:20:15:8) and used to study the interaction of Miltefosine in a concentration-dependent manner using EIS. The membrane resistance changes in response to Miltefosine were modelled by an empirical Langmuir isotherm binding model to provide estimates of binding saturation and equilibrium association constant. Miltefosine was found to have greatest impact on electrochemical properties of the simpler membrane systems; DOPC and DOPC:Chol, where these membranes were found to be more susceptible to membrane thinning, attributed to strong permeation/penetration of the drug whilst, compositions that included both Chol and SM, expected to contain large liquid-ordered domains exhibited weaker changes to membrane resistance but strongest drug association. In contrast, at the MPM membrane, Miltefosine exerts weakest association, which is tentatively attributed to electrostatic effects from the anionic DOPS but some membrane thinning is observed reflected in change in resistance and capacitance values attributed to some weak permeation.

Miltefosine an alkylphosphocholine analogue, is the only drug taken orally for the treatment of leishmaniasis-a parasitic disease caused by sandflies. Although it is believed that Miltefosine exerts its activity by acting at the lipid membrane, detailed understanding of the interaction of this drug with eukaryotic membranes is still lacking. Herein, we exploit microcavity pore suspended lipid bilayers (MSLBs) as a biomimetic platform in combination with a highly sensitive label-free electrochemical impedance spectroscopy (EIS) technique to gain biophysical insight into the interaction of Miltefosine with host cell membrane as a function of lipid membranes composition. Four membrane compositions with increasing complexity were evaluated; DOPC, DOPC:Chol (75:25), domain forming DOPC:SM:Chol (40:40:20) and mammalian plasma membrane (MPM) mimetic DOPC:DOPE:Chol:SM:DOPS (32:25:20:15:8) and used to study the interaction of Miltefosine in a concentration-dependent manner using EIS. The membrane resistance changes in response to Miltefosine were modelled by an empirical Langmuir isotherm binding model to provide estimates of binding saturation and equilibrium association constant. Miltefosine was found to have greatest impact on electrochemical properties of the simpler membrane systems; DOPC and DOPC:Chol, where these membranes were found to be more susceptible to membrane thinning, attributed to strong permeation/penetration of the drug whilst, compositions that included both Chol and SM, expected to contain large liquid-ordered domains exhibited weaker changes to membrane resistance but strongest drug association. In contrast, at the MPM membrane, Miltefosine exerts weakest association, which is tentatively attributed to electrostatic effects from the anionic DOPS but some membrane thinning is observed reflected in change in resistance and capacitance values attributed to some weak permeation.