Graphene Oxide and Fluorescent-Aptamer-Based Novel Aptasensors for Detection of Metastatic Colorectal Cancer Cells

Early diagnosis of metastatic colorectal cancer (mCRC) is extremely critical to improve treatment and extend survival. W3 is an aptamer that can specifically bind to mCRC cells with high affinity. Graphene oxide (GO) is a two-dimensional graphitic carbon nanomaterial, which has widely used in constructing biosensors. In this study, we have developed a no-wash fluorescent aptasensor for one-step and sensitive detection of mCRC LoVo cells. It is based on fluorescence resonance energy transfer (FRET) between GO and the W3 aptamer labeled with 5-carboxyfluorescein (FAM). GO can quench the green fluorescence of the FAM-labeled W3 (FAM-W3). In the presence of the target cells, FAM-W3 preferentially binds the target cells and detaches from the surface of GO, leading to the fluorescence of FAM recovery. It was demonstrated that the fluorescence recovery increases linearly in a wide range of 0~10⁷ cells/mL (R² = 0.99). The GO-based FAM-labeled W3 aptasensor (denoted as FAM-W3-GO) not only specifically recognizes mCRC cell lines (LoVo and HCT116), but also sensitively differentiates the target cells from mixed cells, even in the presence of only 5% of the target cells. Furthermore, FAM-W3-GO was applied to detect LoVo cells in human whole blood, which showed good reproducibility with an RSD range of 1.49% to 1.80%. Therefore, FAM-W3-GO may have great potential for early diagnosis of mCRC. This strategy of GO-based fluorescent aptasensor provides a simple, one-step, and highly sensitive approach for the detection of mCRC cells.