Mapping the intrinsic viscosityof hyaluronic acid at high concentrations of OH-

Hyaluronic acid is commonly used in dermatological fillers in the form of gels. It is established how these gels' firmness is affected by the amount of cross linker and hyaluronic acid respectively. However, the effect of hydroxide ions in solution is rather unknown. This thesis examines how the alkalinity of the solvent affects the intrinsic viscosity of 3 MDa hyaluronic acid by using the method of Ubbelohde capillary viscometry. Sodium hydroxide solutions between 2 and 10 wt% were prepared to study the variation in intrinsic viscosity at concentrations relevant for cross linking (1<wt%). From these respective solutions, four solutions of different mass concentrations of hyaluronic acid were made. The flow time of respective samples were measured between two points in the capillary viscometer in a controlled temperature of 25 °C with an SI Viscoclock to ensure a high accuracy.From the resulting flow times, the intrinsic viscosity was calculated. The intrinsic viscosity varied between 0,55 and 0,70. The relation between intrinsic viscosity and hydroxide ion concentration had a correlation coefficient r < 0,001. No trend could be ensured as the confidence interval for the intrinsic viscosity at the different concentrations was too large