Studies On The Membrane Characteristics Of Alginate-Chitosan (AC) Microspheres For Oral Protein Delivery

The research and development of oral delivery system withcontrolled-release features for protein drugs have been promoted by thecontradiction between clinical demands and the disadvantages of multipleparenteral administration, which is the only route for most protein drugs.Alginate/chitosan (AC)microspheres have been proven to be potential oral proteindelivery carrier, due to the material characteristics, such as biocompatibility,biodegradability and bioadhesiveness, and mild reaction properties. Theprotection of protein drugs from degradation in the gastrointestinal tract (GI) isone of the key functions to oral protein delivery formulations. In order to realizethis objective, studies on the membrane characteristics, such as membranepermeability, membrane strength and controlled release properties were carriedout in this thesis.Firstly, Laser Scanning Confocal Microscope (LSCM) and fluorescencelabelling technique were used to observe the movement of RBITC-labeledproteins into microspheres. It was innovative to use labeled proteins instead oflabeled dextran to study the permeability and find the adsorption of proteins onthe membrane. With variety of the materials, the membrane could cut BSA(Mw67kDa) off the inner of the microspheres, and it could also obstruct the GIenzyme to a certain extent, which showed that 135kDa, the cut-off molecularweight of the membrane obtained using the spectrophotometer was not accurate.Microspheres prepared with 1.5% 140cp alginate and 0.5% 94kDa chitosan for20min showed the lowest enzyme permeability. The characteristics of proteinsalso affect the permeability. Secondly, the volume variety and membrane strength variety of microspheresin the simulated gastric/intestinal solutions were studied. Microspheres preparedwith 1.5% 25cp alginate and 0.5% 19kDa chitosan for 20min showed the higheststability and membrane strength. Finally, using hemoglobin (Hb, Mw64.5kDa) as model drug, the Hb-ACmicrospheres were prepared. The effect of membrane formation reactionconditions on drug loading, entrapment efficiency and release property wereinvestigated. It was found that the release profile in simulated gastric solution wasdetermined by membrane permeability, while determined by membrane strengthin simulated intestinal solution. By increasing the Mw of chitosan whiledecreasing the concentration and membrane formation time, the drug loading andentrapment efficiency could be increased. Microspheres prepared with 0.35%45kDa~94kDa chitosan for 10min showed high drug loading, entrapmentefficiency and a good sustained release behavior.