Studies on the development of 99mTc-labeled biphosphonate alginate beads

The preparation of alginate-dextran pyrophosphate/biphosphonate loaded beads, were labeled with technetium-99m ((99m)Tc) and rhenium-188 ((188)Re). The radiolabelled phosphonic acid derivatives,are well-known bone imaging agents and have also been used for bone pain palliation treatment. The alginates have been used extensively as an excipient in drug products due to their thickening, gel forming and stabilizing behavior. The aim of this study was the preparation of alginate polymeric beads with and without dextran coating, to be used for imaging and possible treatment. We studied (99m)Tc-labelled biphosphonate alginates. We reported our results on the basis of size, swelling capacity and the coating material. The size effect of loading, decreases size and increases loading capacity of alginate beads. Pyrophosphate (PYP) loaded beads had 95% swelling, while ethylene diamine tetramethylene phosphonic acid (EDTMP) loaded beads had 90% (swelling). However combination of both (PYP+EDTMP) loaded beads had 95% swelling. Sustained drug release study indicated different ratios of EDTMP, PYP and EDTMP+PYP loaded beads on different days. Total drug extracted from 30 g beads was 1365.45 μg, 5352.86 μg and 711.8 μg, from EDTMP, PYP and EDTMP+PYP respectively during 15 days of studies. Binding with PYP and EDTMP was 98% and 99% respectively. In conclusion, (chemical and physical characteristics of (99m)Tc-biphosphonate and other alginate beads that we have prepared suggest that the alginate beads could be used for diagnostic and therapeutic purposes.).