A disposable electrochemical biosensor for detection H2S in protoplast

Hydrogen sulfide(H2S) has signal functions under physiological and stress conditions in plants. However, the direct detection of endogenous H2S and its potential emission is still a challenge. Sulfide: quinone oxidoreductase (SQR) from Rhodobacter capsulatus is known to that catalyzes the oxidation of sulfide species to polysulfide. Here a disposable electrochemical biosensor for detection H2S from Arabidopsis thaliana protoplast was developed. In this paper, we constructed pET28a-SQR vector and expressed SQR in Escherichia coli successfully. SQR was immobilized onto the surface of Au particles (AuPs) modified laser-induced graphene (LIG) with Dihexadecylphosphate (DHP) dispersion. The direct electrochemistry of SQR was realized and H2S detection was achieved via oxidation catalyzed by SQR. The biosensor demonstrated a linear response to H2S within the range of 2 nM to 100 nM with a detection limit (LOD) of 0.8 nM (S/N = 3). The biosensor demonstrated high sensitivity, excellent reproducibility and good selectivity. It was applied to measure endogenous H2S and its emission in response to L-cysteine in protoplast. The results were consistent with those obtained using the traditional methylene blue method. The developed biosensor holds significant potential for H2S detection in biologically samples.