Single beam grating coupled interferometry: high resolution miniaturized label-free sensor for plate based parallel screening

Grating Coupled Interferometry (GCI) using high quality waveguides with two incoupling and one outcoupling grating areas is introduced to increase and precisely control the sensing length of the device; and to make the sensor design suitable for plate-based multiplexing. In contrast to other interferometric arrangements, the sensor chips are interrogated with a single expanded laser beam illuminating both incoupling gratings simultaneously. In order to obtain the interference signal, only half of the beam is phase modulated using a laterally divided two-cell liquid crystal modulator. The developed highly symmetrical arrangement of the interferometric arms increases the stability and at the same time offers straightforward integration of parallel sensing channels. The device characteristics are demonstrated for both TE and TM polarized modes. (C)2012 Optical Society of Americ

Sample handling in surface sensitive chemical and biological sensing : a practical review of basic fluidics and analyte transport

This paper gives an overview of the advantages and associated caveats of the most common sample handling methods in surface-sensitive chemical and biological sensing.We summarize the basic theoretical and practical considerations one faces when designing and assembling the fluidic part of the sensor devices. The influence of analyte size, the use of closed and flow-through cuvettes, the importance of flow rate, tubing length and diameter, bubble traps, pressure-driven pumping, cuvette dead volumes, and sample injection systems are all discussed. Typical application areas of particular arrangements are also highlighted, such as themonitoring of cellular adhesion, biomolecule adsorption–desorption and ligand–receptor affinity binding. Our work is a practical review in the sense that for every sample handling arrangement considered we present our own experimental data and critically reviewour experience with the given arrangement. In the experimental partwe focus on sample handling in optical waveguide lightmode spectroscopy (OWLS) measurements, but the present study is equally applicable for other biosensing technologies in which an analyte in solution is captured at a surface and its presence is monitored. Explicit attention is given to features that are expected to play an increasingly decisive role in determining the reliability of (bio)chemical sensingmeasurements, such as analyte transport to the sensor surface; the distorting influence of dead volumes in the fluidic system; and the appropriate sample handling of cell suspensions (e.g. their quasi-simultaneous deposition). At the appropriate places, biological aspects closely related to fluidics (e.g. cellular mechanotransduction, competitive adsorption, blood flow in veins) are also discussed, particularly with regard to their models used in biosensing

Microfluidic channels laser-cut in thin double-sided tapes: cost-effective biocompatible fluidics in minutes from design to final integration with optical biochips

A simple, reliable and cost-effective fluidic channel, fabricated by using double-sided pressure-sensitive tapes, is demonstrated here. A laser-cutting method is applied to engrave structures in sheets of the tapes. After peeling off the tape liners, the structures could be easily integrated at room temperature with label-free optical waveguide biochips without further modifications or additional processing steps. It is shown that the well-defined and controllable height of the channels is advantageous for stopped-flow measurements of analyte binding. The easy fabrication of a fully transparent integrated sensor unit – tape cuvette system is also demonstrated for parallel microscopic investigations. The transparent unit was used to on-line monitor the surface adhesion of Salmonella cells on poly-l-lysine-coated biochip surfaces, followed by the straightforward microscopic visualization of the adhered bacterial cells. The material of the double sided tape is stable in aqueous solutions. Furthermore, its material is biocompatible, making it ideal for biological applications. Excellent, stable and reversible bonding of the microstructured tapes to biocompatible plastic and glass is also demonstrated. The simplicity of the fabrication at ambient temperatures makes the developed processes appealing for lab-on-a-chip applications, particularly if the bonded biochips are precious

Xylan-Degrading Catalytic Flagellar Nanorods

Flagellin, the main component of flagellar filaments, is a protein possessing polymerization ability. In this work, a novel fusion construct of xylanase A from B. subtilis and Salmonella flagellin was created which is applicable to build xylan-degrading catalytic nanorods of high stability. The FliC-XynA chimera when overexpressed in a flagellin deficient Salmonella host strain was secreted into the culture medium by the flagellum-specific export machinery allowing easy purification. Filamentous assemblies displaying high surface density of catalytic sites were produced by ammonium sulfate-induced polymerization. FliC-XynA nanorods were resistant to proteolytic degradation and preserved their enzymatic activity for a long period of time. Furnishing enzymes with self-assembling ability to build catalytic nanorods offers a promising alternative approach to enzyme immobilization onto nanostructured synthetic scaffolds

Environmental and Toxicological Impacts of Glyphosate with Its Formulating Adjuvant

Environmental and toxicological characteristics of formulated pesticides may substantially differ from those of their active ingredients or other components alone. This phenomenon is demonstrated in the case of the herbicide active ingredient glyphosate. Due to its extensive application, this active ingredient was found in surface and ground water samples collected in Békés Country, Hungary, in the concentration range of 0.54–0.98 ng/ml. The occurrence of glyphosate appeared to be somewhat higher at areas under intensive agriculture, industrial activities and public road services, but the compound was detected at areas under organic (ecological) farming or natural grasslands, indicating environmental mobility. Increased toxicity of the formulated herbicide product Roundup compared to that of glyphosate was observed on the indicator aquatic organism Daphnia magna Straus. Acute LC50 values of Roundup and its formulating adjuvant polyethoxylated tallowamine (POEA) exceeded 20 and 3.1 mg/ml, respectively, while that of glyphosate (as isopropyl salt) was found to be substantially lower (690-900 mg/ml) showing good agreement with literature data. Cytotoxicity of Roundup, POEA and glyphosate has been determined on the neuroectodermal cell line, NE-4C measured both by cell viability test and holographic microscopy. Acute toxicity (LC50) of Roundup, POEA and glyphosate on NE-4C cells was found to be 0.013±0.002%, 0.017±0.009% and 6.46±2.25%, respectively (in equivalents of diluted Roundup solution), corresponding to 0.022±0.003 and 53.1±18.5 mg/ml for POEA and glyphosate, respectively, indicating no statistical difference between Roundup and POEA and 2.5 orders of magnitude difference between these and glyphosate. The same order of cellular toxicity seen in average cell area has been indicated under quantitative cell visualization. The results indicate that toxicity of the formulated herbicide is caused by the formulating agent, but in some parameters toxicological synergy occurs between POEA and glyphosate

Self-assembly and structure of flagellin-polyelectrolyte composite layers: Polyelectrolyte induced flagellar filament formation during the alternating deposition process

The simple and cost-effective bottom-up fabrication of complex functionalized nanostructures is extensively researched today. Here, the alternating deposition of the negatively charged protein flagellin and a positively charged polyelectrolyte is studied. The multilayer buildup was followed in situ using Optical Waveguide Lightmode Spectroscopy (OWLS) revealing the deposited surface mass density in real time during the alternating deposition process. The nanostructure of the assembled films was investigated by Atomic Force Microscopy (AFM) measurements. When flagellin was applied in its natural filamentous form no distinct multilayer buildup was observed, the filaments assembled mainly into bundles. In contrast, when thermally treated filament solution or pure flagellin monomer solution was used a systematic linearly growing buildup was seen, and thick, relatively smooth films were fabricated. AFM investigations revealed that the polycation induced assembly of flagellin monomers into nanofilaments during the deposition process. Both the filament formation and the multilayer buildup were completely absent when a truncated flagellin variant-missing the disordered terminal regions-was applied. Since these regions are necessary for filament formation, we conclude that the linearly growing nature of the layer is a clear consequence of filament formation. Therefore, this study first reveals a new type of linearly growing polyelectrolyte multilayer buildup mechanism, when one of the components induces the self-assembly of the oppositely charged component, creating a complex, stable and smooth filamentous nanostructured coating. These composite films can find diverse applications in nanotechnology and in biomedical sciences since the variable D3 domain of flagellin subunits can be easily modified to express enzymatic, fluorescent or molecular binding properties on the surfaces of the filaments. © 2016 The Royal Society of Chemistry