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Monodisperse nonionic phytanyl ethylene oxide surfactants: High throughput lyotropic liquid crystalline phase determination and the formation of liposomes, hexosomes and cubosomes

journal contribution
posted on 2024-11-01, 09:27 authored by Celesta Fong, Asoka Weerawardena, S Sagnella, Xavier Mulet, Lynne Waddington, Irene Krodkiewska, Calum DrummondCalum Drummond
The phase behaviour (both neat and lyotropic) and toxicity of eight new ethylene oxide amphiphiles (EO = 1 to 8) with a single phytanyl chain (3,7,11,15 tetramethylhexadecyl) is reported. There is a discontinuity at EO > 4 where the neat and lyotropic behaviour exhibit a tipping point which is qualitatively rationalised in terms of the molecular geometry of the surfactant. Below four EO units the behaviour of the neat surfactants show only a glass transition, T g ∼ -90 °C. Above four EO units crystallisation (T crys) and crystal-isotropic liquid (T m) transitions are also observed. These increase monotonically with the hydrophilicity of the surfactant; consistent with the greater cohesiveness of the molecules due to van der Waals interactions. The increase in hydrophilicity corresponds to a decrease in curvature of the surfactant layer towards water. However, the exaggerated splay of the phytanyl chain is effective in promoting various self-assembled structures with inverse cubic and hexagonal phases preferred below ambient temperatures for EO < 4, and these are stable to dilution. Variation of the EO head group length promotes an interesting diversity of cubic phases, with an inverse micellar cubic phase (Fd3m) present for EO = 2 and the bicontinuous gyroid cubic (Ia3d) and double diamond cubic (Pn3m) phases present at higher ethoxylation. DIT-NIR microspectroscopy provided a high throughput, low volume, fast equilibrating method for obtaining the approximate partial temperature-composition phase diagrams of the binary systems with water. The toxicity of colloidal dispersions of these amphiphiles was assayed against normal breast epithelial (HMEpiC) and breast cancer (MCF7) cell lines. The IC 50 of the EO amphiphiles was similar in both cell lines with moderate toxicity ranging from ∼80-110 μM in an in vitro cell viability assay.

History

Journal

Soft Matter

Volume

6

Issue

19

Start page

4727

End page

4741

Total pages

15

Publisher

Royal Society of Chemistry

Place published

United Kingdom

Language

English

Copyright

© 2010 The Royal Society of Chemistry

Former Identifier

2006044233

Esploro creation date

2020-06-22

Fedora creation date

2014-07-15

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