Optimal 99mTc radiolabeling and uptake of glucosamine sulfate by cartilage. A potential tracer for scintigraphic detection of osteoarthritis.

Glucosamine sulfate (GS) is used in treatment of human osteoarthritis, but no data for(99m)TcGS scintigraphy are available. Radiolabeling of GS was performed using the (99m)TcO(4)(-)/tin method. We applied two procedures for separation of free (99m)Tc using PD10 and G10 columns. In each eluted fraction, GS content was estimated by the Elson/Morgan method. For optimal radiolabeling, we varied the amount of GS, tin, (99m)Tc activity, and pH. For uptake age matched human rib cartilage (males, 78 and 63 years old) and 5-10 μCi/well of (99m)TcGS were used. Uptake was monitored up to 72 h. Also, washout of the tracer 3 h and 24 h after uptake was investigated. At pH 2, using PD10 column, the uptake of (99m)TcGS amounted to 100.8 ± 2.9%, n = 6 at saturation time of 72 h. Uptake was age-dependent; at pH 5, it amounted to 99.8% as compared to 66.1% at 78 vs 63 years old. When the amount of tin was varied at pH 2, the tracer uptake amounted to 21.37% (1 mg) vs 45.99% (2.5 mg) at saturation. At pH 7, the amount of needed tin was much lower and amounted to 42.50 ± 2.50% using 0.1 mg vs 25.11 ± 1.90% using 0.05 mg. Although the uptake at pH 7 (0.1 mg tin) is comparable with that at pH 2 (2.5 mg tin), the washout of the tracer amounted only to 4.10 ± 1.25% and 2.05 ± 0.65% after 3 h and 24 h, respectively. During degeneration of cartilage, incorporation of (99m)TcGS is high and could therefore be a promising tracer not only to target osteoarthritis but also to monitor the effects of therapy.