Aptamer-Based Electrochemical Sensor for Label-Free Recognition and Detection of Cancer Cells

An electrochemical biosensor was developed for the label-free and selective detection of leukemia cells based oil aptamer-modified gold electrode using electrochemical impedance spectroscopy (EIS) technique. The thiol-terminated aptamer (sgc8c) selected for CCRF-CEM acute leukemia cells was self-assembled onto the gold electrode surface as recognition probe, which was characterized by cyclic voltammetry (CV) and EIS using Fe(CN)(6) (3-/4-) as a redox probe. The surface density of aptamers was determined by chronocoulometric method using a redox cation of Ru(NH3)(6)(3+). Upon incubation of the aptamer-modified electrode with CCRF-CEM cells, the electron-transfer resistance (R-et) of Fe(CN)(6)(3-/4-) on the sensor surface increased substantially. Only a small R,, change of the sensor to the control negative cell line RAJI was observed, indicating the excellent selectivity of the sensor. The selective capture of CCRF-CEM cells on the sensor surface was also confirmed by fluorescence microscopy. A linear relationship between R-et and the logarithmic value of CCRF-CEM cells concentration was found in the range of 1 x 10(4) to 1 x 10(7) cells/mL, with a detection limit of 6 x 10(3) cells/mL. This work provided a simple, convenient, low-cost and label-free method for early leukemia diagnosis.