Imaging of red-shifted photons from bioluminescent tumours using fluorescence by unbound excitation from luminescence

Abstract

Early detection of tumours is today a major challenge and requires sensitive imaging methodologies coupled with new efficient probes. Bioluminescence imaging has been widely used in the field of oncology and several cancer cell lines have been genetically modified to provide bioluminescence signals. However, photons that are emitted by the majority of commonly used luciferases are usually in the blue part of the visible spectrum, where tissue absorption is still very high, making deep tissue imaging non-optimal and calling for optimised optical imaging methodologies. We have previously shown that red-shifting of bioluminescence signal by Fluorescence Unbound Excitation from Luminescence (FUEL) is a mean to increase bioluminescence signal sensitivity detection in vivo. Here, we applied FUEL to tumour detection in two different subcutaneous tumour models: the auto-luminescent human embryonic kidney (HEK293) cell line and the murine B16-F10 melanoma cell line previously transfected with the plasmid Luc2. Tumour size and bioluminescence were measured over time and tumour vascularization characterized. We then locally injected near infrared emitting Quantum Dots (NIR QDs)in the tumour site and observed a red-shifting of bioluminescence signal by (FUEL) indicating that FUEL could be used to allow deeper tumour detection.