Theranostics 2013; 3(3):181-189. doi:10.7150/thno.5984
Lewis Acid-Assisted Isotopic 18F-19F Exchange in BODIPY Dyes: Facile Generation of Positron Emission Tomography/Fluorescence Dual Modality Agents for Tumor Imaging
1. Molecular Imaging Center, Department of Radiology, University of Southern California, Los Angeles 90033, USA.
2. Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA.
3. Department of Radiology, The Third Affiliated Hospital of Sun Yat-sen University, Guangzhou 510630, China.
Liu S, Lin TP, Li D, Leamer L, Shan H, Li Z, Gabbaï FP, Conti PS. Lewis Acid-Assisted Isotopic 18F-19F Exchange in BODIPY Dyes: Facile Generation of Positron Emission Tomography/Fluorescence Dual Modality Agents for Tumor Imaging. Theranostics 2013; 3(3):181-189. doi:10.7150/thno.5984. Available from http://www.thno.org/v03p0181.htm
Positron emission tomography (PET) is a powerful technique for imaging biological pathways in vivo, particularly those that are key targets in disease processes. In contrast, fluorescence imaging has demonstrated to be a superior method for image-guided surgery, such as tumor removal. Although the integration of PET and optical imaging could provide an attractive strategy for patient management, there is a significant shortage of established platforms/methods for PET/optical probe construction. In this study, various reaction conditions were explored to develop a simple and fast method allowing for the introduction of [18F]-fluoride into BODIPY dyes. Through a systematic optimization of the reaction conditions, we found that BODIPY dyes, including commercial amine-reactive BODIPY succinimidyl esters, may be converted into their radioactive analogues in the matter of minutes via a 18F-19F isotopic exchange reaction promoted by a Lewis acid such as SnCl4. An integrin-targeting RGD peptide was also conjugated with [18F]BODIPY® R6G , derived from the commercially available BODIPY® R6G fluorescent tag, to provide a [18F]-RGD conjugate in 82% yield. In vivo evaluation of this imaging probe showed a discernible tumor uptake in the U87MG xenograft model. The dual modality imaging properties of the probe was confirmed by ex vivo fluorescence and microPET imaging experiments. In summary, in the matter of minutes, BODIPY dyes were converted into their “hot” radioactive analogues via a 18F-19F isotopic exchange reaction promoted by a Lewis acid. This approach, which can be applied to commercial BODIPY dyes, provides easy access to positron emission tomography/fluorescence dual modality imaging agents.
Keywords: PET, fluorsence, dual modality, BODIPY, 18F-19F exchange.