Background
Radiolabelled dyes are sought for multimodal imaging and are in development for PET/SPECT- and optical imaging and furthermore for fluorescence-guided intraoperative surgery. NIR-fluorophores show unique optical properties (high quantum yields/extinction coefficients and reduced photobleaching). The radiolabelled dyes are intended to be used for non-invasive PET-imaging (prestaging) followed by fluorescence/(radio)-guided R0-tumour-resection.
Aims
The goal of this work was the characterization of radiolabelled near-infrared (NIR) light-emitting silicon-rhodamines for PET- and optical imaging. The fluorophores were synthesized for their subsequent radiolabelling with fluorine-18 with the aim to elucidate their potential as a new class of imaging agents for the detection of tumours and their resection.
Methods
The combination of PET- and optical imaging leads to new approaches in tumour imaging and resection and allows the accurate differentiation of healthy and affected tumour tissues. We have designed silicon-(Si)-rhodamines (SiR) with near-infrared optical properties. Currently the dyes are going to be radiolabelled by using the alcohol-enhanced and copper-mediated approach for radiofluorination.
Results and Conclusion
The organic synthesis route provided boronic acid functionalized SiRs with overall yields of 43%. The dyes show large extinction coefficients up to 72.000 M-1cm-1, quantum yields of 0.33 and high photostabilities making them potentially useful for NIR-optical imaging. The fluorophores will be radiofluorinated and their utilization for potential PET-imaging will be evaluated.
References
1. Nagano T et al. Development of NIR Fluorescent Dyes Based on Si–rhodamine for in Vivo Imaging. J. Am. Chem. Soc. 2012; 134: 5029–5031.
2. Neumaier B. et al. Alcohol‐Enhanced Cu‐Mediated Radiofluorination. Chem. Eur. J. 2017; 23: 3251–3556.