Fluidization and melting point depression of aqueous dipalmitoylphosphatidylcholine (DPPC, Tm ≈ 315 K) liposomes by compressed/supercritical n-alkanes (C2 and C3; 0.8-20.7 MPa) was quantified and compared to fluidization by liquid n-alkanes (C5-C10) using fluorescence anisotropy. The adsorption of ethane and propane into DPPC bilayers resulted in significant depression of the melting temperature (up to ΔTm = -16.2 K at 7.0 MPa ethane and propane). Pressure-dependent fluidization by gaseous n-alkanes (1.8-20.7 MPa) and pressure-induced reversal of this fluidization was observed at temperatures corresponding to gel (295 K) and fluid (333 K) phases at atmospheric pressure. The ability to manipulate the degree of bilayer ordering, melting temperature, and width of the phase transition region is discussed in terms of the n-alkane concentration in the bilayer, effect of n-alkane molecular size, and van't Hoff enthalpy of the gel-fluid phase transition. The permeability, phase, and solvent properties of the bilayer can be altered with pressurized ethane or propane, which may provide enhanced control for liposome formation and processing.
|Number of pages||8|
|Journal||Colloids and Surfaces A: Physicochemical and Engineering Aspects|
|State||Published - May 15 2006|
Bibliographical noteFunding Information:
The authors gratefully acknowledge the financial support of the National Science Foundation (Grant BES-9817069) and Dr. Mark Meier in the Department of Chemistry at the University of Kentucky for his assistance in calculating the elliptical n -alkane molecular surface area ( A e ).
- Cell membrane
- Compressed solvent
- Lipid bilayer
- Supercritical fluid
ASJC Scopus subject areas
- Surfaces and Interfaces
- Physical and Theoretical Chemistry
- Colloid and Surface Chemistry