Peptide synthesis, characterization and 68Ga-radiolabeling of NOTA-conjugated ubiquicidin fragments for prospective infection imaging with PET/CT

Show simple item record Ebenhan, Thomas Chadwick, Nicholas Sathekge, Mike Machaba Govender, Patrick Govender, Thavendran Kruger, Hendrik G. Marjanovic-Painter, Biljana Zeevaart, Jan Rijn 2014-05-22T09:31:25Z 2014-05-22T09:31:25Z 2014-05
dc.description.abstract INTRODUCTION: Human antimicrobial peptides are of interest for the development of positron emission tomography (PET) tracers as they exhibit desirable characteristics that make them good candidates for targeting vectors. Due to their natural role in the innate immune system they selectively bind to pathogenic bacteria and yeast, whilst remaining minimally immunogenic and cytotoxic to humans. Research into ubiquicidin (UBI)-based tracers has focused on 99mTc as a radionuclide, however, the use of bi-functional chelators such as 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA), in combination with 68Ga as a radionuclide, allows for a simple radiolabeling procedure which is preferable in a clinical setting using PET/CT. METHODS: The peptides fragments UBI29-41, UBI30-41 were synthesized by standard microwave Fmoc/tert-butyl (tBu)-solid phase synthetic protocols. Characterizations were performed using analytical HPLC and LC/MS. Both NOTA-conjugated peptides were exposed to natGa3 +; their complexed form was quantified by direct LC/MS injection. This complexation was utilized to testify bacterial and mammalian cell binding potential of fluorophore-linked NOTA-UBI29-41/30-41. 68Ga labeled NOTA-UBI fragments were also tested for competitive interaction to Staphylococcus aureus to proof the binding target. 68Ga was eluted from SnO2- and TiO2-based 68Ge/68Ga generators using fractionated elution and anion exchanged-based post-procession. NOTA-peptide radiolabeling was carried out including optimization of buffer molarity, NOTA-peptide concentration(s), incubation temperature and –duration as well as considering various SPE purification cartridges. RESULTS: Pure UBI29-41, UBI30-41 and NOTA-UBI30-41 were successfully characterized. Both, NOTA-UBI fragments exhibited complexation rates to natGa3 + ≥ 99%. The percentage binding was significantly higher to Staphylococcus aureus bacilli over Mt4 human leucocytes (P > 0.05) for NOTA-UBI29-41[Lys(Abz)] < NOTA-UBI30-41[Lys(Abz)]. Significant lower binding was observed for both 68Ga-labeled NOTA-UBI fragments (P > 0.03) after pre-incubation with excess unlabeled NOTA-UBI. Reproducible 68Ga radiolabeling ranged for 51–85% and 46–78% for NOTA-UBI29-41 and NOTA-UBI30-41, respectively. CONCLUSION: Aside from successful peptide syntheses the first ever 68Ga-radiolabeling method is reported for NOTA-UBI fragments. The NOTA-conjugation didn’t compromise the selective and specific interaction with bacterial cells in vitro. Both tracers are warranting prospective imaging of infection with PET/CT. en_US
dc.description.librarian hb2014 en_US
dc.description.sponsorship National Research Foundation (NRF), the University of KwaZulu Natal (UKZN) and The Nuclear Technologies in Medicine and the Biosciences Initiative (NTeMBI) en_US
dc.description.uri en_US
dc.identifier.citation Ebenhan, T, Chadwick, N, Sathekge, MM, Govender, P, Govender, T, Kruger, HG, Marjanovic-Painter, B & Zeevaart, JR 2014, 'Peptide synthesis, characterization and 68Ga-radiolabeling of NOTA-conjugated ubiquicidin fragments for prospective infection imaging with PET/CT', Nuclear Medicine and Biology, vol. 41, no. 5, pp. 390-400. en_US
dc.identifier.issn 0969-8051 (print)
dc.identifier.issn 1872-9614 (online)
dc.identifier.other 10.1016/j.nucmedbio.2014.02.001
dc.language.iso en en_US
dc.publisher Elsevier en_US
dc.rights © 2014 Elsevier Inc. All rights reserved. Notice : this is the author’s version of a work that was accepted for publication in Nuclear Medicine and Biology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Nuclear Medicine and Biology, vol. 41, no. 5, May-Jun 2014, pp. 390-400, doi : 10.1016/j.nucmedbio.2014.02.001. en_US
dc.subject Ubiquicidin en_US
dc.subject NOTA en_US
dc.subject 68Gallium en_US
dc.subject Iinfection imaging en_US
dc.subject PET/CT en_US
dc.subject 68Ga-NOTA-UBI en_US
dc.title Peptide synthesis, characterization and 68Ga-radiolabeling of NOTA-conjugated ubiquicidin fragments for prospective infection imaging with PET/CT en_US
dc.type Postprint Article en_US

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