Radiofluorination of a pre-formed gallium(III) aza-macrocyclic complex: towards next-generation positron emission tomography (PET) imaging agents

Bhalla, Rajiv, Levason, William, Luthra, Sajinder K., Mcrobbie, Graeme, Sanderson, George and Reid, Gillian (2015) Radiofluorination of a pre-formed gallium(III) aza-macrocyclic complex: towards next-generation positron emission tomography (PET) imaging agents. Chemistry - A European Journal, 21 12: 4688-4694. doi:10.1002/chem.201405812


Author Bhalla, Rajiv
Levason, William
Luthra, Sajinder K.
Mcrobbie, Graeme
Sanderson, George
Reid, Gillian
Title Radiofluorination of a pre-formed gallium(III) aza-macrocyclic complex: towards next-generation positron emission tomography (PET) imaging agents
Journal name Chemistry - A European Journal   Check publisher's open access policy
ISSN 1521-3765
0947-6539
Publication date 2015-03-16
Year available 2015
Sub-type Article (original research)
DOI 10.1002/chem.201405812
Open Access Status
Volume 21
Issue 12
Start page 4688
End page 4694
Total pages 7
Place of publication Weinheim, Germany
Publisher Wiley
Collection year 2016
Language eng
Formatted abstract
As part of a study to investigate the factors influencing the development of new, more effective metal-complex-based positron emission tomography (PET) imaging agents, the distorted octahedral complex, [GaCl(L)]⋅2 H2O has been prepared by reaction of 1-benzyl-1,4,7-triazacyclononane-4,7-dicarboxylic acid hydrochloride (H2L⋅HCl) with Ga(NO3)3⋅9 H2O, which is a convenient source of GaIII for reactions in water. Spectroscopic and crystallographic data for [GaCl(L)]⋅2 H2O are described, together with the crystal structure of [GaCl(L)]⋅MeCN. Fluorination of this complex by Cl/F exchange was achieved in high yield by treatment with KF in water at room temperature over 90 minutes, although the reaction was complete in approximately 30 minutes if heated to 80 °C, giving [GaF(L)]⋅2 H2O in good yield. The same complex was obtained by hydrothermal synthesis from GaF3⋅3 H2O and Li2L, and has been characterised by single-crystal X-ray analysis, IR, 1H and 19F{1H} NMR spectroscopy and ESI+ MS.

Radiofluorination of the pre-formed [GaCl(L)]⋅2 H2O has been demonstrated on a 210 nanomolar scale in aqueous NaOAc at pH 4 by using carrier-free 18F−, leading to 60–70 % 18F-incorporation after heating to 80 °C for 30 minutes. The resulting radioproduct was purified easily by using a solid-phase extraction (SPE) cartridge, leading to 98–99 % radiochemical purity. The [Ga18F(L)] is stable for at least 90 minutes in 10 % EtOH/NaOAc solution at pH 6, but defluorinates over this time scale at pH of approximately 7.5 in phosphate buffered saline (PBS) or human serum albumin (HSA). The subtle role of the Group 13 metal ion and co-ligand donor set in influencing the pH dependence of this system is discussed in the context of developing potential new imaging agents for PET.
Keyword Imaging agents
Gallium
Positron emission tomography
Radiofluorination
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2016 Collection
Centre for Advanced Imaging Publications
 
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