Electrochemical device based on nonspecific DNAzyme for the high-accuracy determination of Ca2+ with Pb2+ interference.

Calcium is one of the most abundant and indispensable elements in biology, as it is a vital component of nerves, bones, and muscles and maintains the excitability of normal neuromuscular muscles. However, it may be harmful to the human body and even damage the organs if the calcium content exceeds the standard value by several times. To evaluate the level of calcium ions (Ca2+), an electrochemical biosensor (FET/SWNTs/Cazyme) was developed using a nonspecific DNAzyme with high stability, which combined the unique advantage of field-effect transistors and single-walled carbon nanotubes, while being easy-to-use and having excellent sensitivity. The incubation time and voltage after optimization were 15 min and +0.02 V. The nonspecific DNAzyme-based biosensor was sensitive to Ca2+, but it was also interfered with by Pb2+, which affected the detection accuracy. To solve this shortcoming, an electrochemical device was proposed, in which FET/SWNTs/Cazyme combined with other specific biosensors for Pb2+, and then established some data processing models were established through support vector machine regression (SVMR) and artificial neural network fitting (ANNF). For the optimal SVMR, the electrochemical device can determine the Ca2+ concentration in the range of 7.5-1000 μM with a detection limit of 5.48 μM. Finally, the prepared electrochemical device was employed to detect the Ca2+ in different milk and water samples.