Details

Autor(en) / Beteiligte

• Martins, André F.
• Prata, M. I. M.
• Rodrigues, S. P. J.
• Geraldes, Carlos F. G. C.
• Riss, P. J.
• Amor-Coarasa, A.
• Burchardt, C.
• Kroll, C.
• Roesch, F.

Titel

Spectroscopic, radiochemical, and theoretical studies of the Ga3+-N-2-hydroxyethyl piperazine-N′-2-ethanesulfonic acid (HEPES buffer) system: evidence for the formation of Ga3+- HEPES complexes in 68 Ga labeling reactions

Ist Teil von

• Contrast media and molecular imaging, 2013-05, Vol.8 (3), p.265-273

Ort / Verlag

Blackwell Publishing Ltd

Erscheinungsjahr

2013

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Recent reports have claimed a superior performance of HEPES buffer in comparison to alternative buffer systems for 67/68 Ga labeling in aqueous media. In this paper we report spectroscopic (1H and 71 Ga NMR), radiochemical, mass spectrometry and theoretical modeling studies on the Ga3+/HEPES system (HEPES = N‐2‐hydroxyethylpiperazine‐N′‐2‐ethanesulfonic acid) performed with the aim of elucidating a potential contribution of HEPES in the 68/67 Ga radiolabeling process. Our results demonstrate that HEPES acts as a weakly but competitive chelator of Ga3+ and that this interaction depends on the relative Ga3+: HEPES concentration. A by‐product formed in the labeling mixture has been identified as a [68 Ga]Ga(HEPES) complex via chromatographic comparison with the nonradioactive analog. The formation of this complex was verified to compete with [68 Ga]Ga(NOTA) complexation at low NOTA concentration. Putative chelation of Ga3+ by the hydroxyl and adjacent ring nitrogen of HEPES is proposed on the basis of 1H NMR shifts induced by Ga3+ and theoretical modeling studies. Copyright © 2013 John Wiley & Sons, Ltd. We show by spectroscopic, radiochemical, chromatographic, mass spectrometry and theoretical modelling studies that the HEPES buffer acts as a weakly but competitive chelator of Ga3+. This observation explains its superior performance relative to alternative buffer systems for 67/68Ga radiolabelling in aqueous media.