Team:NU Kazakhstan

Diagnosis of certain types of cancer at early stages is still challenging issue. Therefore, many biomarkers for early cancer detection have been investigated. Carcinoembryonic antigen (CEA) is one of the examples of the biomarker which appears at early stages of such types of cancer as colorectal, gastric, pancreatic, lung, and breast carcinoma. In this study, it is planned to develop a biosensor which will be used to detect the presence of CEA. The first part of the study is about selection of ssDNA aptamers, which have strong affinity for CEA, during 12 cycles of SELEX (Systematic Evolution of Ligands by Exponential Enrichment) procedure, followed by characterization of them using dot-blot analysis, ELONA (Enzyme Linked Oligonucleotide Assay) and SPR (Surface Plasmon Resonance) methods. In the last part, it is planned to clone the genes that will assist in expression of streptavidin on the surface of membrane of the model organisms. The model organisms for creating the biosensor are Escherichia coli and Saccharomyces cerevisiae. E. coli will express the streptavidin through Lpp-Omp expression system, while S. cerevisiae will express this protein through Aga1 – Aga2 system. Since streptavidin has strong affinity to biotin, biotinylated aptamers will be used to make a sandwich biosensor for CEA detection. Twelve cycles of SELEX for CEA have been already finished. Keywords: aptamer, carcinoembryonic antigen, biosensor, SELEX.