THE INTERACTION OF PHOSPHOLIPID LIPOSOMES WITH BACTERIA AND THEIR USEIN THE DELIVERY OF BACTERICIDES

Liposomes have been prepared from dipalmitoylphosphatidylcholine (DPPC ) incorporating the cationic lipids stearylamine (SA), dimethyldioctad ecylammonium bromide (DDAB) and dimethylaminoethane carbamoyl choleste rol (DCchol) and the anionic lipids dipalmitoylphosphatidylglycerol (D PPG) and phosphatidylinositol (PI). Their adsorption to biofilms of sk in-associated bacteria (Staphylococcus epidermidis and Proteus vulgari s) and oral bacteria (Streptococcus mutans and sanguis) has been inves tigated as a function of mole % cationic and anionic lipid. Targeting (adsorption) was most effective for the systems DPPC-chol-SA, DPPC-DPP G and DPPC-PI liposomes to S. epidermidis. The effect of extracellular mucopolysaccharide on targeting was investigated for S. epidermiais b iofilms. It was found that targeting increased with the level of extra cellular mucopolysaccharide for all liposome compositions studied. The delivery of the oil-soluble bactericide Triclosan and the water solub le bactericide chlorhexidine was studied for a number of liposomal com positions. Superior delivery of both bactericides relative to the free bactericide occurred for DPPC-chol-SA liposomes and for Triclosan del ivery by DPPC-DPPG and DPPC-PI liposomes targeted to S. epidermidis at low bactericide concentrations. DPPC-chol-SA liposomes were also effe ctive for delivery of Triclosan to S. sanguis biofilms. Double labelli ng experiments using [C-14]-chlorhexidine and [H-3]-DPPC suggested tha t there was exchange between adsorbed liposomes which had delivered ba ctericide to the biofilm and those in the bulk solution implying a dif fusion mechanism for bactericide delivery.