A highly sensitive and adjustable colorimetric assay of hydrogen sulfide by signal amplification based on G-quadruplex-Cu2+ peroxidase mimetics

Abstract

This work reports the first example of a colorimetric H₂S sensor constructed through G-quadruplex-Cu²⁺ (G4-Cu²⁺) peroxidase mimetics employing Cu²⁺ ions and G-rich DNA with signal amplification. In the hydrogen peroxide (H₂O₂)-mediated oxidation of 3,3^′,5,5^′-tetramethylbenzidine (TMB), the catalytic capacity of Cu²⁺ can be greatly improved in the presence of 22AG DNA, where 22AG DNA acts as a signal amplifier. However, G4-Cu²⁺ peroxidase mimetics lose their catalytic abilities after reacting with H₂S. This is employed to develop a colorimetric assay of H₂S without complex synthesis and instrumentation, with a linear range from 0.01 μM to 150 μM and a detection limit of 7.5 nM. The sensitivity of the sensor can also be adjusted by changing the concentration of Cu²⁺. Moreover, the developed sensor is successfully applied for the quantitative determination of H₂S in human serum samples.