Hi,
I am currently trying to optimize the radiolabeling of a peptide (w/ NOTA) but I am ending up with 30% 68Ga-colloid in the reaction. I am using HEPES as the buffer and setting the reaction pH to 3.5, room temperature for 10 min.
I measured the amount of colloid present using iTLC-SG and methanol:ammonium acetate (1:1) buffer.
I am able to purify that colloid but I would like to increase the radiolabeling yield by preventing the formation of colloids...
Any suggestions? Thanks in advance!
Have you checked the purity of Ga-68 solution before labeling?
what was the source of Ga-68? If that come from generator, it's better to purify it by cation exchange resin. Also the use of acetone/HCl mixture for elution could improve both Ga-68 purity and labeling with any chelator
if that came from cyclotron, colloidal Ga(OH)3 usually occured as the effect of radiolysis from high radioactivity of Ga-68, since it has high radioactivity, it should be better you do purification steps before complexation
if your Ga-68 solution was OK, then the colloid was formed in complexation process, try to use other buffer than HEPES and see how much the colloidal Ga-68 formed
Hi, What temperature are you using? We also have the same issue and found about 10% colloid formation with DOTA peptides. We some extent managed by adjusting pH near 3 We purify using cartridge
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