Imaging surface plasmon resonance for multiplex microassay sensing of mycotoxins

A prototype imaging surface plasmon resonance-based multiplex microimmunoassay for mycotoxins is described. A microarray of mycotoxin–protein conjugates was fabricated using a continuous flow microspotter device. A competitive inhibition immunoassay format was developed for the simultaneous detection of deoxynivalenol (DON) and zearalenone (ZEN), using a single sensor chip. Initial in-house validation showed limits of detection of 21 and 17 ng/mL for DON and 16 and 10 ng/mL for ZEN in extracts, which corresponds to 84 and 68 µg/kg for DON and 64 and 40 µg/kg for ZEN in maize and wheat samples, respectively. Finally, the results were critically compared with data obtained from liquid chromatography-mass spectrometry confirmatory analysis method and found to be in good agreement. The described multiplex immunoassay for the rapid screening of several mycotoxins meets European Union regulatory limits and represents a robust platform for mycotoxin analysis in food and feed sample

Nucleic Acids Nanoscience at Interfaces Special Issue

This special issue of Langmuir focuses on the latest developments and provides a look into the future of nucleic acids nanoscience, particularly as it concerns the understanding and exploitation of interfacial phenomena. As Irving Langmuir once said,“The scientist is motivated primarily by curiosity and a desire for truth”. Thus, our goal in assembling this issue was to highlight the importance of fundamental science in driving the field forward (hence, the selection of the term “nanoscience” as opposed to “nanotechnology”). The issue contains 3 Invited Feature Articles and 45 Research Articles on a diverse set of topics involving both long-time entries (e.g., DNA-coated gold nanoparticles) and more recent arrivals (e.g., DNA origami nanostructures), and from the construction of ever more complex and functional nanostructures to the enhanced detection thereof in manifold ways

Role of surface charge and oxidative stress in cytotoxicity of organic monolayer-coated silicon nanoparticles towards macrophage NR8383 cells

Background - Surface charge and oxidative stress are often hypothesized to be important factors in cytotoxicity of nanoparticles. However, the role of these factors is not well understood. Hence, the aim of this study was to systematically investigate the role of surface charge, oxidative stress and possible involvement of mitochondria in the production of intracellular reactive oxygen species (ROS) upon exposure of rat macrophage NR8383 cells to silicon nanoparticles. For this aim highly monodisperse (size 1.6 ± 0.2 nm) and well-characterized Si core nanoparticles (Si NP) were used with a surface charge that depends on the specific covalently bound organic monolayers: positively charged Si NP-NH2, neutral Si NP-N3 and negatively charged Si NP-COOH. Results - Positively charged Si NP-NH2 proved to be more cytotoxic in terms of reducing mitochondrial metabolic activity and effects on phagocytosis than neutral Si NP-N3, while negatively charged Si NP-COOH showed very little or no cytotoxicity. Si NP-NH2 produced the highest level of intracellular ROS, followed by Si NP-N3 and Si NP-COOH; the latter did not induce any intracellular ROS production. A similar trend in ROS production was observed in incubations with an isolated mitochondrial fraction from rat liver tissue in the presence of Si NP. Finally, vitamin E and vitamin C induced protection against the cytotoxicity of the Si NP-NH2 and Si NP-N3, corroborating the role of oxidative stress in the mechanism underlying the cytotoxicity of these Si NP. Conclusion - Surface charge of Si-core nanoparticles plays an important role in determining their cytotoxicity. Production of intracellular ROS, with probable involvement of mitochondria, is an important mechanism for this cytotoxicit

'Nanotechnologie is teamsport'

Innoveren in de nanotechnologie is teamsport, vindt Han Zuilhof, hoogleraar Organische chemie aan Wageningen University, onderdeel van Wageningen UR. Zelf werkt hij met bedrijven en kennisinstellingen aan een chip die longziektes bij kinderen opspoort. Zuilhof vreest dat nieuwe vormen van onderzoeksfinanciering dit soort teamwerk ondergraven

On the Stability and Formation of Pillar[n]arenes: a DFT Study

The increased use of both pillar[5]arenes and pillar[6]arenes, stimulated by increasingly efficient syntheses of both, has brought forward the question as to what drives the intermediates in this Friedel-Crafts ring formation to form a pillar[5]arene, a pillar[6]arene, or any other sized macrocycle. This study sets out to answer this question by studying both the thermodynamics and kinetics involved in the absence and presence of templating solvents using high-end wB97XD/6-311G(2p,2d) DFT calculations

Organic layers on silicon result in a unique hybrid fet

A Field-Effect Transistor (FET) is presented that combines the conventional lay-out of the silicon substrate (channel and source and drain connections) with a Si-C linked organic gate insulator contacted via an organic, conducting polymer. It is shown that this hybrid device combines the excellent electrical behavior of the silicon substrate and the ease of use and good properties of organic insulators and contacting materials.\ud Keywords: organic monolayer, FET, conducting polyme

Antibody orientation on biosensor surfaces: a minireview

Detection elements play a key role in analyte recognition in biosensors. Therefore, detection elements with high analyte specificity and binding strength are required. While antibodies (Abs) have been increasingly used as detection elements in biosensors, a key challenge remains – the immobilization on the biosensor surface. This minireview highlights recent approaches to immobilize and study Abs on surfaces. We first introduce Ab species used as detection elements, and discuss techniques recently used to elucidate Ab orientation by determination of layer thickness or surface topology. Then, several immobilization methods will be presented: non-covalent and covalent surface attachment, yielding oriented or random coupled Abs. Finally, protein modification methods applicable for oriented Ab immobilization are reviewed with an eye to future application

Tunable Supramolecular Ag+-Host Interactions in Pillar[n]arene[m]quinones and Ensuing Specific Binding to 1-Alkynes

We developed an improved, robust synthesis of a series of pillar[6]arenes with a varying number (0-3) of quinone moieties in the ring. This easy-to-control variation yielded a gradually less electron-rich cavity in going from zero to three quinone units, as shown from the strength of host-guest interactions with silver ions. Such macrocycle-Ag2 complexes themselves were shown to display an unprecedented, sharp distinction between terminal alkynes, which strongly bound to such complexes, and internal alkynes, internal alkenes and terminal alkenes, which do hardly bind

A Protein‐Based Pentavalent Inhibitor of the Cholera Toxin B‐Subunit

Protein toxins produced by bacteria are the cause of many life-threatening diarrheal diseases. Many of these toxins, including cholera toxin (CT), enter the cell by first binding to glycolipids in the cell membrane. Inhibiting these multivalent protein/carbohydrate interactions would prevent the toxin from entering cells and causing diarrhea. Here we demonstrate that the site-specific modification of a protein scaffold, which is perfectly matched in both size and valency to the target toxin, provides a convenient route to an effective multivalent inhibitor. The resulting pentavalent neoglycoprotein displays an inhibition potency (IC50) of 104 pM for the CT B-subunit (CTB), which is the most potent pentavalent inhibitor for this target reported thus far. Complexation of the inhibitor and CTB resulted in a protein heterodimer. This inhibition strategy can potentially be applied to many multivalent receptors and also opens up new possibilities for protein assembly strategies

On the Relativistic Description of the Nucleus

We discuss a relativistic theory of the atomic nuclei in the framework of the hamiltonian formalism and of the mesonic model of the nucleus. Attention is paid to the translational invariance of the theory. Our approach is centered on the concept of spectral amplitude, a function in the Dirac spinor space. We derive a Lorentz covariant equation for the latter, which requires as an input the baryon self-energy. For this we either postulate the most general Lorentz-Poincar\'e invariant expression or perform a calculation via a Bethe-Salpeter equation starting from a nucleon-nucleus interaction. We discuss the features of the nuclear spectrum obtained in the first instance. Finally the general constraints the self-energy should satisfy because of analyticity and Poincar\'e covariance are discussed