RESUMO
Methylmercury (MeHg+) is a common form of organic mercury that is substantially more toxic than inorganic mercury and is more likely to accumulate in organisms through biological enrichment. Therefore, developing a method to enable the specific and rapid detection of MeHg+ in seafood is important and remains challenging to accomplish. Herein, a rapid, label-free fluorescence detection method for MeHg+ determination was developed based on SYBR Green I. The detection system implemented "add and measure" detection mode can be completed in 10 min. Under optimal assay conditions, the detection platform showed a linear relationship with the concentration of MeHg+ within 1-50 nM (Y = 8.573x + 42.89, R2 = 0.9928), with a detection limit of 0.3218 nM. The results obtained for competitive substances, such as inorganic mercury ions and anions, show a high specificity of the method. In addition, this method successfully detected MeHg+ in seawater and marine products, with an accompanying spike recovery rate of 96.45-105.1%.
Assuntos
Mercúrio , Compostos de Metilmercúrio , Fluorometria , Água do MarRESUMO
Tuberculosis is a highly infectious disease caused by the bacterium Mycobacterium tuberculosis, and the spread of this agent has caused serious health problems worldwide. The rapid and accurate detection of M. tuberculosis is essential for controlling the spread of infection and for preventing the emergence of multidrug-resistant strains. In this study, the powerful trans-cleavage ability of CRISPR-Cas12a for ssDNA was combined with a surface-enhanced Raman spectroscopy (SERS)-based strategy to establish a CRISPR-SERS sensor for the hypersensitive detection of M. tuberculosis DNA. We observed a linear relationship between the concentration of M. tuberculosis DNA and the output signal over the range of 5 to 100 pM. The equation describing the standard curve was y = 24.10x + 1594, with R2 = 0.9914. The limit of detection was as low as 4.42 pM for genomic DNA, and a plasmid containing an M. tuberculosis-specific sequence was detected at 5 copy/µL. A detection accuracy of 100% was achieved in the analysis of DNA isolated from the sputum of hospitalized patients with tuberculosis. The entire detection process is simple to deploy and only takes 50 min and results in the sensitive and specific detection of M. tuberculosis DNA. This study provides a new method for the detection of tuberculosis. The tool is stable and can be utilized on-site, and it thus broadens the diagnostic application of CRISPR-Cas12a-based sensor technology.
RESUMO
Spread of antibiotic resistance genes (ARGs) in aquatic ecosystems poses a significant global challenge to public health. The potential effects of water temperature perturbation induced by specific water environment changes on ARGs transmission are still unclear. The conjugate transfer of plasmid-mediated ARGs under water temperature perturbation was investigated in this study. The conjugate transfer frequency (CTF) was only 7.16 × 10-7 at a constant water temperature of 5 °C, and it reached 2.18 × 10-5 at 30 °C. Interestingly, compared to the constant 5 °C, the water temperature perturbations (cooling and warming models between 5-30 °C) significantly promoted the CTF. Intracellular reactive oxygen species was a dominant factor, which not only directly affected the CTF of ARGs, but also functioned indirectly via influencing the cell membrane permeability and cell adhesion. Compared to the constant 5 °C, water temperature perturbations significantly elevated the gene expression associated with intercellular contact, cell membrane permeability, oxidative stress responses, and energy driven force for CTF. Furthermore, based on the mathematical model predictions, the stabilization times of acquiring plasmid maintenance were shortened to 184 h and 190 h under cooling and warming model, respectively, thus the water temperature perturbations promoted the ARGs transmission in natural conditions compared with the constant low temperature conditions.