Multimodal PET/PAI/FLI Imaging Probe Based on Meso-O-alkyl Heptamethine Cyanine: Synthesis, [18F]f-Radiolabelling and Photophysical Characterizations

The combination of positron emission tomography (PET)/photoacoustic imaging (PAI)/fluorescence imaging (FLI) for diagnosis allows to exploit the strengths and overcome the weaknesses of each modality. In this context, dyes displaying photophysical properties for both fluorescence and photoacoustic imaging in the near infra -red (NIR) window are ideal to maximize their signal-to-noise ratio. Herein, were synthetized a series of new meso-O- alkyl cyanine-7 derivatives, and the derivative bearing an azide was coupled to a highly functionalized C-glycosyl platform resulting in an imaging probe which exhibited both high molar absorptivity and fluorescence quantum yield (>15 %), excellent characteristics for FLI and for PAI. Successfully radiolabeled with fluorine-18 via a [18F] F-C bond, this probe additionally allowed PET imaging. Altogether, these results revealed the multimodal PET/ PAI/FLI imaging potential of this probe based on meso-O-alkyl heptamethine cyanine. Moreover, a late-stage CuAAC coupling with two model peptides c (RGDfK) was successfully performed to demonstrate the feasibility and the versatility of the vector conjugation step, foreshadowing of the expected targeting possibilities of this original platform for efficient disease diagnosis by multimodal imaging.