A novel and label-free electrochemical sensing platform for sensitive detection of uracil DNA glycosylase (UDG) activity has been developed, which is based on UDG-catalyzed removal of uracil bases inducing strand release with methylene blue (MB) as an electrochemical hybridization indicator. The capture DNA containing a thiol group was first immobilized on the gold electrode whose surface was pre-modified with dendritic gold nanoparticles by direct electrodeposition, followed by hybridization with its complementary single-strand DNA containing four uracil bases located in the intermediate positions. Subsequently, MB was abundantly intercalated into the formed DNA duplex structure, resulting in a measurable electrochemical signal. In the presence of UDG, the uracil bases were specifically hydrolyzed, which could induce the unwinding of the DNA duplex, accompanied by the release of the intercalated MB from the electrode surface, leading to the corresponding proportional reduction of the redox signal. In the present work, the proposed sensing platform exhibits a good linear response to the logarithm of UDG concentration in the range from 0.025 to 2 U mL(-1) with a detection limit of 0.012 U mL(-1). In addition, the proposed strategy shows advantages of desirable sensitivity, high selectivity and low cost. It is the first example that employs the electrochemical assay for the detection of UDG activity. Therefore, this novel method will demonstrate promising prospects in a wide range of applications in the future, such as in-depth researches of UDG and clinical diagnosis. (C) 2013 Elsevier Ltd. All rights reserved.