Optical Aptasensors and the Challenge of Food Contamination With Lead

Contamination of heavy metals in food, especially drinking water and groundwater, has become a serious problem for human health. These metals are mainly the constituent elements of nature widely distributed in the earth's crust, but significant amounts of them are also found in everyday goods. These elements are usually found in combinations with oxygen, chlorine, sulfur, and other anions that generally contain inorganic and organic compounds. Lead is one of the heavy metals with high toxicity that poses serious risks to the environment and humans. Recent advances in nucleic acid research have led to the identification of oligonucleotide sequences that bind with high affinity specifically to target molecules, including proteins. Such single-stranded sequences are called "aptamer" nucleic acids. Aptamers are synthetic single-stranded DNA or RNA sequences of 30 to 100 nucleotides, and their secondary and tertiary structures are folded to make them highly specific for binding to targets. The binding of aptamers to different targets, from a single cell to large chemical and biological molecules, is done with high affinity. This aptamer feature is used to detect lead. In this review article, the designed optical aptasensors for the detection of lead will be reviewed.