Figure 5.

Schematic of the mono- and double-linked 1,4-butanediol di-(propan-2,3-diolyl) ether (BDPE) residues and hyaluronic acid (HA) disaccharide units. The higher MoD percentage indicates more cross-linking modifications. Although a higher MoD is essential, it is equally important to consider the degree of properly (blue-colored) or improperly (red-colored) attached BDDE in conjunction with CrR rather than MoD alone. Instances where MoD is high, but CrR is low indicate inadequate cross-linking, which leads to increased unreacted BDDE (mono-linked BDPE residues) and reduced G′ and cohesiveness: (A) Product 5 exhibits a high MoD, but its CrR value is relatively low at 0.086; (B) Product 7 has a low MoD but a high CrR value of 0.222. MoD, degree of modification; CrR, cross-linking ratio.