Innovative theranostic approaches based on simultaneous drug release and in situ synthesis of fluorophores/photosensitizers – InnoTherano

In vivo chemistry can be defined as the use of cells as reaction vessels and some of their constituents as catalysts to achieve internal construction of molecular nano-objects from exogenous synthetic precursors. This is a growing research field that is seen as having a great future potential for various applications in the field of diagnosis (based on molecular imaging), therapy and synthetic biology. Our project aims to implement this attractive concept to the development of next-generation theranostic agents (abbreviated as NG-FTAs) that may be potentially used either for anti-cancer chemotherapy of for treatment of infectious diseases. Thus, we intend to develop novel fluorogenic pro-drugs using an innovative strategy based on in situ formation of an organic-based fluorophore from a caged precursor responsive to a biomarker related to a disease state (typically, an enzyme belonging to the class of glycosidases). This fluorogenic "covalent-assembly" type process will be accompanied by the concomitant release of a drug molecule through a domino reaction also effective in physiological media. A biocompatible intramolecular cyclization reaction leading to in situ formation of a fluorescent pyronin scaffold will be preferred for the two following reasons: (1) facile tuning of spectral features of formed xanthene dye, within the range 520-660 nm (selected according to the targeted application and the related biological context) by modifying alkyl substituents of -NR2 group and/or replacing the intracyclic oxygen atom by CMe2 or SiMe2 moiety (carbo- or Si-pyronins), of caged precursor ; (2) his combined use with modern tools produced by medicinal chemistry (self-immolative molecular platforms developed for pro-drug strategies) should enable the rapid access to NG-FTAs through simple and effective molecular lego® approach. This is an interesting and important feature of the project aimed at rapidly optimizing physico-chemical and pharmacological properties but also fluorescence imaging and therapy performances of NG-FTAs without resorting to tedious and time-consuming de novo syntheses. Our second objective will be to apply this innovative probe design principle to the development of novel dual-functional drug delivery systems (abbreviated as DF-DDSs) for combined pharmaco-photodynamic therapy (i.e., in situ formation of a ROS-generating photosensitizer and drug release). Indeed, these DF-DDSs may be the cornerstone of novel combined therapy strategies assumed as effective ways to overcome for instance, difficulties inherent to chemotherapy or antibiotics resistance. The caged precursor associated to a self-immolative molecular platform for drug delivery, will be designed to generate after enzymatic activation, a sulfur- or a selenium analog of pyronin, poorly or non-fluorescent but acting as an effective photosensitizer for PDT. Again, molecular lego® approach will be key to access to DF-DDS molecules with optimized properties and performances. Even if our prime ambition is advancing the state of knowledge in the research field of in vivo chemistry, rather than address a specific relevant biomedical need, we plan to make validations of these "smart" molecular diagnostic and/or therapeutic tools be means of in vivo models of cancer and bacterial infection. From a practical point of view, some DF-DDS molecules will be tested on surgical prostheses and implants to monitor their microbiological quality and to eradicate bacteria colonies over their surfaces, through a combined "enzyme-prodrug-therapy" (EPT) and PDT strategy (i.e., bimodal synergistic antimicrobial treatment PDT-prodrug).