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PMMA Particles (pmma + particle)
Selected AbstractsA new technique for foaming submicron size poly(methyl methacrylate) particlesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Hiroyuki Ogawa Abstract About 0.7,2 ,m diameter poly (methyl methacrylate) (PMMA) foamed particles were prepared via thermally induced phase separation (TIPS) from a PMMA/ethanol mixture and vacuum dried. It was found that ethanol, known to be a poor solvent to PMMA, could dissolve PMMA when the temperature was over 60°C. The solubility of PMMA (Mw = 15,000 and Mw = 120,000) in ethanol was measured and was found to increase as the temperature increased. PMMA particles on the scale of submicron and single micron diameter could be precipitated from the PMMA/ethanol solution by temperature quenching. Then, since the precipitated particles contained a certain amount of ethanol, the precipitated particles could be foamed using the ethanol as a foaming agent in a vacuum drying process. Vacuum drying at temperatures slightly below the glass transition temperature of the polymer could make the particles foam. The effects of foaming temperature and the molecular weight of the polymer on the size of foamed particles were investigated. The experimental results showed that the vapor pressure and the molecular weight of the polymer are key factors determining the expandability of the micro particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Human monocyte response to retrieved polymethylmethacrylate particlesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 3 2002Masatsugu Miyaguchi Abstract The purpose of this study was to compare retrieved polymethylmethacrylate (PMMA) particles from failed total hip arthroplasties in terms of size, shape, and the response of human monocytes with commercially available particles. PMMA particles were isolated from peri-implant tissues of five failed cemented total hip arthroplasties using tissue digestion and a sucrose density gradient technique. Prepolymerized cement powder and those from which barium sulfate had been removed were examined for comparison. After exposure of peripheral human monocytes to PMMA particles, tumor necrosis factor-, and interleukin-6 in medium were measured by using enzyme-linked immunosorbent assays. Image analysis revealed that retrieved particles were larger (retrieved: 1.24 ,m; prepolymerized cement powder: 0.83 ,m; barium sulfate-free powder: 0.87 ,m) and were more irregular in shape and rougher than commercially available particles. Cytokine release was increased by all PMMA particle species. However, commercially available PMMA particles stimulated the release of necrosis factor-, and interleukin-6 more strongly than did retrieved particles at very high doses. The observed difference in monocyte response might be due to the volume of the challenged particles. Another possible reason for the difference might be alteration of the surface chemistry of particles in situ and the difference in surface morphology between them. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 331,337, 2002 [source] Polymethylmethacrylate particles impair osteoprogenitor viability and expression of osteogenic transcription factors Runx2, osterix, and Dlx5JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2010Richard Chiu Abstract Polymethylmethacrylate (PMMA) particles have been shown to inhibit the differentiation of osteoprogenitor cells, but the mechanism of this inhibitory effect has not been investigated. We hypothesize that the inhibitory effects of PMMA particles involve impairment of osteoprogenitor viability and direct inhibition of transcription factors that regulate osteogenesis. We challenged MC3T3-E1 osteoprogenitors with PMMA particles and examined the effects of these materials on osteoprogenitor viability and expression of transcription factors Runx2, osterix, Dlx5, and Msx2. MC3T3-E1 cells treated with PMMA particles over a 72-h period showed a significant reduction in cell viability and proliferation as indicated by a dose- and time-dependent increase in supernatant levels of lactate dehydrogenase, an intracellular enzyme released from dead cells, a dose-dependent decrease in cell number and BrdU uptake, and the presence of large numbers of positively labeled Annexin V-stained cells. The absence of apoptotic cells on TUNEL assay indicated that cell death occurred by necrosis, not apoptosis. MC3T3-E1 cells challenged with PMMA particles during the first 6 days of differentiation in osteogenic medium showed a significant dose-dependent decrease in the RNA expression of Runx2, osterix, and Dlx5 on all days of measurement, while the RNA expression of Msx2, an antagonist of Dlx5-induced osteogenesis, remained relatively unaffected. These results indicate that PMMA particles impair osteoprogenitor viability and inhibit the expression of transcription factors that promote osteoprogenitor differentiation. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:571,577, 2010 [source] Involvement of complement receptor 3 (CR3) and scavenger receptor in macrophage responses to wear debrisJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 11 2006Diptendu S. Rakshit Abstract The ability of prosthetic wear debris to induce pro-inflammatory responses in macrophages is widely appreciated, but little is known about the molecular mechanisms involved in particle recognition. Specifically, the nature of the cell surface receptors that interact with wear debris is poorly understood. Elucidating the identities of these receptors and how they interact with different types of wear debris are critical to understanding how wear debris initiates periprosthetic osteolysis. We examined the involvement of opsonization, complement receptor 3 (CR3), and scavenger receptor A (SRA), in responses to polymethylmethacrylate (PMMA) and titanium wear particles. Serum dependence of pro-inflammatory responses to PMMA and titanium was tested, and serum proteins that adhered to these two types of particles were identified. Several serum proteins, including known opsonins such as C3bi and fibronectin, adhered to PMMA but not titanium, and serum was required for pro-inflammatory signaling induced by PMMA, but not by titanium. Phagocytosis of PMMA and titanium by macrophages was demonstrated by flow cytometry. Blocking CR3 specifically inhibited phagocytosis of PMMA by macrophages, whereas blocking SRA specifically inhibited titanium uptake. Direct involvement of CR3 and SRA in cell,particle interaction was assessed by expression of these receptors in nonphagocytic HEK293 cells. CR3 specifically induced cell binding to PMMA particles and adhesion to PMMA-coated plates, while SRA specifically induced binding to titanium particles and adhesion to titanium-coated plates. Taken together, these results suggest involvement of opsonization, complement, and integrin receptors, including CR3 and fibronectin receptors, in PMMA action, and an involvement of scavenger receptors in responses to titanium. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:2036,2044, 2006 [source] PMMA particles and pressure,a study of the osteolytic properties of two agents proposed to cause prosthetic looseningJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 2 2003Björn Skoglund Amongst the wear debris particles implicated in the particle hypothesis for prosthetic loosening are polymethylmethacrylate (PMMA), and particularly PMMA with barium sulphate contrast agent. Another suggested cause for loosening is hydrostatic pressure. PMMA particles were combined with hydrostatic pressure in a study to investigate whether there could be a synergistic or additive effect between these two factors. Titanium plates were fastened onto tibiae of 59 rats. After osseointegration, PMMA particles with barium sulphate were administered to the bone-implant interface. Further, PMMA particles were introduced into a previously published model for hydrostatic pressure induced osteolysis. There was measurable resorption in response to the PMMA particles but no additive or synergistic effect from introducing particles to the pressure model, and the effect of pressure was far greater than that of particles. These results suggest that, whereas particles can be shown to elicit an osteolytic response, the much less studied osteolytic effects of pressure could be far more important. © 2002 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved. [source] Non-Fluorous Random Copolymeric Stabilizers for Dispersion Polymerizations of MMA in Supercritical CO2MACROMOLECULAR RAPID COMMUNICATIONS, Issue 9 2006Ha Soo Hwang Abstract Summary: The dispersion polymerization of MMA in supercritical CO2 was successfully carried out utilizing the first non-fluorous random copolymers composed of 3-tris(trimethoxysilyl)propyl methacrylate and 2-dimethylaminoethyl methacrylate, poly(SiMA- co -DMAEMA) as a stabilizer. The resulting high yield (>93%) of micron-sized PMMA was formed in the presence of 5% (w/w to MMA) of copolymeric stabilizers. While the PSiMA and PDMAEMA homopolymer produced nondescript solid and irregular shape aggregate, respectively, the random copolymer of 71% SiMA-content resulted in spherical and uniform powder. SEM image of PMMA particles prepared in supercritical CO2 using poly(SiMA- co -DMAEMA) (71:29) stabilizer. [source] Model filled polymers: The effect of particle size on the rheology of filled poly(methyl methacrylate) compositesPOLYMER ENGINEERING & SCIENCE, Issue 3 2004Joshua Qingsong Li The effect of size of crosslinked monodisperse spherical polymer particles on the steady shear and dynamic rheology of filled poly(methyl methacrylate) (PMMA) composites was studied for PMMA and polystyrene (PS) particles in the range from 0.1 to 1.3 micron particle size. For PMMA matrices filled with crosslinked PS particles, reduction in filler size increases non-Newtonian behavior. Particle size effects on the rheology of filled PMMA were much less pronounced for PMMA filler. The rate of growth of steady shear viscosity with aging time was much larger for PMMA filled with PS particles than with PMMA particles. The apparent yield stress of filled PMMA composites was estimated from Casson plots. The yield stress was negligible for PMMA filler but increased with decreasing particle size for PS filler. We suggest that PS particles are rejected by the PMMA matrix and form clusters, causing large enhancements in viscosity and moduli. Polym. Eng. Sci. 44:452,462, 2004. © 2004 Society of Plastics Engineers. [source] | ||||||||||