Abstract
Developing new strategies to rapidly incorporate the fac-[MI(CO)3]+ (M = Re, 99mTc) core into biological targeting vectors in radiopharmaceuticals continues to expand as molecules become more complex and as efforts to minimize nonspecific binding increase. This work examines a novel isothiocyanate-functionalized bifunctional chelate based on 2,2′-dipicolylamine (DPA) specifically designed for complexing the fac-[MI(CO)3]+ core. Two strategies (postlabeling and prelabeling) were explored using the isothiocyanate-functionalized DPA to determine the effectiveness of assembly on the overall yield and purity of the complex with amine containing biomolecules. A model amino acid (lysine) examined (1) amine conjugation of isothiocyanate-functionalized DPA followed by complexation with fac-[MI(CO)3]+ (postlabeling) and (2) complexation of fac-[MI(CO)3]+ with isothiocyanate-functionalized DPA followed by amine conjugation (prelabeling). Conducted with stable Re and radioactive 99mTc analogs, both strategies formed the product in good to excellent yields under macroscopic and radiotracer concentrations. A synthetic peptide (AE105) which targets an emerging biomarker in CaP prognosis, urokinase-type plasminogen activator receptor (uPAR), was also explored using the isothiocyanate-functionalized DPA strategy. In vitro PC-3 (uPAR+) cell uptake assays with the 99mTc-labeled peptide (8a) showed 4.2 ± 0.5% uptake at 4 h. In a murine model bearing PC-3 tumor xenografts, in vivo biodistribution of 8a led to favorable tumor uptake (3.7 ± 0.7% ID/g) at 4 h p.i. with relatively low accumulation (<2% ID/g) in normal organs not associated with normal peptide excretion. These results illustrate the promise of the isothiocyanate-functionalized approach for labeling amine containing biological targeting vectors with fac-[MI(CO)3]+.
Original language | English |
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Pages (from-to) | 130-142 |
Number of pages | 13 |
Journal | Bioconjugate Chemistry |
Volume | 27 |
Issue number | 1 |
DOIs | |
State | Published - Jan 20 2016 |
Externally published | Yes |
Funding
The authors wish to thank Mary Dyszlewski of Covidien, Inc., for the Isolink kits and Dr. Gerhard Munske of the Washington State University Molecular Biology and Genomics Core for performing the MALDI-TOF analysis. This research was funded in part by the Office of Science (BER), U.S. Department of Energy (DE-SC0008397), the NIH/NIGMS Biotechnology Training Program at Washington State University (Institutional Award T32 GM008336), the Auvil Fellows Program, the College of Arts and Sciences, and the Chemistry Department at Washington State University.
Funders | Funder number |
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Chemistry Department at Washington State University | |
Mary Dyszlewski of Covidien, Inc. | |
NIH/NIGMS | T32 GM008336 |
U.S. Department of Energy | DE-SC0008397 |
U.S. Department of Energy | |
National Institute of Neurological Disorders and Stroke | T32NS048039 |
National Institute of Neurological Disorders and Stroke | |
Office of Science | |
Biological and Environmental Research | |
Washington State University | |
College of Arts and Sciences, Boston University |