Janus micromotors for motion-capture-ratiometric fluorescence detection of circulating tumor cells

Abstract

The rapid and sensitive detection of circulating tumor cells (CTCs) remains technical challenges due to extremely low abundance. In the current study, Janus micromotors (JMs) are developed to achieve motion-enhanced CTC capture and capture-induced ratiometric fluorescence signaling. JMs are constructed via catalase grafting on one side of Janus rods (JRs) to catalyze the decomposition of H2O2 as power source. JMs with different aspect ratios show random, spiral, rotational or linear motion trajectories, and JMs with the aspect ratio of 2 (JM-2) display rotational motion with significantly larger mean-square-displacement (MSD) values than other JMs. TLS11a aptamers are conjugated on the other side of JRs for specific capture of tumor cells, and tetraphenylethene (TPE) derivatives and fluorescein isothiocyanate (FITC) are labeled on aptamers via base-pair interactions. The competitive binding of tumor cells with aptamers causes the release of TPE and FITC from JMs, which relieves the aggregation-induced emission (AIE) effect of TPE and aggregation-caused quenching (ACQ) profile of FITC on JMs. Thus, JMs displays apparent ratiometric fluorescence changes from blue (I450) to green (I526) after capture of tumor cells. The fluorescence intensity ratios of I526/I450 could be fitted against cell levels, and the limit of detection is around 25 cells/mL within 1 min. In addition, the HepG2 detection by JM-2 exhibits no interference in the presence of other tumor cells (4T1 and H22), and the recovery rate of HepG2 cells in blood samples was over 95%. Thus, JMs demonstrate the motion-capture-ratiometric fluorescence sensing capabilities and provide a feasible strategy for real-time, rapid and sensitive detection of cells in laboratory, hospital and remote settings.