To assess the sensitivity and the quantitative range of the proposed cytosensor, the analytical performance of the prepared cytosensor was explored by quantifying the K562 cancer GPLG0634 with different concentrations including a blank one as a reference under the optimized condition. The ECL intensity corresponding to the blank sample probably was ascribed to the physical adsorption. Fig. 5 displayed the ECL intensity responses of the BSA/aptamer/Pt-CNTs/GCE corresponding to K562 cells at different concentrations. Calibration plots displayed a good linear relationship between the ECL intensity and the logarithm of the K562 cancer cells concentration in the range from 500 to 5.0 × 106, and the equation of linear regression was ΔECL = 2222.19–5389.74 lgccell (cells mL−1), with a correlation coefficient of 0.9916. The error bar represents the SD of six independent experiments. The limit of detection (LOD) value for cancer cells was determined at 500 cells mL−1, which was partially lower than most of the other cytosensor. Compared with previous studies ( Table 1), a wider linear range and lower detection limit were both achieved for cancer cells.