Department of Bioengineering. University of Pennsylvania, 210 S. 33rd St, Philadelphia PA, 19104, USA.
School of Biomedical Engineering, Science and Health Systems, Drexel University Philadelphia, PA 19104, USA.
Biomaterials. 2019 Nov;222:119451. doi: 10.1016/j.biomaterials.2019.119451. Epub 2019 Aug 23.
Hyaluronic acid (HA) is a linear polysaccharide of d-glucuronic acid and N-acetyl-d-glucosamine that is native to many tissues and interacts with cells via cell-surface receptors (e.g., CD44). HA has been extensively explored as a chemically-modified macromer for crosslinking into biomaterials, such as hydrogels and macroporous scaffolds. However, the influence of the extent and type of HA modification on its binding to CD44 is not well understood or quantified. To address this, we modified HA at either the carboxylic acid or the primary alcohol with various chemical groups (e.g., norbornenes, methacrylates) and magnitudes (~10, 20, or 40% of disaccharides) and then characterized binding in both soluble and hydrogel forms. HA binding to CD44 immobilized on plates or presented by cells was influenced by the extent and type of its modification, where increased modification (i.e., ~40%) generally decreased binding. The adhesion of CD44-modified beads to hydrogels as measured by atomic force microscopy revealed a similar trend, particularly with decreased adhesion with hydrophobic modifications to the carboxylic acid. Further, the chondrogenesis of mesenchymal stromal cells when encapsulated in hydrogels fabricated from modified HA macromers was reduced at high modification, behaving similarly to inert hydrogel controls. This work suggests that the types and extents of modification of polysaccharides are important factors that should be considered in preserving their biological function when processed as hydrogels.
透明质酸（HA）是一种线性多糖，由 D-葡萄糖醛酸和 N-乙酰-D-葡萄糖胺组成，存在于许多组织中，并通过细胞表面受体（例如 CD44）与细胞相互作用。HA 已被广泛探索作为一种化学修饰的大分子单体，用于交联成生物材料，如水凝胶和大孔支架。然而，HA 修饰的程度和类型对其与 CD44 结合的影响尚未得到很好的理解或量化。为了解决这个问题，我们在 HA 的羧酸或伯醇上用各种化学基团（例如降冰片烯、甲基丙烯酸酯）进行修饰，修饰程度约为 10%、20%或 40%的二糖，并在可溶性和水凝胶形式下对其结合进行了表征。HA 与固定在平板上或由细胞呈现的 CD44 的结合受到其修饰程度和类型的影响，其中修饰程度增加（即~40%）通常会降低结合。原子力显微镜测量的 CD44 修饰珠粒对水凝胶的粘附也显示出类似的趋势，特别是与羧酸的疏水性修饰相比，粘附降低。此外，当包裹在由修饰的 HA 大分子单体制成的水凝胶中时，间充质基质细胞的软骨生成在高修饰时减少，其行为类似于惰性水凝胶对照。这项工作表明，多糖的修饰类型和程度是在将其加工成水凝胶时保留其生物功能的重要因素。
