Silver-ion-mediated DNAzyme switch for the ultrasensitive and selective colorimetric detection of aqueous Ag+ and cysteine.

Two states, two applications! An Ag(+)-mediated DNAzyme switch has been designed to detect Ag(+) and cysteine with high sensitivity and selectivity. In the closed state, Ag(+) turns on the switch through the formation of cytosine-Ag(+)-cytosine base pairs, whereas adding cysteine turns off the open switch because it competitively binds to Ag(+). This feature endows the DNAzyme switch with two sensing applications.