DNA APTAMER-IMMOBILIZED BLOCK COPOLYMER SURFACE FOR CIRCULATING TUMOR CELL CAPTURE IN LIQUID BIOPSY

Objective: Detecting circulating liquid biopsy components is essential for early cancer diagnosis and monitoring disease progression. Current biosensors detect circulating tumor cells in later stages, prompting a search for more effective techniques. In this study, we developed a novel surface modified with PGMA-b-PPDSMA block copolymer and functionalized with AS1411 aptamer for sensitive detection of circulating tumor cells. Materials and Methods: The PGMA-b-PPDSMA block copolymer was synthesized and characterized by NMR spectroscopy and GPC. Glass slides were modified with APTES, allowing covalent attachment of the block copolymer via PGMA epoxy groups. The pyridyl disulfide groups of PPDSMA enabled site-specific immobilization of thiol-modified anti-nucleolin DNA aptamer (AS1411). Immobilization efficiency and aptamer specificity were validated using fluorescence microscopy with MCF-7 breast cancer cells. Results: NMR and GPC results showed that PGMA-b-PPDSMA block copolymer with a molecular weight of 6 kDa, consisting of 4.8 kDa PGMA and 1.2 kDa PPDSMA block, was synthesized and purified. APTES modification on glass surfaces was confirmed by absorbance signals in the range of 1500-1650 cm-¹ belonging to the NH2 group in the FTIR spectrum. The binding efficiency of thiol-modified AS1411 aptamer to the PPDS group of PGMA-b-PPDSMA block copolymer was followed by absorbance change between 250-400 nm of pyridin-2-thione by-product formed during the reaction with time. Conclusion: After DAPI staining and washing, Fluorescence microscopy images showed selective binding of MCF-7 cells to the AS1411-modified surfaces. These results suggest the surface provides a promising platform for sensitive capture of circulating cancer cells in early-stage liquid biopsy applications.