Poly Methyl Methacrylate Microbeads Research Articles

Meniscus regeneration with injectable Pluronic/PMMA-reinforced fibrin hydrogels in a rabbit segmental meniscectomy model

Injectable hydrogel systems are a facile approach to apply to the damaged meniscus in a minimally invasive way. We herein developed a clinically applicable and injectable semi-interpenetrated network (semi-IPN) hydrogel system based on fibrin (Fb), reinforced with Pluronic F127 (F127) and polymethyl methacrylate (PMMA), to improve the intrinsic weak mechanical properties. Through the dual-syringe device system, the hydrogel could form a gel state within about 50 s, and the increment of compressive modulus of Fb hydrogels was achieved by adding F127 from 3.0% (72.0 ± 4.3 kPa) to 10.0% (156.0 ± 9.8 kPa). The shear modulus was enhanced by adding PMMA microbeads (26.0 ± 1.1 kPa), which was higher than Fb (13.5 ± 0.5 kPa) and Fb/F127 (21.7 ± 0.8 kPa). Moreover, the addition of F127 and PMMA also delayed the rate of enzymatic biodegradation of Fb hydrogel. Finally, we confirmed that both Fb/F127 and Fb/F127/PMMA hydrogels showed accelerated tissue repair in the in vivo segmental defect of the rabbit meniscus model. In addition, the histological analysis showed that the quality of the regenerated tissues healed by Fb/F127 was particularly comparable to that of healthy tissue. The biomechanical strength of the regenerated tissues of Fb/F127 (3.50 ± 0.35 MPa) and Fb/F127/PMMA (3.59 ± 0.89 MPa) was much higher than that of Fb (0.82 ± 0.05 MPa) but inferior to that of healthy tissue (6.63 ± 1.12 MPa). These results suggest that the reinforcement of Fb hydrogel using FDA-approved synthetic biomaterials has great potential to be used clinically.

High-throughput and Multimodal Separation of Microbeads Using Cyclical Induced-charge Electro-osmotic Vortices and Its Application in Size Fractionation of Crumpled Graphene Oxide Balls

Crumpled graphene oxide (CGO) balls are new 3D applied materials, which present good potential in the development of energy storage and conversion devices for the advantages of high surface areas and resistant to aggregation. Utilizing ready-made CGO balls with defined sizes to synthesize desired materials or modify existing components, if achieved, we may make the functions and properties of the final products more controllable and programmable. However, acquiring uniform-size CGO particles still remains under challenge now, because uniform-size pristine graphene oxide is difficult to obtain and the size of CGO balls is sensitive to many parameters during the synthesis. An alternative potential solution, classifying the synthetized CGO balls to obtain uniform-size CGO balls may ingeniously circumvent above tricky issue. Here we designed tilted-angle ridge floating electrode sequence (TARFES) to actuate cyclical asymmetrical ICEO (AICEO) vortices to achieve particle separation and augment the throughput capability (105 particles/h), overcoming the limitation of existing vortex-based separation criteria. We firstly conducted simulations to identify the optimum configuration of TARFES. According to spatial features of cyclic AICEO vortices, two separation modes were developed. We separated silica and polymethyl methacrylate (PMMA) microbeads to validate the capability of the first separation mode, and studied the effects of voltage and flow speed on the separation results, obtaining 97.3% separation efficiency. We then separated PMMA microbeads and yeast cells with 93.1% separation efficiency to evidence the second separation mode. Also, we accomplished the simultaneous separation of multiple particles. Depending on characterization of CGO balls, the second separation mode was successfully engineered to realize size fractionation of CGO balls in continuous flow, yielding clear separation. Finally, we also modulated the voltage input to isolate nanoscale CGO balls from the background. This operative separation technique offers a unique route to acquire uniform-size CGO balls with potential applications in the fabrications of batteries and ultracapacitors.

Fabrication of porous boron nitride by using polyborazylene as precursor, polymethylmeth-acrylate as reaction agent

A novel process for the production of micro-molecular boron nitride foams has been developed through foaming of boron nitride preceramic polymer with the help of sacrificial microbeads of polymethylmethacrylate (PMMA), followed by pyrolysis under inert atmosphere. The process parameters of porous BN ceramics were studied by thermo gravimetric analysis, thermo mechanical analysis, X-ray diffraction, scanning electron microscopy, mercury porosimetry and elemental analysis. The microstructure and element composition of the porous ceramics were also studied by the above methods. The results showed that: when using polyborazylene from thermolization of borazine at 60°C as boron nitride precursor, PMMA microbeads with pore size of 25μm as sacrificial microbeads, adding into polyborazylene powder with 80 wt% in the foaming mixture. After warm-pressing the powders under 74MPa at 60°C, subsequently pyrolyzing the powders under ammonia to 1000°C then to 1450°C under nitrogen atmosphere, we can obtain boron nitride foams. Through scanning electron microscopy observation, X-ray diffraction analysis and porosity measurement, it was confirmed that the obtained boron nitride pieces were microcellular foams with homogeneous distributed pore size average at ∼19.15μm and had a mostly interconnected porosity of 79.06 vol%. The temperature should be increased to 1700-1800°C to prepare porous BN ceramic with a certain degree of crystallinity (layer spacing d002 = 0.335-0.333 nm)

Solvent-free synthesis of zeolite LTA monolith with hierarchically porous structure from metakaolin

We report a simple and effective process for preparing self-supporting zeolite LTA monoliths with hierarchical structure via the solvent-free crystallization route followed by a calcination process, using polymethyl methacrylate microbeads as sacrificial template. SEM images demonstrate the formation of interconnected macropores. Cube-shaped zeolite particles are intergrown at their interfaces, establishing a stable porous system. XRD results confirm the purity and crystallinity of zeolite LTA. BET and MIP results indicate three levels of pores (micro-, meso- and macrospores) present in the zeolite monolith. In addition, the BET surface area, bulk density, true density of the hierarchical zeolite are 57.67 m2/g, 0.684 g/cm3 and 2.771 g/cm3, respectively, and the total porosity is up to 75.3 vol%.

An optimized process for in situ formation of multi-walled carbon nanotubes in templated pores of polymer-derived silicon oxycarbide

A reliable and optimized process to grow carbon nanotubes (CNTs) in templated pores of polymer derived ceramic (PDC) matrix was developed. It is realized through the pyrolysis of a preceramic polymer, i.e., poly (methyl-phenyl-silsesquioxane) (denoted as PMPS), in argon atmosphere at 1000°C together with nickel-catalyst-coated poly-methyl-methacrylate (PMMA) microbeads (denoted as PMMA-Ni). PMPS served as both a precursor for the ceramic matrix and a carbon source for the CNT growth. PMMA microbeads were used as sacrificial pore formers and coated with nickel via an electroless plating method, which provides an improved control of particle size of the catalyst and its distribution in the material. The influence of PMMA-Ni loading on the in situ growth of CNTs and the properties of CNTs/SiOC nanocomposites were studied through thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and density/porosity measurements. Under optimized conditions, uniform distribution of in situ grown CNTs was observed within the templated pores of the SiOC matrix. The optimized process leads to reproducible high yield of CNTs in the pores. The development of such novel CNT/cellular ceramic nanocomposite materials is of significant interest for a variety of sensor applications.

Zeolite decorated highly porous acicular calcium silicate ceramics

Macrocellular calcium silicate (wollastonite) ceramic foams possessing ~86vol% total porosity were produced from commercial calcium silicate hydrate (xonotlite) nano-size acicular crystals and poly-methyl-methacrylate microbeads (PMMA) (used as sacrificial pore formers). Open cell wollastonite foams had a bi-modal pore size distribution with major modes located ~100nm due to interparticle porosity and ~100µm due to the sacrificial pore former. These macrocellular ceramics were then used as a scaffold for MFI type zeolite (silicalite-1) synthesis. Monolayer coffin shaped zeolite crystals (~3µm size, measured from the c-axis and ~300nm thickness) were observed with almost full coverage on the inner macro-cell walls. The specific surface area of the components increased from 9.6m2/g to 108.2m2/g via zeolite functionalization, leading to components possessing multiscale porosity.

Chronic Ocular Hypertensive Rat Model using Microbead Injection: Comparison of Polyurethane, Polymethylmethacrylate, Silica and Polystyene Microbeads

Purpose: To establish and assess an ocular hypertensive rat model using intracameral injection with various microbeads of different sizes and materials.Methods: Chronic elevation of intraocular pressure (IOP) was induced by the injection of various microbeads into the anterior chamber of Sprague-Dawley rat eyes. We compared the IOPs induced by the injection of different microbeads [7- and 17-µm polyurethane (PU), 7- and 15-µm polymethylmethacrylate (PMMA), 13-µm silica, and 15-µm polystyrene (PS)] and selected the appropriate microbeads for a chronic ocular hypertensive model in terms of IOP elevation and adverse events. IOP changes were observed for 4 weeks after microbead injections. Axonal degeneration was assessed with transmission electron microscopic photographs and RGC loss was assessed with retrograde labeling.Results: Seventy-eight rats were included. Three days after a single injection of microbeads, IOPs were increased by 24.0% by 7-µm PU microbeads, 101.8% by 17-µm PU microbeads, 56.6% by 7-µm PMMA microbeads, 22.0% by 15-µm PMMA microbeads, 153.0% by 13-µm silica microbeads, and 34.7% by 15-µm PS microbeads. 17-µm PU microbeads produced constant IOP elevation with good reproducibility (standard deviation of <6.5 mmHg). Silica injected eyes showed severe inflammation. Sustained IOP elevation by two injections of 17-µm PU microbeads resulted in a 42% axon loss and 36.5% RGC loss (p < 0.05, Mann–Whitney U test).Conclusions: PU microbead injections offer an applicable and versatile model for a chronic ocular hypertensive model in rats. Among several biomaterials, PU microbeads produced a more stable IOP elevation without adverse events.

Effect of starting PMMA content on microstructure and properties of gel casting BN/Si3N4 ceramics with spherical-shaped pore structures

By gel casting with polymethylmethacrylate microbeads (PMMA) as pore-forming agent, porous boron nitride/silicon nitride (BN/Si3N4) composite ceramics were successfully prepared. The obtained ceramic shows bimodal hierarchical structures that composed of spherical-shaped micro pores depending on PMMA content and irregular sub-micro pores formed by the stacking of ceramic particles. Porosity of the porous BN/Si3N4 ceramics can be well controlled from 53.0 to 60.6 % by the PMMA content from 10 to 40 wt%, as well as the mechanical and dielectric properties. Effect of PMMA content on phase composition and the relationship between microstructure and the basic properties of the porous BN/Si3N4 ceramics was discussed in detail. Microstructure analysis reveals that the sub-micro pores acted as channels between micro pores. BN particles have a relatively denser distribution on the wall of spherical-shaped micro pores with a window between micro and sub-micro pores, and resulting in a half-closed micro pore structure, which is meaningful for material design with concentration of BN particles on the wall of pore structure.

Polymer-derived microcellular SiOC foams with magnetic functionality

SiOC microcellular ceramic foams possessing soft-ferromagnetic properties were produced from a pre-ceramic polymer, poly-methyl-methacrylate microbeads (PMMA) (used as sacrificial pore formers) and iron silicide micro-powders (as functional filler). The interactions between the matrix and the filler were studied as a function of the amount of powders introduced and the pyrolysis temperature. Magnetic and mechanical properties were also investigated.

Micro- and macro-cellular sintered glass-ceramics from wastes

Glass obtained from melting a mixture of industrial wastes (panel glass from dismantled cathode ray tubes, mining residues from feldspar excavation and lime from fume abatement systems of the glass industry) has been employed for manufacturing micro- and macro-cellular sintered glass-ceramics. Micro-cellular glass-ceramics, with a closed porosity, were prepared by the direct foaming of the glass mass, determined by viscous flow sintering of fine powders (<37 μm), due to addition of a SiC-based waste (from the polishing of glass articles). The surface crystallization of glass, upon sintering, limited the porosity (being about 50%), but imparted a remarkable crushing strength to the products (up to about 80 MPa), useful for construction applications. Micro- and macro-cellular glass-ceramics, with an open porosity and very low relative density (from 40 to less than 10%), were prepared by the sintering of fine glass powders mixed with sacrificial poly-methyl methacrylate microbeads or deposited on sacrificial poly-urethane sponges. The crystallization, besides imparting a good mechanical strength, allowed the maintenance of the open-celled morphology, useful for filtering applications.

Microcellular ceramics by using silicone preceramic polymer and PMMA polymer sacrificial microbeads

Microcellular silicon oxycarbides have been produced by pyrolysis of methylsilicone resin with the help of sacrificial microbeads of polymethyl methacrylate (PMMA). The PMMA microbeads were added in the range from 0 to 80 wt%, and the pyrolysis was performed at 800–1200 °C. The volume shrinkage resulting from the polymer-to-ceramic conversion becomes constant at the pyrolysis temperature above 1000 °C, and the shrinkage value reaches about 60% by a PMMA addition of 80 wt%. In the all range of PMMA additive ratios, the spherical micro pores with the wide range diameter from 1 to 10 μm are produced in the matrix. The open-cells, which are formed above 30 wt% of PMMA addition, have the open pores size bigger than 0.5 μm. The bending strength and the elastic modulus of the product exhibit the maximum values, i.e., 24.1 MPa and 16.0 GPa, respectively, when PMMA addition is 50 wt%.

Porous HA ceramic for bone replacement: role of the pores and interconnections - experimental study in the rabbit.

Hydroxyapatite (HA) porous ceramics are increasingly used in biomedical applications. Their physical characteristics, such as porous volume, require perfect control of the pore shape, as well as the number and the size of their interconnections. The aim of our study was to evaluate a new HA ceramic using polymethylmethacrylate microbeads (PMMA) as the porous agent. Four interconnection sizes (30, 60, 100 and 130 microm) with a 175-260 microm pore size and three pore sizes (175-260, 260-350 and 350-435 microm) for a 130 microm interconnection size were tested. Various HA implants were appraised by microscopic evaluation in a 4.6 x 10 mm rabbit femur cancellous bone defect 12 weeks after implantation. The best osteoconduction result was obtained in the center of the ceramic by means of a 130 microm interconnection size and a 175-260 microm mean pore size. Bone formation obtained within the pores was double that obtained in our previous study where naphtalen microbeads were used as the porous agents.

Preparation and characterization of magnetic polymethylmethacrylate microbeads carrying ethylene diamine for removal of Cu(II), Cd(II), Pb(II), and Hg(II) from aqueous solutions

Magnetic polymethylmethacrylate (mPMMA) microbeads carrying ethylene diamine (EDA) were prepared for the removal of heavy metal ions (i.e., copper, lead, cadmium, and mercury) from aqueous solutions containing different amount of these ions (5–700 mg/L) and at different pH values (2.0–8.0). Adsorption of heavy metal ions on the unmodified mPMMA microbeads was very low (3.6 μmol/g for Cu(II), 4.2 μmol/g for Pb(II), 4.6 μmol/g for Cd(II), and 2.9 μmol/g for Hg(II)). EDA-incorporation significantly increased the heavy metal adsorption (201 μmol/g for Cu(II), 186 μmol/g for Pb(II), 162 μmol/g for Cd(II), and 150 μmol/g for Hg(II)). Competitive adsorption capacities (in the case of adsorption from mixture) were determined to be 79.8 μmol/g for Cu(II), 58.7 μmol/g for Pb(II), 52.4 μmol/g for Cd(II), and 45.3 μmol/g for Hg(II). The observed affinity order in adsorption was found to be Cu(II) > Pb(II) > Cd(II) > Hg(II) for both under noncompetitive and competitive conditions. The adsorption of heavy metal ions increased with increasing pH and reached a plateau value at around pH 5.0. The optimal pH range for heavy-metal removal was shown to be from 5.0 to 8.0. Desorption of heavy-metal ions was achieved using 0.1 M HNO3. The maximum elution value was as high as 98%. These microbeads are suitable for repeated use for more than five adsorption-desorption cycles without considerable loss of adsorption capacity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 81–89, 2000

Modified PMMA monosize microbeads for glucose oxidase immobilization

Glucose oxidase (GOD) was immobilized onto modified polymethylmethacrylate (PMMA) microspheres by covalent bonding. Monosize PMMA microbeads with 1.5 μm diameter were produced by dispersion polymerization of methylmethacrylate by using polyvinyl alcohol as a stabilizer. Hydroxyl groups on the microbeads were first converted to aldehyde groups by periodate oxidation. Three amino compounds, namely ammonium hydroxide, ethylene diamine and hexamethylene diamine were incorporated through the aldehyde groups. Then, GOD molecules were immobilized through the spacer-arms by using glutaraldehyde. The highest amount of immobilization and activity were obtained in which hexamethylene diamine was used as the spacer-arm with 14 atom length, and were 2.1 mg g −1 polymer and 129 IU g −1 polymer, respectively. The optimal conditions for GOD immobilization were obtained as follows: pH, 6.0; temperature, 30 °C; immobilization time, 60 min; and GOD initial concentration, 0.10 mg ml −1. The optimal conditions for the GOD-immobilized PMMA microbeads were at pH 6.0 and at a temperature of 30 °C. The K m and V max values of the GOD-immobilized PMMA microbeads were, 13.79 mM and 26.31 mM min −1 calculated by non-linear regression, respectively.

Protein a Carrying Monosize PMMA Microbeads for the Removal of HlgG 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.