A Convenient Fluorescent/Electrochemical Dual-Mode Biosensor for Accurate Detection of Pb2+ Based on Dnazyme Cycle

Abstract

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, accurate, and sensitive method for the detection of heavy metals. Currently, most of the methods for detecting lead ions 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 strong 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 with the DNA 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 the optimal conditions, the signal response of the constructed dual-mode biosensor showed a good linear relationship with the concentration of Pb2+. The detection range in the electrochemical channel is 0.05-1000 nM, and the detection limit is 0.004 nM. The detection range in the fluorescent channel is 0.1-500 nM, and the detection limit is 0.01 nM. The DNAzyme-based fluorescent/electrochemical dual-mode biosensor achieved sensitive and selective detection of Pb2+ with good accuracy and reliability, opening up a new way for the development of biosensing strategies for Pb2+ detection. More importantly, the sensor has high sensitivity and accuracy for the detection of Pb2+ in the actual sample analysis. According to the t-test method, the calculated results of t in the quality control samples of rice flour, seaweed, and fans were all less than the t of 4.303 (0.95 n=3) with 95% confidence level. The test results indicated that the dual-mode sensor could be used as a potential platform for Pb2+ detection.

Keywords: lead ion, fluorescent/electrochemical, dual-mode biosensor, DNAzyme