Surface modified hexagonal upconversion nanoparticles for the development of competitive assay for biodetection.

Up-conversion nanoparticles (UCNPs) of sodium yttrium fluoride with ytterbium and erbium ions as sensitizer and activator (β-NaYF/Yb/Er) have been synthesised by a solvothermal method. The synthesised particles were found to be highly uniform in size (~50 nm) and of hexagonal crystal phase producing strong up-conversion luminescence dominated in the green wavelength region. During the synthesis, photoluminescence properties of the reaction mixture were monitored at regular intervals to ensure the required particle size distribution and luminescence efficiency.

Barium yttrium fluoride based upconversion nanoparticles as dual mode image contrast agents.

Dual labeled contrast agents could provide better complementary information for bioimaging than available solely from a single modality. In this paper we investigate the suitability of Yb and Er-doped BaYF upconversion nanoparticles (UCNPs) as both optical and X-ray micro computed tomography (μCT) contrast agents. Stable, aqueous UCNP dispersions were synthesised using a hydrothermal method with the addition of polyethyleneimine (PEI).

Selective cellular imaging with lanthanide-based upconversion nanoparticles.

Upconversion nanoparticles (UCNPs) with sodium yttrium fluoride, NaYF (host lattice) doped with Yb (sensitizer) and Er (activator) were synthesized via hydrothermal route incorporating polyethyleneimine (PEI) for their long-term stability in water. The cationic PEI-modified UCNPs with diameter 20 ± 4 nm showed a zeta potential value of +36.5 mV and showed an intense, visible red luminescence and low-intensity green emission with 976 nm laser excitation.

Redox-Dependent Modulation of T-Type Ca(2+) Channels in Sensory Neurons Contributes to Acute Anti-Nociceptive Effect of Substance P.

Aims: Neuropeptide substance P (SP) is produced and released by a subset of peripheral sensory neurons that respond to tissue damage (nociceptors). SP exerts excitatory effects in the central nervous system, but peripheral SP actions are still poorly understood; therefore, here, we aimed at investigating these peripheral mechanisms.

Results: SP acutely inhibited T-type voltage-gated Ca(2+) channels in nociceptors.

The chronic toxicity of CuO nanoparticles and copper salt to Daphnia magna.

In this study, the effects of CuO nanoparticles and CuCl2·2H2O were tested on Daphnia magna under chronic exposure scenarios. During a 21-day exposure to the nanoparticles and salt, the reproduction was followed by a daily count of the number of offspring. After the exposure, the adult Daphnia length and uptake of copper was measured.

Direct characterization of fluid lipid assemblies on mercury in electric fields.

Phospholipid monolayers on mercury (Hg) surfaces have received substantial and extensive scientific interest not only because of their use as a biomembrane model but also for their application as a successful toxicity-sensing element. The monolayers show characteristic and very reproducible phase transitions manifest as consecutive voltammetric peaks in response to applied transverse electric fields. Unfortunately, apart from the results of simulation studies, there is a lack of data on the lipid phase structures to help interpret these voltammetric peaks.

Electrochemical modelling of QD-phospholipid interactions.

Hypothesis: The aggregation of quantum dots (QDs) and capping of individual QDs affects their activity towards biomembrane models.

Experiments: Electrochemical methods using a phospholipid layer on mercury (Hg) membrane model have been used to determine the phospholipid monolayer activity of thioglycollic acid (TGA) coated quantum dots (QDs) as an indicator of biomembrane activity. The particles were characterised for size and charge.

Electrochemical screening of biomembrane-active compounds in water.

Interactions of biomembrane-active compounds with phospholipid monolayers on microfabricated Pt/Hg electrodes in an on-line high throughput flow system are demonstrated by recording capacitance current peak changes as rapid cyclic voltammograms (RCV). Detection limits of the compounds' effects on the layer have been estimated from the data. Compounds studied include steroids, polycyclic aromatic hydrocarbons, tricyclic antidepressants and tricyclic phenothiazines.

The chronic toxicity of ZnO nanoparticles and ZnCl2 to Daphnia magna and the use of different methods to assess nanoparticle aggregation and dissolution.

In this study, the effect of ZnO nanoparticles and ZnCl2 on growth, reproduction and accumulation of zinc in Daphnia magna was determined in a 21-day chronic toxicity test. A variety of techniques were used to distinguish the free zinc ion, dissolved, nanoparticle and aggregated zinc fraction in the Daphnia test medium. The results showed similar chronic effects on growth, reproduction and accumulation for the ZnO nanoparticles (EC10, 20, 50 reproduction: 0.

Interaction of imidazolium-based room-temperature ionic liquids with DOPC phospholipid monolayers: electrochemical study.

To test the biocompatible character of room-temperature ionic liquids (ILs), the interaction of various ILs with biological membrane (biomembrane) models was studied in this work. Dioleoyl phosphatidylcholine (DOPC) adsorbed on a mercury (Hg) electrode forms an impermeable defect-free monolayer which is a well established biomembrane model, prone to be studied by electrochemical techniques. We have monitored the modifications of the Hg supported monolayer caused by ILs using rapid cyclic voltammetry (RCV), alternating current voltammetry (ACV), and electrochemical impedance spectroscopy (EIS).

Interaction of poly(N-isopropylacrylamide) (pNIPAM) based nanoparticles and their linear polymer precursor with phospholipid membrane models.

Poly(N-isopropylacrylamide) (pNIPAM) is a thermoresponsive polymer which has promising applications in nanomedicine for drug delivery. The cross-linking of pNIPAM based copolymer using the chain collapse method leads to the synthesis of pNIPAM based polymer nanoparticles. This study looks at the interaction of pNIPAM polymers and pNIPAM nanoparticles with biomembrane models of, (i) a dioleoyl phosphatidylcholine (DOPC) monolayer on a mercury (Hg) electrode and (ii) DOPC and dimyristoyl phosphatidylcholine (DMPC) vesicles.

Electrochemical modeling of the silica nanoparticle-biomembrane interaction.

The interaction of amorphous colloidal silica (SiO(2)) nanoparticles of well-defined sizes with a dioleoyl phosphatidylcholine (DOPC) monolayer on a mercury (Hg) film electrode has been investigated. It was shown using electrochemical methods and microcalorimetry that particles interact with the monolayer, and the electrochemical data shows that the extent of interaction is inversely proportional to the particle size. Scanning electron microscopy (SEM) images of the electrode-supported monolayers following exposure to the particles shows that the nanoparticles bind to the DOPC monolayer irrespective of their size, forming a particle monolayer on the DOPC surface.

The preparation of size-controlled functionalized polymeric nanoparticles in micelles.

The reverse micellar system of dioctyl-sulfosuccinate (AOT)/octane and toluene have been used as a template for polymerization of acrylamide (AA)/bisacrylamide (BAA)-based functionalized polymeric nanoparticles. Such nanoparticles are typically sized between 20 and 90 nm. They can be synthesized with different functional groups according to the monomers added to the polymerization mixture.

Sonochemically fabricated enzyme microelectrode arrays for the environmental monitoring of pesticides.

This paper describes the development of a novel sonochemically fabricated microelectrode based acetylcholinesterase and polyaniline carbon/cobalt phthalocyanine biosensor for the ultra-sensitive determination of pesticides. Arrays of this type are fabricated using microelectrode templates with population densities of 2 x 10(5) cm(-2). The enzymatic response of the sensors is inhibited upon incubation with the pesticide and in this report it is shown that paraoxon may be determined down to concentrations of 1 x 10(-17) M.