The effect of grafted poly(ethylene glycol) on the electrophoretic properties of phospholipid liposomes and their adsorption to bacterial biofilms

Liposomes have been prepared from the phospholipids, dimyristoyl, dipalmito yl and distearoyl phosphatidylcholine (DMPC, DPPC. DSPC, respectively) cont aining dimethyldioctadecylammonium bromide (DDAB) or phosphatidylinositol ( Pl) and variable amounts (0-9 mole%) of dipalmitoylphosphatidylethanolamine bonded to poly(ethylene glycol) [PEG] of molecular mass 2000 (DPPE-PEG-200 0). The electrophoretic mobilities of the liposomes and corresponding zeta potentials were found to decrease in magnitude for both cationic (DDAB) and anionic (PI) liposomes with increasing DPPE-PEG-2000 incorporation. The ch ain length of the major lipids in the liposomes (DMPC, DPPC and DSPC) did n ot significantly affect the zeta potentials of cationic liposomes but had a small effect on anionic liposomes. The zeta potentials were larger for DMP C-PI liposomes where the acyl chains were in the lamellar liquid crystallin e phase. The adsorption of the liposomes to immobilised biofilms of Staphyl ococcus aureus was found to be represented satisfactorily by the Langmuir i sotherm. The affinity of the liposomes for the biofilms was inhibited by pe gylation suggesting that the 'stealth' property of pegylated liposomes appl ies to bacterial biofilms. Both the surface coverage and the magnitude of t he Gibbs energy of adsorption decrease with the extent of pegylation. (C) 2 001 Elsevier Science B.V. All rights reserved.