Ring-opening copolymerization of DL-lactide and poly(ethylene glycol) initiated by lanthanum acetate and application of the copolymer as matrix of microspheres containing Vibrio cholera antigens

Poly-dl-lactide-poly(ethylene glycol) (PELA) triblock copolymers were synth esized with lanthanum acetate as the initiator. PELA microspheres with entr apped Vibrio Cholera antigen and outer membrane protein (OMP) were prepared by a double emulsion W/O/W based on solvent extraction methods. The obtain ed microspheres showed smooth and spherical surface and their size varied b etween 0.5 and 5.0 mu m, which are suitable for oral targeting delivery sys tem. The distribution tests in rabbits and mice through scanning electronic micrography and fluorescence microscope indicated that microspheres have s uccessfully reached the immunization-related tissues, such as the liver, sp leen and intestinal peyer's patches, following oral administration. The PEL A microspheres were also evaluated as an efficient antigen delivery system by enhancing a higher protective ratio against live Vibrios Cholera.