Controlling the formation of halogenated byproducts in the chlorination of source waters by oxidative pre-treatment with the Fe(II)/Fe(III)-S(IV)-air system.

Breakpoint chlorination is a generally accepted method for removing ammonium ion from source waters in drinking water treatment technologies. This process is often accompanied by the formation of halogenated organic byproducts. The presence of these compounds in potable water is of primary concern. In this paper, we demonstrate that the concentration of the precursors of the halogenated species can sufficiently be decreased by oxidizing the organic pollutants with the Fe(II)/Fe(III) - S(IV) - air system. Pre-oxidative treatment of the source waters results in a substantial reduction of chemical oxygen demand, while the ammonium ion concentration remains unaffected. The breakpoint chlorination produces substantially less trihalomethanes (THMs) and adsorbable halogenated organic compounds (AOXs) in oxidatively pre-treated source waters than in raw waters. These results offer a possibility to improve drinking water treatment technologies for better controlling the formation of antagonistic byproducts. It is demonstrated that reaching the regulated concentration levels of THMs is feasible with this method even in source waters containing organic pollutants at relatively high concentration levels. The main advantage of the procedure is that the reagents used for the oxidative pre-treatment are converted into non-toxic products (Fe(III) and SO42-) by the end of the process.

Oxidization increases the binding of EGCG to serum albumin revealed by kinetic data from label-free optical biosensor with reference channel.

Epigallocatechin-gallate (EGCG) is the main polyphenol ingredient of green tea. This compound is a strong antioxidant and oxidizes easily. Numerous studies demonstrated its beneficial effects on the human health, for example its anticancer and anti-inflammatory activity. In the body, EGCG is transported by serum albumin. EGCG easily oxidizes and the interactions of the oxidized form presumably present significant differences. However, the presence of oxidized EGCG is usually neglected in the literature and its effects have not been investigated in detail. Here, we applied the label-free grating coupled interferometry method that performs dual-channel measurements. The measured kinetic signal can be compensated with a signal of a reference channel at each measurement time. By testing both hydrophilic and hydrophobic platforms, we found that EGCG can bind to a wide range of surfaces. Exploiting the dual-channel referencing ability as well as the unique sensitivity and throughput of the employed label-free technique, the experiments revealed the specific interactions between bovine serum albumin (BSA) and EGCG and determined the characteristic dissociation constant (Kd) of the binding equilibrium. The obtained binding constants were compared to literature values, showing reasonable agreement with NMR data. Besides the native EGCG, the oxidized form of EGCG was also examined, whose binding behaviors to serum albumins have never been studied. Overstoichiometric binding obtained; BSA has stronger and weaker binding sites, which could be characterized by two separate Kd values. Furthermore, EGCG oxidization increased the bound amount.

Aesthetic smile evaluation--a non-invasive solution.

UNLABELLED: Enhancement of the aesthetic zone is a common reason for patients to seek dental care. This article describes a protocol for the examination, assessment and treatment planning for a patient seeking a solution to an aesthetic concern. The technique of undertaking an intra-oral'mock-up' using resin composite as a diagnostic approach can be particularly helpful when planning for future prosthodontic rehabilitation. The latter can allow the operator and patient to visualize crudely what is aesthetically and functionally possible, given the constraints imposed by that patient. The patient has ultimately managed in a minimally invasive manner. CLINICAL RELEVANCE: It can be very tempting for a dental operator to impose his/her concepts of the'artistic ideal' when planning for care in the smile zone. Such ideals are largely based on established universal aesthetic principles of tooth colour, size, shape, form, position, symmetry and proportion. However, beauty is a very subjective matter. It is essential for the operator to listen attentively to his/her patient's concerns. Meticulous patient examination and assessment are absolutely critical factors in attempting to attain a successful outcome. The use of reversible, chairside intra-oral mock-up techniques can not only help with the transference of essential information to the dental technician when planning for restorative intervention in the smile zone, but can also allow the patient to gain an insight and indeed contribute his/her views to the possible restorative endpoint, respectively.

Grating-coupled interferometry reveals binding kinetics and affinities of Ni ions to genetically engineered protein layers.

Reliable measurement of the binding kinetics of low molecular weight analytes to their targets is still a challenging task. Often, the introduction of labels is simply impossible in such measurements, and the application of label-free methods is the only reliable choice. By measuring the binding kinetics of Ni(II) ions to genetically modified flagellin layers, we demonstrate that: (1) Grating-Coupled Interferometry (GCI) is well suited to resolve the binding of ions, even at very low protein immobilization levels; (2) it supplies high quality kinetic data from which the number and strength of available binding sites can be determined, and (3) the rate constants of the binding events can also be obtained with high accuracy. Experiments were performed using a flagellin variant incorporating the C-terminal domain of the nickel-responsive transcription factor NikR. GCI results were compared to affinity data from titration calorimetry. We found that besides the low-affinity binding sites characterized by a micromolar dissociation constant (Kd), tetrameric FliC-NikRC molecules possess high-affinity binding sites with Kd values in the nanomolar range. GCI enabled us to obtain real-time kinetic data for the specific binding of an analyte with molar mass as low as 59 Da, even at signals lower than 1 pg/mm2.

Human primary endothelial label-free biochip assay reveals unpredicted functions of plasma serine proteases.

Tissue-on-a-chip technologies are more and more important in the investigation of cellular function and in the development of novel drugs by allowing the direct screening of substances on human cells. Constituting the inner lining of vessel walls, endothelial cells are the key players in various physiological processes, moreover, they are the first to be exposed to most drugs currently used. However, to date, there is still no appropriate technology for the label-free, real-time and high-throughput monitoring of endothelial function. To this end, we developed an optical biosensor-based endothelial label-free biochip (EnLaB) assay that meets all the above requirements. Using our EnLaB platform, we screened a set of plasma serine proteases as possible endothelial cell activators, and first identified the endothelial cell activating function of three important serine proteases - namely kallikrein, C1r and mannan-binding lectin-associated serine-protease 2 (MASP-2) - and verified these results in well-established functional assays. EnLaB proved to be an effective tool for revealing novel cellular mechanisms as well as for the high-throughput screening of various compounds on endothelial cells.

Label-free optical biosensor for real-time monitoring the cytotoxicity of xenobiotics: A proof of principle study on glyphosate.

Rapid and inexpensive biosensor technologies allowing real-time analysis of biomolecular and cellular events have become the basis of next-generation cell-based screening techniques. Our work opens up novel opportunities in the application of the high-throughput label-free Epic BenchTop optical biosensor in cell toxicity studies. The Epic technology records integrated cellular responses about changes in cell morphology and dynamic mass redistribution of cellular contents at the 100-150 nm layer above the sensor surface. The aim of the present study was to apply this novel technology to identify the effect of the herbicide Roundup Classic, its co-formulant polyethoxylated tallow amine (POEA), and its active ingredient glyphosate, on MC3T3-E1 cells adhered on the biosensor surface. The half maximal inhibitory concentrations of Roundup Classic, POEA and glyphosate upon 1 h of exposure were found to be 0.024%, 0.021% and 0.163% in serum-containing medium and 0.028%, 0.019% and 0.538% in serum-free conditions, respectively (at concentrations equivalent to the diluted Roundup solution). These results showed a good correlation with parallel end-point assays, demonstrating the outstanding utility of the Epic technique in cytotoxicity screening, allowing not only high-throughput, real-time detection, but also reduced assay run time and cytotoxicity assessment at end-points far before cell death would occur.

Green tea polyphenol tailors cell adhesivity of RGD displaying surfaces: multicomponent models monitored optically.

The interaction of the anti-adhesive coating, poly(L-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) and its Arg-Gly-Asp (RGD) functionalized form, PLL-g-PEG-RGD, with the green tea polyphenol, epigallocatechin-gallate (EGCg) was in situ monitored. After, the kinetics of cellular adhesion on the EGCg exposed coatings were recorded in real-time. The employed plate-based waveguide biosensor is applicable to monitor small molecule binding and sensitive to sub-nanometer scale changes in cell membrane position and cell mass distribution; while detecting the signals of thousands of adhering cells. The combination of this remarkable sensitivity and throughput opens up new avenues in testing complicated models of cell-surface interactions. The systematic studies revealed that, despite the reported excellent antifouling properties of the coatings, EGCg strongly interacted with them, and affected their cell adhesivity in a concentration dependent manner. Moreover, the differences between the effects of the fresh and oxidized EGCg solutions were first demonstrated. Using a semiempirical quantumchemical method we showed that EGCg binds to the PEG chains of PLL-g-PEG-RGD and effectively blocks the RGD sites by hydrogen bonds. The calculations supported the experimental finding that the binding is stronger for the oxidative products. Our work lead to a new model of polyphenol action on cell adhesion ligand accessibility and matrix rigidity.

Flagellin based biomimetic coatings: From cell-repellent surfaces to highly adhesive coatings.

UNLABELLED: Biomimetic coatings with cell-adhesion-regulating functionalities are intensively researched today. For example, cell-based biosensing for drug development, biomedical implants, and tissue engineering require that the surface adhesion of living cells is well controlled. Recently, we have shown that the bacterial flagellar protein, flagellin, adsorbs through its terminal segments to hydrophobic surfaces, forming an oriented monolayer and exposing its variable D3 domain to the solution. Here, we hypothesized that this nanostructured layer is highly cell-repellent since it mimics the surface of the flagellar filaments. Moreover, we proposed flagellin as a carrier molecule to display the cell-adhesive RGD (Arg-Gly-Asp) peptide sequence and induce cell adhesion on the coated surface. The D3 domain of flagellin was replaced with one or more RGD motifs linked by various oligopeptides modulating flexibility and accessibility of the inserted segment. The obtained flagellin variants were applied to create surface coatings inducing cell adhesion and spreading to different levels, while wild-type flagellin was shown to form a surface layer with strong anti-adhesive properties. As reference surfaces synthetic polymers were applied which have anti-adhesive (PLL-g-PEG poly(l-lysine)-graft-poly(ethylene glycol)) or adhesion inducing properties (RGD-functionalized PLL-g-PEG). Quantitative adhesion data was obtained by employing optical biochips and microscopy. Cell-adhesion-regulating coatings can be simply formed on hydrophobic surfaces by using the developed flagellin-based constructs. The developed novel RGD-displaying flagellin variants can be easily obtained by bacterial production and can serve as alternatives to create cell-adhesion-regulating biomimetic coatings. STATEMENT OF SIGNIFICANCE: In the present work, we show for the first time that.