DOTA derivatives for site-specific biomolecule-modification via click chemistry: synthesis and comparison of reaction characteristics.
ABSTRACT Due to the high stability of its complexes with many M(2+) and M(3+)-ions, DOTA (1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid) is the most commonly used chelator for the derivatization and radiolabeling of bioactive molecules. Most of the currently used DOTA derivatives comprise amine-reactive functionalities, limiting their application to the derivatization of fully protected molecules or otherwise resulting in randomly distributed conjugation sites of undefined number. Click chemistry reactions are a valuable alternative to this unspecific conjugation as they proceed efficiently and chemoselectively under mild conditions allowing a site-specific derivatization of unprotected biomolecules. In this work, we describe straightforward syntheses of DOTA derivatives containing thiol, maleimide, aminooxy, aldehyde, alkyne, and azide functionalities, amenable to the currently most often used click chemistry reactions. Furthermore, the efficiency of the respective click reactions introducing DOTA into bioactive molecules was investigated. For each of the synthesized DOTA synthons, the site-specific and efficient conjugation to Tyr(3)-octreotate could be shown. Among these, the addition and oxime formation reactions proceeded fast and without side reactions, giving the products in high yields of 64-83% after purification. The copper-catalyzed triazole formation reactions produced some side-products, giving the desired products in lower, but still reasonable overall yields of 19-25%. All synthesized peptide-DOTA-conjugates were labeled with (68)Ga in high radiochemical yields of 96-99% and high specific activities providing compounds of high purity, demonstrating the applicability of all synthons for biomolecule modification and subsequent radiolabeling.
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ABSTRACT: Attachment of poly(ethylene glycol) (PEG) to proteins, peptides, liposomes, drugs, and nanoparticles can improve pharmaceutical pharmacokinetic properties and enhance in vivo biological efficacy. Since the first PEGylated product was approved by the Food and Drug Administration in 1990, increasing numbers of PEGylated compounds have entered clinical use. Successful clinical development of PEGylated pharmaceuticals requires accurate methods for the qualitative and quantitative analysis of intact PEG conjugates in biological fluids. In this article, we review assay methods that can be utilized for the detection and measurement of PEGylated pharmaceuticals in complex biological samples for determination of biodistribution and pharmacokinetic properties. In particular, we describe relevant colorimetric, chromatographic, radiolabeled, biological, and enzyme-linked immunosorbent assays for the pharmacokinetic study of PEGylated molecules.Bioconjugate Chemistry 02/2012; · 4.93 Impact Factor