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  • Solasodine br Cell capture and electrochemical

    2019-10-21


    3.6. Cell capture and electrochemical detection
    Different concentrations of the MCF-7 cell were detected under the optimal detection conditions. Fig. 4A showed that the DPV peak cur-rents increased significantly with the increase of cell concentrations. The DPV response (Current) was linearly related to the logarithm of cell concentration, with a linear range of 20 to 1 × 107 cells/mL. The linear regression equation is Current (μA) = −0.7376 + 4.1865 lgCcell (cells/mL) (R2 = 0.9989) (Fig. 4B). The detection limit of the proposed cytosensor was calculated to be 6 cells/mL for MCF-7 Solasodine at 3σ. Compared with the electrochemical methods in other literature, such as CV, electrochemiluminescence, biofuel cells etc. (Table S2), the cyto-sensor exhibited wider range and lower detection limit. The perfor-mances of the aptasensor are attributed to the following points. Firstly,
    TDN provides an orderly sensing interface increasing the stretchability of the aptamer. Dual aptamers recognize MCF-7 cells well, thus en-hancing the efficiency of cells capture. Secondly, the nanomaterial PCN-224-Pt further amplifies the signal with satisfactory catalase-like ac-tivity, high specific surface area and good biocompatibility. The last but not the least, the formation of natural HRP and GQH HRP-mimicking DNAzyme enlarges the catalytic activity of the nanoprobes again. All of the above factors increase the sensitivity and selectivity of the apta-sensor, hence exhibiting wider linear dynamic range and lower detec-tion limit.
    Next, the repeatability of the proposed electrochemical sensor was evaluated by three independent experiments with each sample in tri-plicate in a short time interval. The relative standard deviation of in-dependent testing of the sensor for 0, 20 and 1 × 104 cells/mL of MCF-7 cells was 6.08%, 3.61% and 5.94%, respectively, proving that the cy-tosensor showed acceptable repeatability.
    Moreover, the selectivity of the cytosensor was verified using three cell lines (HepG2 hepatocellular carcinoma cell, HCT116 colon carci-noma cell and B16 melanoma cell) and the blank without cells as control. As shown in Fig. 4C, an obvious electrochemical signal change was just observed with MCF-7 cells. The high selectivity showed that the cytosensor had a great potential for tumor cell detection.
    To further evidence the real applicability of the biosensor, 1 × 104 cells/mL of MCF-7 cells were spiked into human blood, which have been described in the Supplemental Material, and detected using the same method. Fig. 4C showed that it made little difference of DPV signals whether in PBS buffer or in blood sample. Thus, the feasibility of the method was demonstrated for MCF-7 cells in sample.
    3.7. Cell release and viability analysis
    Regeneration of the GE was another preponderances for the pro-posed cytosensor [53,54]. After cell detection, an electrochemical re-ductive desorption tactic was used to break the chemical bonding of AueS and detach all components on the electrode surface followed by
    Fig. 5. (A) Schematic illustration of the cyto-sensor for cell release. (B) The microscope image of trypan blue staining of collected cells (The red arrow points to the dead cell, the white arrow points to the living cell). (C) EIS of
    (a) bare electrode and (b) the regenerated electrode in 0.5 M KCl solution containing 5 mM [Fe(CN)6]4−/3−. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).
    cell viability analysis and EIS performing (Fig. 5A). Analysis of trypan blue staining, 93% of the cells maintained their original viability (Fig. 5B). As shown in Fig. S7, the cells were evenly dispersed in the medium; after 6 h, the cells adhered and began to differentiate; after 12 h, a large number of cells splited and proliferated; after 24 h, the cells were divided into 1–2 generations. According to the reported re-sults, the method can collect the cells released by GE without losing biological activity. EIS curves (Fig. 5C) showed that the bare electrode (curve a) and regenerated electrode (curve b) were the same impedance spectra and peak current, with concluded that desorption of all com-ponents from the electrode surface was successful and the regenerated electrode was reusable. These results of EIS curves and cell viability analysis have proved that the cytosensor can be regenerated without significant loss of sensitivity.