Insight into chromium adsorption from contaminated soil using Mg/Al LDH-zeolite.

The study investigated the effectiveness of Mg/Al LDH-zeolite (MALZ) in immobilizing exchangeable Cr (e-Cr) within the soil. The research systematically evaluated various variables affecting the immobilization of e-Cr in contaminated soil (CS), including soil pH levels (ranging from 5.0 to 9.0), different weight ratios of MALZ (1 %, 3 %, and 5 %), durations of differing incubation periods (15, 30 and 45 days), and different SM content levels (30 %, 50 %, and 70 %). The initial concentration of Cr in the CS was maintained at 50 mg/kg. The investigation findings revealed that the optimal conditions for immobilizing the e-Cr were a soil pH of 5.0, an MALZ weight ratio of 3 %, an incubation period of 30 days, and an SM level of 70 %. Under these ideal conditions, the percentage of e-Cr within the CS decreased significantly, from 87.49 % (45.64 mg/kg) in the control treatment (CT) to just 19.82 % (10.08 mg/kg) when incubated with MALZ. The primary mechanisms responsible for immobilizing the e-Cr onto MALZ included pore filling, reduction processes, co-precipitation, organic interactions and electrostatic attractions leading to the formation of carbonate-bound complexes such as Cr(VI)-carbonate, Cr(III)-carbonate, and organic complexes. Surface functional groups on MALZ, housing iron and aluminium oxyhydroxides and silicon and oxygen elements, expedited these procedures. This study provided a valuable understanding of the mitigation of soils contaminated with chromium and contributed to understanding the relations between MALZ and the e-Cr in the soil. The discoveries carry substantial consequences for the advancement of efficient remediation technologies.

Enhanced simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi) ions from aqueous solution using cassava root husk-derived biochar loaded with ZnO nanoparticles.

This study presents the modification of cassava root husk-derived biochar (CRHB) with ZnO nanoparticles (ZnO-NPs) for the simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi). By conducting batch-mode experiments, it was concluded that 3% w/w was the best impregnation ratio for the modification of CRHB using ZnO-NPs, and was denoted as CRHB-ZnO3 in this study. The optimal conditions for heavy metal adsorption were obtained at a pH of 6-7, contact time of 60 min, and initial metal concentration of 80 mg L-1. The heavy metal adsorption capacities onto CRHB-ZnO3 showed the following tendency: Pb(ii) > Cd(ii) > As(iii) > Cr(vi). The total optimal adsorption capacity achieved in the adsorption of the 4 abovementioned metals reached 115.11 and 154.21 mg g-1 for CRHB and CRHB-ZnO3, respectively. For each Pb(ii), Cd(ii), As(iii), and Cr(vi) metal, the maximum adsorption capacities of CRHB-ZnO3 were 44.27, 42.05, 39.52, and 28.37 mg g-1, respectively, and those of CRHB were 34.47, 32.33, 26.42 and 21.89 mg g-1, respectively. In terms of kinetics, both the pseudo-first-order and the pseudo-second-order fit well with metal adsorption onto biochars with a high correlation coefficient of R 2, while the best isothermal description followed the Langmuir model. As a result, the adsorption process of heavy metals onto biochars was chemisorption on homogeneous monolayers, which was mainly controlled by cation exchange and surface precipitation mechanisms due to enriched oxygen-containing surface groups with ZnO-NP modification of biochar. The FTIR and EDS analysis data confirmed the important role of oxygen-containing surface groups, which significantly contributed to removal of heavy metals with extremely high adsorption capacities, comparable with other studies. In conclusion, due to very high adsorption capacities for metal cations, the cassava root husk-derived biochar modified with ZnO-NPs can be applied as the alternative, inexpensive, non-toxic and highly effective adsorbent in the removal of various toxic cations.

Enhancement of exchangeable Cd and Pb immobilization in contaminated soil using Mg/Al LDH-zeolite as an effective adsorbent.

In the present study, experiments using zeolite and Mg/Al LDH-zeolite for immobilization of Cd and Pb ions in artificial soil were conducted. The conditions which affect Cd and Pb ion immobilization in soil were evaluated, namely soil pH (5-7), the mass ratio of adsorbents (1%, 3% and 5%), incubation time (15 days, 30 days and 45 days) and soil moisture (30%, 50% and 70%). The results indicated that the optimal soil pH, mass ratio of adsorbents, incubation time and soil moisture for immobilization of Cd and Pb ions by the adsorbent were, respectively, 7.0, 3%, 30 days and 70%. The exchangeable Cd ion content in the contaminated soil dropped from 22.17 mg kg-1 (87.65%) to 11.03 mg kg-1 (43.48%) and 6.47 mg kg-1 (26.36%) on incubation with zeolite and Mg/Al LDH-zeolite, respectively, while the exchangeable Pb content fell from 23.28 mg kg-1 (90.02%) to 14.12 mg kg-1 (54.04%) and 9.47 mg kg-1 (35.24%) using zeolite and Mg/Al LDH-zeolite as absorbents in contaminated soil, respectively. Fe-Mn oxide occluded (F2), carbonate bound (F3) and organically complexed (F4) were the main forms for immobilization of the exchangeable Cd and Pb when the zeolite and Mg/Al LDH-zeolite absorbents were separately cultivated into soil. Precipitation, co-precipitation and electrostatic attraction were the main mechanisms of exchangeable Cd and Pb immobilization onto the Mg/Al LDH-zeolite to form carbonate metals (CdCO3 and PbCO3). This was due to the surface functional groups of the adsorbent and the presence of Fe and Al oxyhydroxides, Mn oxides, and Si and O elements in the Mg/Al LDH-zeolite's constituents. The efficiency of Cd and Pb immobilization by the Mg/Al LDH-zeolite was higher than that by zeolite from 1.5 to 1.6 times. The Mg/Al LDH-zeolite showed an enhanced ability of exchangeable Cd and Pb immobilization in contaminated soil.

Kinetics of CD4+ T Helper and CD8+ Effector T Cell Responses in Acute Dengue Patients.

Background: The protective or pathogenic role of T lymphocytes during the acute phase of dengue virus (DENV) infection has not been fully understood despite its importance in immunity and vaccine development. Objectives: This study aimed to clarify the kinetics of T lymphocyte subsets during the clinical course of acute dengue patients. Study design: In this hospital-based cohort study, 59 eligible Vietnamese dengue patients were recruited and admitted. They were investigated and monitored for T cell subsets and a panel of clinical and laboratory parameters every day until discharged and at post-discharge from the hospital. Results: We described for the first time the kinetics of T cell response during the clinical course of DENV infection. Severe cases showed significantly lower levels of effector CD8+ T cells compared to mild cases at day -1 (p = 0.017) and day 0 (p = 0.033) of defervescence. After defervescence, these cell counts in severe cases increased rapidly to equalize with the levels of mild cases. Our results also showed a decline in total CD4+ T, Th1, Th1/17 cells during febrile phase of dengue patients compared to normal controls or convalescent phase. On the other hand, Th2 cells increased during DENV infection until convalescent phase. Cytokines such as interferon-γ, IL-12p70, IL-5, IL-23, IL-17A showed tendency to decrease on day 0 and 1 compared with convalescence and only IL-5 showed significance indicating the production during acute phase was not systemic. Conclusion: With a rigorous study design, we uncovered the kinetics of T cells in natural DENV infection. Decreased number of effector CD8+ T cells in the early phase of infection and subsequent increment after defervescence day probably associated with the T cell migration in DENV infection.

Plasma cell-free DNA: a potential biomarker for early prediction of severe dengue.

BACKGROUND: Considerable progress has been made in dengue management, however the lack of appropriate predictors of severity has led to huge number of unwanted admissions mostly decided on the grounds of warning signs. Apoptosis related mediators, among others, are known to correlate with severe dengue (SD) although no predictive validity is established. The objective of this study was to investigate the association of plasma cell-free DNA (cfDNA) with SD, and evaluate its prognostic value in SD prediction at acute phase. METHODS: This was a hospital-based prospective cohort study conducted in Vietnam. All the recruited patients were required to be admitted to the hospital and were strictly monitored for various laboratory and clinical parameters (including progression to SD) until discharged. Plasma samples collected during acute phase (6-48 h before defervescence) were used to estimate the level of cfDNA. RESULTS: Of the 61 dengue patients, SD patients (n = 8) developed shock syndrome in 4.8 days (95% CI 3.7-5.4) after the fever onset. Plasma cfDNA levels before the defervescence of SD patients were significantly higher than the non-SD group (p = 0.0493). From the receiver operating characteristic (ROC) curve analysis, a cut-off of > 36.9 ng/mL was able to predict SD with a good sensitivity (87.5%), specificity (54.7%), and area under the curve (AUC) (0.72, 95% CI 0.55-0.88; p = 0.0493). CONCLUSIONS: Taken together, these findings suggest that cfDNA could serve as a potential prognostic biomarker of SD. Studies with cfDNA kinetics and its combination with other biomarkers and clinical parameters would further improve the diagnostic ability for SD.

Alpha tryptase allele of Tryptase 1 (TPSAB1) gene associated with Dengue Hemorrhagic Fever (DHF) and Dengue Shock Syndrome (DSS) in Vietnam and Philippines.

We previously reported, significantly higher levels of Chymase and Tryptase in early stage plasma of DSS patients prior to the occurrence of shock suggesting a possible role of mast cells in dengue pathogenesis. To further investigate, we analyzed CMA1 promoter SNP (rs1800875) and TPSAB1 gene alleles, which encode the Human Chymase and α- and ß- tryptase 1 enzymes respectively, for susceptibility to Dengue Hemorrhagic Fever (DHF) and Dengue Shock Syndrome (DSS) in patients from hospitals in Vietnam (Ho Chi Minh City and Vinh Long) and the Philippines. While the CMA1 promoter SNP (rs1800875) was not associated with DHF/DSS, the homozygous form of α-tryptase allele was associated with DSS patients in Vinh Long and the Philippines (OR=3.52, p<0.0001; OR=3.37, p<0.0001, respectively) and with DHF in Ho Chi Minh City (OR=2.54, p=0.0084). Also, a statistically significant association was observed when DHF and DSS were combined in Vinh Long (OR=1.5, p=0.034) and the Philippines (OR=2.36, p=0.0004); in Ho Chi Minh City when DHF and DSS were combine an association was observed, but it was not statistically significant (OR=1.5, p=0.0505). Therefore, the α-tryptase might have a possible effect on the susceptibility to severe form of Dengue infection.

The association of cytokines with severe dengue in children.

BACKGROUND: Dengue virus infection is a major public health problem. A hypothesis put forward for severe dengue is the cytokine storm, a sudden increase in cytokines that induces vascular permeability. Previous studies and our recent meta-analysis showed that IL-6, IL-8, IFNγ, TNFα, VEGF-A and VCAM-1 are associated with dengue shock syndrome. Therefore, in this study we aim to validate the association of these cytokines with severe dengue. METHODS & FINDINGS: In a hospital based-case control study in Vietnam, children with dengue fever, other febrile illness and healthy controls were recruited. Dengue virus infection was confirmed by several diagnostic tests. Multiplex immunoassay using Luminex technology was used to measure cytokines simultaneously. A positive association with dengue shock syndrome was found for VCAM-1, whereas a negative association was found for IFNγ. Furthermore, multivariate logistic analysis also showed that VCAM-1 and IFNγ were independently correlated with dengue shock syndrome. CONCLUSION: IFNγ and VCAM-1 were associated with dengue shock syndrome, although their role in the severe dengue pathogenesis remains unclear. Additional studies are required to shed further light on the function of these cytokines in severe dengue.

Development of clinical decision rules to predict recurrent shock in dengue.

INTRODUCTION: Mortality from dengue infection is mostly due to shock. Among dengue patients with shock, approximately 30% have recurrent shock that requires a treatment change. Here, we report development of a clinical rule for use during a patient's first shock episode to predict a recurrent shock episode. METHODS: The study was conducted in Center for Preventive Medicine in Vinh Long province and the Children's Hospital No. 2 in Ho Chi Minh City, Vietnam. We included 444 dengue patients with shock, 126 of whom had recurrent shock (28%). Univariate and multivariate analyses and a preprocessing method were used to evaluate and select 14 clinical and laboratory signs recorded at shock onset. Five variables (admission day, purpura/ecchymosis, ascites/pleural effusion, blood platelet count and pulse pressure) were finally trained and validated by a 10-fold validation strategy with 10 times of repetition, using a logistic regression model. RESULTS: The results showed that shorter admission day (fewer days prior to admission), purpura/ecchymosis, ascites/pleural effusion, low platelet count and narrow pulse pressure were independently associated with recurrent shock. Our logistic prediction model was capable of predicting recurrent shock when compared to the null method (P < 0.05) and was not outperformed by other prediction models. Our final scoring rule provided relatively good accuracy (AUC, 0.73; sensitivity and specificity, 68%). Score points derived from the logistic prediction model revealed identical accuracy with AUCs at 0.73. Using a cutoff value greater than -154.5, our simple scoring rule showed a sensitivity of 68.3% and a specificity of 68.2%. CONCLUSIONS: Our simple clinical rule is not to replace clinical judgment, but to help clinicians predict recurrent shock during a patient's first dengue shock episode.

Association of mast cell-derived VEGF and proteases in Dengue shock syndrome.

BACKGROUND: Recent in-vitro studies have suggested that mast cells are involved in Dengue virus infection. To clarify the role of mast cells in the development of clinical Dengue fever, we compared the plasma levels of several mast cell-derived mediators (vascular endothelial cell growth factor [VEGF], soluble VEGF receptors [sVEGFRs], tryptase, and chymase) and -related cytokines (IL-4, -9, and -17) between patients with differing severity of Dengue fever and healthy controls. METHODOLOGY/PRINCIPAL FINDINGS: The study was performed at Children's Hospital No. 2, Ho Chi Minh City, and Vinh Long Province Hospital, Vietnam from 2002 to 2005. Study patients included 103 with Dengue fever (DF), Dengue hemorrhagic fever (DHF), and Dengue shock syndrome (DSS), as diagnosed by the World Health Organization criteria. There were 189 healthy subjects, and 19 febrile illness patients of the same Kinh ethnicity. The levels of mast cell-derived mediators and -related cytokines in plasma were measured by ELISA. VEGF and sVEGFR-1 levels were significantly increased in DHF and DSS compared with those of DF and controls, whereas sVEGFR-2 levels were significantly decreased in DHF and DSS. Significant increases in tryptase and chymase levels, which were accompanied by high IL-9 and -17 concentrations, were detected in DHF and DSS patients. By day 4 of admission, VEGF, sVEGFRs, and proteases levels had returned to similar levels as DF and controls. In-vitro VEGF production by mast cells was examined in KU812 and HMC-1 cells, and was found to be highest when the cells were inoculated with Dengue virus and human Dengue virus-immune serum in the presence of IL-9. CONCLUSIONS: As mast cells are an important source of VEGF, tryptase, and chymase, our findings suggest that mast cell activation and mast cell-derived mediators participate in the development of DHF. The two proteases, particularly chymase, might serve as good predictive markers of Dengue disease severity.

Elevated levels of cell-free circulating DNA in patients with acute dengue virus infection.

BACKGROUND: Apoptosis is thought to play a role in the pathogenesis of severe dengue and the release of cell-free DNA into the circulatory system in several medical conditions. Therefore, we investigated circulating DNA as a potential biomarker for severe dengue. METHODS AND FINDINGS: A direct fluorometric degradation assay using PicoGreen was performed to quantify cell-free DNA from patient plasma. Circulating DNA levels were significantly higher in patients with dengue virus infection than with other febrile illnesses and healthy controls. Remarkably, the increase of DNA levels correlated with the severity of dengue. Additionally, multivariate logistic regression analysis showed that circulating DNA levels independently correlated with dengue shock syndrome. CONCLUSIONS: Circulating DNA levels were increased in dengue patients and correlated with dengue severity. Additional studies are required to show the benefits of this biomarker in early dengue diagnosis and for the prognosis of shock complication.