Effect of saccharides on the freezing and thawing of liposome dispersion.

Abstract

The cryoprotective activities of saccharides on liposome dispersion prepared from a mixture of egg yolk lecithin and dicetylphosphate (10:1 in molar ratio) were investigated in terms of the leakage of the entrapped marker (calcein), and the changes of the turbidity and the half band-width of CH2 signals in the 1H-NMR spectrum. In the presence of more than 100 mM D-glucose in both the inner and outer aqueous phases of liposomes (concentration of phospholipid; 6.4 mM), the liposome dispersion was stable to freezing at -70.degree. C. D-Galactose, D-mannose, maltose and maltotriose showed similar activities to D-glucose. However, maltopentaose and DextranT-100 had no cryoprotective effect on the liposome dispersion. Sodium chloride, potassium chloride and urea also showed cryoprotective activities above their eutectic temperatures. The mechanism of the cryoprotective action of saccharides on the freezing of liposomes is discussed in terms of differential scanning calorimetry data and Raman spectra of aqueous saccharide solutions at low temperature.