Cationic vesicles were produced by incorporating positively-charged st
earylamine into the lipid bilayers. The addition of stearylamine has b
een shown to facilitate targeting of liposomes to the skin-associated
bacterium Staphylococcus epidermidis. The adsorption of the liposomes
to films of the bacteria immobilized on a solid surface has been studi
ed. The extent of adsorption as a function of liposomal lipid concentr
ation could be described in terms of a Langmuir adsorption isotherm, a
pplicable to situations in which species are adsorbed as monolayers on
solid surfaces. Analysis on the basis of the Langmuir model enabled t
he determination of the maximum theoretical targeting to the bacteria
and association/dissociation constants for the interaction. The adsorp
tion was examined under conditions of varying ionic strength. Increasi
ng the ionic strength had the effect of decreasing the extent of targe
ting and suggested that the interaction between the cationic vesicles
and sites on the bacterial surface was mediated by electrical double-l
ayer effects. It follows that electrostatic effects make a major contr
ibution to the interaction between these vesicles and S. epidermidis.
The attachment of the vesicles is reversible and ionic strength-induce
d removal of vesicles from the bacteria could be used as a tool to stu
dy the delivery of liposomally encapsulated bactericide to the biofilm
.