Nanozyme based colorimetric detection of biogenic gaseous H2S using Ag@Au core/shell nanoplates with peroxidase-like activity

A highly sensitive and facile colorimetric assay is introduced for detecting biogenic gaseous H2S using peroxidase (POD)like catalytic activity of silver core/gold shell nanoplates (Ag@Au NPls). H2S can react with Ag@Au NPls to form Ag2S or Au2S on their surface, which can reduce POD-like activity of Ag@Au NPls and consequently decrease the absorbance at 650 nm due to oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2). For in situ and multiple detection of H2S, we utilized a microplate cover with 24 polydimethylsiloxane inner wells where Ag@Au NPls reacted with H2S gas followed by treatment with TMB/H2O2. As a result, the change in absorbance at 650 nm showed a linear relationship with the H2S concentration in the range 0.33 to 2.96 mu M (0.36 absorbance/mu M H2S in PBS, R-2 = 0.994) with a limit of detection of 263 nM and a relative standard deviation of 4.4%. Finally, this assay could detect H2S released from Eikenella corrodens, used as a model bacterium, in a short time (20 min) or at a low number of bacteria (1 x 10(4) colony forming units/mL). Therefore, this assay is expected to be applied for the study of H2S signaling in bacterial physiology, as well as measure H2S production released from other oral bacteria that cause halitosis and oral diseases, leading to the subsequent diagnosis.