A novel sandwich-like cytosensor based on aptamers-modified magnetic beads and carbon dots/cobalt oxyhydroxide nanosheets for circulating tumor cells detection

Abstract

Abstract As a part of fluid biopsy, circulating tumor cells (CTCs) contain enormous tumor information, so the detection of CTCs is very helpful in clinical diagnosis and therapy. Here, we applied aptamers-modified magnetic beads (Apt@MBs) and carbon dots/cobalt oxyhydroxide nanosheets systems (CDs/CoOOH) to develop a new cytosensor for ultrasensitive and specific detection of CTCs. At first, amino-modified magnetic beads (MBs) were cross-linked with carboxyl-modified MUC1 aptamers (Apt) to gain Apt@MBs. Then, folic acid (FA) functionalized carbon dots (FA@CDs) were assembled onto cobalt oxyhydroxide nanosheets (CoOOH) to obtain FA@CDs/CoOOH with fluorescence quenching. In the detection systems, Apt@MBs identified and accumulated MCF-7 cells, forming Apt@MBs/MCF-7 cells, which then combined with FA@CDs/CoOOH to obtain sandwich-like Apt@MBs/MCF-7 cells/FA@CDs/CoOOH. Finally, ascorbic acid (AA) decomposed CoOOH to release carbon dots (CDs), and the fluorescence of abundant CDs act as efficient signal output. The cytosensor detected MCF-7 cells with a wide dynamic range (10 ∼ 105 cells/mL) and a low limit of detection (5 cells/mL), owing to the specific identification and effective enrichment of Apt@MBs as well as anti-interference capability and signal amplification of FA@CDs/CoOOH. Most importantly, the cytosensor successfully discriminated MCF-7 cells from white blood cells, exhibiting potentiality in ultrasensitive CTCs detection in clinical diagnosis.