Preparation of hydroxyapatites lebelled with ²²³Ra and ^99mTc and their in vitro stabililty

Česká verzia

Authors: Petra Mičolová; Martin Vlk; Eva Málková; Anna Bajzíková; Ján Kozempel
Authors place of work: Fakulta jaderná a fyzikálně inženýrská, Katedra jaderné chemie, ČVUT v Praze, ČR
Published in the journal: NuklMed 2016;5:4-9
Category: Original Article

Summary

Introduction:
Increasing attention in targeted radionuclide cancer therapy is given to alpha emitters. ²²³Ra and ^99mTc labelled hydroxyapatites (nHAp) are suitable candidates for using in therapy and diagnostics of bone metastases. Moreover, both radionuclides and hydroxyapatites are already approved by Food and Drug Administration Agency (FDA) to be used in a number of applications.

Material and methods:
Nano-hydroxyapatite particles were prepared by precipitation of 1,2 M Ca(NO₃)₂ . 2H₂O with 0,8 M (NH₄)₂HPO₄ at pH 10-–11 and laboratory temperature. Stock ²²³Ra was prepared from ²²⁷Ac/²²⁷Th/²²³Ra generator in our laboratory, which was eluted by 0,7 M HNO₃ and methanol (2 : 8). Stock ^99mTc was obtained from commercial ⁹⁹Mo/^99mTc generator (DRYTEC™, GE Healthcare) and was eluted with 0.9% saline. Radionuclidic purity was evaluated by gamma-spectrometry with high resolution (in case of ²²³Ra also by alpha-spectrometry). Two strategies were chosen for nanoparticles labelling i.e. surface sorption of radionuclides and intrinsic incorporation of radionuclides and subsequently stability control in saline was performed during 5 half-lives.

Results:
Surface-labelled nHAp were obtained with yields ranging from 80 to 95 %. In the latter strategy, intrinsically labelled nHAp were obtained in the yields of 90–97 %.

Conclusion:
Labelling yields of intrinsically labelled [²²³Ra]nHAp were slightly higher than surface-labelled nHAp. The obtained labelling yields of [^99mTc]nHAp were comparable in both methods. Released activity was below 8 % in all cases.

Keywords:
^99mTc, ²²³Ra, nanomaterials, hydroxyapatite, therapy and diagnostics, bone metastases

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