Synthesis and studies of new chromophores for two-photon PDT and of bimodal systems for two-photon PDT and MRI

There is an increasing interest in the emerging field of "theranostic" whose aim is to improve the diagnosis and to monitor the treatment of the disease. This can be achieved by combining a diagnostic and a therapeutic agent within the same system.[1] We are currently developing systems which combine a PDT (Photodynamic Therapy) sensitizer activated by a two-photon absorption process and a MRI (Magnetic Resonance Imaging) contrast agent. Classical PDT treatments based on one-photon absorbing photosensitizers are performed outside the therapeutic window (700-900 nm), are limited to superficial tissues and lead to photodamages.[2] Several porphyrin based conjugates were reported as efficient two-photon sensitizer for PDT.[3] New photosensitizers capable of being excited in the therapeutic window by a process of simultaneous absorption of two photons (A2P) will be presented. They consist of a porphyrin linked to a diketopyrrolopyrrole. Photophysical characterisations and cellular studies were realised and have shown the potential of the compounds as two-photon PDT photosensitizers. [4] One of the two-photon chromophore was combined with a Gd(III)-based complex leading to a bimodal system for two-photon PDT and MRI. Preliminary results related to the photophysical properties and relaxivity measurements of the bimodal system will be presented.