Σύνθεση, χαρακτηρισμός και ιδιότητες κυκλοδεξτρινών με πιθανές βιολογικές εφαρμογές

Abstract

Porphyrins are organic molecules that act as photosensitizers in Photodynamic Therapy (PDT) of tumors and diseased tissues. The current thesis aims to expand the range of applications of the porphyrins by combining PDT properties with chemotherapeutic capability. This combination is achieved by the covalent conjugation of porphyrins with cyclodextrins (CDs) which are water soluble cyclic oligomers of glucose able to encapsulate a variety of molecules and already approved drug carriers. Novel conjugates of CD derivatives with porphyrins were synthesized, that can combine (a) presence of a photoactive porphyrin and (b) presence of a host cavity for drug transport and delivery (c) aqueous solubility. Three new, water-soluble conjugates were thus synthesized and identified by detailed analysis of their NMR and MS spectra. UV/Vis and emission spectra revealed that the conjugates display typical porphyrin-like behavior (strong molar absorption and intense red fluorescence in aqueous solution). Dynamic Light Scattering (DLS) experiments showed that P-CDs tend to form aggregates in aqueous solution, the aggregate size dispersion depending on the conjugate. The P-CDs were tested for cell penetration properties using the cancer cell lines DU145 and MCF7. The cells incubated with the P-CDs were imaged in a Confocal Microscope and showed that the new conjugates are indeed cell penetrating, dispersing in the cytosol and localizing in the membranes but not in the cell nucleus. These P-CDs were also used to carry successfully the insoluble anticancer drug Tamoxifen inside the cells. Phototoxicity experiments of P-CDs with the above cell lines showed that the conjugates are, like the starting porphyrins, phototoxic, while presenting rather low dark toxicity. Moreover, by conjugating δ-aminolevulinic acid (δ-ΑLA), the precursor of protoporphyrin IX, with an amino-CD derivative, an ALA-CD ester was produced (~2.5 molecules ALA per CD) and characterized with NMR, IR and MS spectra. ALA-CD acts as a pro-drug for PDT, as shown with biological experiments on cells and Confocal Microscopy, as it is converted in situ to protoporphyrin IX. Simultaneously, ALA-CD can transport in the cells a water insoluble molecular guest. Finally, the sparingly water soluble antibiotic Rifaximin was coupled with a cell penetrating amino-CD producing a water soluble product that was shown to be efficiently transferred inside the cells.