Giant liposomes in physiological buffer using electroformation in a flow chamber

Biochim Biophys Acta. 2005 Jun 30;1712(2):152-60. doi: 10.1016/j.bbamem.2005.03.012. Epub 2005 Apr 20.


We describe a method to obtain giant liposomes (diameter 10-100 microm) in solutions of high ionic strength to perform a membrane-binding assay under physiological conditions. Using electroformation on ITO electrodes, we formed surface-attached giant liposomes in solutions of glycerol in a flow chamber and then introduced solutions of high ionic strength (up to 2 M KCl) into this chamber. The ionic solution exchanged with the isoosmolar glycerol solution inside and outside the liposomes. An initial mismatch in index of refraction between the inside and outside of liposomes allowed for the observation of solution replacement. Ions and small polar molecules exchanged into and out of surface-attached liposomes within minutes. In contrast, liposomes formed in solutions of macromolecules retained molecules larger than 4 kDa, allowing for encapsulation of these molecules for hours or days even if the solution outside the liposomes was exchanged. We propose that solutes entered liposomes through lipid tubules that attach liposomes to the film of lipids on the surface of the ITO electrode. The method presented here makes it straightforward to perform flow-through binding assays on giant liposomes under conditions of physiological ionic strength. We performed a membrane-binding assay for annexin V, a calcium-dependent protein that binds to phosphatidylserine (PS). The binding of annexin V depended on the concentration of PS and decreased as ionic strength increased to physiological levels.

MeSH terms

  • Animals
  • Annexin A5 / chemistry
  • Biochemistry / methods
  • Calcium / metabolism
  • Chickens
  • Electrochemistry / methods
  • Electrodes
  • Fluorescent Dyes / pharmacology
  • Glycerol / chemistry
  • Ions / chemistry
  • Lipid Metabolism
  • Lipids / chemistry
  • Liposomes / chemistry*
  • Liposomes / metabolism
  • Macromolecular Substances / chemistry
  • Models, Biological
  • Phosphatidylcholines / chemistry
  • Phosphatidylserines / chemistry
  • Phospholipids / chemistry
  • Protein Binding
  • Sodium Chloride / pharmacology
  • Time Factors


  • Annexin A5
  • Fluorescent Dyes
  • Ions
  • Lipids
  • Liposomes
  • Macromolecular Substances
  • Phosphatidylcholines
  • Phosphatidylserines
  • Phospholipids
  • Sodium Chloride
  • Glycerol
  • Calcium