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(68)Ga small peptide imaging: comparison of NOTA and PCTA.
MedLine Citation:
PMID:  23035991     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
In this study, a bifunctional version of the chelate PCTA was compared to the analogous NOTA derivative for peptide conjugation, 68Ga radiolabeling and small peptide imaging. Both p-SCN-Bn-PCTA and p-SCN-Bn-NOTA were conjugated to cyclo-RGDyK. The resulting conjugates, PCTA-RGD and NOTA-RGD, retained their affinity for the peptide target, the αvβ3 receptor. Both PCTA-RGD and NOTA-RGD could be radiolabeled with 68Ga in >95% radiochemical yield (RCY) at room temperature within 5 min. For PCTA-RGD higher effective specific activities, up to 55 MBq/nmol, could be achieved in 95% RCY with gentle heating at 40°C. The 68Ga-radiolabeled conjugates were >90% stable in serum and in the presence of excess apo-transferrin over 4 h; 68Ga-PCTA-RGD did have slightly lower stability than 68Ga-NOTA-RGD, 93±2% compared to 98±1%, at the 4 h time point. Finally, the tumor and non-target organ uptake and clearance of 68Ga-radiolabeled PCTA-RGD and NOTA-RGD was compared in mice bearing HT-29 colorectal tumor xenografts. Activity cleared quickly from the blood and muscle tissue with >90% and >70% of the initial activity was cleared within the first 40 min, respectively. The majority of activity was observed in the kidney, liver and tumor tissue. The observed tumor uptake was specific with up to 75% of the tumor uptake blocked when the mice were pre-injected with 160 nmol (100 µg) of unlabeled peptide. Uptake observed in the blocked tumors was not significantly different than the background activity observed in muscle tissue. The only significant difference between the two 68Ga-radiolabeled bioconjugates in vivo was the kidney uptake. 68Ga-radiolabeled PCTA-RGD had significantly lower (p < 0.05) kidney uptake (1.1±0.5%) at 2 h post-injection compared to 68Ga-radiolabeled NOTA-RGD (2.7±1.3%). Overall, 68Ga-radiolabeled PCTA-RGD and NOTA-RGD performed similarly, but the lower kidney uptake for 68Ga-radiolabeled PCTA-RGD may be advantageous in some imaging applications.
Authors:
Cara L Ferreira; Donald Yapp; Derek Mandel; Rajanvir K Gill; Eszter Boros; May Q Wong; Paul Jurek; Garry E Kiefer
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-5
Journal Detail:
Title:  Bioconjugate chemistry     Volume:  -     ISSN:  1520-4812     ISO Abbreviation:  Bioconjug. Chem.     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-5     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9010319     Medline TA:  Bioconjug Chem     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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