Anion-exchange high-performance liquid chromatography of technetium-labeled phosphonoacetic acid skeletal imaging agent preparations

Synthesis, characterization and biodistribution of bisphosphonates Sm-153 complexes: correlation with molecular modeling interaction studies

Bisphosphonates (BPs) are characterized by a P-C-P backbone structure and two phosphonic acid groups bonded to the same carbon, and are established as osteoclast-mediated bone resorption inhibitors. The nature of the groups attached to the central carbon atom are responsible in determining the potency of bisphosphonates as anti-resorption drugs. However, it is not yet clear the exact relationship between their molecular structure and pharmacologic activities. In this study, molecular geometries of pamidronate, alendronate and neridronate, differing only in the length of the aliphatic chains, were predicted by molecular mechanics and their interactions with hydroxyapatite, the main bone mineral component, were examined. We report the synthesis and radiochemical characterization of 153Sm complexes with pamidronate, alendronate and neridronate. Hydroxyapatite binding and biodistribution studies of these complexes have shown a good correlation with the theoretical molecular modeling interaction studies. So, it is possible to conclude that computational chemistry techniques are a good approach to evaluate specific interactions and may play a relevant role in determining the relative ability of BPs to mineral bone, and open new perspectives to the design of new BPs with increased pharmacological activity. These techniques could be extended to BPs as ligands to carrier radioactive metals, aiming for new bone therapeutic radiopharmaceuticals.

Radiochromatography in pharmaceutical and biomedical analysis

Recent advances in the chromatographic analysis of radiolabelled compounds are discussed, with emphasis on the optimization of radioactivity detection in modern chromatographic techniques. Applications are mentioned only infrequently. The state-of-the-art of common radioactivity detection methods is reviewed, as well as promising new detection principles. The latter include flow-through liquid scintillation counting of reversed-phase column eluates based on post-column extraction and solvent segmentation, flow-through heterogeneous counting using a flow cell constructed from axially aligned scintillation fibres, flow cells especially constructed for the detection of beta-emitting radioisotopes in capillary zone electrophoresis, position-sensitive analysers employed in radio planar chromatography and, finally 14C atom counting (as opposed to 14C decay counting) by accelerator mass spectrometry.