A label-free DNAzyme-Mediated biosensor for fluorescent detection of Lead (II) ion.

Lead ion (Pb²⁺) is a common environmental contaminant, extremely toxic, persistent, and easily adsorbed, concentrated, and enriched by agricultural products. Ingestion of this ion can result in health problems for humans, including neurological disorders, heart disease, brain damage, and mental deficiency. In this research, a sensitive fluorescent biosensing method for detecting Pb²⁺ was developed using DNAzyme as the target recognition element and SYBR Green (SG) fluorescent dye as the signal indicator. Through catalytic action on a strand of DNA with ribo-adenine (rA), the DNAzyme was able to cut it in the presence of Pb²⁺. This led to the removal of intercalation sites for SG molecules, resulting in a decrease in fluorescence response. The newly developed biosensor was capable of identifying Pb²⁺ ions within a range of 0.1-600 µM with a detection limit of 0.018 µM. This label-free fluorescent biosensor proved to be both convenient and efficient in accurately measuring the levels of Pb²⁺ ions in blood serum and milk samples, yielding recovery rates between 96.81 % and 100.00 %. The DNAzyme-based biosensor offers an economical and easy-to-use sensing assay for Pb²⁺ ion.