An amine-derivatized, DOTA-loaded polymeric support for Fmoc solid phase peptide synthesis

Abstract

An amine-derivatized DOTA has been used to modify the surface of a polymeric support for conventional Solid Phase Peptide Synthesis (SPPS) following standard Fmoc chemistry methods. This methodology was used to synthesize a peptide-DOTA conjugate that was demonstrated to be a PARACEST MRI contrast agent. Therefore, this synthesis methodology can facilitate Fmoc SPPS of molecular imaging contrast agents. Keywords DOTA; SPPS; Fmoc; PARACEST; MRI; Molecular ImagingMolecular imaging has recently emerged as a powerful method to provide medical information at the molecular level.1 Molecular imaging contrast agents have been conjugated to many types of peptides that target cell receptors and enzymes, in order to diagnose pathological tissues and assess early therapeutic responses.2 -5 Macrocyclic metal chelates, such as metallated 1,4,7,10-tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid (DOTA) have been conjugated to peptides and detected with MRI, PET and SPECT imaging.6 -8 As a testament to their potential, 23% (187 of 820) of the journal publications that describe molecular imaging contrast agents with metal chelates contain one or more peptidyl ligands. As a testament to their demonstrated utility for biomedical imaging, 8% (46 of 594) of the entries in the Molecular Imaging Contrast Agent Database (MICAD) consist of metal chelates with one or more peptidyl ligands.9The facile synthesis of metal chelate contrast agents that include peptides is needed to accelerate the research and clinical translation of molecular imaging. Previously reported methods have conjugated the carboxylates of DOTA to the amines of peptides, including the N-terminus, the side chain of lysine, and unnatural amino acid derivatives. 10 DOTA derivatives of succinimide and isothiocyanate have also been conjugated to peptide amino groups. 11,12 However, coupling DOTA only to peptide amines can limit synthesis methodologies. 13,14 * To whom correspondence should be addressed. Mark D. Pagel, Associate Professor, The University of Arizona, Arizona Cancer Center, #4949B, 1515 N. Campbell Avenue, Tucson, AZ 85724-5024, Phone : (520) 404-7049, Fax : (520) 626-0395, E-Mail: mpagel@u.arizona.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptTo resolve these limitations in the synthesis of peptidyl DOTA conjugates, we previously developed an amine-derivatized DOTA and used this product to couple DOTA to the Cterminus of a peptide using soution-phase methods. 15 We have also loaded an aminederivatized DOTA onto ...

Solid phase synthesis, radiolabeling and biological evaluation of a99mTc-labeled αVβ3tripeptide (RGD) conjugated to DOTA as a tumor imaging agent

“…The method of synthesis mentioned in this paper is the new way for synthesis of DOTA-peptide. [18][19][20] Bifunctional chelating agents derived from the macrocyclic 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) have the ability to incorporate lanthanide ions to make strong and stable chelates under physiological conditions. synthesized DOTA-α V β 3 -tripeptide has been completely assembled on solid phase, we have studied the radiochemical properties of the labeled conjugate and finally we proceeded with the in vivo evaluation in U-87MG human malignant glioma cells which overexpress α V β 3 integrins.…”

A single diamagnetic catalyCEST MRI contrast agent that detects cathepsin B enzyme activity by using a ratio of two CEST signals

“…1B). To date, CEST agents for catalyCEST MRI have been developed that detect the activity of caspase-3 (2), urokinase Plasminogen Activator (1,3), cathepsin D (4), transglutaminase (5), β-galactosidase (6), esterase (7), protein kinase A (8), and cytosine deaminase enzymes (9). …”

Detecting Enzyme Activities with Exogenous MRI Contrast Agents

“…For example, similar PARACEST agents with a different peptide ligand can detect the protease activity of cathepsin-D [57] and urokinase Plasminogen Activator. [58] These examples used a Tm(III) chelate, which demonstrates that a variety of metal chelates may be used in this approach to expand this platform technology. More recently, a DIACEST agent has exploited a similar approach to detect the activity of cytosine deaminase.…”