The visualisation of the targeting of phospholipid liposomes to bacteria

Anionic and cationic phospholipid liposomes have been prepared from dipalmitoylphosphatidylcholine (DPPC) — phosphatidylinositol (PI) and DPPC-cholesterol-stearylamine (SA) mixtures over a range of composition and targeted to biofilms of the skin-associated bacterium Staphylococcus epidermidis to establish the optimum PI and SA content for targeting. The interaction of liposomes of optimum composition with the bacteria were visualized by electron microscopy using negative staining with uranyl acetate and phosphotungstic acid. It has been demonstrated that the liposomes absorb extensively to the bacterial surface. Immunoliposomes have been prepared with a covalently linked monoclonal antibody raised to antigenic determinants on the surface of the oral bacterium Streptococcus oralis. The targeting of the immunoliposomes to this bacterium has been visualized using a second gold labelled anti-antibody. As for the anionic and cationic liposomes the immunoliposomes adsorb to the surface of the bacteria. The results add support to the concept of using liposomes for the delivery of bactericides or therapeutic agents to bacteria.