Elliott Donaghue Irja, Shoichet Molly S
Department of Chemical Engineering and Applied Chemistry, University of Toronto, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Canada.
Department of Chemical Engineering and Applied Chemistry, University of Toronto, Canada; Institute of Biomaterials and Biomedical Engineering, University of Toronto, Canada; Department of Chemistry, University of Toronto, Canada.
Acta Biomater. 2015 Oct;25:35-42. doi: 10.1016/j.actbio.2015.08.002. Epub 2015 Aug 6.
Polymer excipients, such as low molar mass poly(ethylene glycol) (PEG), have shown contradictory effects on protein stability when co-encapsulated in polymeric nanoparticles. To gain further insight into these effects, platelet-derived growth factor (PDGF-AA) was encapsulated in polymeric nanoparticles with vs. without PEG. PDGF-AA is a particularly compelling protein, as it has been demonstrated to promote cell survival and induce the oligodendrocyte differentiation of neural stem/progenitor cells (NSPCs) both in vitro and in vivo. Here we show, for the first time, the controlled release of bioactive PDGF-AA from an injectable nanoparticle/hydrogel drug delivery system (DDS). PDGF-AA was encapsulated, with high efficiency, in poly(lactide-co-glycolide) nanoparticles, and its release from the drug delivery system was followed over 21 d. Interestingly, the co-encapsulation of low molecular weight poly(ethylene glycol) increased the PDGF-AA loading but, unexpectedly, accelerated the aggregation of PDGF-AA, resulting in reduced activity and detection by enzyme-linked immunosorbent assay (ELISA). In the absence of PEG, released PDGF-AA remained bioactive as demonstrated with NSPC oligodendrocyte differentiation, similar to positive controls, and significantly different from untreated controls. This work presents a novel delivery method for differentiation factors, such as PDGF-AA, and provides insights into the contradictory effects reported in the literature of excipients, such as PEG, on the loading and release of proteins from polymeric nanoparticles.
Previously, the polymer poly(ethylene glycol) (PEG) has been used in many biomaterials applications, from surface coatings to the encapsulation of proteins. In this work, we demonstrate that, unexpectedly, low molecular weight PEG has a deleterious effect on the release of the encapsulated protein platelet-derived growth factor AA (PDGF-AA). We also demonstrate release of bioactive PDGF-AA (in the absence of PEG). Specifically, we demonstrate the differentiation of neural stem and progenitor cells to oligodendrocytes, similar to what is observed with the addition of fresh PDGFAA. A differentiated oligodendrocyte population is a key strategy in central nervous system regeneration. This work is the first demonstration of controlled PDGF-AA release, and also brings new insights to the broader field of protein encapsulation.
聚合物辅料，如低摩尔质量的聚乙二醇（PEG），在与蛋白质共包封于聚合物纳米颗粒中时，对蛋白质稳定性表现出相互矛盾的影响。为了进一步深入了解这些影响，将血小板衍生生长因子（PDGF - AA）包封于含PEG和不含PEG的聚合物纳米颗粒中。PDGF - AA是一种特别引人关注的蛋白质，因为已证明它在体外和体内均能促进细胞存活并诱导神经干细胞/祖细胞（NSPCs）向少突胶质细胞分化。在此，我们首次展示了生物活性PDGF - AA从可注射纳米颗粒/水凝胶药物递送系统（DDS）中的控释。PDGF - AA被高效包封于聚（丙交酯 - 共 - 乙交酯）纳米颗粒中，并对其从药物递送系统中的释放情况进行了21天的跟踪。有趣的是，低分子量聚乙二醇的共包封增加了PDGF - AA的负载量，但出乎意料的是，加速了PDGF - AA的聚集，导致其活性降低且酶联免疫吸附测定（ELISA）检测结果不佳。在没有PEG的情况下，释放的PDGF - AA保持生物活性，这通过NSPC少突胶质细胞分化得以证明，类似于阳性对照，且与未处理对照有显著差异。这项工作提出了一种用于分化因子（如PDGF - AA）的新型递送方法，并为文献中报道的辅料（如PEG）对聚合物纳米颗粒中蛋白质负载和释放的相互矛盾影响提供了见解。
此前，聚合物聚乙二醇（PEG）已被用于许多生物材料应用中，从表面涂层到蛋白质包封。在这项工作中，我们意外地证明了低分子量PEG对包封的蛋白质血小板衍生生长因子AA（PDGF - AA）的释放具有有害影响。我们还证明了生物活性PDGF - AA的释放（在没有PEG的情况下）。具体而言，我们证明了神经干细胞和祖细胞向少突胶质细胞的分化，类似于添加新鲜PDGFAA时观察到的情况。分化的少突胶质细胞群体是中枢神经系统再生的关键策略。这项工作首次证明了PDGF - AA的控释，也为更广泛的蛋白质包封领域带来了新的见解。
