Abstract：
Cryogel formation is an effective approach to produce porous scaffolds for tissue engineering. In this study, cryogelation was performed to produce boron-containing scaffolds for bone tissue engineering. A combination of the synthetic polymer, poly(vinyl alcohol) (PVA), and the natural polymers, chitosan and starch, was used to formulate the cryogels. Boron was used with a dual purpose: as an additive to alter gelation properties, and to exploit its bioactive effect since boron has been found to be involved in several metabolic pathways, including the promotion of bone growth. This project designs a fabrication protocol enabling the competition of both physical and chemical cross-linking reactions in the cryogels using different molecular weight PVA and borax content (boron source). Using a high ratio of high-molecular-weight PVA resulted in the cryogels exhibiting greater mechanical properties, a lower degradation rate (0.6-1.7% vs. 18-20%) and a higher borax content release (4.98 vs. 1.85, 1.08 nanomole) in contrast to their counterparts with low-molecular-weight PVA. The bioactive impacts of the released borax on cellular behaviour were investigated using MG63 cells seeded into the cryogel scaffolds. It was revealed that the borax-containing scaffolds and their extracts induced MG63 cell migration and the formation of nodule-like aggregates, whilst cryogel scaffolds without borax did not. Moreover, the degradation products of the scaffolds were analysed through the quantification of boron release by the curcumin assay. The impact on cellular response in a scratch assay confirmed that borax released by the scaffold into media (~0.4 mg/mL) induced bone cell migration, proliferation and aggregation. This study demonstrated that boron-containing three-dimensional PVA/starch-chitosan scaffolds can potentially be used within bone tissue engineering applications.
摘要：
冷冻凝胶的形成是制备用于组织工程的多孔支架的有效途径。在这项研究中,进行低温凝胶化以生产用于骨组织工程的含硼支架。合成聚合物的组合，聚乙烯醇(PVA)，和天然聚合物，壳聚糖和淀粉，被用来配制冷冻凝胶。硼具有双重用途：作为改变凝胶特性的添加剂，并利用其生物活性效应，因为硼已被发现参与几种代谢途径，包括促进骨骼生长。该项目设计了一种制造方案，可以使用不同分子量的PVA和硼砂含量（硼源）在冷冻凝胶中进行物理和化学交联反应的竞争。使用高比例的高分子量PVA导致冷冻凝胶表现出更高的机械性能，较低的降解率(0.6-1.7%与18-20%）和更高的硼砂含量释放（4.98vs.1.85，1.08纳摩尔）与低分子量PVA的对应物相反。使用接种到冷冻凝胶支架中的MG63细胞研究了释放的硼砂对细胞行为的生物活性影响。揭示了含硼砂支架及其提取物诱导MG63细胞迁移和结节样聚集体的形成,而没有硼砂的冷凝胶支架没有。此外，通过姜黄素测定法对硼的释放进行定量来分析支架的降解产物。在划痕试验中对细胞反应的影响证实，由支架释放到培养基中的硼砂（〜0.4mg/mL）诱导骨细胞迁移，增殖和聚集。这项研究表明，含硼的三维PVA/淀粉-壳聚糖支架可潜在地用于骨组织工程应用中。
