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MODS is a novel liquid culture based technique that has been shown to be effective and rapid for early diagnosis of tuberculosis (TB). We evaluated the MODS assay for diagnosis of TB in children in Viet Nam. 217 consecutive samples including sputum (n = 132), gastric fluid (n = 50), CSF (n = 32) and pleural fluid (n = 3) collected from 96 children with suspected TB, were tested by smear, MODS and MGIT. When test results were aggregated by patient, the sensitivity and specificity of smear, MGIT and MODS against “clinical diagnosis” (confirmed and probable groups) as the gold standard were 28.2% and 100%, 42.3% and 100%, 39.7% and 94.4%, respectively. The sensitivity of MGIT and MODS was not significantly different in this analysis (P = 0.5), but MGIT was more sensitive than MODS when analysed on the sample level using a marginal model (P = 0.03). The median time to detection of MODS and MGIT were 8 days and 13 days, respectively, and the time to detection was significantly shorter for MODS in samples where both tests were positive (P<0.001). An analysis of time-dependent sensitivity showed that the detection rates were significantly higher for MODS than for MGIT by day 7 or day 14 (P<0.001 and P = 0.04), respectively. MODS is a rapid and sensitive alternative method for the isolation of M.tuberculosis from children.

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In this study, a simple one-step synthesis procedure for the fabrication of a gold nanoparticle (Au NP)@sulfur-doped graphene quantum dot (Au@S-GQD) with tunable size was developed for the sensitive and selective detection of 4-nitrophenol in water and wastewater with a complex matrix. The particle size of two to six layered S-GQD is in the range of 1–7 nm with a mean diameter of 4.0 ± 0.5 nm. The S-GQD serves as a reducing agent for both Au ions and 4-nitrophenol reduction to generate Au@S-GQD nanocomposites as well as to produce the absorption signal of 4-aminophenol at 307 nm. The particle size of Au@S-GQD is tunable by simply adjusting the Au precursor concentration, and the mean diameter increases from 5 to 25 nm when the Au precursor concentration increases from 50 to 200 μM. Moreover, the Au@S-GQD nanocomposite exhibits good UV–visible absorption properties, and the change of wavelength ratio between 307 and the SPR peak of Au at 530 nm (A 307/A 530) is used to detect nanomolar levels of 4-nitrophenol after the interaction of 4-nitrophenol with S-GQD by π–π stacking interaction. A wide dynamic range of 4 orders of magnitude with a limit of detection (LOD) of 3.5 nM in deionized water is achieved. The UV–visible response of Au@S-GQD also shows good selectivity to 4-nitrophenol detection over other aromatic and nitroarene compounds. In addition, the Au@S-GQD sensing platform is successfully applied to the detection of 0.05–50 μM 4-nitrophenol in highly contaminated food wastewater with an LOD of 8.4 nM. The recovery of 0.1–20 μM 4-nitrophenol in three different aqueous solutions with a complex matrix is in the range of 97 ± 2 to 110 ± 3%. Results obtained clearly indicate the superiority of using Au@S-GQD as the optical sensing probe for the detection of nano- to micromolar levels of 4-nitrophneols in aqueous solutions, which can be developed as a high performance and robust sensing platform for rapid detection of nitroaromatics in a wide variety of water and wastewater.