179 research outputs found
Interaction of 4 allotropic modifications of carbon nanoparticles with living tissues
Environmental pollution and technological progress lead to carbon nanoparticles that pose a serious health risk. They are present in soot, dust, and printing toner and can also be formed during grinding and cutting. Human neutrophils are able to sequester foreign material by formation of neutrophil extracellular traps (NETs), a process that can cause a strong inflammatory response. In the current work we compared proinflammatory properties of different carbon-based nanostructures: nanodiamonds, graphene oxide, fullerenes C60 and carbon dots. We tested adjuvant properties of carbon nanoparticles in a murine immunization model by investigating humoral (specific IgG and IgM antibodies) and cellular (delayed type hypersensitivity) immune responses. The ability of NETs to sequester nanoparticles was analyzed in a mouse air pouch model and neutrophil activation was verified by in vivo tracking of near-infrared labeled nanodiamonds and ex vivo fluorescent assays using human blood-derived neutrophils. All carbon nanoparticles exhibited proinflammatory adjuvant-like properties by stimulating production of specific IgG but not IgM antibodies (humoral immune response). The adjuvant-like response decreased in this order: from nanodiamonds, graphene oxide, fullerenes C60 to carbon dots. None of the studied carbon nanoparticles triggered a delayed type hypersensitivity reaction (cellular immune response). Nanodiamonds and fullerenes C60 were sequestrated in the body by NETs, as confirmed in the air pouch model and by in vivo fluorescent tracking of near-infrared labeled nanodiamonds
Gold/Silica biochips: applications to Surface Plasmon Resonance and fluorescence quenching
We report Gold/Silica biochips for low cost biosensor devices. Firstly, the
study of biochemical interactions on silica by means of Surface Plasmon
Resonance (SPR) is presented. Secondly, Gold/Silica biochips are employed to
reduce the strong quenching that occurs when a fluorophore is close to the gold
surface. Furthermore, the control of the Silica-like thickness allows
optimizing the distance between the metallic surface and the fluorophore in
order to enhance the fluorescent signal. These results represent the first
steps towards highly sensitive, specific and low cost biosensors based, for
example, on Surface Plasmon Coupled Emission (SPCE) techniques
Highly sensitive SPR response of Au/chitosan/graphene oxide nanostructured thin films toward Pb (II) ions
Optical sensors based on surface plasmon resonance (SPR) are utilized for detecting toxic heavy metals in solutions. To improve the sensitivity of SPR sensors, nanostructured thin films with active layers can be synthesized. In this study, the response to Pb (II) was measured and compared for SPR sensors incorporating gold–chitosan–graphene oxide (Au/CS/GO) nanostructured thin films and Au/CS films. The characterization of Au/CS/GO using FESEM analysis revealed a film composed of nanosheets with wrinkled, rough surfaces. The results from XRD analysis confirmed the successful incorporation of GO in the prepared films. Additionally, AFM analysis determined that the Au/CS/GO films had a root mean square (rms) roughness of 28.38 nm and were considerably rougher than the Au/CS films. Upon exposure to a 5 ppm Pb (II) ion solution, the Au/CS/GO films exhibited higher SPR sensitivity, as much as 1.11200 ppm−1, than Au/CS films, 0.77600 ppm−1. This enhancement of the SPR response was attributed to strong covalent bonding between CS and GO in these films. These results indicated that the Au/CS/GO films show potential for the detection of heavy metal pollution in environmental applications
Placement and orientation of individual DNA shapes on lithographically patterned surfaces
Artificial DNA nanostructures show promise for the organization of functional materials to create nanoelectronic or nano-optical devices. DNA origami, in which a long single strand of DNA is folded into a shape using shorter 'staple strands', can display 6-nm-resolution patterns of binding sites, in principle allowing complex arrangements of carbon nanotubes, silicon nanowires, or quantum dots. However, DNA origami are synthesized in solution and uncontrolled deposition results in random arrangements; this makes it difficult to measure the properties of attached nanodevices or to integrate them with conventionally fabricated microcircuitry. Here we describe the use of electron-beam lithography and dry oxidative etching to create DNA origami-shaped binding sites on technologically useful materials, such as SiO_2 and diamond-like carbon. In buffer with ~ 100 mM MgCl_2, DNA origami bind with high selectivity and good orientation: 70–95% of sites have individual origami aligned with an angular dispersion (±1 s.d.) as low as ±10° (on diamond-like carbon) or ±20° (on SiO_2)
Delineation of Stage Specific Expression of Plasmodium falciparum EBA-175 by Biologically Functional Region II Monoclonal Antibodies
EBA-175 binds its receptor sialic acids on glycophorin A when invading erythrocytes. The receptor-binding region (RII) contains two cysteine-rich domains with similar cysteine motifs (F1 and F2). Functional relationships between F1 and F2 domains and characterization of EBA-175 were studied using specific monoclonal antibodies (mAbs) against these domains..The role of the F1 and F2 domains in erythrocyte invasion and binding was elucidated with mAbs. These mAbs interfere with native EBA-175 binding to erythrocyte in a synergistic fashion. The stage specific expression of EBA-175 showed that the primary focus of activity was the merozoite stage. A recombinant RII protein vaccine consisting of both F1 and F2 domains that could induce synergistic activity should be optimal for induction of antibody responses that interfere with merozoite invasion of erythrocytes
Simple and clear evidence for positive feedback limitation by bipolar behavior during scanning electrochemical microscopy of unbiased conductors
On the basis of an experimentally validated simple theoretical
model, it is demonstrated unambiguously that when an unbiased
conductor is probed by a scanning electrochemical tip (scanning electrochemical
microscopy, SECM), it performs as a bipolar electrode. Though
already envisioned in most recent SECM theories, this phenomenon is
generally overlooked in SECM experimental investigations. However, as is
shown here, this may alter significantly positive feedback measurements
when the probed conductor is not much larger than the ti
Label-Free Detection of Tobramycin in Serum by Transmission-Localized Surface Plasmon Resonance
Preparation and characterization of thin organosilicon films deposited on SPR chip
International audienceThe paper reports on the preparation and characterization of organosilicon thin polymer films deposited on glass slides coated with 5 nm adhesion layer of titanium and 50 nm of gold. The polymer was obtained by the decomposition of 1,1,3,3-tetramethyldisiloxane precursor (TMDSO) premixed with oxygen induced in a N2 plasma afterglow using remote plasma-enhanced chemical vapor deposition (PECVD) technique. The film thickness was controlled by laser interferometry and was 9 nm. The chemical stability of the gold substrate coated with the organosilicon polymer film (p-TMDSO) was studied in different acidic and basic solutions (pH 1–14). While the gold/polymer interface showed a high stability in acidic media, the film was almost completely removed in basic solutions. The resulting surfaces were characterized using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), water contact angle measurements, cyclic voltammetry, and surface plasmon resonance (SPR)
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