A simple and sensitive DNA impedance sensor was prepared for the detection of chronic lymphocytic leukemia. The DNA electrochemical biosensor is worked based on the electrochemical impedance spectroscopic (EIS) detection of the sequence-specific DNA related to chronic lymphocytic leukemia. The ssDNA probe was immobilized on the surface of the gold nanoparticles. Compared to the bare gold electrode, the gold nanoparticles-modified electrode could improve the density of the probe DNA attachment and hence the sensitivity of the DNA sensor greatly. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy were performed in a solution containing 1.0 mmol L-1 K-3[Fe(CN)(6)]/K-4[Fe(CN)(6)] and 50 mmol L-1 phosphate buffer saline pH 6.87 plus 50 mmol L-1 KCl. In the CV studied, the potential was cycled from 0.0 to +0.65 V with a scan rate of 50 mV s(-1). Using EIS, the difference of the electron transfer resistance (Delta R-et) was linear with the logarithm of the complementary oligonucleotides sequence concentrations in the range of 7.0 x 10(-12)-2.0 x 10(-7) mol L-1. with a detection limit of 1.0 x 10(-12) mol L-1. In addition, the DNA sensor showed a good reproducibility and stability during repeated regeneration and hybridization cycles. (C) 2011 Elsevier Ltd. All rights reserved.