A high-sensitivity AuNPs/MWCNTs-MB/DNA-GCE quadruplex biosensor for Pb detection in medicinal teas through in-situ monitoring microstructure and conformational switch by SECM

Medicinal teas (MT) were popular in Asian countries for its various effective components. However, Pb pollution poses a serious threat to MT consumption due to the irreversible effect on enzyme activity and neurodegenerative disease. Owing to its toxicity and matrix interference, a rapid screening method for Pb at trace level with high sensitivity and accuracy is urgent for MT consumers. Herein, a simple and ultra-sensitive AuNPs/MWCNTs-MB/DNA-GCE quadruplex biosensor was developed and investigated. Specifically, the monitoring technology of scanning electrochemical microscope was utilized to analyze the assembly and application process for screening key parameters in complex matrix, through in-situ characterization of the microstructure changes on stepwise modified sensors. According to the combined results of electrochemical test and Randles-Sevcik equation, the proposed sensor showed a wide linear range from 5.0 * 10−15 to 5.0 * 10−13 M with LOD of 0.9 fM. In addition, the optimized sensor exhibited an excellent selectivity under the inference of metals and medicinal components. The proposed biosensor was successfully implemented for the ultrasensitive monitoring Pb pollution in MT while its water infusions recoveries maintained within acceptable range (81–118 %, 82–129 %). In all, AuNPs/MWCNTs-MB/DNA-GCE provided a new insight into the design, optimization, application and mechanism analysis of sensor for reliable sensing in controlling MT pollution and consumption safety.