Nitrogen-doped carbon dots for dual-wavelength excitation fluorimetric assay for ratiometric determination of phosalone.

N-doped carbon dots (N-CDs) were fabricated in a simple procedure by hydrothermal treatment of cellobiose and urea. When excited at 235 nm or 327 nm, only one emission peak at around 420 nm has been observed. With the addition of phosalone, the excitation band at 235 nm was efficiently quenched within 1 min, while the excitation band at 327 nm showed little change. Accordingly, the fluorescence of the N-CDs-phosalone mixture showed quenching under 254-nm UV light, while nearly no fluorescence quenching could be observed under 365-nm UV light. This phenomenon provides a novel anti-false-positive mechanism for phosalone identification. Therefore, the label-free ratiometric sensor for rapid, naked-eye, and anti-false-positive detection of phosalone was proposed for the first time based on the intrinsic dual-excitation N-CDs. Under the optimum experimental conditions, the linear ranges of the excitation-based ratiometric assay were 0.08~4.0 µg/mL and 4.0~14.0 µg/mL; the limit of detection was 28.5 ng/mL. The as-constructed sensor was applied to detect phosalone residue in actual samples, and results were compared with the standard gas chromatographic (GC) method. The recoveries of the established sensor were between 90.0% and 110.0% with RSD lower than 6.6%, while that for the GC method was between 92.5% and 113.0% with RSD lower than 5.8%. Results reveal that the accuracy (recovery) and precision (RSD) of the as-constructed method are comparable to the standard GC method. In this paper, dual-excitation N-doped carbon dots (N-CDs) were synthesized by a simply one-step hydrothermal method for the first time. The novel dual-excitation ratiometric sensor based on the sole intrinsic N-CDs was constructed for phosalone sensing.

Longitudinal characteristics of lymphocyte responses and cytokine profiles in the peripheral blood of SARS-CoV-2 infected patients.

BACKGROUND: The dynamic changes of lymphocyte subsets and cytokines profiles of patients with novel coronavirus disease (COVID-19) and their correlation with the disease severity remain unclear. METHODS: Peripheral blood samples were longitudinally collected from 40 confirmed COVID-19 patients and examined for lymphocyte subsets by flow cytometry and cytokine profiles by specific immunoassays. FINDINGS: Of the 40 COVID-19 patients enrolled, 13 severe cases showed significant and sustained decreases in lymphocyte counts [0·6 (0·6-0·8)] but increases in neutrophil counts [4·7 (3·6-5·8)] than 27 mild cases [1.1 (0·8-1·4); 2·0 (1·5-2·9)]. Further analysis demonstrated significant decreases in the counts of T cells, especially CD8+ T cells, as well as increases in IL-6, IL-10, IL-2 and IFN-γ levels in the peripheral blood in the severe cases compared to those in the mild cases. T cell counts and cytokine levels in severe COVID-19 patients who survived the disease gradually recovered at later time points to levels that were comparable to those of the mild cases. Moreover, the neutrophil-to-lymphocyte ratio (NLR) (AUC=0·93) and neutrophil-to-CD8+ T cell ratio (N8R) (AUC =0·94) were identified as powerful prognostic factors affecting the prognosis for severe COVID-19. INTERPRETATION: The degree of lymphopenia and a proinflammatory cytokine storm is higher in severe COVID-19 patients than in mild cases, and is associated with the disease severity. N8R and NLR may serve as a useful prognostic factor for early identification of severe COVID-19 cases. FUNDING: The National Natural Science Foundation of China, the National Science and Technology Major Project, the Health Commission of Hubei Province, Huazhong University of Science and Technology, and the Medical Faculty of the University of Duisburg-Essen and Stiftung Universitaetsmedizin, Hospital Essen, Germany.

Real-time polymerase chain reaction for the diagnosis of necrotizing herpes stromal keratitis.

AIM: To design, optimize and validate a rapid, internally controlled real-time polymerase chain reaction (RT-PCR) test for herpes simplex virus (HSV) in the diagnosis of necrotizing herpes stromal keratitis. METHODS: Tears alone or together with corneal epithelium scrapings from 30 patients (30 eyes) suspected of necrotizing herpes stromal keratitis were tested for HSV DNA by RT-PCR. The samples were collected during the first visit and then on the subsequent 7, 14, 28, 42, and 56d. The symptoms of the patients were scored before treatment to determine the correlation between HSV concentration in the corneal epithelium scrapings and clinical scores. RESULTS: The positive rate (46.4%) in the corneal epithelium group before the therapy was significantly higher than that (13.3%) in the tears group (P=0.006). There were 13 positive HSV patients before the therapy, the concentration of HSV DNA in corneal epithelium scrapings group was significantly higher than that in the tears group (paired t-test, P=0.0397). Multilevel mixed-effects model analysis showed that the difference between the corneal epithelium scrapings group and the tears group was statistically significant (P=0.0049). The Spearman rank correlation analysis indicated a positive correlation between the HSV concentration in the corneal epithelium scrapings and clinical scores before the treatment (r=0.844, P<0.0001). CONCLUSION: RT-PCR appears to be a powerful molecular tool for the diagnosis of necrotizing herpes stromal keratitis.