Nm. Sanderson et al., THE INTERACTION OF CATIONIC LIPOSOMES WITH THE SKIN-ASSOCIATED BACTERIUM STAPHYLOCOCCUS-EPIDERMIDIS - EFFECTS OF IONIC-STRENGTH AND TEMPERATURE, Biochimica et biophysica acta. Biomembranes, 1283(2), 1996, pp. 207-214
Cationic liposomes have been prepared from dipalmitoylphosphatidylchol
ine (DPPC), cholesterol (Chol) and stearylamine (SA). These phospholip
id vesicles were exposed to adsorbed biofilms of the skin-associated b
acteria Staphylococcus epidermidis, to which they showed a strong affi
nity. The interaction (as assessed by the apparent monolayer coverage
of the biofilms by liposomes) was described in terms of a Langmuir ads
orption isotherm which enabled determination of the maximum theoretica
l coverage of the bacterial surface and association/dissociation const
ants. The interaction was shown to be dependent on the ionic strength
of the surrounding medium; on increasing the ionic strength the biofil
m-vesicle dissociation constant decreased. This suggested that the ads
orption was mediated by electrostatic effects. The adsorption of the v
esicles was examined at various temperatures, enabling determination o
f thermodynamic parameters for the interaction. The adsorbed state of
the liposomes was energetically favoured and the interaction was entha
lpy driven. The Gibbs energies of adsorption were in a range from - 15
to - 19 kJ mol(-1) and the enthalpies of adsorption from - 26 to - 22
kJ mol(-1). Studies using cell populations of different hydrophobicit
y showed that the hydrophobic character of the bacterial cells also ha
d an effect on the adsorption of the vesicles to the biofilm.