Simple and Sensitive Detection of Bacterial Hydrogen Sulfide Production Using a Paper-Based Colorimetric Assay

Hydrogen sulfide (H₂S) is known to participate in bacteria-induced inflammatory response in periodontal diseases. Therefore, it is necessary to quantify H₂S produced by oral bacteria for diagnosis and treatment of oral diseases including halitosis and periodontal disease. In this study, we introduce a paper-based colorimetric assay for detecting bacterial H₂S utilizing silver/Nafion/polyvinylpyrrolidone membrane and a 96-well microplate. This H₂S-sensing paper showed a good sensitivity (8.27 blue channel intensity/μM H₂S, R² = 0.9996), which was higher than that of lead acetate paper (6.05 blue channel intensity/μM H₂S, R² = 0.9959). We analyzed the difference in H₂S concentration released from four kinds of oral bacteria (Eikenella corrodens, Streptococcus sobrinus, Streptococcus mutans, and Lactobacillus casei). Finally, the H₂S level in Eikenella corrodens while varying the concentration of cysteine and treatment time was quantified. This paper-based colorimetric assay can be utilized as a simple and effective tool for in vitro screening of H₂S-producing ability of many bacteria as well as salivary H₂S analysis.