Abstract
The detection of the Cerenkov radiation (CR) is an emerging preclinical imaging technique which allows monitoring the in vivo distribution of radionuclides. Among its possible advantages, the most interesting is the simplicity and cost of the required instrumentation compared, e.g., to that required for PET scans. On the other hand, one of its main drawbacks is related to the fact that CR, presenting the most intense component in the UV-vis region, has a very low penetration in biological tissues. To address this issue, we present here multifluorophoric silica nanoparticles properly designed to efficiently absorb the CR radiation and to have a quite high fluorescence quantum yield (0.12) at 826 nm. Thanks to a highly efficient series of energy transfer processes, each nanoparticle can convert part of the CR into NIR light, increasing its detection even under 1.0-cm thickness of muscle.
Highlights
Cerenkov luminescence imaging (CLI) is a novel preclinical modality to image the biodistribution of radiotracers, based on the detection of Cerenkov radiation (CR) using optical imaging (Spinelli et al, 2010)
We synthesized pluronic–silica (PluS) nanoparticles doped with five different dyes that have been chosen to efficiently absorb CR in all the visible ranges and to efficiently funnel the excitation energy toward the lowest energy dye, a Cy7 derivative, presenting a fluorescence emission in the near-infrared region (NIR)
The triethoxysilane derivatives of DEAC (CU), tetramethyl bodipy (BO), Cy5.5 (C5), and Cy7 (C7) were obtained by amide coupling with 3-aminopropyltriethoxy silane, while the rhodamine B derivative (RB) was obtained by reaction of the corresponding rhodamine B piperazine amide derivative with 3isocyanatopropyltriethoxysilane
Summary
Cerenkov luminescence imaging (CLI) is a novel preclinical modality to image the biodistribution of radiotracers, based on the detection of Cerenkov radiation (CR) using optical imaging (Spinelli et al, 2010). It is possible to enable a broad range of applications, taking profit of CR escaping from living subjects, to monitor the biodistribution of radioisotopes by optical imaging as an alternative to PET (Yang et al, 2015). A shift in the CR spectrum in the near-infrared region (NIR) would improve the detection of radionuclides deeper inside the tissues and increase the output signal. This shift can be obtained through the so-called Cerenkov resonance energy transfer (CRET) process (Hu et al, 2014) that has been used to sensitize porphyrins in photodynamic therapy (Ni et al, 2018). Considering the broad wavelength range of CR, the use of a single organic
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