Widmer M S, Gupta P K, Lu L, Meszlenyi R K, Evans G R, Brandt K, Savel T, Gurlek A, Patrick C W, Mikos A G
Department of Chemical Engineering and Institute of Biosciences and Bioengineering, Rice University, Houston, TX 77251-1892, USA.
Biomaterials. 1998 Nov;19(21):1945-55. doi: 10.1016/s0142-9612(98)00099-4.
We have fabricated porous, biodegradable tubular conduits for guided tissue regeneration using a combined solvent casting and extrusion technique. The biodegradable polymers used in this study were poly(DL-lactic-co-glycolic acid) (PLGA) and poly(L-lactic acid) (PLLA). A polymer/salt composite was first prepared by a solvent casting process. After drying, the composite was extruded to form a tubular construct. The salt particles in the construct were then leached out leaving a conduit with an open-pore structure. PLGA was studied as a model polymer to analyze the effects of salt weight fraction, salt particle size, and processing temperature on porosity and pore size of the extruded conduits. The porosity and pore size were found to increase with increasing salt weight fraction. Increasing the salt particle size increased the pore diameter but did not affect the porosity. High extrusion temperatures decreased the pore diameter without altering the porosity. Greater decrease in molecular weight was observed for conduits manufactured at higher temperatures. The mechanical properties of both PLGA and PLLA conduits were tested after degradation in vitro for up to 8 weeks. The modulus and failure strength of PLLA conduits were approximately 10 times higher than those of PLGA conduits. Failure strain was similar for both conduits. After degradation for 8 weeks, the molecular weights of the PLGA and PLLA conduits decreased to 38% and 43% of the initial values, respectively. However, both conduits maintained their shape and did not collapse. The PLGA also remained amorphous throughout the time course, while the crystallinity of PLLA increased from 5.2% to 11.5%. The potential of seeding the conduits with cells for transplantation or with biodegradable polymer microparticles for drug delivery was also tested with dyed microspheres. These porous tubular structures hold great promise for the regeneration of tissues which require tubular scaffolds such as peripheral nerve, long bone, intestine, or blood vessel.
我们采用溶剂浇铸和挤出相结合的技术，制备了用于引导组织再生的多孔、可生物降解的管状导管。本研究中使用的可生物降解聚合物为聚（DL-乳酸-乙醇酸共聚物）（PLGA）和聚（L-乳酸）（PLLA）。首先通过溶剂浇铸法制备聚合物/盐复合材料。干燥后，将复合材料挤出形成管状结构。然后将结构中的盐颗粒浸出，留下具有开孔结构的导管。以PLGA作为模型聚合物，分析盐重量分数、盐粒径和加工温度对挤出导管孔隙率和孔径的影响。发现孔隙率和孔径随盐重量分数的增加而增加。增大盐粒径会增大孔径，但不影响孔隙率。较高的挤出温度会减小孔径，但不改变孔隙率。在较高温度下制造的导管观察到分子量有更大的降低。在体外降解长达8周后，对PLGA和PLLA导管的力学性能进行了测试。PLLA导管的模量和断裂强度比PLGA导管高约10倍。两种导管的断裂应变相似。降解8周后，PLGA和PLLA导管的分子量分别降至初始值的38%和43%。然而，两种导管都保持了其形状，没有塌陷。PLGA在整个时间过程中也保持无定形，而PLLA的结晶度从5.2%增加到11.5%。还用染色微球测试了在导管中接种细胞进行移植或接种可生物降解聚合物微粒进行药物递送的潜力。这些多孔管状结构对于需要管状支架的组织再生，如周围神经、长骨、肠道或血管，具有很大的前景。
