Polymethacrylate Particles Research Articles

Improved packing of preparative biochromatography columns by mechanical vibration.

The bioprocessing industry relies on packed-bed column chromatography as its primary separation process to attain the required high product purities and fulfill the strict requirements from regulatory bodies. Conventional column packing methods rely on flow packing and/or mechanical compression. In this work, the application of ultrasound and mechanical vibration during packing was studied with respect to packing density and homogeneity. We investigated two widely used biochromatography media, incompressible ceramic hydroxyapatite, and compressible polymethacrylate-based particles, packed in a laboratory-scale column with an inner diameter of 50 mm. It was shown that ultrasonic irradiation led to reduced particle segregation during sedimentation of a homogenized slurry of polymethacrylate particles. However, the application of ultrasound did not lead to an improved microstructure of already packed columns due to the low volumetric energy input (~152 W/L) caused by high acoustic reflection losses. In contrast, the application of pneumatic mechanical vibration led to considerable improvements. Flow-decoupled axial linear vibration was most suitable at a volumetric force output of ~1,190 N/L. In the case of the ceramic hydroxyapatite particles, a 13% further decrease of the packing height was achieved and the reduced height equivalent to a theoretical plate (rHETP) was decreased by 44%. For the polymethacrylate particles, a 18% further packing consolidation was achieved and the rHETP was reduced by 25%. Hence, it was shown that applying mechanical vibration resulted in more efficiently packed columns. The application of vibration furthermore is potentially suitable for in situ elimination of flow channels near the column wall.

Parametric study of immobilized cellulase-polymethacrylate particle for the hydrolysis of carboxymethyl cellulose

Biocarriers are pivotal in enhancing the reusability of biocatalyst that would otherwise be less economical for industrial application. Ever since the induction of enzymatic technology, varied materials have been assessed for their biocompatibility with enzymes of distinct functionalities. Herein, cellulase was immobilized onto polymethacrylate particles (ICP) as the biocarrier grafted with ethylenediamine (EDA) and glutaraldehyde (GA). Carboxymethyl cellulose (CMC) was used as a model substrate for activity assay. Enzyme immobilization loading was determined by quantifying the dry weight differential of ICP (pre-& post-immobilization). Cellulase was successfully demonstrated to be anchored upon ICP and validated by FTIR spectra analysis. The optimal condition for cellulase immobilization was determined to be pH 6 at 20 °C. The maximum CMCase activity was achieved at pH 5 and 50 °C. Residual activity of ∼50% was retained after three iterations and dipped to ∼18% on following cycle. Also, ICP displayed superior pH adaptability as compared to free cellulase. The specific activity of ICP was 65.14 ± 1.11% relative to similar amount of free cellulase.

Interfacial activation of lipases on hydrophobic support and application in the synthesis of a lubricant ester

n-Octyl oleate was synthetized by enzymatic esterification reaction of oleic acid and n-octanol. Lipases from porcine pancreatic (PPL), Mucor javanicus (MJL), Candida sp. (CALA), Rhizomucor miehei (RML) and Thermomyces lanuginosus (TLL) were immobilized via interfacial activation on poly-methacrylate particles (PMA) and tested as biocatalysts. Their catalytic properties were determined in the hydrolysis of olive oil emulsion. Among them, TLL–PMA was the biocatalyst that yielded the highest hydrolytic activity (217.8±1.1 IU/g) and immobilized protein loading (37.5±0.4mg/g). This biocatalyst was also the most active in n-octyl oleate synthesis, thus selected for further studies. Maximum conversion percentage of 95.1±1.3% was observed after 60min of reaction at 45°C, 10% m/v of TLL–PMA, and molar ratio oleic acid:n-octanol of 1:1.5 in a solvent-free system. The biocatalyst fully retained its original activity after twelve cycles of reaction of 60min each. The product was confirmed by attenuated total reflectance Fourier transform infrared (ATR–FTIR) spectroscopy analysis and their physico-chemical properties were determined according to ASTM standard methods. These results show that the immobilization of an alkalophilic and thermostable lipase (TLL) on PMA particles allowed the preparation of a highly active biocatalyst in hydrolysis and esterification reactions.

Enzymatic synthesis of isoamyl butyrate catalyzed by immobilized lipase on poly-methacrylate particles: optimization, reusability and mass transfer studies.

Isoamyl butyrate (banana flavor) was synthesized by esterification reaction of isoamyl alcohol and butyric acid in heptane medium. Immobilized Thermomyces lanuginosus lipase (TLL) prepared via physical adsorption on mesoporous poly-methacrylate particles (PMA) was used as biocatalyst. The factors that affect the esterification reaction were optimized by response surface methodology (RSM). Under optimal experimental conditions, maximum ester conversion percentage of 96.1 and 73.6% was reached after 50 and 90 min, respectively, for esterification reaction performed at equimolar ratio alcohol:acid at 500 and 2000 mM of each substrate. Under these experimental conditions, the esterification reaction was not controlled by external and intra-particle mass transfer effects. The product (isoamyl butyrate) was confirmed by proton nuclear magnetic resonance ((1)H NMR) spectroscopy. Reusability tests showed that the biocatalyst retained around 96 and 31% of its initial activity after eight successive esterification cycles performed at 500 and 2000 mM, respectively. The application of the biocatalyst prepared showed to be a promising strategy to catalyze flavor ester synthesis in a non-aqueous medium.

Synthesis and application of novel phenylboronate affinity materials based on organic polymer particles for selective trapping of glycoproteins

We report on synthesis concepts for the fabrication of various novel phenylboronate affinity materials based on polymethacrylate epoxy beads (Fractogel EMD Epoxy (M) 40-90 microm) and the testing of these functionalized polymer particles for selective trapping of a glycoprotein from a standard mixture containing a glycosylated and a nonglycosylated protein. Two inherently different approaches for the functionalization of the bare beads with boronate groups have been elucidated. In the first, the epoxy residues of the polymer particles were converted into reactive thiol groups which were subsequently used as anchor moieties for the immobilization of 4-vinylphenylboronic acid by radical addition or radical polymerization reaction. Three different ways for the generation of sulfhydryl groups have been examined leading to materials with distinct linker chemistries. In the second and more straightforward approach, the epoxy groups were reacted with 4-mercaptophenylboronic acid. The novel materials were thoroughly characterized by (i) quantitation of the sulfur content by elemental analysis, (ii) reactive sulfhydryls were determined in a photospectrometric assay, (iii) boron content was measured by inductively coupled plasma-atomic emission spectrometry, and (iv) the amount of reactive boronate groups was evaluated in a fast binding assay employing adenosine as test compound. A maximum concentration of 1.2 mmol boronate groups per gram dry beads could be achieved by the presented synthesis routes. Employing the novel phenylboronate affinity materials in capture and release experiments in the batch mode, a standard glycoprotein, viz. transferrin (Tf) from human serum was separated from a nonglycosylated protein, BSA. A commercial boronate affinity material based on 3-aminophenylboronic acid modified agarose gel was employed as reference material and was found to perform significantly worse compared to the herein presented novel polymethacrylate particles.

A micromachined high throughput Coulter counter for bioparticle detection and counting

We describe a micromachined Coulter counter with multiple sensing microchannels for quantitative measurement of polymethacrylate particles and pollen. A unique design with sensing microelectrodes in the center of the microchannels is demonstrated. This design creates isolation resistances among channels, and thus circumvents the crosstalk caused by automatic electrical connection among microchannels. When implemented using microfluidic channels, this design is appropriate for the sensing of microscale particles in deionized water or in dilute electrolyte solution. Our design has multiple channels operating in parallel, but integrated with just one sample reservoir and one power source. The results with a four-channel device show that this device is capable of differentiating and counting micro polymethacrylate particles and Juniper pollen rapidly. Moreover, the device throughput is improved significantly in comparison to a single-channel device. The concept can be extended to a large number of sensing channels in a single chip for significant improvement in throughput.

A label-free high throughput resistive-pulse sensor for simultaneous differentiation and measurement of multiple particle-laden analytes

We describe an all-electronic, label-free, resistive-pulse sensor that utilizes multiple microchannels for parallel detection, counting and differentiation of multiple biological particles simultaneously. Four particle solutions, including 20 µm and 40 µm polymethacrylate particles, Juniper Scopulorum (Rocky Mountain Juniper) pollen and Populus deltidoes (Eastern Cottonwood) pollen, were loaded to the four peripheral reservoirs, respectively, and were driven to the central reservoir through four microchannels, all operating simultaneously for particle detection and counting. Experiments demonstrated that this sensor was able to differentiate and count multiple particle solutions simultaneously through its four microchannels fabricated on polymer membranes. Thus the sensing throughput has been improved significantly in contrast to typical Coulter counters without sacrificing accuracy, sensitivity and reliability. Furthermore, the experimental results also proved the feasibility of differentiating various pollens from polymethacrylate microparticles with the multi-channel resistive-pulse sensor. The differentiation is based on difference in size and surface charge for the bioparticles, with no need for labeling of samples. Possible improvements and extensions to other biological particle detection are discussed.

Detection and counting of micro-scale particles and pollen using a multi-aperture Coulter counter

We demonstrate a high throughput, all-electronic Coulter-type sensor with four sensing microapertures to detect and count micro-scale particles. Four particle samples are utilized for this study: polymethacrylate particles 40 µm and 20 µm in diameter, Juniper Scopulorum (Rocky Mountain Juniper) pollen and Cottonwood pollen particles. The two types of pollen particles are roughly 20 µm in diameter. The particles are mixed with deionized water and forced to pass through the microapertures. Voltage pulses across all four apertures are recorded and analysed. Results demonstrate that the sensor can detect and count particles through its four sensing apertures simultaneously. Thus, the counting efficiency of the four-aperture sensor is approximately 300% higher than that of a single-channel Coulter counter, while maintaining the same accuracy, sensitivity and reliability. The counting efficiency can be improved further by integrating more sensing channels on a single micromachined chip. Results also demonstrate that the device can be used to differentiate between pollen and polymethacrylate particles; differentiation is based on a difference in surface charge for the two types of particles.

Factors Influencing Electrorheological Properties and Stability of Suspensions Obtained Directly from Inverse Emulsion Polymerization

Electrorheological (ER) suspensions containing lithium polymethacrylate particles were prepared directly by inverse emulsion polymerization. Some factors affecting the stability and ER properties of the suspensions were investigated. The stability of the ER suspension increases by decreasing the average diameter of the particles and increasing the amount of copolymer of methacrylic acid and cetyl methacrylate used as stabilizer in the inverse emulsion polymerization. For the most stable ER suspension, chlorinated paraffin oil seems to be the best dispersing medium. Both the yield stress and current density vs. temperature obey the Arrhenius plot. Activation energies for the yield stress and for the current density were estimated to be 0.15 and 0.70 eV, respectively. The higher the electric field strength, the higher the yield stress and the current density A maximum yield stress occurs at about 3 wt% water content at room temperature. The current density of the ER suspension increases with the average diameter and water content of the particles and also the molar ratio of the lithium salt to polymethacrylic acid used in the synthesis, but it decreases with increasing amounts of the polymeric stabilizer. A minimum current density exists at 0.3 wt% of methylene bisacrylamide used as a cross‐linking agent in the synthesis. These ER phenomena are discussed in terms of the ionic polarization mechanism.

A new low-cost electroviscometer

The design and construction of an electroviscometer, which can be constructed in a good workshop, is presented; it is intended for use with high-performance electro-rheological (ER) fluids. The instrument allows several properties of ER fluids to be investigated including: the functional dependence of torque transmitted on applied voltage, including the value of the applied electric field needed for the onset of the ER effect; the response time of the ER effect; and the influence of shear rate on the ER effect. All these parameters need to be evaluated in designing fluids required for practical devices. The performance of the electroviscometer is illustrated using data obtained from lithium polymethacrylate particles dispersed in a silicone oil.