Colorimetric detection of hydrogen sulfide based on terbium-G-quadruplex-hemin DNAzyme

It is of great importance to simply and sensitively detect hydrogen sulfide (H2S) because of its role in various physiological processes as well as its inherent toxicity. In this work, a colorimetric method for H2S detection was developed by employing terbium-G-quadruplex-hemin (Tb/G4-hemin) DNAzyme as a peroxidase mimic, which can catalyze H2O2-mediated oxidation of 2,2′-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) to produce radical cation (ABTS+). Compared with the G4-hemin DNAzyme promoted by K+ and Na+, Tb/G4-hemin DNAzyme exhibits a higher catalytic activity. In the presence of Ag+, the peroxidase-like activity of Tb/G4-hemin DNAzyme can be inhibited significantly owing to the disruption of G-quadruplex structure. However, the addition of H2S can effectively suppress such negative behavior by competitive binding with Ag+, leading to the recovery of the peroxidase-like activity of Tb/G4-hemin DNAzyme, which can be reflected by an increase in absorbance signal of ABTS+. The absorbance of ABTS+ was enhanced linearly with increasing H2S concentration from 20 nM to 2 μM. The detection limit for H2S is 13 nM, which is much lower than most of previous methods. Moreover, the proposed method possesses the features of simple preparation, easy reproducibility and good biocompatibility. Given the fine performances and striking properties, we believe that the Tb/G4-hemin DNAzyme would have a great promise for analytical applications.