Orbis Biosciences, 2002 W. 39th Ave., Kansas City, KS 66103, USA.
Mater Sci Eng C Mater Biol Appl. 2013 Oct;33(7):4343-51. doi: 10.1016/j.msec.2013.06.026. Epub 2013 Jun 28.
Macromolecule release from poly(d,l-lactide-co-glycolide) (PLGA) microspheres has been well-characterized, and is a popular approach for delivering bioactive signals from tissue-engineered scaffolds. However, the effect of some processing solvents, sterilization, and mineral incorporation (when used in concert) on long-term release and bioactivity has seldom been addressed. Understanding these effects is of significant importance for microsphere-based scaffolds, given that these scaffolds are becoming increasingly more popular, yet growth factor activity following sintering and/or sterilization is heretofore unknown. The current study evaluated the 6-week release of transforming growth factor (TGF)-β3 and bone morphogenetic protein (BMP)-2 from PLGA and PLGA/hydroxyapatite (HAp) microspheres following exposure to ethanol (EtOH), dense phase carbon dioxide (CO2), or ethylene oxide (EtO). EtO was chosen based on its common use in scaffold sterilization, whereas EtOH and CO2 were chosen given their importance in sintering microspheres together to create scaffolds. Release supernatants were then used in an accelerated cell stimulation study with human bone marrow stromal cells (hBMSCs) with monitoring of gene expression for major chondrogenic and osteogenic markers. Results indicated that in microspheres without HAp, EtOH exposure led to the greatest amount of delivery, while those treated with CO2 delivered the least growth factor. In contrast, formulations with HAp released almost half as much protein, regardless of EtOH or CO2 exposure. Notably, EtO exposure was not found to significantly affect the amount of protein released. Cell stimulation studies demonstrated that eluted protein samples performed similarly to positive controls in PLGA-only formulations, and ambiguously in PLGA/HAp composites. In conclusion, the use of EtOH, subcritical CO2, and EtO in microsphere-based scaffolds may have only slight adverse effects, and possibly even desirable effects in some cases, on protein availability and bioactivity.
聚（DL-丙交酯-共-乙交酯）（PLGA）微球的大分子释放已得到充分研究，是从组织工程支架中传递生物活性信号的一种常用方法。然而，一些加工溶剂、灭菌和矿物质掺入（当协同使用时）对长期释放和生物活性的影响很少被提及。鉴于这些支架越来越受欢迎，了解这些影响对于基于微球的支架非常重要，但迄今为止，尚不清楚烧结和/或灭菌后生长因子的活性。本研究评估了暴露于乙醇（EtOH）、高密度二氧化碳（CO2）或环氧乙烷（EtO）后，PLGA 和 PLGA/羟基磷灰石（HAp）微球中转化生长因子（TGF）-β3 和骨形态发生蛋白（BMP）-2 的 6 周释放情况。选择 EtO 是基于其在支架灭菌中的常用性，而选择 EtOH 和 CO2 是因为它们在将微球烧结在一起以制造支架方面的重要性。然后将释放的上清液用于人类骨髓基质细胞（hBMSCs）的加速细胞刺激研究，监测主要软骨和成骨标志物的基因表达。结果表明，在没有 HAp 的微球中，EtOH 暴露导致最大量的递送，而 CO2 处理的微球则释放最少的生长因子。相比之下，含有 HAp 的配方无论暴露于 EtOH 还是 CO2，释放的蛋白质几乎少一半。值得注意的是，未发现 EtO 暴露显著影响释放的蛋白质量。细胞刺激研究表明，洗脱的蛋白质样品在仅含 PLGA 的配方中与阳性对照表现相似，而在 PLGA/HAp 复合材料中表现不明确。总之，在基于微球的支架中使用 EtOH、亚临界 CO2 和 EtO 可能仅对蛋白质的可用性和生物活性产生轻微的不利影响，在某些情况下甚至可能产生有利影响。
