It is possible to manipulate the surface characteristics of lipid vesi
cles, a unique class of colloidal particle, either through the lipid c
omposition of the bilayer or by the introduction of surface macromolec
ules. Their value as potential drug-carrier systems has led to surface
manipulations to facilitate vesicle targeting and to prevent non-spec
ific adsorption by the introduction of hydrophilic polymers (steric st
abilization of vesicles). The modification of vesicle surfaces in rela
tion to their powers of adsorption, aggregation and/or fusion has stim
ulated much interest in the surface properties and interactions of ves
icles and presents a major challenge in surface and colloidal science.