The interaction of phospholipid liposomes with mixed bacterial biofilms and their use in the delivery of bactericide

Abstract

The interaction of cationic liposomes, prepared by the extrusion technique (VETs) from dimyristoylphosphatidylcholine (DMPC), cholesterol and dimethyldioctadecylammonium bromide (DDAB), covering a range of compositions from 0–18.5 mole% DDAB, with a range of biofilms of oral bacteria has been studied. It has been found that the adsorption of the liposomes to the biofilms showed specificities with respect to bacterial species and strains, adsorption was greatest for strains of Streptococcus salivarius. Using this information, the adsorption of cationic liposomes to mixed biofilms of two bacteria, differing in adsorption characteristics, ( S. salivarius DBD and Streptococcus sanguis C104) was investigated as a function of biofilm composition. A linear relationship between liposome adsorption and biofilm composition was found, which showed that each bacterium in the biofilm adsorbed independently. Similar results were obtained for the adsorption of anionic liposomes (composition DMPC-phosphatidylinositol), although the extent of adsorption was smaller, and for cationic liposomes (composition dipalmitoylphosphatidylcholine (DPPC)-cholesterol-stearylamine) adsorbed to mixed biofilms of skin-associated bacteria ( Staphylococcus epidermidis and Proteus vulgaris). The cationic and anionic liposomes were used to deliver the bactericide Triclosan to S. salivarius DBD and S. sanguis C104 biofilms and their mixed biofilms. Anionic liposomes were most effective in inhibiting growth of S. sanguis C104 biofilms whereas, growth of S. salivarius DBD could not be effectively inhibited by liposomal Triclosan. Growth inhibition of mixed biofilms by liposomal Triclosan, reflected the effects found on the single species biofilms, anionic liposomes showing growth inhibitions in biofilms with a high content of S. sanguis C104.