title: Predicting solubilisation features of ternary phase diagrams of fully dilutable lecithin linker microemulsions.
abstract: Fully dilutable microemulsions (μEs), used to design self-microemulsifying delivery system (SMEDS), are formulated as concentrate solutions containing oil and surfactants, without water. As water is added to dilute these systems, various μEs are produced (water-swollen reverse micelles, bicontinuous systems, and oil-swollen micelles), without the onset of phase separation. Currently, the formulation dilutable μEs follows a trial and error approach that has had a limited success. The objective of this work is to introduce the use of the hydrophilic-lipophilic-difference (HLD) and net-average-curvature (NAC) frameworks to predict the solubilisation features of ternary phase diagrams of lecithin-linker μEs and the use of these predictions to guide the formulation of dilutable μEs. To this end, the characteristic curvatures (Cc) of soybean lecithin (surfactant), glycerol monooleate (lipophilic linker) and polyglycerol caprylate (hydrophilic linker) and the equivalent alkane carbon number (EACN) of ethyl caprate (oil) were obtained via phase scans with reference surfactant-oil systems. These parameters were then used to calculate the HLD of lecithin-linkers-ethyl caprate microemulsions. The calculated HLDs were able to predict the phase transitions observed in the phase scans. The NAC was then used to fit and predict phase volumes obtained from salinity phase scans, and to predict the solubilisation features of ternary phase diagrams of the lecithin-linker formulations. The HLD-NAC predictions were reasonably accurate, and indicated that the largest region for dilutable μEs was obtained with slightly negative HLD values. The NAC framework also predicted, and explained, the changes in microemulsion properties along dilution lines.
authors.affiliation: University of Toronto, Department of Chemical Engineering and Applied Chemistry, 200 College Street, Room 131, Toronto, Ontario M5S 3E5, Canada.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Nouraei
authors.affiliation: University of Toronto, Department of Chemical Engineering and Applied Chemistry, 200 College Street, Room 131, Toronto, Ontario M5S 3E5, Canada. Electronic address: edgar.acosta@utoronto.ca.
authors.forename: Edgar J
authors.initials: EJ
authors.lastname: Acosta
mesh_terms: D004337:Drug Carriers / Q000737:chemistry*; D004339:Drug Compounding; D004655:Emulsions; D057927:Hydrophobic and Hydrophilic Interactions; D054709:Lecithins / Q000737:chemistry*; D008823:Micelles; D010316:Particle Size; D044367:Phase Transition; D012995:Solubility; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D004337:Drug Carriers; D004655:Emulsions; D054709:Lecithins; D008823:Micelles; D013501:Surface-Active Agents; D014867:Water
keywords: Drug delivery; Food; Lecithin; Microemulsions; Pharma; Ternary phase diagram