J. DRUG DEL. SCI. TECH., 15 (4) 301-306 2005

C. Martin, S. Somavarapu, H.O. Alpar*

Vaccine Delivery Group, Centre for Drug Delivery Research, University of London,

School of Pharmacy, 29-39, Brunswick Square, London, WC1N 1AX, United Kingdom

*Correspondence: oya.alpar@ulsop.ac.uk

The aim of this study was to prepare stable liposomes coated or loaded with bioadhesive polymers and test their efficacy following oral, nasal  (IN) or intramuscular (IM) delivery of diphtheria toxoid (DT) in raising systemic antibody responses. The stability of these liposomes in three  different media mimicking gastrointestinal (GI) fluids of the stomach and small intestine was also examined. Fluorescence microscopy of the rat  small intestine showed preferential adsorption/association of polymer-coated liposomes versus free FITC-BSA. Finally, the efficacy liposomes  composed of dipalmitoylphosphatidylcholine, dicetyl phosphate and cholesterol (DPPC:DCP:CH, 7:3:2 molar ratio) for delivery of DT to mice  was assessed. Immunisation through the IM route with these liposomes produced the highest DT specific serum IgG antibody titres; liposomes  loaded with chitosan chloride were the only formulation to elicit a specific measurable IgG response when delivered orally with the present protocol.  IN delivery of liposomes loaded with PVA resulted in a significantly better IgG antibody response (p < 0.05) when compared to uncoated

liposomes.