A turn-on signal biosensor for cadmium(II) based on DNAzyme and stem-loop qPCR

Cadmium is a heavy metal that is exceedingly hazardous to humans and can enter the body through tainted food or drink, causing severe harm. It is critical to develop a technology for detecting cadmium in food and water that is sensitive and accurate. One such approach, which employs nucleases, is uncommon. A cadmium(II) turn-on biosensor was successfully created in this work using repetitive cleavage of certain specific nucleases for signal conversion and sophisticated stem-loop qPCR (quantitative polymerase chain reaction) for quick signal amplification and output. The method has strong selectivity and sensitivity for precise quantification, with a detection limit of 6 nmol L−1, i.e. 0.948 g L−1, which is far lower than the 5.0 g L−1 set by the United States Environmental Protection Agency, and it also operates well in retail rice samples.