Aptamers based photodiagnostic

Nucleic acid aptamers are molecules that are being used in a large number of biomedical applications. Aptamers have the properties to bind to a wide range of molecules with high specificity and affinity for their target. These properties together with their small size and their ease of synthesis make them very attractive and promising for targeting diseases. Aptamers can serve as cancer diagnostic tools by detecting specific biomarkers, circulating cancer cells or imaging diseased tissue. On the other hand, aptamers can be used as therapeutic agents due to their potential antagonist activity, or as targeting agents. The objective of this work is to use a fluorescent labelled aptamer to detect cancer cells. A nuclease resistant 2'Fluoro-Pyrimidine RNA aptamer has been selected using the cell-SELEX strategy and binds a cell surface biomarker that seems to be overexpressed in several cancers. Identification of its target is ongoing. A fluorescent moiety (Alexa Fluor probes) is added on the aptamer for labelling. We have characterised the affinity of this aptamer for several cancer cell lines using flow cytometry and binding experiments. An efficient binding has been obtained with the breast adenocarcinoma MCF-7 and the pharynx squamous cell carcinoma FaDu cell lines (92% and 82% labelling respectively). Localisation and internalisation studies of the fluorescent aptamer are also realised on the selected cell lines using fluorescent microscope. Finally, our ongoing studies aim the coupling of this aptamer to a chlorin loaded nanoparticle for aptamer-targeted photodynamic treatment.