Department of Materials and Department of Bioengineering, Imperial College London, London SW7 2AZ, UK.
Adv Healthc Mater. 2012 May;1(3):308-15. doi: 10.1002/adhm.201200036. Epub 2012 Apr 5.
Poly(γ-glutamic acid) (γ-PGA) is a biocompatible, enzymatically-degradable, natural polymer with a higher resistance to hydrolysis than polyesters commonly used for tissue engineering scaffolds such as poly(L-lactide) (PLLA). Notably, γ-PGA's free carboxyl side groups allow for simple chemical functionalization, making it a versatile candidate for producing scaffolds. Here, a series of water-resistant fibrous scaffolds were engineered from ethyl (Et), propyl (Pr) and benzyl (Bn) esterifications of γ-PGA. All scaffolds were non-cytotoxic and γ-PGA-Bn showed an increase in cell adhesion of hMSCs compared to γ-PGA-Et and γ-PGA-Pr. Moreover, cells on γ-PGA-Bn showed three-fold higher viability at day 14 and significantly higher adhesion when compared with PLLA scaffolds, despite having a similar hydrophobicity. Cell attachment decreased by 40% when the polymer was only partially modified with benzyl groups (γ-PGA-Bn-77%), but was restored when integrin-binding RGD peptide was conjugated to the remaining free carboxylic groups, indicating the peptide was accessible and able to bind integrins. The mechanism behind the cell-material interactions on γ-PGA-Bn scaffolds was further investigated through protein adsorption and fibronectin conformation experiments. These results, in addition to the cell-adhesion studies, suggest an inherent effect of the benzyl modification in the mechanism of cell attachment to γ-PGA-Bn scaffolds. Finally, γ-PGA-Bn scaffolds cultured in osteogenic media were also efficient in supporting hMSCs differentiation towards an osteogenic lineage as determined by alkaline phosphatase and Runx2 gene expression. Taken together these data suggest that esterified γ-PGA polymer scaffolds are new and versatile candidates for tissue engineering applications and that, intriguingly, aromatic functionality plays a key role in the cell-scaffold interaction.
聚（γ-谷氨酸）（γ-PGA）是一种生物相容性、可酶降解的天然聚合物，其水解抗性高于组织工程支架中常用的聚酯，如聚（L-丙交酯）（PLLA）。值得注意的是，γ-PGA 的游离羧基侧基允许简单的化学官能化，使其成为生产支架的多功能候选物。在这里，通过 γ-PGA 的乙酯（Et）、丙酯（Pr）和苄酯（Bn）酯化，设计了一系列耐水纤维状支架。所有支架均无细胞毒性，与 γ-PGA-Et 和 γ-PGA-Pr 相比，γ-PGA-Bn 显示出 hMSC 细胞黏附增加。此外，与 PLLA 支架相比，细胞在 γ-PGA-Bn 上的活力在第 14 天提高了三倍，黏附性显著提高，尽管它们的疏水性相似。当聚合物仅用苄基部分修饰（γ-PGA-Bn-77%）时，细胞附着减少了 40%，但当整合素结合的 RGD 肽与剩余的游离羧基结合时，细胞附着恢复，表明肽是可及的并且能够结合整合素。通过蛋白质吸附和纤连蛋白构象实验进一步研究了 γ-PGA-Bn 支架上细胞-材料相互作用的机制。除了细胞黏附研究外，这些结果表明苄基修饰在细胞附着到 γ-PGA-Bn 支架的机制中具有固有作用。最后，在成骨培养基中培养的 γ-PGA-Bn 支架也能够有效地支持 hMSC 向成骨谱系分化，这可通过碱性磷酸酶和 Runx2 基因表达来确定。总之，这些数据表明酯化 γ-PGA 聚合物支架是组织工程应用的新型多功能候选物，并且有趣的是，芳族功能在细胞-支架相互作用中起着关键作用。
