Objectves: A20 and A20-36 peptides can be labelled with fluorine-18 as a potential radiopharmaceutical for quantitative in vivo mapping of B Cell receptors (BCR) in Murine B-cell lynphoma. We used the F-18 N-succinimidyl 4-fluorobenzoate to label the amino group of terminal aminoacid of A20 and A20-36 peptides and we could obtain radiolabelling yields of >15%. Results: In labelling with fluorine-18 the yield of peptides synthesis showed to be very low. The analysis of every step of radiosynthesis, measuring the activity of every utilized stuff in dose calibrator revealed that a great part of radioactivity stuck in the reactivial where both the water was eliminated and the fluorine-18 nucleofilic substitution reaction took place. In addition to this some radioactivity was present in the silica purification cartridge. Finally a loss of fluorine-18 isotope was evident in the first phase of synthesis. This fact, present in every synthesis, excludes the hypothesis of a loss of activity due to the manipolation of radiosynthesis itself, as it takes place in the initial phase. On the basis of my direct experience on cyclotron I have supposed a fault in fluorine-18 production: in particolar a loss of Silver cations from target chamber itself during bombardment. The Silver cations effectively can seize a part of fluorine-18 product, in the initial phase eliminating it. The tests have supported our hypotesis: 1) Evaporating the target water at 105°C with argon stream the day after the irradiation, it has been noticed the presence of metal grey residual in the conical bottom of reactivial. 2) Filtering the target water by 0.2 mm HPLC filter immediately after irradiation and making the fluorine-18 labelling synthesis there was a 10% increased of yield. 3) Utilizing a scx resin cartridge, which eliminates Silver cations from water, there was a further increase of the yield. In conclusion it is evident the presence of Silver cations in the irradiated water which reduces the final product yield. A20 and A20-36 peptides labelled with 18F-N-succinimidyl 4-fluorobenzoate is presently purfied with gradient analytical HPLC in Vydac column (5micron, 250mm, 4.6mm) using ethanol and water as the eluent. This method allows to inject directly the radiocompounds into the animals.
IMPROVEMENTS OF 18F-PEPTIDES LABELING SYNTHESIS
Mariarosaria Panico;Michele Larobina;Sara Gargiulo;Matteo Gramanzini;Bruno Alfano;Marco Salvatore
2010
Abstract
Objectves: A20 and A20-36 peptides can be labelled with fluorine-18 as a potential radiopharmaceutical for quantitative in vivo mapping of B Cell receptors (BCR) in Murine B-cell lynphoma. We used the F-18 N-succinimidyl 4-fluorobenzoate to label the amino group of terminal aminoacid of A20 and A20-36 peptides and we could obtain radiolabelling yields of >15%. Results: In labelling with fluorine-18 the yield of peptides synthesis showed to be very low. The analysis of every step of radiosynthesis, measuring the activity of every utilized stuff in dose calibrator revealed that a great part of radioactivity stuck in the reactivial where both the water was eliminated and the fluorine-18 nucleofilic substitution reaction took place. In addition to this some radioactivity was present in the silica purification cartridge. Finally a loss of fluorine-18 isotope was evident in the first phase of synthesis. This fact, present in every synthesis, excludes the hypothesis of a loss of activity due to the manipolation of radiosynthesis itself, as it takes place in the initial phase. On the basis of my direct experience on cyclotron I have supposed a fault in fluorine-18 production: in particolar a loss of Silver cations from target chamber itself during bombardment. The Silver cations effectively can seize a part of fluorine-18 product, in the initial phase eliminating it. The tests have supported our hypotesis: 1) Evaporating the target water at 105°C with argon stream the day after the irradiation, it has been noticed the presence of metal grey residual in the conical bottom of reactivial. 2) Filtering the target water by 0.2 mm HPLC filter immediately after irradiation and making the fluorine-18 labelling synthesis there was a 10% increased of yield. 3) Utilizing a scx resin cartridge, which eliminates Silver cations from water, there was a further increase of the yield. In conclusion it is evident the presence of Silver cations in the irradiated water which reduces the final product yield. A20 and A20-36 peptides labelled with 18F-N-succinimidyl 4-fluorobenzoate is presently purfied with gradient analytical HPLC in Vydac column (5micron, 250mm, 4.6mm) using ethanol and water as the eluent. This method allows to inject directly the radiocompounds into the animals.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
