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 µM (0.36 absorbance/µM H2S in PBS, R2 = 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 × 104 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.

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.

Prediction model for mortality in cancer patients with pneumonia: comparison with CURB-65 and PSI.

INTRODUCTION AND OBJECTIVES: We aimed to develop a new prediction model of mortality in cancer patients with pneumonia and to compare its performance with CURB-65 and the Pneumonia Severity Index (PSI). METHODS: Active cancer patients who were diagnosed with pneumonia at the Emergency Department (ED) from 7/1/2014 to 12/31/2014 were consecutively included. Clinical data were collected through a medical chart review. The primary outcome was the 28-day mortality, and clinical factors were analyzed using logistic regression analysis. RESULTS: Among a total of 218 analyzed patients with a median age of 64.0 years (IQR, 56.8-71.0) and a male proportion of 72%, 42 (19.3%) died within 28 days of ED admission. By multivariate logistic regression analysis, an ECOG performance status (PS) 3 (OR: 8.54, 95% CI: 3.42-21.33) or 4 (OR: 13.17, 95% CI: 3.19-54.32), SpO2 <90% (OR: 3.06, 95% CI: 1.17-8.00), and elevated lactic acid levels (OR: 1.42, 95% CI: 1.12-1.81) were significantly associated with mortality. With these three variables, a new prediction model with total scores ranged from 0 to 6 was generated. The area under the curve of the new prediction model was 0.840, compared with 0.673 and 0.586 for CURB-65 and PSI, respectively. CONCLUSION: In cancer patients with pneumonia, a poor ECOG PS, SpO2 <90%, and lactic acid elevation are independent predictors of mortality. The new prediction model, comprising three predictors, performs better in predicting mortality in cancer patients than CURB-65 or PSI.