Interaction of activated leukocytes with polymeric microspheres

Three types of polymeric particles with different surface wettabilities, i.e., poly(methylmethacrylate) (PMMA), poly(methylmethacrylate-hydroxyethylmethacrylate) (P(MMA/HEMA)) and poly(methylmethacrylate)/poly(vinyl alcohol) PMMA/PVAL with a diameter of 1.5 microm were produced in this study These particles were incubated with blood samples obtained both from three patients undergoing cardiopulmonary bypass. In the blood samples taken before the bypass operations, there was considerable phagocytosis and/or adhesion of the PMMA particles, i.e., 14+/-4 particles per monocyte and 11+/-3 particles per neutrophil. While there was almost no phagocytosis and/or adhesion of the P(MMA/HEMA) and PMMA/PVAL particles. In the blood samples which were taken during bypass operations, phagocytosis and/or adhesion of PMMA microspheres increased significantly. The P(MMA/HEMA) and/or PMMA/PVAL particles adhered, or were even phagocytosed by the activated leukocytes in this case. Leukocytes activated during the bypass operations gradually returned to normal in about 24 h.     

Antioxidation Study of Sm（Co, Cu, Fe, Zr）z-Sintered Permanent Magnets by Metal Injection Molding

2∶17type Sm(Co ,Cu ,Fe ,Zr)zpermanent mag-nets originatedfromthe investigationinthe 1970s .Sm(Co ,Cu ,Fe ,Zr)zpermanent magnets have excellentintrinsic magnetic properties such as very high Curietemperature , high anisotropy fields , and relativelyhigh saturation magnetizations[1 ~4]. Hence the mag-nets play an i mportant role in national defence andmodernindustry .Because of the high brittleness of Sm(Co ,Cu ,Fe ,Zr)zpermanent magnets ,theirtransfor-mationinto complex,small ,precision …     

Effect of silane coupling agents on flowability and compressibility of compound for bonded NdFeB magnet

Based on the difference of the Y-terminal functional group of the silane coupling agent (Y–Si(X)₃), four different silane coupling agents were employed to pretreat the surface of the NdFeB powders. The effects of silane coupling agents on the flowability and compressibility of compounds for preparing bonded NdFeB magnets were studied. It is indicated that compounds pretreated by silane coupling agents have weaker friction and meshing force. The apparent density is increased by 0.3 g/cm³ compared with the compound without silane coupling agent, and the radial crushing strength is significantly increased by about 3–4 times. In addition, the epoxy resin is more evenly distributed on the surface of the compounds treated by silane coupling agents observed by scanning electron microscopy, and some agglomerated particles are produced. Also, the compressibility of compounds with silane coupling agents is significantly improved due to the fact that hardening exponents are reduced. However, the addition of silane coupling agents has almost no effect on the magnetic properties of bonded magnets. The special energy was used to manifest the flowability of magnetic powder particles representing the macroscopic performance of the force between powder particles, providing a new direction for the study of the interface compatibility of two-phase or multiphase composite materials.     

Protein A carrying monosize PMMA microbeads for the removal of HIgG from human plasma

Protein A-incorporated polymethylmethacrylate (PMMA) microbeads were investigated for specific removal of HIgG from human plasma. The microbeads were prepared by a phase inversion polymerization, and activated by periodate oxidation. Protein A was then incorporated by covalent binding onto these microbeads through hydroxyl groups coming from the stabilizer. The amount of incorporated protein A was controlled by the initial concentrations of protein A in the immobilization medium and pH. The maximum protein A immobilization of 0.615 mg protein A/g PMMA, was observed at a pH of 9.5 corresponding to an initial protein A concentration of 0.1 mg/ml. There was no HIgG adsorption onto the plain PMMA microbeads, while high HIgG adsorptions of up to 32 mg HIgG/g PMMA were achieved with human plasma.     

Structure and Corrosion Resistance of a Composite γ-Amino Propyl Triethoxy Silane and γ-Glycidoxy Propyl Trimethoxy Silane Conversion Coating on Galvanized Steel

 In an aqueous solution of the mixtures of γ-amino propyl triethoxy silane and γ-glycidoxy propyl trimethoxy silane, a composite silane conversion coating was developed on galvanized steel. FESEM (field emission scanning electron microscope), XPS (X-ray photoelectron spectroscopy), ATR-FTIR (attenuated total reflection Flourier transform infrared spectroscopy) and SST (salt spray test) were used to characterize the obtained composite silane conversion coating and also the coating formation process was studied. The result showed that the surface of the composite silane conversion coating was complete, consecutive and compact. The coating could endure a neutral salt spray test for 72 h without corrosion. The result of salt spray test indicated that the composite silane conversion coating can provide a better corrosion inhibition than the coating which was composed of the single silane. Based on observation and analysis, it was proposed that the formation process of the silane coating on zinc should consist of three steps: the hydrolysis of the silane molecules, silane chemical adsorption and silane crosslinking condensation. The crosslinking reactions took place between γ-amino propyl triethoxy and γ-glycidoxy propyl trimethoxy silane during the forming process of the coating, and a high crosslinked density interpenetrating structure network was obtained, so the composite silane conversion coating could keep the corrosive substances from the zinc more effectively.     

Effect of methacrylic acid:methyl methacrylate monomer ratios on polymerization rates and properties of polymethyl methacrylates

Five binary formulations were prepared from methyl methacrylate (MMA) and methacrylic acid (MAA) monomers, and six ternary formulations were prepared from polysols of 30% wt polymethyl methacrylate (PMMA)/MMA and MAA. Using thermal analyses (DSC and TGA) the polymerization kinetics, condition of postcuring, relative amount of residual monomers, and glass transition temperature (Tg) were determined. From bar-shaped samples, 25 x 5 x 0.9 mm in dimensions, mechanical properties [flexural moduli (E) and maximum strengths (sigma)] were measured in three-point bending. Polymerization kinetics of binary formulations improved over pure PMMA (from 15 to 4 min) as a result of over a 60-fold increase in propagation-to-termination constants (Kp/Kt) of MAA/MMA. The further addition of PMMA increased the viscosity, slowed down termination, and, consequently, improved the polymerization kinetics twofold. These enhancements occurred without a substantive change in the Tg of the ternary system (ca. 107 degrees C) over pure PMMA (ca. 112 degrees C). Moreover, the Es of the four ternary formulations averaged 2.94 GPa, which was comparable with many values reported in the literature. In contrast the sigma s of these same formulations averaged 97 MPa, which was about 25% better than earlier investigations of pure acrylic. When a thermoplastic material is required for pultruding profiles that cure fast and have good thermal-mechanical properties, ternaries of PMMA/MMA/MAA should be considered.     

Adherence of staphylococci of different hydrophobicity. Study of various intraocular lenses

BACKGROUND: A major goal in research on intraocular lenses (IOL) is the development of new polymers and modifications to reduce foreign-body reactions after implantation. This effect may be achieved by a reduction in the surface hydrophobicity of the polymers. To illustrate the influence of surface modifications on bacterial adhesiveness, the most often isolated organism in "low-grade" postoperative endophthalmitis, Staphylococcus epidermidis, was used. MATERIALS AND METHODS: For this reason three strains of this species, the type strain ATCC 14990 and two clinical isolates (8687, 6579 I) with different hydrophobic surface properties were studied. IOL, used in the experiments were either made of PMMA or silicone with modified surfaces (unpolished, polished, heparinized). The adhesiveness of H3-thymidin-labeled bacteria was calculated/mm2 of lens surface. Each experiment was performed in triplicate and repeated three times. RESULTS: The hydrophobic-type strain showed stronger adherence to unpolished PMMA surface (8000 bacteria per mm2) compared to the polished (5200 bacteria/mm2). In contrast, the hydrophilic strain adhered with 2000 bacteria/mm2 to the unpolished and with 4200 bacteria/mm2 to the polished surface. Polishing PMMA lenses diminished the differences between the three strains. However, surface passivation of silicone lenses increased the adhesion rate of the hydrophilic strain up to 9600 bacteria/mm2. Treatment of PMMA lenses with heparin increased the adhesiveness of the hydrophilic strain and reduced the adhesion rate of the hydrophobic type strain to 250 bacteria/mm2. CONCLUSIONS: It was demonstrated that bacterial adherence to IOL also involves hydrophobic interactions. Obviously, however, that adherence reflects a complex of interactions between the two surfaces.     

Reinforcement of acrylic resins for provisional fixed restorations. Part II: Changes in mechanical properties as a function of time and physical properties

In Part I, it was found that (i) 2 vol.% admixture of reinforcing elements in PMMA (Jet) resin matrix had a significant beneficial effects on the mechanical properties, and (ii) among these, zirconia exhibited the greatest improvements in modulus of elasticity, transverse strength, toughness, and hardness number. Using the best combination (i.e., PMMA resin matrix and 2 vol.% ZrO2), exothermic temperature raise and polymerization shrinkage were further investigated. Deterioration in mechanical properties due to prolonged water sorption were also studied for 5 weeks. The following can be concluded: (1) By increasing liquid/powder ratio for PMMA control samples, the peak temperature occurrence was retarded by 3 min and raised by 8 degrees C. (2) The effect of admixed oxide particles to PMMA resin matrix or the heat generated during polymerization was not significant. (3) The polymerization volumetric shrinkage was influenced by the a mixture of particles, with increases as large as 0.9% (or 0.3% in linear shrinkage). (4) PMMA resin admixed with 2 vol.% of zirconia particles showed a continuous weight gain due to water sorption, mechanical properties appears to be increasing up to 1-week sorption, followed by rapid drop of all properties. (5) Autopolymerizing acrylic resins are a resin-resin composite material of pre-polymerized beads embedded in a newly formed acrylic matrix. The main fracture modality appears to occur through the matrix and at the interface, although some trans-beads fractures were identified. (6) It was suggested that incorporating certain type of oxide particles into the pre-polymerized beads would provide stronger resin matrix.     

改性多孔钢渣/橡胶复合材料的制备及其性能

用磷酸、硅烷KH550和钢渣制备改性多孔钢渣, 以改性多孔钢渣取代部分炭黑.利用改性多孔钢渣、炭黑、橡胶、促进剂、硫磺、硬脂酸和氧化锌进行复合, 制备一系列改性多孔钢渣/橡胶复合材料, 研究了磷酸/钢渣质量比、硅烷KH550/多孔钢渣质量比、促进剂/硫磺质量比、硬脂酸/氧化锌质量比和改性多孔钢渣/炭黑质量比对改性多孔钢渣/橡胶复合材料力学性能的影响, 并且分析其影响机理.结果表明, 当磷酸用量为1.2 g、钢渣用量为30 g、硅烷KH550用量为0.3 g、炭黑用量为20 g、促进剂用量为0.8 g、硫磺用量为1.2 g、硬脂酸用量为0.8 g、氧化锌用量为2.2 g和橡胶用量为100 g时, 改性多孔钢渣/橡胶复合材料的力学性能较好, 即拉伸强度为18.4 MPa、邵尔A硬度为68.8、撕裂强度为44.6 kN·m-1.磷酸与硅烷KH550可以改善钢渣的孔结构与表面结构; 适量的促进剂/硫磺质量比与硬脂酸/氧化锌质量比可以消除硫磺形成的内硫环, 促使橡胶交联键稳定.改性多孔钢渣与橡胶以物理方式进行复合形成良好的包裹结构.      

Effect of ivermectin treatment on microfilarial load in patients with Onchocerca volvulus in Bebeka, Ethiopia

Improvement of the siloxane layer on minerals by using a bisfunctional silane, such as 1,6-bis(trichlorosilyl) hexane and 1,8 bis(trichlorosilyl)octane, and the effects on adhesion of methacrylic resin to glass plates treated with the silanes were studied. The tensile bond strength of the resin to the glass plate treated with bisfunctional silane alone was high (about 20MPa) in spite of the fact that the molecule contains no double bonds. Furthermore, a mixture of bisfunctional silane and 3-methacryloxypropyltrichlorosilane showed an excellent effect for tensile bond strength and water-resistance. Based on the results, it is suggested that the better water resistant adhesion of the mixed silane depends on the higher degree of crosslinking in the siloxane phase and on the formation of an interpenetrating polymer network between the siloxane layer and the matrix resin.     

Endotoxin rejection by ultrafiltration through high-flux, hollow fiber filters

The efficacy of endotoxin (ET) rejection of four hollow fiber membranes with comparable sieving properties was evaluated in an ultrafiltration experiment. The solution conditioned with type I lipopolysaccharide (LPS) from Escherichia coli, 80,000 endotoxin units (EU)/L, was filtered through polyesterpolymer alloy (PEPA), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and polysulfone (PS) membranes. The ET activity of the filtrate was not detectable in PEPA and PMMA, 6.4 +/- .04 (mean +/- SD) EU/L in PAN, and 10.3 +/- 1.1 EU/L in PS. The ET activity of the filtrate of type II LPS from Acinetobacter solution, 80,000 EU/L, was not detectable in PEPA, 3.7 +/- 0.4 EU/L in PMMA, 16.5 +/- 1.5 EU/L in PAN, and 20.7 +/- 1.4 EU/L in the PS filter. The order of the rejection capability coincided with the adsorptive capacity as shown by the decrement in ET levels of solutions filled within the filter modules in the adsorption equilibrium experiment. In conclusion complete rejection of ET molecules can be achieved by ultrafiltration through hydrophobic membranes having a high adsorptive capacity in addition to an appropriate sieving property for ET molecules.     

Review of the biological response to a novel bone cement containing poly(ethyl methacrylate) and n-butyl methacrylate

This review describes work published independently elsewhere in which the biological reactions to poly(ethyl methacrylate) n-butyl methacrylate (PEMBMA) have been studied. This material has been compared throughout with conventional poly(methyl methacrylate) (PMMA). Butyl methacrylate monomer used in PEMBMA was slightly less toxic than methyl methacrylate monomer used in PMMA when injected intraperitoneally in mice. No differences in cardiorespiratory effects were found between n-butyl and methyl monomer infused intravenously into anaesthetized rabbits. The tissue reaction to the beaded polymers of poly(methyl methacrylate) and poly(ethyl methacrylate) implanted subcutaneously was identical. The surface appearance of the two materials differed significantly when viewed by scanning electron microscopy, showing a series of elevations resembling tightly packed spheres in the case of PMMA, but a smooth surface with only occasional smooth elevations in the case of PEMBMA. Intramuscular implantation showed more fibrous tissue and tissue damage in relation to PMMA cured in situ compared with PEMBMA and there was more bone necrosis and a thicker fibrous tissue layer adjacent to PMMA than PEMBMA when cured intraosseously.     

Improving corrosion resistance of epoxy coatings modified with silane monomers on AZ31D magnesium alloy

Abstract

In recent years, there has been growing interest in developing high performance silane containing epoxy coatings. In this work, two silane monomers (3-glycidoxypropyltrimethoxysilane and vinyltrimethoxy silane) were incorporated in epoxy coatings. The results demonstrated that the incorporation of 5 wt-% 3-glycidoxypropyltrimethoxysilane in coating formulation improved the anticorrosive performance of the epoxy coating on AZ31D magnesium alloy. The improving effect of 3-glycidoxypropyltrimethoxysilane was much better than that of vinyltrimethoxy silane, which can be ascribed to the compatibility of the former with epoxy vehicle. The adhesion between epoxy coatings and substrate was also strengthened by addition of the two silane monomers.

Ces dernières années, on note un intérêt grandissant dans le développement de revêtements à haute performance de résine époxy contenant du silane. Dans ce travail, on a incorporé deux monomères de silane (3-glycidoxypropyltriméthoxysilane et vinyltriméthoxy silane) dans des revêtements de résine époxy. Les résultats ont démontré que l’incorporation de 5% en poids de 3-glycidoxypropyltriméthoxysilane dans la formule du revêtement améliorait le rendement anti-corrosif du revêtement de résine époxy sur l’alliage au magnésium AZ31D. L’amélioration du 3-glycidoxypropyltriméthoxysilane était bien meilleure que celle du vinyltriméthoxy silane, ce que l’on peut attribuer à la compatibilité du premier avec le véhicule de la résine époxy. L’adhésion entre les revêtements de résine époxy et le substrat était également renforcée par l’addition des deux monomères de silane.     

Preparation and Fluorescence Properties of Polymethyl Methacrylate Resin Incorporated with Sodium Tris （Pyridine Dicarboxylato）Europate

Based on the strong fluorescence and the highly thermal stability of sodium tris (pyridine dicarboxylato)eruopate(Na3Eu(DPA)3),polymethyl methacrylate(PMMA)composite material incorporated with the complex,PMMA:Na3Eu(DPA)3,was prepared at 250℃，The fluorescence behavior of PMMA:Na3Eu(DPA)3material was examined,The results show that the composite material keeps the luminescent characteristics of the Eu^3 chelate after PMMA is incorporated with Na3Eu(PDA)3,and strong orange-red emission of the composite wsa observed.The fluorescence intensity of the composite material increases with the increase of the weight ratio of Na3Eu(PDA)3to PMMA,but the relationship is not linear.     

Improved cortical histology after cementation with a new MMA-DMA-IBMA bone cement: an animal study

The histological response of bone to inert bone wax, conventional polymethylmethacrylate (PMMA), and a new formulation of bone cement, methylmethacrylate/n-decylmethacrylate/isobornylmethacrylate (MMA/DMA/IBMA) was investigated in canine tibial diaphysis. The new formulation of cement is characterized by a reduced exothermic temperature at curing and reduced leakage of chemicals to the adjacent bone. In comparison with bone wax, the MMA/DMA/IBMA bone cement did not differ significantly with respect to periosteal apposition and bone remodeling, although a tendency to inhibit the biological response was encountered. The MMA/DMA/IBMA was clearly superior to PMMA bone cement in respect to both bone necrosis and repair, as well as bone remodeling.     

Fibromyalgia: from information to questions

A previous study has shown that sandblasting and silane priming a post-cured inlay resin gave a secure bond to dual-cure luting resin. To determine the influence of salivary contamination 4 additional groups of 15 post-cured resin discs were mounted in acrylic cylinders, their faces sandblasted with 50 microns alumina and silane primed. Surface treatments with saliva (sa), air/water spray (a/w), phosphoric acid gel (pa), and silane (si) followed in the order listed: A) control, no further treatment; B) sa, a/w; C) sa, a/w, si; D) sa, a/w, pa a/w; E) sa, a/w, pa, a/w, si. A 3.9 mm diameter column of dual-cure resin lute was then bonded to the dry stored in water surfaces. Specimens were stored in water for 2 weeks after which the dual-cure resin columns were sheared off the post-cured resin discs. Shear bond strengths were A) 19.2 +/- 3.7, B) 17.4 +/- 3.9, C) 16.7 +/- 3.1, D) 15.6 +/- 3.5, E) 15.4 +/- 2.3 MPa. One-way ANOVA and Duncan's Multiple Range Procedure showed groups D and E to be significantly lower than the uncontaminated control group A (p < 0.05). There were 2 adhesive failures in group B and all others were cohesive within the post-cured resin discs. This implies that air/water alone after salivary contamination is an unreliable cleansing method. The low shear bond values for Groups D and E may have been related to inadequate clearance of the phosphoric acid gel. It was concluded that salivary contamination adversely affected the quality of the bonds studied and decontamination using phosphoric acid gel resulted in significantly reduced shear bond strengths.     

Effects of different surface treatment methods on the bond strength of composite resin to porcelain

In this study failures of composite resin/ porcelain interfaces under shear loading were examined. Porcelain firing were made onto metal cylinders and porcelain surfaces were roughened with burrs or treated with hydrofloric acid gel and/ or sandblasted with a Microetcher. Two silane coupling agents were used in five groups, each of which had 22 samples. All of the treated samples were restored with a hybrid-type composite resin. Then each group was divided into two subgroups according to storage times of 24 h and 30 days. After thermocyling the samples which were stored for 30 days, all of the groups were subjected to shear force at the composite resin/porcelain interface until fracture occurred. The results showed that there were differences both in the 24-h and 30-day storage period bond strengths between the various surface treatment methods. The samples treated with all three of the Microetcher, hydrofloric acid and silane exhibited the highest shear bond values after 24 h storage, followed by the microetched/silane and the hydrofluoric acid/silane groups (F: 570.31, P: 0.00). After 30 days, the highest mean shear bond strength values were again with samples treated by all three processes. The storage period and thermocycling decreased the bond strength of samples, however, there was a significant difference among groups (F: 1388-55, P: 0.00). Silane pre-treatment of porcelain was important as the mean bond strength of sandblasted/etched specimens were significantly lower than the other groups which were treated mechanically, in 24 h. Sandblasting seems to have little effect on the bonding. The comparison of 24-h and 30-day samples have also significant difference (F: 91.4376, P: 0.00).     

Anterior capsule contraction and intraocular lens dislocation in eyes with pseudoexfoliation syndrome

OBJECTIVE: To quantitatively compare the extent of posterior capsule opacification (PCO) after polymethylmethacrylate (PMMA), silicone, and soft acrylic intraocular lens implantation. PATIENTS AND METHODS: A total of 240 eyes from 240 patients undergoing implant surgery were randomized into 3 groups based on the type of lens implanted: PMMA, silicone, and soft acrylic. The density value of PCO in 185 eyes was quantitated approximately 2 years after surgery by a new measurement method using the Scheimpflug videophotography system. RESULTS: Twenty-one eyes (30.4%) in the PMMA group, 4 (5.7%) in the silicone group, and 2 (2.7%) in the acrylic group had already undergone Nd:YAG laser posterior capsulotomy. The mean +/- SD PCO values were 26.3 +/- 12.2 computer-compatible tape steps (CCT) in the PMMA group, 12.0 +/- 8.3 CCT in the silicone group, and 16.0 +/- 10.3 CCT in the acrylic group. The PCO value in the PMMA group was significantly greater than that in the silicone or acrylic group (P < .001). The visual acuity loss in the PMMA group was also greater than that in the silicone or acrylic group (P < .001). CONCLUSION: Based on the PCO value and capsulotomy rate, the PCO was more extensive with the PMMA lens than with either the silicone or soft acrylic lens, which led to visual acuity loss.     

ER Effect of PMMA Wrapped Alumina-Siloxane Gel Doped with Rare Earths

PMMA wrapped alumina-siloxane gel was obtained by using poly (methyl methacrylate) (PMMA) to wrap alumina-siloxane sol which was made from water glass, aluminum nitrate and a-methacrylic acid. Meanwhile, rare earth ions were used to dope in the course of reaction, and stable suspensions was produced by putting PMMA wrapped microcapsule powder doped with rare earths into methy-silicon oil. It is found that its electrorheologlcal (ER) effect improves strikingly after loading electric field. At a certain concentration, the immediate viscosity increases from 95 to 178 Pa‘s compared to the system without doping.     

Spontaneous erythroid colony formation as the clue to an underlying myeloproliferative disorder in patients with Budd-Chiari syndrome or portal vein thrombosis

Results from this laboratory have shown that bone metabolism is directly related to extracellular pH and that high concentrations of tobramycin released from impregnated polymethylmethacryrate (PMMA) beads has pH-dependent toxic effects on bone. In the present study, beneficial effects of calcium hydroxide-impregnated PMMA were investigated regarding tobramycin toxicity and bone metabolism in chick embryo tibiae in vitro. Also using Ca(OH)2 as a pH regulator, the antibiotic efficacy of tobramycin-impregnated PMMA was evaluated with respect to inhibition of Staphylococcus aureus growth. When Ca(OH)2 was added to PMMA beads containing tobramycin, the beads released hydroxyl and calcium ions into the culture medium and released more antibiotic than beads containing only tobramycin. Bone metabolism (glycolysis, total protein synthesis, and collagen synthesis) was enhanced by Ca(OH)2-impregnated beads with or without tobramycin. Additionally, bacterial growth was inhibited more strongly when S. aureus was incubated with tobramycin- and Ca(OH)2-impregnated PMMA disks than with disks containing only tobramycin. This study demonstrates the feasibility of adding Ca(OH)2 to tobramycin-impregnated PMMA beads as a regulator of local pH and a promoter of bone metabolism for protection of bone when high concentrations of tobramycin are used to treat osteomyelitis. It also suggests that lower concentrations of antibiotic may be effective if Ca(OH)2 and tobramycin are administered simultaneously.