Electrochemical evaluation of dsDNA—Liposomes interactions

The aim of the present work was to evaluate the interaction between double-stranded DNA (dsDNA) and liposomes by voltammetric methods. The experimental results were analyzed considering the initial studies regarding the oxidation mechanism of dsDNA purine bases by cyclic and differential pulse voltammetry at the glassy carbon electrode (GCE). The interaction between dsDNA and 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) was studied in a suspension containing both dsDNA and DMPC liposomes, prepared in pH = 7.0, 0.1 M phosphate buffer and using different incubation time periods. The formation of dsDNA-liposome complex was put in evidence by the decrease of the dsDNA oxidation peaks, dependent upon the incubation time. This behavior was explained considering the electroactive centers of dsDNA, guanosine monophosphate and adenosine monophosphate residues, part of them hidden inside the dsDNA-liposome complex structure and thus being unable to reach the GC electrode and preventing their oxidation. The electrochemical results are relevant for a better physicochemical characterisation of the dsDNA and dsDNA-liposome complex, which can be important for the development of gene therapy vectors

Global assessment of chemical quality of drinking water: The case of trihalomethanes

(c) The Author/sBACKGROUND: Trihalomethanes (THM), a major class of disinfection by-products, are widespread and are associated with adverse health effects. We conducted a global evaluation of current THM regulations and concentrations in drinking water. METHODS: We included 120 countries (∼7000 million inhabitants in 2016), representing 94% of the world population. We searched for country regulations and THM routine monitoring data using a questionnaire addressed to referent contacts. Scientific and gray literature was reviewed where contacts were not identified or declined participation. We obtained or estimated annual average THM concentrations, weighted to the population served when possible. RESULTS: Drinking water regulations were ascertained for 116/120 (97%) countries, with 89/116 (77%) including THM regulations. Routine monitoring was implemented in 47/89 (53%) of countries with THM regulations. THM data with a varying population coverage was obtained for 69/120 (58%) countries consisting of ∼5600 million inhabitants (76% of world's population in 2016). Population coverage was ≥90% in 14 countries, mostly in the Global North, 50-89% in 19 countries, 11-49% among 21 countries, and ≤10% in 14 countries including India, China, Russian Federation and Nigeria (40% of world's population). DISCUSSION: An enormous gap exists in THM regulatory status, routine monitoring practice, reporting and data availability among countries, especially between high- vs. low- and middle-income countries (LMICs). More efforts are warranted to regulate and systematically assess chemical quality of drinking water, centralize, harmonize, and openly report data, particularly in LMICs.Publishe

Global assessment of chemical quality of drinking water: The case of trihalomethanes

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Iodo-THM Formation During Chlorination of Source Waters With Naturally Occurring Ammonium and High Sodium Content

The current study investigates the occurrence and specific conditions that favour the formation of iodo-THMs during the disinfection of source waters with elevated sodium content (over 200 mg/L sodium) and naturally occurring ammonium. Based on the previous data, the current study focused on 16 water treatment plants (WTPs) using source waters with sodium content between 10 mg/L and 760 mg/L and naturally occurring ammonium. Source water, treated water and mid-point distribution water samples were collected under both winter and summer conditions. Samples were stabilized, shipped cold, and analysed within 4 days from collection for the six iodo-THMs, using solid phase micro extraction gas chromatography with electron-capture detection (SPME-GC-ECD). Data for 20 other neutral DBPs (including THMs, haloacetaldehydes, haloacetonitriles, chloropicrin, cyanogen chloride, cyanogen bromide), 7 nitrosamines, as well as general water quality parameters, elemental analysis, free/total chlorine and bromide concentrations, were also collected. Questionnaires were used to collect information about the plant treatment processes. One or more of the iodo-THM congeners were detected in 15/16 WTPs investigated. Maximum total iodo-THM concentrations determined in the survey ranged from 0.11 µg/L to 26.82 µg/L. The maximum total iodo-THM concentrations were &amp;gt; 1 µg/L, in 8/16 WTPs and the highest maximum total iodo-THM concentration of &amp;gt;10 µg/L was seen in 4/16 WTPs. The total concentrations and the speciation of iodo-THMs were strongly influenced by the presence of ammonium in the source water and by the treatment regime (e.g., free chlorine residual). The bromide content of the source water did not have a significant influence on iodo-THM concentrations or speciation. The results of this study show that elevated sodium levels and the presence of naturally occurring ammonium in the source water are good markers for selecting WTP with the potential to form elevated levels of iodo-THMs in the treated water and thus, could provide the basis for future decisions regarding changing secondary disinfectant from chlorine to chloramine. This is important in Canada since WTPs using water sources with elevated salinity typically have difficulty maintaining the total THM levels to within the guideline level of 100 µg/L. These findings also support the need to monitor for naturally occurring ammonia, especially in high saline waters. Because iodo-THMs were found to occur in a large number of the systems investigated, more information about the toxicology of iodo-THMs would be important in assessing the potential risks for human exposure to iodo-THMs.</jats:p

Development and characterization of layer-by-layer biosensors based on PEI(+)/GOx(-) layers using label-free methods

Biosensors, as analytical devices, demonstrate unique efficiency in translating biochemical events into easily measurable electrical signals by using biological recognition elements, especially enzymes. Of the possible enzyme immobilisation methods, the layer-by-layer (LBL) technique, based on electrostatic interactions between layers, has the advantages of low cost, using small amount of materials, and leads to the formation of highly ordered and reproducible biosensor architectures. In this study, LbL biosensor construction has been evaluated. The substrates used were Au surfaces and mediated carbon-ink screen-printed electrodes. The gold electrodes were first functionalized with amino moieties by covalent linkage of cysteamine (Cys) through Au-S bonds. These allowed the linking of polyethyleneimine (PEI) through hydrogen-bonding to the gold surface and increased the stability of subsequent multilayers. PEI was directly adsorbed on the SPE surface. PEI is a short chain polymer and thence an efficient electron carrier, and being positively charged, it allows the formation of LBL structures with negatively charged enzymes. The multilayer formation of PEI(+)/GOx(-) was monitored by cyclic voltammetry, electrochemical impedance spectroscopy, and gravimetry. The influence of each enzymatic layer on the performance of the developed biosensor was analysed by fixed potential amperometric measurements

New strategies for early diagnosis of heart allograft rejection.

BACKGROUND: Allograft rejection is mediated by T cells that recognize allogeneic major histocompatibility complex (MHC) molecules via the direct and indirect pathway. The direct pathway involves T cells that react against MHC/peptide complexes expressed on the surface of donor antigen-presenting cells (APCs). In contrast, T cells involved in the indirect pathway recognize peptides derived from processing and presentation of allogeneic MHC molecules by self (recipient) APCs. To explore the relative contribution of these two pathways to rejection, we have evaluated the response of peripheral blood T cells from 50 heart transplant recipients against donor APCs (direct recognition) and against self APCs pulsed with synthetic peptides corresponding to the hypervariable region of the mismatched HLA-DR antigens of the donor (indirect recognition). METHODS: T cell reactivity against donor APCs was quantitated by measuring the expression of CD69 on allostimulated CD3+ LDA1+ cells. Reactivity to synthetic allopeptides was determined in limited dilution assays. RESULTS: Serial studies of the kinetics of direct and indirect recognition showed that both pathways contribute to early acute rejection episodes. Primary rejection was accompanied invariably by indirect recognition of a dominant allopeptide. Intermolecular spreading of T cell epitopes was observed during recurrent rejections. Enhanced recognition of donor alloantigens via the direct pathway was found predominantly during early rejection episodes. A single form of allorecognition was shown to occur in some rejection episodes. CONCLUSIONS: Monitoring of the direct and indirect pathway of allorecognition provides a reliable method for prediction and differential diagnosis of acute rejection of heart allografts