A DNAzyme Catalytic Beacon Sensor for Paramagnetic Cu²⁺ Ions in Aqueous Solution with High Sensitivity and Selectivity

Abstract

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. Although significant progresses have been made in designing fluorescent sensors for diamagnetic metal ions, few effective Cu2+ sensors are known because of the paramagnetic nature of the metal ion. We herein report a highly sensitive and selective “turn-on” fluorescent Cu2+ sensor based on an in vitro selected DNAzyme (also known as catalytic DNA or deoxyribozyme). 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. Initially, the fluorescence was quenched. Addition of Cu2+ induced oxidative cleavage of the substrate, and the fluorescence intensity increased by 13-fold. The sensor has a detection limit of 35 nM and a dynamic range up to 20 μM. The sensor selectivity is more than 2000-fold for Cu2+ over Fe2+ and UO2 2+ and more than 10 000-fold over any other metal ions. The DNAzyme catalytic beacon method demonstrated here can be applied to designing turn-on fluorescent sensors for other paramagnetic metal ions.

The Composites of Cationic Polyelectrolyte and Glutathione‐capped Quantum Dots for Selective Fluorescence Detection of Cu2+

“…Besides, fluorescence resonance energy transfer from the fluorophore to the quencher has been applied to sensing of Cu 2+ with high sensitivity and selectivity. [17][18][19] Recently, colloidal semiconductor nanocrystals (quan- 22 The same phenomenon has been discovered in the case of 2-mercaptioethane sulfonic acid-modified CdSe QDs. 23 The addition of F -to a solution of QDs can further improve the selectivity of QDs owing to the formation of the colorless complex FeF 6 3-.…”

An Ultrasensitive Light-up Cu2+ Biosensor Using a New DNAzyme Cleaving a Phosphorothioate-Modified Substrate

“…This is over 20 times more sensitive compared to the previously reported DNA-cleaving DNAzyme Cu 2+ sensor. 17 We compared our sensor with many representative Cu 2+ optical sensors reported in the literature (Table S4), and our sensor has the best detection limit. The relative standard deviation is typically below 10%.…”

Recent developments on nanomaterials-based optical sensors for Hg2+ detection

“…As mentioned above, most of the developed QDs-based sensors for Hg 2+ worked in a "turn off " mode. Compared with "turn-off " Hg 2+ sensors, the "turn-on" sensing mode can offer advantage to reduce the likelihood of a false positive signal [81]. So, a "turn-on" sensor is preferred.…”