Abstract DNA aptamers are small single stranded DNA molecules that possess antibody-like characteristics; they bind with high affinity to specific antigens as a result of their three dimensional structure and chemical properties. Carcinoembryonic antigen (CEA) is expressed on the surface of 95% of adenocarcinomas. Anti-CEA antibodies have been used diagnostically in vitro to monitor possible metastases and clinically for the treatment of tumors in vivo. The aim of this research was to isolate aptamers against CEA for vivo imaging and treatment of cancer cells. Fluorescence polarization assay was used to measure affinity and specificity of the candidate aptamers sequences towards purified CEA and related proteins. Additionally, we showed that these aptamers bind specifically to CEA on the surface of cancerous cell lines: MCF7 (human breast adenocarcinoma). We also demonstrated that CEA specific DNA aptamer does not bind to the surface of a CEA negative cell line: COLO320DM (human colon adenocarcinoma). To detect the binding of our DNA aptamers to CEA on the surface of cells, fluorescence microscopy was used.

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