title: Monodisperse nonionic isoprenoid-type hexahydrofarnesyl ethylene oxide surfactants: high throughput lyotropic liquid crystalline phase determination.
abstract: The neat and lyotropic phase behavior of eight new ethylene oxide amphiphiles (EO = 1-8) with a hexahydrofarnesyl chain (3,7,11-trimethyldodecyl) and narrow polydispersity (>98.5% purity) is reported. Below five EO units the behavior of the neat surfactants show only a glass transition, Tg ∼ -90 °C. Above four EO units, crystallization (Tcrys) and crystal-isotropic liquid (Tm) transitions are also observed that increase with degree of ethoxylation of the surfactant headgroup. The lyotropic liquid crystalline phase behavior spans a complex spectrum of surfactant-water interfacial curvatures. Specifically, inverse phases are present below ambient temperatures for EO < 4, with HFarn(EO)2 exhibiting an inverse hexagonal (H(II)) phase stable to dilution. The phase diagram of HFarn(EO)3 displays both the gyroid (Ia3d) and double diamond (Pn3m) inverse bicontinuous cubic phases, with the latter being thermodynamically stable in excess water within the physiological regime. There is a strong preference for planar bilayer structures at intermediate headgroup ethoxylation, with the crossover to normal phases occurring at HFarn(EO)(7-8) which exhibits normal hexagonal (H(I)) and cubic (Q(I)) phases at ambient temperatures. The toxicity of colloidal dispersions of these EO amphiphiles was assayed against normal breast epithelial (HMEpiC) and breast cancer (MCF7) cell lines. The IC50 of the EO amphiphiles was similar in both cell lines with moderate toxicity ranging from ca. <5 to 140 μM in an in vitro cell viability assay. Observations are qualitatively rationalized in terms of the molecular geometry of the surfactant. The physicochemical behavior of the HFarnesyl ethylene oxide amphiphiles is compared to other ethylene oxide surfactants.
authors.affiliation: CSIRO Materials Science & Engineering (CMSE), Bag 10, Clayton South, VIC 3169, Australia.
authors.forename: Celesta
authors.initials: C
authors.lastname: Fong
authors.forename: Asoka
authors.initials: A
authors.lastname: Weerawardena
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Sagnella
authors.forename: Xavier
authors.initials: X
authors.lastname: Mulet
authors.forename: Irena
authors.initials: I
authors.lastname: Krodkiewska
authors.forename: Josephine
authors.initials: J
authors.lastname: Chong
authors.forename: Calum J
authors.initials: CJ
authors.lastname: Drummond
mesh_terms: D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D003460:Crystallization; D004305:Dose-Response Relationship, Drug; D005027:Ethylene Oxide / Q000737:chemistry* / Q000494:pharmacology; D005204:Farnesol / Q000031:analogs & derivatives* / Q000737:chemistry; D006801:Humans; D061986:MCF-7 Cells; D011092:Polyethylene Glycols / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013501:Surface-Active Agents / Q000737:chemistry* / Q000494:pharmacology; D013729:Terpenes / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D013501:Surface-Active Agents; D013729:Terpenes; D011092:Polyethylene Glycols; D005204:Farnesol; D005027:Ethylene Oxide