Radioiodination of Alginate via Covalently-Bound Tyrosinamide Allows Monitoring of its Fate In Vivo

Tb monitor the fate of alginate following systemic administration, a method was developed that allowed the covalent incorporation of approximately 1 mol% tyrosinamide. The product could be radioiodinated to a high specific activity, and was subsequently stable on storage at 4°C for 30 days, with very little (c 1%) free [125I] iodide released over that period. Twenty-four hours following intravenous administration, the low molecular weight fraction (<48,000) of the injected polymer was excreted in the urine while the larger polymer fraction remained in the circulation and did not readily accumulate in any of the tissues. Almost all of the dose administered by intraperitoneal injection was transferred from the peritoneal cavity to the blood compartment within 24 h, with the low molecular weight fraction of the polymer excreted in the urine. Following subcutaneous administration, the majority (-70%) of the injected dose was retained at the site of injection at 24 h.