Preparation and evaluation of a new radiopharmaceutical for radiosynovectomy, 111Ag-labelled hydroxyapatite (HA) particles.

Many radionuclides, namely, 166Ho, 90Y, 165Dy, 32P, 198Au, 186Re, etc. have been used for radio-synovectomy. Silver-111 (T 1/2 7.45 d) can be produced in a nuclear reactor and is a potential therapeutic radionuclide decaying by beta(-) emission (92% E beta max=1.037MeV and 8% by beta(-) decay associated with emission of gamma-rays (E gamma=245.4keV, I gamma=1.33%; E gamma=342.1keV, I gamma=6.7%)). Because of the production feasibility and favourable nuclear properties, 111Ag may find use as a suitable radionuclide for radio-synovectomy. Hydroxyapatite (HA), Ca10(PO4)6(OH)2 is one of the preferred particulates for this application. In this work, [111Ag]Ag-HA particulates were successfully prepared with high-labelling yield ( approximately 97%) at various pH values. The radiochemical purity of the [111Ag]Ag-HA particles was 99.9%. Stability studies for 7 days showed that the [111Ag]Ag-HA particles retained their stability. gamma camera images at 15 min, 24h and 5 d after injection of the particles into rabbits revealed the retention of the activity in the synovial joints of the knee, thereby indicating excellent in vivo stability of [111Ag]Ag-HA particles. Therefore, [111Ag]Ag-HA particles would be a potential therapeutic agent in the management of arthritis.