This communication reports on a novel biosensor to study the hybridization specificity based on erichrome cyanine R (ECR) monolayer film modified glassy carbon electrode (GCE). Differential pulse voltammetry (DPV) was used to monitor the hybridization reaction on the ECR-modified electrode. The decrease of the peak current of methylene blue (MB). an electroactive indicator, was observed upon hybridization of the probe with the target DNA. Electrochemical investigations indicated that ECR modified biosensor displayed a wide linear range of 5.0-200 pM with a detection limit of 0.982 pM. This new biosensor exhibited good selectivity for one-base mismatch and complementary sequence after hybridization in detecting promyelocytic leukemia/retinoic acid receptor alpha (PML/RAR alpha) fusion gene in acute promyelocytic leukemia (APL). (C) 2012 Published by Elsevier Ltd.