Layered material platform for surface plasmon resonance biosensing.

Plasmonic biosensing has emerged as the most sensitive label-free technique to detect various molecular species in solutions and has already proved crucial in drug discovery, food safety and studies of bio-reactions. This technique relies on surface plasmon resonances in ~50 nm metallic films and the possibility to functionalize the surface of the metal in order to achieve selectivity. At the same time, most metals corrode in bio-solutions, which reduces the quality factor and darkness of plasmonic resonances and thus the sensitivity. Furthermore, functionalization itself might have a detrimental effect on the quality of the surface, also reducing sensitivity. Here we demonstrate that the use of graphene and other layered materials for passivation and functionalization broadens the range of metals which can be used for plasmonic biosensing and increases the sensitivity by 3-4 orders of magnitude, as it guarantees stability of a metal in liquid and preserves the plasmonic resonances under biofunctionalization. We use this approach to detect low molecular weight HT-2 toxins (crucial for food safety), achieving phase sensitivity~0.5 fg/mL, three orders of magnitude higher than previously reported. This proves that layered materials provide a new platform for surface plasmon resonance biosensing, paving the way for compact biosensors for point of care testing.

Using a chitosan nanolayer as an efficient pH buffer to protect pH-sensitive supramolecular assemblies.

It is attractive to control the properties of macro objects and films by employing simple nanolayer composites, as in the case of nanoarchitectured Layer-by-Layer (LbL) coating. In this paper, we use chitosan as a surface-based pH buffer to protect adsorbed supramolecular fibres from pH-mediated disassembly. Protons are generated on a titania surface under illumination at 405 nm leading to an appreciable pH change on the surface. We find that supramolecular polymers that are highly sensitive to pH change will not disassemble after irradiation if a nanolayer of chitosan is present. We propose that chitosan can be used as an efficient pH-responsive protective layer for pH sensitive soft materials.

Polyelectrolyte multilayered nanofilms as a novel approach for the protection of hydrogen storage materials.

This work describes the encapsulation of hydrogen storage materials from organic solvents. Due to complex formation the shell provides stability and selective permeability. Specifically, sodium borohydride particles were encapsulated within polymer films by the layer-by-layer self-assembly of oppositely charged polyelectrolytes (polyethyleneimine and poly(acrylonitrile-co-butadiene-co-acrylic acid)). The polymer nanofilm fabrication was performed using dichloromethane as a working media. IR spectroscopy was applied to investigate the chemical interaction between the polyelectrolytes. The multilayer film preparation was verified by Z-potential measurements, scanning electron microscopy, and confocal laser microscopy. The stability of sodium borohydride protected with a polyelectrolyte shell was increased compared to that of the pure material under ambient conditions.

Novel type of self-assembled polyamide and polyimide nanoengineered shells--fabrication of microcontainers with shielding properties.

Two types of microcontainers were prepared by using the adsorption of polyamide on the surface of micrometer-sized inorganic porous calcium carbonate microparticles followed by thermal conversion of the polyamide layers into polyimide coatings. The effect of the preparation conditions on the structure and morphology of the microcontainers was studied by transmission electron microscopy and scanning electron microscopy. The smoothest and defect-free coatings were prepared using polyethylenimine as the supporting polymer. The thickness of the polyamide/polyimide shells was estimated by atomic force microscopy and scanning electron microscopy between 50 and 150 nm depending on the quantity of the layers. The water-soluble antibiotic, doxorubicin hydrochloride, was used as a model compound to demonstrate the efficiency of the microcontainers for encapsulation. The resistance of the novel microcontainers to solvent treatment was visualized by the confocal scanning fluorescence microscopy. It was demonstrated that the combination of the high thermal and chemical resistance of polyamide/polyimide shell and the sorption capacity of the CaCO3 is very useful for development of highly protective microcontainers and thermal detectors for smart fabrics.

[The diagnostic and prognostic significance of the indices of the immune response to streptococcal group A antigens in rheumatism]. / Diagnosticheskoe i prognosticheskoe znachenie pokazatelei immunnogo otveta na antigeny streptokokka gruppy A pri revmatizme.

Serum samples obtained from 33 patients with acute rheumatic fever (ARF), 60 patients with rheumatic heart disease (RHD) and 30 adult healthy persons have been studied. Antibodies to streptococcal A polysaccharide (SAP) and lypoteichoic acid (LTA) were examined by ELISA, to streptolysin O by standard technique. SAP antibodies in high titers persisted from 5 to 12 months in ARF and rheumatic carditis patients especially when RHD was developing. High titers of antibodies to LTA and SLO persisted for 3 months since ARF onset, then fell (p < 0.05). ELISA proved sensitive in determination of antibodies to SAP and LTA. Its combination with determination of the titers to SLO antigens confirmed Streptococcus A infection involvement in emergence of ARF in all the cases including insidious or late-onset carditis and chorea. High levels of antibodies to SAP and LTA were more frequently detected in patients with RHD than in healthy persons (p < 0.001). Correlation between frequency of high levels of antibodies to SAP and bicillin 5 or erythromycin administration, duration of RHD was not established.