title: Improved68Ga-labeling method using ethanol addition: Application to the α-helical peptide DOTA-FAMP.
abstract: We examined the68Ga labeling of the α-helical peptide, DOTA-FAMP, and evaluated conformational changes during radiolabeling.68Ga-DOTA-FAMP is a positron emission tomography probe candidate for atherosclerotic plaques. The labeling yield achieved by Zhernosekov's method (using acetone for68Ga purification) was compared with that achieved by the original and 2 modified Mueller's methods (using NaCl solution). Modified method I involves desalting the68Ga prior to labeling, and modified method II involves the inclusion of ethanol in the labeling solution. The labeling yield using Zhernosekov's method was 62% ± 5.4%. In comparison, Mueller's original method gave 8.9% ± 1.7%. Modified method I gave a slight improvement of 32% ± 2.1%. Modified method II further increased the yield to 66% ± 3.4%. Conformational changes were determined by circular dichroism spectroscopy, revealing that these differences could be attributed to conformational changes. Heat treatment affects peptide conformation, which leads to aggregation and decreases the labeling yield. Mueller's method is simpler, but harsh conditions preclude its application to biomolecules. To suppress aggregation, we included a desalting process and added ethanol in the labeling solution. These changes significantly improved the labeling yield. Before use for imaging, conformational changes of biomolecules during radiolabeling should be evaluated by circular dichroism spectroscopy to ensure the homogeneity of the labeled product.
authors.affiliation: Center for Instrumental Analysis, Kyoto Pharmaceutical University, Kyoto, Japan.
authors.forename: Koki
authors.identifier: 0000-0002-1479-2534
authors.initials: K
authors.lastname: Hasegawa
authors.affiliation: Department of Cardiology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Emi
authors.initials: E
authors.lastname: Kawachi
authors.affiliation: Department of Cardiology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.|Faculty of Sports and Health Science, Fukuoka University, Fukuoka, Japan.
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Uehara
authors.affiliation: Department of Radiology, Koga Hospital 21, Kurume, Fukuoka, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Yoshida
authors.affiliation: Department of Cardiology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Imaizumi
authors.affiliation: Department of Cardiology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ogawa
authors.affiliation: Department of Cardiology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Shin-Ichiro
authors.initials: SI
authors.lastname: Miura
authors.affiliation: Department of Cardiology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Keijiro
authors.initials: K
authors.lastname: Saku
mesh_terms: D060326:Chemistry Techniques, Synthetic / Q000379:methods; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry; D005710:Gallium Radioisotopes / Q000737:chemistry; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D019275:Radiopharmaceuticals / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: C000625387:68Ga-DOTA-FAMP; D056831:Coordination Complexes; D005710:Gallium Radioisotopes; D006573:Heterocyclic Compounds, 1-Ring; D010455:Peptides; D019275:Radiopharmaceuticals; C071349:1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid; D000431:Ethanol
keywords: 68Ga; CD spectroscopy; DOTA; FAMP; PET imaging; atherosclerotic plaques; biomolecule; labeling