Deep-Tissue Reporter-Gene Imaging with Fluorescence and Optoacoustic Tomography: A Performance Overview
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A primary enabling feature of near-infrared fluorescent proteins (FPs) and fluorescent probes is the ability to visualize deeper in tissues than in the visible. The purpose of this work is to find which is the optimal visualization method that can exploit the advantages of this novel class of FPs in full-scale pre-clinical molecular imaging studies.
Nude mice were stereotactically implanted with near-infrared FP expressing glioma cells to from brain tumors. The feasibility and performance metrics of FPs were compared between planar epi-illumination and trans-illumination fluorescence imaging, as well as to hybrid Fluorescence Molecular Tomography (FMT) system combined with X-ray CT and Multispectral Optoacoustic (or Photoacoustic) Tomography (MSOT).
It is shown that deep-seated glioma brain tumors are possible to visualize both with fluorescence and optoacoustic imaging. Fluorescence imaging is straightforward and has good sensitivity; however, it lacks resolution. FMT-XCT can provide an improved rough resolution of ∼1 mm in deep tissue, while MSOT achieves 0.1 mm resolution in deep tissue and has comparable sensitivity.
We show imaging capacity that can shift the visualization paradigm in biological discovery. The results are relevant not only to reporter gene imaging, but stand as cross-platform comparison for all methods imaging near infrared fluorescent contrast agents.
Key wordsFluorescent proteins Reporter genes Optical imaging Optoacoustic (photoacoustic) tomography Glioma
The authors would like to acknowledge the help of Irene Ho and Uwe Klemm in the cell culture, Dr. Nicolas Bézière in MSOT imaging, and Dr. Vladislav Verkhusha for providing the U87-iRFP cells and the FP extracts. V.N. acknowledges support from the European Research Council (ERC) Advanced Researcher Grant. D.R. acknowledges support from the German Research Foundation (DFG) Research Grant (RA 1848/1) and the European Research Council (ERC) Starting Independent Researcher Grant.
V.N., D.R., and N.C.D. conceived the research, N.C.D., A.A., K.R., N.C.B., K.S., and S.M. designed the experiments, K.S. did the cell culture, N.C.B and N.C.D. carried out the brain implantations, and N.C.D., A.A., K.R., and S.M. carried out the imaging experiments and performed data analysis. All authors contributed in writing the manuscript.
Conflict of Interest
V.N. and D.R. have financial interest with iThera Medical GmbH, while N.C.B. and S.M. are employees of iThera Medical GmbH.
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