Preparation and the kinetic stability of hyaluronan radiolabeled with 111In, 125I and 14C

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.