A convenient fluorescent/electrochemical dual-mode biosensor for accurate detection of Pb²⁺ based on DNAzyme cycle

The presence of heavy metals in the ecological environment is a serious threat to human health. Therefore, it is very important to establish a simple and sensitive method for the detection of heavy metals. Currently, most of the methods are single-channel sensing, and these methods are prone to false-positive signals, which reduces the accuracy. In this work, Pb²⁺-DNAzyme was immobilized on magnetic beads (MBs) using a linkage of biotin and streptavidin and successfully applied to the construction of a fluorescent/electrochemical dual-mode (DM) biosensor. The supernatant after magnetic separation formed a double strand on the electrode, which was combined with methylene blue (MB) for electrochemical detection (EC). At the same time, FAM-d was added to the precipitate, and after magnetic separation, the supernatant was subjected to fluorescent detection (FL). Under optimal conditions, the signal response of the constructed dual-mode biosensor showed a good linear relationship with the concentration of Pb²⁺. The DNAzyme-based dual-mode biosensor achieved sensitive and selective detection of Pb²⁺ with good accuracy and reliability, opening a new way for the development of biosensing strategies for the detection of Pb²⁺. More importantly, the sensor has high sensitivity and accuracy for the detection of Pb²⁺ in actual sample analysis.