An ultrasensitive and label-free electrochemical DNA biosensor for detection of DNase I activity

An ultrasensitive and label-free DNA biosensor for the detection of deoxyribonuclease I (DNase I) activity was comprehensively studied based on electrochemical methods by cyclic voltammetry (CV) and square wave voltammetry (SWV). For the preparation of the DNA biosensor, the arbitrary 76-bp single-stranded DNA reporter probes and electrochemical indicator methylene blue (MB) were modified on the Au electrode. Initially, the sensor generated a strong signal because of the redox indicator MB. In the presence of DNase I, the enzyme cleaved single-stranded DNA at their phosphate backbone, and then the MB was removed from the electrode, resulting in the reduction of current signals. The differential current signals were directly proportional to the logarithm of the concentration of DNase I in the range of 10(-5) units per mL to 0.5 units per mL with a detection limit of 10(-6) units per mL (S/N = 3). The sensor exhibits a wide linear range and superior sensitivity and can be applied in more bioanalytical systems.