Ethanol effects on ⁶⁸Ga-radiolabelling efficacy and radiolysis in automated synthesis utilizing NaCl post-processing

Recent studies showed that ethanol in the reaction mixture improves radiolabelling with trivalent radiometals in terms of precursor amount, reaction time, reaction temperature and radiolysis. With regard to clinical application, this effect is of practical interest in radiopharmacy. The aim of this study was to evaluate whether the positive effect of ethanol can be exploited in automated systems utilizing NaCl-post processing.

Gallium-68 was obtained from a 1.85 GBq ⁶⁸Ge/⁶⁸Ga-generator. Radiolabelling was performed on an automated ⁶⁸Ga-labelling cassette module. The standard labelling protocol was used without modifications. 0-40 vol% ethanol were added to the reaction mixture. Quality control was performed using radioHPLC and radioTLC.

Utilization of additional ethanol on an automated cassette module can be achieved by adding ethanol directly to the buffer solution without further modifications of the standard procedure. Radiolysis was decreased significantly as analysed by radioHPLC.

It was possible to combine the positive effects of ethanol on radiolabelling efficacy and radiolysis with the standard labelling procedure of an automated cassette module system. The whole process guarantees safe preparation of highly pure ⁶⁸Ga-peptide for clinical application.