title: In-situ phase transition from microemulsion to liquid crystal with the potential of prolonged parenteral drug delivery.
abstract: This study is the first to investigate and demonstrate the potential of microemulsions (MEs) for sustained release parenteral drug delivery, due to phase transition behavior in aqueous environments. Phase diagrams were constructed with Miglyol 812N oil and a blend of (co)surfactants Solutol HS 15 and Span 80 with ethanol. Liquid crystal (LC) and coarse emulsion (CE) regions were found adjacent to the ME region in the water-rich corner of the phase diagram. Two formulations were selected, a LC-forming ME and a CE-forming ME and each were investigated with respect to their rheology, particle size, drug release profiles and particularly, the phase transition behavior. The spreadability in an aqueous environment was determined and release profiles from MEs were generated with gamma-scintigraphy. The CE-forming ME dispersed readily in an aqueous environment, whereas the LC-forming ME remained in a contracted region possibly due to the transition of ME to LC at the water/ME interface. Gamma-scintigraphy showed that the LC-forming ME had minimal spreadability and a slow release of (99m)Tc in the first-order manner, suggesting phase conversion at the interface. In conclusion, owing to the potential of phase transition, LC-forming MEs could be used as extravascular injectable drug delivery vehicles for prolonged drug release.
authors.affiliation: School of Pharmacy, The University of Auckland, Auckland, New Zealand.
authors.forename: Xiazhong
authors.initials: X
authors.lastname: Ren
authors.forename: Darren
authors.initials: D
authors.lastname: Svirskis
authors.forename: Raid G
authors.initials: RG
authors.lastname: Alany
authors.forename: Sara
authors.initials: S
authors.lastname: Zargar-Shoshtari
authors.forename: Zimei
authors.initials: Z
authors.lastname: Wu
mesh_terms: D016503:Drug Delivery Systems; D004355:Drug Stability; D004655:Emulsions / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry; D006601:Hexoses / Q000737:chemistry; D007263:Infusions, Parenteral; D050866:Liquid Crystals / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D044367:Phase Transition; D011092:Polyethylene Glycols / Q000737:chemistry; D011374:Progesterone / Q000737:chemistry; D013024:Soybean Oil / Q000737:chemistry; D013229:Stearic Acids / Q000737:chemistry; D013501:Surface-Active Agents / Q000737:chemistry; D014280:Triglycerides / Q000737:chemistry; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D004655:Emulsions; D006601:Hexoses; D013229:Stearic Acids; D013501:Surface-Active Agents; D014280:Triglycerides; D014867:Water; C018665:sorbitan monooleate; D000431:Ethanol; D011092:Polyethylene Glycols; D011374:Progesterone; C067028:Solutol HS 15; D013024:Soybean Oil