The sensor has a detection limit of 35 nM and a dynamic range up to 20 μM. Addition of Cu 2+ induced oxidative cleavage of the substrate, and the fluorescence intensity increased by 13-fold. Initially, the fluorescence was quenched. The substrate strand of the DNAzyme was labeled with a fluorophore on the 3‘-end and a quencher on the 5‘-end, and the enzyme strand was labeled with a second quencher on the 5‘-end. We herein report a highly sensitive and selective “turn-on” fluorescent Cu 2+ sensor based on an in vitro selected DNAzyme (also known as catalytic DNA or deoxyribozyme).
Although significant progresses have been made in designing fluorescent sensors for diamagnetic metal ions, few effective Cu 2+ sensors are known because of the paramagnetic nature of the metal ion. Copper is a key metal ion both in environment monitoring and in biology, and exposure to high concentration of copper can cause adverse health effects.
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