Oxide Beads Research Articles

One-Pot Preparation and Uranyl Adsorption Properties of Hierarchically Porous Zirconium Titanium Oxide Beads using Phase Separation Processes to Vary Macropore Morphology

A simple and engineering friendly one-step process has been used to prepare zirconium titanium mixed oxide beads with porosity on multiple length scales. In this facile synthesis, the bead diameter and the macroporosity can be conveniently controlled through minor alterations in the synthesis conditions. The precursor solution consisted of poly(acrylonitrile) dissolved in dimethyl sulfoxide to which was added block copolymer Pluronic F127 and metal alkoxides. The millimeter-sized spheres were fabricated with differing macropore dimensions and morphology through dropwise addition of the precursor solution into a gelation bath consisting of water (H(2)O beads) or liquid nitrogen (LN(2) beads). The inorganic beads obtained after calcination (550 °C in air) had surface areas of 140 and 128 m(2) g(-1), respectively, and had varied pore architectures. The H(2)O-derived beads had much larger macropores (5.7 μm) and smaller mesopores (6.3 nm) compared with the LN(2)-derived beads (0.8 μm and 24 nm, respectively). Pluronic F127 was an important addition to the precursor solution, as it resulted in increased surface area, pore volume, and compressive yield point. From nonambient XRD analysis, it was concluded that the zirconium and titanium were homogeneously mixed within the oxide. The beads were analyzed for surface accessibility and adsorption rate by monitoring the uptake of uranyl species from solution. The macropore diameter and morphology greatly impacted surface accessibility. Beads with larger macropores reached adsorption equilibrium much faster than the beads with a more tortuous macropore network.

Metal Oxide Nanoparticles Induce Unique Inflammatory Footprints in the Lung: Important Implications for Nanoparticle Testing

BackgroundMetal oxide nanoparticles (NPs) have been widely used in industry, cosmetics, and biomedicine.ObjectivesWe examined hazards of several well-characterized high production volume NPs because of increasing concern about occupational exposure via inhalation.MethodsA panel of well-characterized NPs [cerium oxide (CeO2NP), titanium dioxide (TiO2NP), carbon black (CBNP), silicon dioxide (SiO2NP), nickel oxide (NiONP), zinc oxide (ZnONP), copper oxide (CuONP), and amine-modified polystyrene beads] was instilled into lungs of rats. We evaluated the inflammation potencies of these NPs 24 hr and 4 weeks postinstillation. For NPs that caused significant inflammation at 24 hr, we then investigated the characteristics of the inflammation. All exposures were carried out at equal-surface-area doses.ResultsOnly CeO2NP, NiONP, ZnONP, and CuONP were inflammogenic to the lungs of rats at the high doses used. Strikingly, each of these induced a unique inflammatory footprint both acutely (24 hr) and chronically (4 weeks). Acutely, patterns of neutrophil and eosinophil infiltrates differed after CeO2NP, NiONP, ZnONP, and CuONP treatment. Chronic inflammatory responses also differed after 4 weeks, with neutrophilic, neutrophilic/lymphocytic, eosinophilic/fibrotic/granulomatous, and fibrotic/granulomatous inflammation being caused respectively by CeO2NP, NiONP, ZnONP, and CuONP.ConclusionDifferent types of inflammation imply different hazards in terms of pathology, risks, and risk severity. In vitro testing could not have differentiated these complex hazard outcomes, and this has important implications for the global strategy for NP hazard assessment. Our results demonstrate that NPs cannot be viewed as a single hazard entity and that risk assessment should be performed separately and with caution for different NPs.

Cyclosporine a-nanosuspension: formulation, characterization and in vivo comparison with a marketed formulation.

Cyclosporine A-nanosuspensions were prepared using zirconium oxide beads as a milling media, Poloxamer 407 as a stabilizer and distilled water as an aqueous medium using the Pearl Milling technique. The optimized formulation was characterized in terms of particle size distribution, surface morphology, drug-surfactant interaction, drug content, saturation solubility, osmolarity, and stability. The nanoparticles consisting of Poloxamer-bound cyclosporin A with a mean diameter of 213 nm revealed a spherical shape and 5.69 fold increased saturation solubility as compared to the parent drug. The formulation was found to be iso-osmolar with blood and stable up to 3 months at 2–8°C. In-vivo studies were carried out in albino rats and the pharmacokinetic parameters were compared with a marketed formulation, which indicated better results of the prepared formulation than the marketed one.

Study of the process of stirred ball milling of poorly water soluble organic products using factorial design

Abstract The objective of this work was to investigate the mechanism of very fine grinding in a wet ball mill as a function of process parameters, i.e. rotation speed of the mill and grinding medium bead size. The ball mill used was a Dynomill and the grinding medium consisted of zirconium oxide beads. The product is a poorly water-soluble organic compound. Laser diffraction was used to analyze the particle size distribution. During grinding the average particle diameter of the product was reduced to a minimum size, which was constant within the range of tested operating conditions. The grinding parameters were studied to control the grinding process with respect to the required grinding time for reaching the minimum particle size and wear of the set-up. The grinding time was strongly dependent on the grinding medium bead size and on the rotation speed. The grinding process became faster when the rotation speed increased and the grinding medium bead size decreased. The wear of the set-up, and therefore the contamination of the final product with heavy metals, strongly increased with the rotation speed. A similar trend was observed with an increase of grinding medium bead size. The degradation rate of the product was not significant in the range of grinding parameters studied.

Filtration and loading characteristics of granular bed filters

The purpose of this study was to investigate the filtration and loading characteristics of granular bed filters. Stainless steel holders (diameter 71.6 mm, height 70 mm) were fabricated to accommodate 500 g of zirconium oxide (ZrO 2) beads, as the packed media of granular bed. Monodisperse ZrO 2 granules (0.3, 0.8, 2 and 4 mm in diameter) were used to demonstrate the effect of the granule size and packing geometry on both pressure drop and aerosol penetration. From the filter quality perspective, the selection of the ‘best” filter is complicated. Assuming a low face velocity (e.g., 0.58 cm/s), large granule size is more cost-effective because of the higher filter quality factor. The phenomenon implies that the gain in filtration efficiency due to larger surface area (of small granules in the filter) did not compensate for the increase in air resistance. After the cake formation point, the dust cake on glass fiber filter became compressed. This dust cake compaction caused the pressure to drop precipitously and intermittently. In contrast, the rate of increase in pressure drop of the dust cake formed on the granular bed filters decreased with time probably due to the pinhole channels in the increasing mass load. The size and density of the pinholes are determined by the granule size, the face velocity and the size of the challenge aerosols.

Mesoporous Zirconium Titanium Oxides. Part 3. Synthesis and Adsorption Properties of Unfunctionalized and Phosphonate-Functionalized Hierarchical Polyacrylonitrile-F-127-Templated Beads

A method is presented for the preparation of zirconium titanate mixed oxides in bead form having hierarchical pore structure. This method entailed the use of both preformed polyacrylonitrile (PAN) polymer beads and surfactants as templates. The templates were removed by calcination at temperatures below about 500 degrees C, resulting in mixed oxide beads with trimodal pore size distributions and interconnected pores. The pore size distributions as determined using nitrogen adsorption-desorption showed clear maxima at 4.5 and 45 nm length scales and also clear evidence of microporosity. The macroporous framework morphology was a replica of the PAN beads with radial structure. The mesoporous framework possessed wormhole-like pores with pore size of about 6 nm that was consistent with the F-127 triblock copolymer template used. The mixed oxide beads exhibited surface areas of 215 and 185 m2/g after calcination at 500 and 600 degrees C. Thermal stability up to 650 degrees C is unprecedented for bulk systems. The adsorption properties were characterized using uranyl as the target cation and the mass transport in the beads with the present hierarchical architectures has been shown to be exceptional. The beads were functionalized with 4-amino,1-hydroxy,1,1-bis-phosphonic acid (HABDP) and amino-tris-methylene phosphonic acid (ATMP) and the adsorption properties for the extraction of uranyl sulfate complexes from acidic solution examined. Of the two molecules investigated, ATMP functionalization resulted in the best extraction efficiency with equilibrium uptake of about 90% of uranium available in solution between pH 1 and 2. The beads could potentially be utilized as catalysts, catalyst supports, adsorbents, and separation materials.

Identification of the grinding mechanisms and their origin in a stirred ball mill using population balances

The objective of this work was to understand the origin of the stresses and the nature of the grinding mechanisms in a high-shear ball mill. The ball mill used was a Dynomill and the grinding media consisted of zirconium oxide beads. The ground powder was a poorly water soluble product. The particle size distribution was analyzed with laser diffraction. A population balance model enabled to calculate the breakage function from the experimental data. The breaking parameters were used to determine the grinding mechanism at different grinding conditions. The grinding mechanism depends on the orientation and intensity of the forces applied on the particles. The grinding mechanisms were determined from the grinding experiments and correlated to the movement of the grinding media in the grinding chamber and the applied mechanical stresses. The observed grinding mechanisms are cleavage and some fracture for coarse particles ( 15 μ m ) , cleavage and abrasion for intermediate particles ( 0.8 μ m ) and cleavage for fine particles (smaller than 0.15 μ m ). The grinding mechanisms are related to the movement of the grinding media in the grinding chamber. Cleavage and abrasion of particles are the result of compression forces and shear in the centrifuged packed bed of grinding beads. The grinding mechanism does not change when changing the operating conditions and the packed bed of media is similar in the studied ranges of operating conditions.

Quantitative determination of predictive cancer biomarkers in formalin-fixed, paraffin-embedded tissue using a new, fully automated method for RNA isolation

11032 Background: Personalized cancer therapy depends on the evaluation of tissue-based biomarkers in routine tumor samples. As many new biomarkers are measured on the mRNA level, standardized procedures for mRNA analysis in formalin-fixed, paraffin-embedded (FFPE) tissue are needed. In this study, we present a novel, standardized, and fully automated method for fast isolation of total RNA from FFPE tissue sections. Methods: Tissue samples (n = 501) from 167 breast carcinomas which had been stored between 2 months and 21 years were investigated. Total RNA was extracted from tissue sections using a new method based on silica-coated iron oxide beads in combination with a specific liquid-handling robot. Novel and unique features of the method are an automated extraction-integrated deparaffinization step and a bead-based negative selection step to eliminate any undigested tissue. Yield of RNA was assessed using the Ribogreen assay. mRNA fragment lengths were estimated by reverse transcription PCR (RT-PCR) for G6PDH. Expression of the breast cancer biomarkers ESR1, PGR and HER2 was measured by kinetic RT-PCR (kPCR) and compared with immunohistochemistry (IHC). Results: RNA was successfully isolated from all samples, with a mean yield of 1.4 μg/sample (range: 0.1–7.8 μg) and fragment lengths of at least 150 bp in 99% of samples. PCR analyses could be performed in all samples. Investigating three sections of each tumor, we observed a low section-to-section variability of kPCR results (root of mean squared errors of relative ESR1, PGR or HER2 expression in three sections: 0.2–0.5 Ct values). Comparing kPCR results with IHC, we detected a good concordance between both methods, with agreements of 98.4% (standard error [SE]: 2.7%) for ESR1, 84.4% (SE: 5.3%) for PGR and 89.9% (SE: 8.9%) for HER2. Conclusions: This novel RNA extraction method is a major technical improvement for implementation of reproducible, high-throughput and cost-efficient testing of cancer biomarkers in the clinical routine and in gene-expression research studies using archived FFPE material in molecular labs. [Table: see text]

In this issue: Proteomics 2/2008

AbstractIn this issue of Proteomics you will find the following highlighted articles:Particular particles pick out phosphopeptides promptlyPhosphorylation/dephosphorylation is the most commonly used post‐translational signal in eukaryotic organisms. With a single site it might turn a pathway on or off, up or down; multiple site series can incrementally change the level of expression, effects can be direct or indirectly induced. Needless to say, phosphoproteins are extremely important subjects of study. Li et al. have developed a method for rapid collection and analysis of phosphopeptides: gallium oxide‐coated magnetic beads. Effective at very low phosphopeptide concentrations, a MALDI sample can be bound to the beads in 30 seconds. After a few washes, a small amount of the bead slurry is spotted on a MALDI plate, 2,5‐dihydroxybenzoic acid spotted as matrix, then, “Fire away!” The gallium oxide beads dramatically out perform silica‐Fe beads, Fe+3‐IMAC resin, and TiO2 beads.Li, Y. et al., Proteomics 2008, 8, 238–249.Plasma butyrylcholinesterase: multiple N‐glycan sites support multiple rolesCholinesterases have been of interest since their discovery in the early 1930’s. Acetylcholinesterase is the target of insecticides and nerve gases. Butyrylcholinesterase (BChE) plays a variety of roles because of its “relaxed” substrate requirements, able to detoxify heroin and aspirin as well as choline‐containing molecules. Of particular interest is its function as a scavenger of organophosphates to protect nerve‐associated acetylcholinesterase. Kolarich et al. explored the complexities of glycosylation of BChE, with 9 of 10 potential N‐glycosylation sites occupied in the 85 kDa protein. Of the variety of techniques applied to elucidating the glycan structures at particular sites, perhaps the most informative was porous graphitic carbon LC/MS. It yielded more information in 80 minutes than an overnight “classical” procedure. No evidence of O‐glycosylation or other post‐translational modifications were seen.Kolarich, D. et al., Proteomics 2008, 8, 254–263.DIGE digs up skeletal muscle fateThe gradual loss of strength and muscle mass is a normal event in aging, measurable by published statistics for professional athletes, or by how long we take to push away from the table. Sarcopenia is the drastic form of muscle loss, resulting in severe impairment. Doran et al. selected the rat model of muscle mass loss between 3 months (young adult) and 30 months (old) to study, avoiding confounding human variables. Applying DIGE/MALDI‐TOF to gastrocnemius samples, they found 2493 spots, of which 69 exhibited dramatic up‐ or down‐regulation. The functional changes suggested by the quantitative changes included increased dependence on aerobic oxidative metabolism and fibre remodeling, probably due to impaired fibre repair. These findings were confirmed by Western blots and fluorescent confocal microscopy and concur with other published studies.Doran, P. et al., Proteomics 2008, 8, 364–377.

Cross-linking of chitosan and chitosan/poly(ethylene oxide) beads: A theoretical treatment

The major aim of this study was to get deeper insight into the process of polymer cross-linking and the resulting structure of beads based on chitosan (CS) or chitosan/poly(ethylene oxide) (CS/PEO) semi-interpenetrating networks (semi-IPNs) as new carrier materials for oral drug delivery. Spherical hydrogels were prepared by a dropping method. The uptake kinetics of the cross-linking agent glyoxal into the beads were monitored and quantitatively described using Fick’s second law of diffusion. High-resolution synchrotron infrared microspectroscopy (SIRM) was used to characterize the inner structures of the beads. Importantly, the diffusion of glyoxal through the hydrogels was found to be much slower than the cross-linking reaction and the mesh size of the created networks to be much larger than the hydrodynamic diameter of glyoxal. The presence of PEO chains slightly decreased the diffusivity of glyoxal due to obstruction effects. However, the cross-linking reaction was not affected. Interestingly, the polymers were homogeneously cross-linked throughout the beads, except for a thin outer shell showing an elevated cross-linking density. Thus, the obtained cross-linked hydrogel-based beads exhibit well-defined polymeric structures and offer an interesting potential as novel oral drug delivery systems.

Quantification of the expression level of integrin receptor αvβ3 in cell lines and MR imaging with antibody‐coated iron oxide particles

Targeted imaging requires site-specific accumulation of a contrast agent (CA), and the properties of that agent must be selected according to the abundance of the target to obtain a signal above the detection limit of the instrument. However, numerical estimates of receptors per cell are rarely found in the literature. Integrin receptors would be particularly promising targets because of their accessibility from the blood stream and expression on activated neovascular endothelial cells. We systematically estimated the number of integrin receptors of cell lines and primary cells by flow cytometry analysis. Since integrin receptors are heterodimeric molecules, and alpha(v) forms complexes with various beta subunits, the numbers of alpha(v) and beta(3) subunits are therefore dissimilar. The observed values are 3 . 10(3)-1.4 . 10(4)/cell for alpha(v), and 5.3 . 10(2)-1.1 . 10(4)/cell for beta(3). Despite the low number of exposed receptors, we show that up to single-cell MR visualization can be achieved with the use of iron oxide beads complexed with antibodies as CAs.

Controlled release of DNA/polyamine complex by photoirradiation of a solid phase presenting o-nitrobenzyl ether tethered spermine or polyethyleneimine

Various gene transfer and automated/monitorized analytical applications require the controlled release of nucleic acid. A solid phase with spermine or polyethyleneimines (PEI, 600 MW) tethered by o-nitrobenzyl linkages was synthesized with polyethylene oxide beads (Argo Gel-NH 2). The photolysis of test compound O-2-nitrophenethyl O, O-diethyl phosphate or solid phase with o-nitrobenzyl group as synthetic linker was completely degradable with photoirradiation at 365 nm for 10–18 min at 3.5 mW/cm 2. DNA binding with polyamine of the solid phase and releasing of DNA/polyamine were monitored by UV measurement and gel electrophoresis. The potential exists to employ a DNA-loaded solid phase for spatially, temporally, or dose-controlled release of DNA, at extracellular or intracellular sites.

Cytoskeleton changes of cultured human retinal pigment epithelial cells in a mechanical stress model

To observe changes of the cytoskeleton of cultured human retinal pigment epithelium (hRPE) cells in a mechanical stress model in vitro. Ferric oxide beads, coated with collagen, were added to dishes containing substrate-attached hRPE cells. After incubation, the cells were washed to remove unbound beads. The cells were pretreated by actin polymerization inhibitor cytochalasin D (0.05 mmol/L, 25 min). Before and 4, 8, 12 and 24 h after vertical magnetic force application the cells were stained for actin and vimentin using immunity fluorescence double labelled technique and analyzed with confocal microscopy. Four hours after force application, the polarity of hRPE cells was changed, and actin was polymerized into filaments in array of them along with the direction of the force. Cytoskeleton filaments were located mainly around the nucleus and the ferric oxide beads. Pretreatment with cytochalasin D, the same changes as described above occurred 8 h after magnetic force application. Mechanical force could induce changes of distribution of cytoskeleton in hRPE cells, which are some biological characteristics of muscle cells, and this may facilitate the cellular migration and proliferation.

Injectable biomaterials for incontinence and vesico‐ureteral reflux: Current status and future promise

Many injectable biomaterials have been produced as bulking agents for compression of urethral sphincter or ureteral orifice for treating adult stress incontinence or vesico-ureteral reflux in pediatrics. The agents being developed include glutaraldehyde crosslinked collagen, dextranomer/hyaluronic acid copolymer, pyrolytic carbon-coated zirconium oxide beads, polydimethyl-siloxane microparticles, polytetrafluoroethylene paste, autologous fats, autologous chondrocytes, and others. Though less invasive nature of these agents has gained their popularity as a quick solution of the disease symptoms, most of such treatments fail to produce good long-term efficacy. The failure is likely caused by the rapid degradation of material implants and the lack of tissue regeneration/integration properties. We thus believe that a good injectable biomaterial for incontinence should possess the following two properties: (1) to resist degradation and to reside in the implantation sites for a long period of time or (2) to enhance tissue regeneration and to establish permanent periurethral or subureteric tissue. Here we report some recent results for supporting this hypothesis.

Effects of mechanical stress on expressions of monocyte chemoattractant protein-1 and interleukin-8 of cultured human retinal pigment epithelial cells

To investigate the expressions of monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8) of cultured human retinal pigment epithelial (hRPE) cells under mechanical stress in vitro, so as to mimic and understand the role of these 2 inflammatory cytokines in the early stage of development of primary retinal detachment. Ferric oxide beads coated with collagen were added to the culture plate containing wall-attaching hRPE cells and then the cells were incubated and washed to remove the unbound beads. A magnet was put to the culture plate to provide vertical magnetic force. Cytochalasin D (CD) was added to the culture fluid to inhibit the phagocytizing, secreting, and moving functions of the hRPE. Before the experiment and 15 min, 0.5 h, 1 h, 4 h, and 8 h the beginning of experiment, the MCP-1 mRNA and IL-8 mRNA in the hRPE cells were measured with reverse transcriptase polymerse chain reaction (RT-PCR), and the MCP-1 and IL-8 protein expression in the supernatants was tested with enzyme-linked immunosorbent assay (ELISA) kits. MCP-1 and IL-8 mRNA were expressed at very low levels in the RPE cells and supernatant not exposed to magnetic force. After exposure to magnetic force, both MCP-1 and IL-8 mRNA demonstrated "double peaks" expression. Their first peak levels appeared within 0.5 h, being 3.30 ng/L +/- 0.12 ng/L and 1.88 ng/L +/- 0.08 ng/L respectively. The first peaks of MCP-1 and IL-8 protein expression were within 1 h, being 552.05 ng/L +/- 7.64 ng/Land 236.67 ng/L +/- 14.30 ng/L respectively, and the second peaks appeared about 4 hours later. After cytochalasin D pretreated, the expression and secretion of both MCP-1 and IL-8 of the hRPE cells were significantly decreased to the levels of 2.36 ng/L +/- 0.27 ng/L and 1.64 ng/L +/- 0.08 ng/L, and 353.80 ng/L +/- 16.68 ng/L and 101.86 ng/L +/- 15.92 ng/L respectively. Mechanical stress induces the RPE cells to express MCP-1 and IL-8, and this effect was inhibited in part by pretreatment of CD, indicating that the cytoskeleton may be involved in the effect and that these two inflammatory cytokines take a part in the early stage of development of primary retinal detachment.

Synthesis of Hierarchically Porous Silica and Metal Oxide Beads Using Emulsion-Templated Polymer Scaffolds

Uniform, hierarchically porous inorganic beads (SiO2, Al2O3, TiO2, and ZrO2) have been produced using emulsion-templated polymer beads as templates. The polymer scaffolds were prepared by oil-in-water-in-oil (O/W/O) sedimentation polymerization (Zhang, H.; Cooper, A. I. Chem. Mater. 2002, 14, 4017). The inorganic beads were prepared by simply immersing the polymer scaffold beads in a range of inorganic precursor solutions, followed by sol−gel condensation in air and subsequent calcination of the polymer phase. The hierarchical structures are composed of mesopores (diameters 2−5 nm), micropores (in the case of silica beads), and large emulsion-templated macropores of around 5−10 μm. All of the pores are highly interconnected. The inorganic beads exhibit high macropore volumes as characterized by mercury intrusion porosimetry. Polymer−silica composite beads with micropores and high macropore volumes were also produced. These large inorganic beads (diameters 1.0−1.5 mm) are easily handled and separated and m...

Cadmium Ion Adsorption on Carboxyl-Terminated Iron Oxide Beads

The affinity of Cd2+ toward carboxyl-terminated iron oxide beads (C-TIOB, Sigma) suspended in aqueous solutions was investigated using anodic stripping voltammetry (ASV) as a function of both pH and [Cd2+] in the μM range. Advantage was taken of the superparamagnetic character of C-TIOB to confine and/or remove the beads within the enclosed vessel, using an external magnet, and thus assess the influence of dispersed C-TIOB on the amount of Cd2+ detected by ASV. Within experimental error, the difference between ASV data recorded before and after adding and then confining the particles by magnetic means, which provides a measure of the amount of Cd2+ adsorbed on C-TIOB, was found to yield results comparable to those of identical measurements with fully dispersed C-TIOB. Adsorption data collected as a function of [Cd2+] and pH revealed a marked increase in the binding constant of Cd2+ for carboxylate ions upon attachment to the solid support, over values predicted strictly from standard solution phase equili...

WGA-coated yttrium oxide beads enable an imaging-based adenosine 2a receptor binding scintillation proximity assay suitable for high throughput screening.

Adenosine receptors belong to the superfamily of G protein-coupled receptors and are involved in a variety of physiologic functions. Traditionally, binding assays to detect adenosine 2a (A2a) antagonists and agonists have used filtration methods that are cumbersome to run and not amenable to HTS. We developed scintillation proximity assays (SPA trade mark ) utilizing HEK293 RBHA2AM cell membranes, either wheat germ agglutinin (WGA)-coated yttrium silicate (YSi) or red-shifted yttrium oxide (YO) beads and the A2a-selective radioligand [(3)H]SCH 58261. Both beads gave windows (total binding/nonspecific binding) of >5 and K(d) values of 2-3 nM for the radioligand, in agreement with results obtained by filtration. In contrast, WGA-polyvinyltoluene as well as other bead types had windows of <3 and significant radioligand binding to the uncoated beads. A 384-well WGA-YO bead SPA was optimized utilizing a LEADseeker imaging system and an automated trituration process for dispensing the dense yttrium-based beads. Signals were stable after 4 h, and Z' values were 0.7-0.8. The LEADseeker imaging assay tolerated 2% dimethyl sulfoxide and generated IC(50) values of 3-5 nM for the A2a antagonist CGS 15943, comparable to that obtained by the filtration method. A number of adenosine and xanthine analogues were identified as hits in the Library of Pharmacologically Active Compounds (LOPAC). This imaging-based A2a SPA enables HTS and is a major improvement over the filtration method.

微小径ビーズを用いた湿式ビーズミル処理によるナノシリカ粒子の分散性検討

Wet dispersion mechanism of manometer-sized silica powder was investigated in a verticaltype beads mill using fine zirconium oxide (zirconia) beads. Zirconia beads of various sizes were used to disperse coagulated silica powders in nanometer size. The dispersed particles were measured by TEM and a dynamic light scattering technique and the contamination during the dispersion was also evaluated. Fine beads with the average diameters of 20μm and 50μm were found to be very effective for suppressing contamination from the beads as well as for achieving its homodispersity. 300μm-zirconia beads used in the present work had a very rough surface, which resulted in the silica powder contamination with zirconia in the level of 3250ppm. On the contrary, the surface of 20μm-beads was smooth and zirconia-contamination in the silica powder was decreased to 240ppm. The observation of bead surface and the amount of zirconia (impurity) suggested that the surface of large bead is easily worn away due to the collisions between the beads compared to smaller beads. The coagulated silica powder can be dispersed homogeneously using the beads with size smaller than 50μm, whereas coagulated silica particles were observed using the beads with size larger than 100μm. For coagulates of nanoparticles, main dispersion mechanism with large beads is pulverization while that with small beads is deflocculation. It is important not to give excessive energy to the coagulated particles for preventing the recoagulation and the contamination from the beads. Smaller beads (below 100μm) is suitable in this case.

Peptide nucleic acid modified magnetic beads for intercalator based electrochemical detection of DNA hybridization

The specific binding of peptide nucleic acid (PNA) to its complementary DNA target is combined with magnetic separation to enable discrimination against single nucleotide polymorphisms (SNP). PNA probes with biotin label at 5'-end were attached to strepavidin coated superparamagnetic iron oxide beads. PNA modified beads were then challenged with non-complementary, SNP containing and perfect-match DNA targets. PNA probe showed no affinity towards non-complementary DNA. The non-specific binding of SNP containing DNA target was suppressed by the washing step of the beads by using sodium dodecylsulfate in blank buffer solution. Then, an electro-active intercalator, 7-dimethyl-amino-1,2-benzophenoxazinium salt (Meldola’s blue, MDB) was introduced to the beads. MDB intercalated between the double-helix of the hybrid molecules on the beads. After removing the excessive MDB, the beads were collected from the solution by immersing a biotin modified carbon paste electrode into the solution. Specific hybridization between PNA probe and DNA target was determined by monitoring the voltammetric peak of MDB. Numerous factors affecting the MDB signal, such as target DNA concentration, intercalator concentration and accumulation time were investigated. MDB signal indicated a detection limit of 2 pM in connection with 20 min hybridization time.