Photoelectrochemical detection of circulating tumor cells based on aptamer conjugated Cu2O as signal probe

In this work, a sensitive and reliable photoelectrochemical (PEC) biosensor was proposed based on hexagonal carbon nitride tubes (HCNT) as photoactive material for detection of circulating tumor cells (CTCs). Magnetic Fe3O4 nanospheres (MNs) and Cu2O nanoparticles (Cu2O NPs) were utilized for highly efficient magnetic capture of CTCs and for signal amplification, respectively. First, anti-epithelial cell adhesion molecule (EpCAM) antibody was linked onto MNs for capture and enrichment of CTCs. With the captured MCF-7 coated onto the electrode, the photocurrent intensity of HCNT was decreased due to the steric hindrance derived from MCF-7. Then, when the Cu2O-aptamer probe was bound onto the CTC surface, the photocurrent intensity was further decreased because Cu2O NPs competed with HCNT for absorption of exciting light and the aptamer molecules increased the steric hindrance, which leads to significantly decreased photocurrent response, thus realizing dual signal amplification. Using the breast cancer cell MCF-7 as a model, the proposed PEC biosensor displays good performances with a linear range from 3 to 3000 cell mL(-1) and limit of detection down to 1 cell mL(-1). The HCNT-based PEC biosensor shows good performance for detection of CTCs, which may have potential applications in cancer diagnostics and therapeutics.