Preparation and the kinetic stability of hyaluronan radiolabeled with In,I and C

Three different procedures for the labeling of hyaluronan (HA) with ¹¹¹In, ¹²⁵I and ¹⁴C radionuclides were compared, and the kinetic stability of radiolabeled HA under different conditions (saline, artificial gastric juice and plasma) was established. Modification of HA structure with bifunctional chelating agents (DTPA) or with the prosthetic group (tyramine or tyrosine) was essential prior ¹¹¹In and ¹²⁵I labeling. These chemical labeling techniques were fast, simple and inexpensive, and labeled agents with a high specific activity were obtained. The only disadvantage of these methods was the occurrence of unknown functional groups in the HA molecule requiring further characterization of the compound. Conversely, HA labeling with ¹⁴C by biotechnological synthesis was found to be rather expensive and time-consuming process. Although, the final product ¹⁴C-HA was identical to natural HA its low specific activity presents certain limitation for its application in biological experiments. Stability studies showed that ¹⁴C-HA and ¹²⁵I-Tm-HA were stable in all studied mediums. In the case of ¹²⁵I-Trs-HA, stability slightly decreased in rat plasma and in artificial gastric juice with increasing time. The least stable was ¹¹¹In-DTPA-HA, which degraded completely after 48 h in artificial gastric juice. Kinetic stability studies may provide primary information concerning the properties of radiolabeled HA in vitro, which is essential for the use and explanation of its behavior in biological experiments.