Simple and efficient radiolabeling of hyaluronic acid and its in vivo evaluation via oral administration

The aim of this study was to synthesize hyaluronic acid–tyramine (HA–Tm) conjugate and label it with radioisotopes for in vivo biodistribution study. Radiolabeling of HA–Tm was carried out using ¹²⁵I and ¹³¹I and the observed radiochemical yield were 96 and 98 % respectively. Biodistribution study of radiolabeled HA–Tm was performed with normal Balb/c mice via oral administration. The uptake values of [¹³¹I]HA–Tm in organs were measured by gamma-counter at different time points. Biodistribution results showed that most radioactivities were observed in the gastrointestinal tract at initial time point. A small part of [¹³¹I]HA–Tm was then absorbed into the bloodstream from the small intestine and distributed in some organs. SPECT/CT images of orally administered [¹²⁵I]HA–Tm were well matched with the biodistribution data. The results in the present study would provide an efficient radiolabeling method of hyaluronic acid and also present quantitative organ distributions of orally administered HA.