Abstract
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Objectives Cerenkov Radiation Energy Transfer (CRET) is a secondary light produced from Cerenkov radiation which is converted to longer wavelength by a fluorophore. This radionuclide-based bioluminescence has high signal to background ratios compare to other optical imaging techniques. Combining with PET system, Cerenkov luminescence tomography (CLT) could provide additional molecular imaging information. Qunatum dot (QD) nanoparticles (NPs) are ideal carrier for CRET because it can absorb blue light and emit typical wavelength. In this study, we developed PET/optical multimodal imaging probes, which could be labeled with radioisotope directly as a Cerenkov luminescence source to give CRET effect to QD NPs.
Methods QD655 (quantum dot 655) was encapsulated with polysorbate 60 and SCN-Bn-NOTA conjugated stearylamine (NOTA-SA). Encapsulated QD655 (100 nM) was labeled with Ga-68. Ga-68-NOTA-QD655 in 5 different radioactivities (0.023, 0.046, 0.093, 0.185, and 0.37 MBq) were added in a black 96-well plate (n=3). 68GaCl3 was added in same radioactivities for control. Plate was imaged in an IVIS® Lumina II (binning 4, FOV=12.5, 1/f stop, 60 sec exposure) imaging system. Images were obtained in open (515-875 nm) emission filters. Region of interest were drawn in each wells and counted the radiance (p/s/cm2/sr) in Living Image® software (version 2.5).
Results NOTA-QD655 was obtained in 16.2 ± 1.37 nm. NOTA-QD655 was labeled with Ga-68 with high radiochemical yield (>99%). Ga-68 labeled NOTA-QD655 showed luminescent signals without any machinery excitation light. And it was significantly higher than free Ga-68 signals (P<.05) at all radioactivities.
Conclusions We produced multimodal QD NPs using encapsulation method. The CRET image was obtained with Ga-68-NOTA-QD655 successfully.
Research Support NRF-2012M2A2A7035853