PT - JOURNAL ARTICLE AU - Maria Erlandsson AU - Jacob Madsen AU - Carsten Nielsen AU - Camilla Bardram Johnbeck AU - Andreas Kjaer TI - Separation of [<sup>18</sup>F]Annexin V from [<sup>18</sup>F]fluorobenzoic acid DP - 2012 May 01 TA - Journal of Nuclear Medicine PG - 1755--1755 VI - 53 IP - supplement 1 4099 - http://jnm.snmjournals.org/content/53/supplement_1/1755.short 4100 - http://jnm.snmjournals.org/content/53/supplement_1/1755.full SO - J Nucl Med2012 May 01; 53 AB - 1755 Objectives [18F]Annexin V has been investigated as a PET tracer for apoptosis imaging. [18F]Annexin V is commonly isolated by a method based on size-exclusion chromatography, using different aqueous buffer solutions. However, our results indicate that this method unintentionally can result in insufficient separation of [18F]Annexin V and the hydrolysed by-product [18F]fluorobenzoic acid ([18F]FBA) and consequently compromise imaging data. Methods N-succinimidyl-4-[18F]fluorobenzoate ([18F]SFB) was synthesised in a 3-step one pot reaction procedure. Annexin V was labelled with 18F based on reaction with the amine-group reactive prosthetic group [18F]SFB. Purification was performed by size-exclusion HPLC (BioSep SEC S-2000, 300 x 21.2 mm) or Corning® Spin-X®UF Concentrator (molecular weight cut-off (MWCO) 10 kDa). The radiochemical purity (RCP) was determined by protein precipitation and SDS-page analysis. Results Varying the amount of Annexin V from 100 to 700 µg indicated that higher amounts of Annexin V result in more consistent radiochemical yields. Despite large differences in molecular mass, 36 kDa versus 140 g/mol, [18F]Annexin V and [18F]FBA show the same elution profile on size-exclusion chromatography. When a size-exclusion HPLC column like BioSep SEC S-2000 was used to purify [18F]Annexin V a RCP of 13 ± 6% (n=5) could be obtained due to contamination with [18F]FBA. However, when a filtration with a MWCO filter was used it was possible to increase the RCP to 91 ± 5% (n=6). The radiochemical yield of [18F]Annexin V was 27% non d.c. (n=6) based on [18F]SFB. Conclusions An increase in the RCP of [18F]Annexin V from 13% to 91% could be obtained using a filtration method based on a low binding polyethersulfone membrane with a MWCO filter instead of using a size-exclusion HPLC column