| Since the 70's of the 20th century, micro-encyst and micro-balling technology have been the new artwork and technology applied in pharmaceutical preparations. Biodegradable polymeric materials as drug carriers applied in medicine are becoming more and more dramatic, especially making the drug encapsulate in the microspheres prepared by polymeric materials. Microspheres which can be specific distribution in vivo, can elevate pharmacal biological availability by reducing pharmacal toxicity adverse reaction by using its target quality to specific organs and tissues and its quality of the delayed release of drugs.Polyurethane (PU) has good biocompatibility and excellent physics mechanical properties, and also has satisfactory physio-acceptability on human body. Moreover it can maintain long-term stability after being implanted in the human body. The physical and chemical properties of polyurethane can be changed by changing the composition of the soft-hard segment in the molecular chain. Because of its proper characters, polyurethane microspheres have enormous application perspective in a great many domains as superordinary delayed and controlled release materials.In this paper, biodegradable polyurethane microspheres were prepared with polyethylene glycol((PEG, Mn = 200,400,600) and polycaprolactone (PCL) and isophorone diisocyanate (IPI) as raw materials, dimethylolpropionic acid (DMPA) as chain extender, synthesized by combining prepolymerization, chain-extention, neutralization and emulsification methods. The factors impacting the product quality of the biodegradable polyurethane microspheres were researched. The structure and morphous of biodegradable polyurethane microspheres were measured with infrared spectrum and scanning electron microscope , and we found the best conditions to synthesize the biodegradable polyurethane microspheres. Besides, the degradation disposition, swelling disposition and absorption rate of biodegradable polyurethane microspheres were measured. The microspheres whose weight were lost about 38.2 percent in the 60th day had lost the integrity original form, what demonstrated that the microspheres which we prepared could be degradable. With the polarity of organic solvent increasing, the swelling rate of microspheres would increase. With the molecular weight of soft segment of PU increasing, the swelling rate of microspheres would also increase. With the molecular weight of hydrophilic segment and soft segment of PU increasing, the water absorption of microspheres would increase.Biodegradable polyurethane microspheres packaging bovine serum albumin (BSA) were prepared by using the multiple emulsion system (W1/O/W2) of the solvent evaporation method. The factors impacting the morphous and grain size of microspheres were researched, The grain size of microspheres decreased with the stirring rate increasing when emulsification time did not change. Microspheres which had small grain size increased with emulsification time getting longer when the stirring rate did not change. The grain size of microspheres became larger with the proportion of BSA increasing. When the molar ratio was less than 10%, the globular rate was relatively low. The carried dosage and envelopment rate of biodegradable polyurethane microspheres increased with the concentration of BSA in the water phase increasing. And the carried dosage and envelopment rate of biodegradable polyurethane microspheres could increase when a certain amount of sodium alginate and CaCl2 were put in the water phase. The release performance in vitro was studied, and the stability of microspheres was also researched. The drug release rate could get faster when the carried dosage of microspheres increased. The pH value of medium hardly influenced the drug release rate. The drug release rate could get faster when surface active agent was put into the release medium. The temperature and humidity hardly influenced the drug release rate.Biodegradable polyurethane microspheres prepared in this article will have a very good application prospect as the protein drug carrier. |
