离心粘结法制备孔隙连通的三维细胞支架

Preparation of Well-Interconnected Three-Dimensional Scaffolds with Centrifugal Effect

目的:改进多孔支架制备技术,使多孔支架具有孔隙结构均匀、孔隙连通性良好的特性。方法:间歇离心技术与湿度粘结方法结合,改善致孔剂粘结的均匀性;溶液浇注/颗粒沥析技术制备三维多孔细胞支架;扫描电镜观察支架的孔隙结构,原子吸收光谱检测致孔剂残余,力学实验仪与重量法表征支架的其它物理性能与制备条件的关系。结果:三维多孔支架的孔隙呈球形、分布均匀、孔隙相互连通、通道呈规则的圆形;支架中无残余致孔剂。以聚乳酸为原料制备的支架,其孔隙率、压模量、吸水率分别高达94.7±0.5%、509±6kPa、208.2±20.3%。结论:间歇离心粘结——溶剂浇注/颗粒沥析技术,能够制备出孔隙结构均匀、孔隙相互完全连通的三维细胞支架,支架的孔隙大小和通道尺寸人为可控,支架的孔隙率和强度高,孔隙结构符合组织工程的要求,是一种比较理想的三维细胞支架制备方法。

Porous scaffolds composed of biodegradable polymers plays pivotal role in tissue engineering. A novel method used to improve uniformity of bonded porogen assembly and a newly water dissoluble spherical porogen （a pore generating materials） were studied and used to modify solvent casting / particulate leaching technique to generate porous scaffolds with homogeneous and complete-interconnected pore structure. The spherical porogen was made from sodium chlorate with solution dispersion method in silica oil. sodium chlorate spheres were harvested and washed with chloroform for 10 to 15 times to remove the residual silica oil. After being dried under vacuum, the spheres were sorted and stored in a desiccator until use. The progen spheres were added in a polypropylene mold （cylindrical vial with microholes on bottom for solution leaving off）, the mold containing sodium chlorate spheres was subjected to 25℃ and 80% humidity environment to form bonded porogen assembly, during the bonding period, the mold was centrifuged （ALC, PK110） at the force of 161g for five minutes after treatment at 25℃ and 80% humidity every 10 h to get rid of accumulated water （we called it intermittent centrifugal effect）, then the bonded porogen assemblies were cut into halves with a razor blade after dried in desiccator. The upper, middle and bottom sections of assemblies were observed by optical microscope to prepare a solution of a desired concentration [ weight of PDLLA （g）/volume of Chloroform （ml）], the polymer solution was cast onto the assembly, and additional casting was repeated after the solvent was evaporated. The dried porogen/polymer discs were removed from the mold, and the top and bottom layers were cut away to obtain flat surfaces. Immersed the discs in distilled water to remove porogen, dried under vacuum. The remains of porogen in scaffolds was detected by Atomic Absorption Spectroscopy through sodium, and the structural uniformity, interpore connectivity, porosity, and mechanic properties of the scaffold were studied respectively. It was confirmed that intermittent centrifugal effect obviously improved bonding uniformity of bonded porogen assembly, and the bonding degree might be controlled at some extent, resulting in scaffolds with homogeneous pore structure, spherical pore and complete interconnectivity. The pore sizes and diameter of openings between pores were controllable by varying porogen size and bonding degree, respectively. The porosity decreased with increase casting times and concentration of polymer solution, compressive modulus of scaffolds decreased with increase porosity, and water uptake increased with increase diameter of the porogen. The compressive modulus, porosity, and water uptake of scaffolds may reach up to 509 ±6kPa, 94.7 ±0.5%, 208.2± 20.3, respectively. Most importantly, there is no remains detected in scaffolds, implied that the fabrication process did not change the chemical property of scaffolds. These results suggested that this novel water dissoluble porogen combination with intermittent centrifugal effect were able to tailor the polymer scaffolds with “homogeneous and controllable pore structure”, and the resulting completely interconnected scaffolds have implications for facilitated cell migration, nutrients or waste exchange, abundant cell - cell interaction, and potentially improved neural and vascular growth within tissue engineering scaffolds.