Detection by protection

Bioassays DNA aptamers are oligonucleotides that bind with high specificity to targets ranging from metal ions to whole proteins. Binding of the desired target can introduce structural changes in the DNA and thus signal the concentration of the target. Canoura et al. designed a DNA aptamer–based bioassay that can determine the concentration of multiple small molecules at once. If no target is present, enzymes degrade the DNA aptamer, which is unprotected on its own. Binding of the aptamer target locks the DNA in a stable conformation, protecting it from degradation and enabling readout through a second, labeled DNA. The assay was used to detect ATP and cocaine in a complex sample simultaneously. J. Am. Chem. Soc. 140 , 9961 (2018).