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Substance P - nanozeolite labeled with 224Ra and 225Ra - new potential radiobioconjugate for internal alpha therapy

The 223Ra, 224Ra and 225Ra radioisotopes exhibit very attractive nuclear properties for application in radionuclide therapy. Unfortunately the lack of appropriate bifunctional ligand for radium was the reason why these radionuclides did not find application in receptor targeted therapy. In the present work the potential usefulness of the NaA nanozeolite as a carrier for radium radionuclides has been studied. 224Ra and 225Ra, the α-particle emitting radionuclides, have been absorbed in the nanometer-sized NaA zeolite through simple ion-exchange. 224,225Ra-nanozeolites have shown very good stability in solutions containing: physiological salt, EDTA, amino acid and human serum. To make NaA nanozeolite particles dispersed in water their surface has been modified with silane coupling agent containing poly(ethylene glycol) (PEG) molecules. In the next step short peptide substance P were covalently attach to the PEG-nanozeolite surface. The stability, cell affinity and cytotoxicity studies of the obtained radiobioconjugate are in progress.