TY - JOUR
T1 - Characterization of chemical, radiochemical and optical properties of a dual-labeled MMP-9 targeting peptide
AU - Azhdarinia, Ali
AU - Wilganowski, Nathaniel
AU - Robinson, Holly
AU - Ghosh, Pradip
AU - Kwon, Sunkuk
AU - Lazard, Zawaunyka W.
AU - Davis, Alan R.
AU - Olmsted-Davis, Elizabeth
AU - Sevick-Muraca, Eva M.
N1 - Funding Information:
The authors acknowledge Robert P. Hammer (New England Peptide) for his technical assistance with design and synthesis of the peptide conjugate. This work was supported by Defense Advanced Research Projects Agency W911NF-09-1-0040 and Department of Defense W81XWH-07-0281 (EO-D) and W81XWH-07-1-025 (EO-D).
PY - 2011/6/15
Y1 - 2011/6/15
N2 - Optical imaging possesses similar sensitivity to nuclear imaging and has led to the emergence of multimodal approaches with dual-labeled nuclear/near-infrared (NIR) agents. The growing impact of 68Ga (t 1/2 = 68 min) labeled peptides on preclinical and clinical research offers a promising opportunity to merge the high spatial resolution of NIR imaging with the clinically-accepted positron emission tomography (PET). Previously, dual-labeled agents have been prepared with longer-lived radiometals and showed no detrimental effects on optical properties as a result of radiolabeling. In this study, we selected a peptide (M 2) that targets MMP-2/9 and is dual-labeled with IRDye 800CW and 68Ga. Since 68Ga chelation typically requires low pH (3.5-4) and elevated heating temperatures (95 °C), we sought to evaluate the impact of 68Ga labeling on the optical properties of M 2. An efficient method for preparation of 68Ga-M 2 was developed and reaction conditions were optimized. Stability studies in PBS, DTPA, and serum were performed and high levels of intact agent were evident under each condition. The addition of multiple reporters to a targeting agent adds further complexity to the characterization and validation and thus requires not only testing to ensure the agent is stable chemically and radiochemically, but also optically. Therefore, fluorescence properties were evaluated using a spectrofluorometer as well as by fluorescence detection via HPLC. It was determined that 68Ga-labeling conditions did not impair the fluorescent properties of the agent. The agent was then used for in vivo imaging in a mouse model of heterotopic ossification (HO) with activated MMP-9 expression as an early biomarker which precedes mineralization. Although 68Ga-complexation greatly reduced binding affinity of the peptide and negated tracer uptake on PET, NIR imaging showed consistent fluorescent signal that correlated to MMP-9 expression. This attests to the feasibility of using 68Ga/NIR for dual-labeling of other peptides or small molecules for multimodality molecular imaging.
AB - Optical imaging possesses similar sensitivity to nuclear imaging and has led to the emergence of multimodal approaches with dual-labeled nuclear/near-infrared (NIR) agents. The growing impact of 68Ga (t 1/2 = 68 min) labeled peptides on preclinical and clinical research offers a promising opportunity to merge the high spatial resolution of NIR imaging with the clinically-accepted positron emission tomography (PET). Previously, dual-labeled agents have been prepared with longer-lived radiometals and showed no detrimental effects on optical properties as a result of radiolabeling. In this study, we selected a peptide (M 2) that targets MMP-2/9 and is dual-labeled with IRDye 800CW and 68Ga. Since 68Ga chelation typically requires low pH (3.5-4) and elevated heating temperatures (95 °C), we sought to evaluate the impact of 68Ga labeling on the optical properties of M 2. An efficient method for preparation of 68Ga-M 2 was developed and reaction conditions were optimized. Stability studies in PBS, DTPA, and serum were performed and high levels of intact agent were evident under each condition. The addition of multiple reporters to a targeting agent adds further complexity to the characterization and validation and thus requires not only testing to ensure the agent is stable chemically and radiochemically, but also optically. Therefore, fluorescence properties were evaluated using a spectrofluorometer as well as by fluorescence detection via HPLC. It was determined that 68Ga-labeling conditions did not impair the fluorescent properties of the agent. The agent was then used for in vivo imaging in a mouse model of heterotopic ossification (HO) with activated MMP-9 expression as an early biomarker which precedes mineralization. Although 68Ga-complexation greatly reduced binding affinity of the peptide and negated tracer uptake on PET, NIR imaging showed consistent fluorescent signal that correlated to MMP-9 expression. This attests to the feasibility of using 68Ga/NIR for dual-labeling of other peptides or small molecules for multimodality molecular imaging.
KW - Dual-labeling
KW - Gallium-68
KW - MMP
KW - Near-infrared fluorescence
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U2 - 10.1016/j.bmc.2011.04.054
DO - 10.1016/j.bmc.2011.04.054
M3 - Article
C2 - 21612930
AN - SCOPUS:79958290869
SN - 0968-0896
VL - 19
SP - 3769
EP - 3776
JO - Bioorganic and Medicinal Chemistry
JF - Bioorganic and Medicinal Chemistry
IS - 12
ER -