Solid supported vesicles for bactericide delivery

Cationic and anionic liposomes have been prepared by extrusion from dipalmi toylphosphatidylcholine (DPPC) and its mixtures with cholesterol and dimeth yldioctadecyltrimethylammonium bromide (DDAB) and with phosphatidylinositol (PI) respectively covering a range of composition from 0 to 19 mole % DDAB and PI. The adsorption of liposomal lipid from the liposome dispersion ont o particles of silica and titanium dioxide in suspension has been studied a s a function of liposome composition and concentration. The adsorption isot herms have been fitted using a Langmuir equation from which the binding con stants and maximum surface coverage were obtained. The Gibbs energies of ad sorption for the cationic liposomes were on average -61.0 +/- 2.1 kJ mol(-1 ) (on silica) and -50.6 +/- 2.9 kJ mol(-1) (on titanium dioxide). On averag e saturation adsorption is equivalent to 3 to 10 lipid monolayers on silica and 3 to 7 on titanium dioxide. Using liposomes encapsulating D-glucose it is demonstrated that there is almost no release of glucose on adsorption o f the lipid, indicating that the liposomes are adsorbed intact to form a li posome monolayer on the particle surfaces. Adsorption of intact liposomes t o form a close-packed liposome monolayer of solid supported vesicles (SSV) is shown to be equivalent to on average 7.0 +/- 0.2 phospholipid monolayers . The SSVs are shown to have increased stability to disruption by surfactan ts and when carrying the oil-soluble bactericide, Triclosan(TM), to be capa ble of inhibiting the growth of oral bacteria from immobilised biofilms.