超临界CO_2发泡法制备PLGA多孔组织工程支架

利用超临界CO2(SC-CO2)发泡法制备了一系列聚(乳酸-乙醇酸)共聚物(PLGA)多孔支架材料,研究了PLGA分子量和组成、发泡过程温度、压力以及泄压速率等对泡孔尺寸及形态的影响.结果表明,随着PLGA组成中乳酸含量的增加,泡孔平均孔径增大且连通性增强;提高过程压力易形成孔径小且泡孔密度大的微孔结构材料;降低泄压速率,泡孔易合并形成大孔.聚合物处于高弹态时,较低的发泡温度易导致特殊的多面体结构大孔的形成;而当温度较高时,泡孔塌缩形成球形微孔结构,且泡孔尺寸随着温度升高而增大.SC-CO2发泡法能有效地去除有机溶剂,避免在高温条件下操作,可以实现5～500μm范围内孔径可控的PLGA多孔支架材料的制备.

FABRICATION OF POROUS POLY(LACTIC ACID-co-GLYCOLIC ACID) SCAFFOLDS USING SUPERCRITICAL CARBON DIOXIDE

Supercritical carbon dioxide(SC-CO2) foaming technology was applied to fabricate highly porous poly(lactic acid-co-glycolic acid)(PLGA) scaffolds.The effects of polymer chemical composition(the mole percentage of glycolic acid in the polymer was 15 and 50 respectively),molecular weight(50 kDa and 200 kDa) and the processing parameters including foaming pressure(from 10 MPa to 25 MPa),temperature(from 35℃ to 85℃) and depressurization rate(0.05 MPa/s and 0.20 MPa/s) on the scaffold structure were investigated in detail.Morphologies of the scaffolds were characterized by scanning electron microscopy(SEM) and pore size distribution was obtained via analysis of SEM images.Porosity and interconnectivity of the scaffolds were measured by pycnometer(Archimedes' principle) and mercury intrusion technique,respectively.The results showed that the pore size and interconnectivity increased while increasing the lactic acid content of the polymer.Higher pressure led to higher cell density and smaller pores,and pore coalescence occurred at low depressurizing rates.Glass transition temperature(Tg) of the polymer decreased under SC-CO2,and large polygonal cells were formed when the foaming temperature was set below 45℃.Differently,higher foaming temperature resulted in globular cells,with cell size decreased sharply.However,further increasing the temperature led to slightly larger pore sizes.Supercritical carbon dioxide foaming method makes it possible to fabricate the macro-cellular and micro-cellular foams of PLGA without using organic solvents and high temperature,which provide a way to fabricate porous polymer scaffolds for potential applications in tissue engineering.