The story of “Hyaluronan Putty”

Hyaluronic Acid (HA) or hyaluronan displays remarkable properties of elasticity and water retention at a specific and narrow pH range of 2.4–2.6. The behavior and mechanical properties have been characterized using a variety of methodologies including ultracentrifuge sedimentation, rheometry, rate and extent of diffusion, and NMR. Various explanations have been presented in order to explain the phenomenon, including reaching the isoelectric point by manipulating pH, strong chain–chain interactions and transient and dynamic hydrogen bonding. Overall, the novel properties of hyaluronan at pH 2.5 have enormous biological and industrial potential, though more efforts to recreate the same properties at neutral pH are needed.