Characterization of alginate beads formed by a two fluid annular atomizer

Applied Biochemistry and Biotechnology - A two fluid atomizer for the formation of small alginate beads has been described. It produces beads of narrow size distribution, with mean diameters in the...     

Simple tools for resin distribution

Two simple instruments allowing uniform distribution of resin beads for solid-phase synthesis are described. The first tool simplifies distribution of resin into microtiterplates. The second tool was designed for distribution of a variable amount of resin beads into any number of reaction vessels, and the technique is applicable to resin beads with a wide range of physical properties (density).     

Synthesis of quercetin-encapsulated alginate beads with their antioxidant and release kinetic studies

Abstract

In this present study, different forms of quercetin encapsulated beads were synthesized, namely ionic cross-linked gel beads and cryogel beads. Fourier Transform Infrared (FT-IR) spectra of the beads were used to characterize and prove quercetin encapsulation in alginate beads. Swelling and drying profiles were studied. Besides, release kinetics of quercetin molecules from gel beads and cryogels were carefully investigated in two different solvent/media; dimethyl sulfoxide (DMSO) and Roswell Park Memorial Institute Medium (RPMI-1640). Based upon the release kinetic studies, it is found that quercetin release from alginate cryogel beads fits the first-order release model in DMSO and it depends on the concentration of quercetin in the beads. The release of quercetin from alginate gel beads was described by the Higuchi release model, which highlights the release of quercetin molecules through the pores of the matrix. In RPMI-1640, the release of quercetin from both forms of alginate beads fits zero-order release model and it indicates a constant release of quercetin per unit time. Finally, the radical scavenging activity of the quercetin quantities was tested by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) test, and successful results were obtained compared to reference material.     

Adsorption of tannic acid, humic acid, and dyes from water using the composite of chitosan and activated clay

Chitosan is a well-known excellent adsorbent for a number of organics and metal ions, but its mechanical properties and specific gravity should be enhanced for practical operation. In this study, activated clay was added in chitosan slurry to prepare composite beads. The adsorption isotherms and kinetics of two organic acids (tannic acid, humic acid) and two dyes (methylene blue, reactive dye RR222) using composite beads, activated clay, and chitosan beads were compared. With composite beads as an adsorbent, all the isotherms were better fitted by the Freundlich equation. The adsorption capacities with composite beads were generally comparable to those with chitosan beads but much larger than those with activated clay. The pseudo-first-order and pseudo-second-order equations were then screened to describe the adsorption processes. It was shown that the adsorption of larger molecules such as tannic acid (MW, 1700 g mol(-1)), humic acid, and RR222 from water onto composite beads was better described by the pseudo-first-order kinetic model. The rate parameters of the intraparticle diffusion model for adsorption onto such adsorbents were also evaluated and compared to identify the adsorption mechanisms.     

Coating of poly(styrene-co-divinylbenzene) beads with copolymer of styrene and divinylbenzene

The production of beads with cross-link density varying from the centre to the surface is described.     

The preconcentration of mercury and methylmercury on dithizone-coated polystyrene beads

The preconcentration of "inorganic" and methyl mercury cations from aqueous solution is described. The procedure involves collection of mercury on dithizone-coated macroreticular resin beads prior to analysis by cold-vapour atomic absorption spectroscopy. The beads are readily prepared before use and give rise to quantitative selective recovery of "inorganic" and methyl mercury from fresh and saline water samples.     

Recognition of Staphylococcus enterotoxin via molecularly imprinted beads

The synthesis of molecularly imprinted beads for the recognition of the protein Staphylococcus enterotoxin B (SEB) is described. Two kinds of organic silane (3-aminopropyltrimethoxysilane (APTMS) and octyltrimethoxysilane (OTMS)) were polymerized on the surface of polystyrene microspheres after the SEB template was covalently immobilized by forming imine bonds. The resulting imprinted beads were selective for SEB. The Langmuir adsorption models were applied to describe the equilibrium isotherms. The results showed that an equal class of adsorption was formed in the molecularly imprinted polymer (MIP) with the maximum adsorption capacity of 3.86 mg SEB/g imprinted beads. The MIP has much higher adsorption capacity for SEB than the nonimprinted polymer, and the MIP beads have a higher selectivity for the template molecule.     

General methods to render macroporous stationary phases nonporous and deformable,exemplified with agarose and silica beads and their use in high-performance ion-exchange and hydrophobic-interaction chromatography of proteins

Summary New general methods for the preparation of nonporous beads from macroporous beads are described. One method is based on filling the inner volume of the beads with a solution of a monomer which binds to the matrix at the same time as it is allowed to polymerize. The method is illustrated with agarose and silica as matrices and glycidol as monomer. In an alternative, but principally similar method, we first attached allyglycidyl ether to agarose via the epoxide groups and then allowed acrylamide to react with the immobilized allyl groups during polymerization. In an analogous way, nonporous silica beads were prepared by coupling -methacryloxypropyltrimethoxy silane to the macroporous beads followed by polymerization of acrylamide or N-methylolacrylamide on the immobilized methacryl groups. The latter monomer has the advantage of giving a polymer rich in OH groups, which can be used for crosslinking or/and attachment of different ligands (the glycidol polymers have the same advantage).The nonporous agarose beads have chromatographic properties similar to those of the previously described nonporous agarose beads prepared by shrinkage and subsequent crosslinking. For instance, the beds are compressible, which favors the resolution: compressed beds of large beads give the same or higher resolution than do beds of small beads. Another similarity is that the resolution is independent of flow rate or is even enhanced upon an increase in flow rate, maybe in part owing to the generation of a flow pattern which transports the solute from one bead to another faster than does diffusion. These similarities are demonstrated by anion-exchange and hydrophobic-interaction chromatography of proteins. Even the nonporous silica beads are somewhat deformable owing to the relatively thick polymer coating and share with the nonporous agarose beads the attractive relation between resolution and flow rate. In addition, in comparison with naked silica beads they exhibit very little protein adsorption and are more pH stable. A compressed bed of nonporous, coated 30–45 m silica beads gave in an HIC experiment a resolution comparable to that obtained with a bed of noncompressed, nonporous 1.5-m silica beads, which give a very high resolution, as shown by Unger and coworkers [5].     

Preparation of poly(N-normalpropyl- acrylamide) gel beads

 The gel beads of N-normal-propylacrylamide are prepared by the radical copolymerization of N-normalpropylacrylamide and N,N′-methylene-bis-acrylamide in water. The optimum reaction conditions to obtain the gel beads are revealed from the phase diagram of the reaction system together with the scanning electron microscopy of the reaction products. The scanning electron microscopy of the reaction products also indicates the formation of the spherical gel beads of sub-micron size ranging from 250 to 500 nm in diameter. The viscosity measurements of the suspension of the gel beads indicate that the concentration dependence of the viscosity of the suspension is well described by Einstein’s theory of the viscosity of colloidal particles. The intrinsic viscosity of the suspension of gel beads is then determined. The density of the gel beads, which was obtained from the intrinsic viscosity of the suspension, indicates that the gel beads are in the swollen state at a temperature of 20 ^°C. Received: 12 September 1997 Accepted: 17 December 1997     

Synthesis of polyacrylamide gel beads with electrostatic functional groups for the molecular imprinting of bovine serum albumin

Synthetic materials capable of recognizing proteins are important in separation, biosensors and biomaterials. In this study, bovine serum albumin-imprinted soft-wet polyacrylamide gel beads were prepared via inverse-phase suspension polymerization, using acrylamide and N,N′-methylene diacrylamide as polymeric matrix components and methacrylic acid as functional monomer. The adsorption study showed, through the imprinting process, that the imprinted gel beads had much higher adsorption capacity than the nonimprinted gel beads, and that the matching of the surface zeta-potential between the templates and the imprinted gel beads can enhance the imprinting effect. Adsorption kinetics indicated that the adsorption process could be described as an apparent first-order kinetic process for the gel beads. From the adsorption isotherm curve, we found that the adsorption of the imprinted gel beads was in agreement with the Langmuir adsorption model. Moreover, selectivity testing of the imprinted gel beads showed that imprinted gel beads exhibited good recognition for BSA as compared to the control protein. We speculate that the formation of complementary shapes and multiple-point electrostatic interactions between the imprinting cavities and the template proteins are the two factors that lead to the imprinting effect.      

Preparation of Designer Resins via Living Free Radical Polymerization of Functional Monomers on Solid Support

Merrifield resin is converted to a solid-supported free radical initiator by reacting with the TEMPO-Na. Heating TEMPO-methyl resin with a variety of functionalized styrene and acrylate monomers gives larger resin beads via living free radical polymerization. We have coined the term Rasta resin to describe resin beads prepared in this fashion. The process can be described as a solvent-free suspension polymerization. It is particularly well suited for preparation of resin beads from monomers which contain electrophilic groups that would be destroyed upon suspension polymerization in water. Rasta resins have a novel macromolecular architecture wherein long straight chain polymers bearing reactive functional groups emanate from the phenyl groups of a cross-linked polystyrene core. With judicious choice of co-monomers and polymerization strategy, the solvent affinity, loading capacity, and distance of functionality from the cross-linked core may be controlled giving beads with properties that are tailored to specific uses as synthesis supports and scavenging resins.     

Vibrational spectroscopic encoding of polystyrene-based resin beads: converting the encoding peaks into barcodes

A detailed approach is described for the vibrational spectroscopic encoding of polystyrene-based resin beads by converting the infrared absorption peaks suitable for encoding (encoding peaks) into barcodes. Based on combining the FT-IR measurements and the quantum-chemical computations, the vibrational characteristics of p-tert-butylstyrene monomer, polystyrene and poly(p-tert-butylstyrene) resin beads are analyzed, which are helpful for the selection of encoding peaks. The vibrational spectroscopic encoding of polystyrene-based resin beads could be obtained by converting the wavenumber, intensity and full width at half maximum (FWHM) of the encoding peaks into barcodes automatically through a computer program designed in our laboratory.     

Adsorption of anionic dye by anionic surfactant modified chitosan beads: Influence of hydrophobic tail and ionic head-group

In this paper, how chitosan hydrogel beads were modified by anionic surfactants (SDS, SDOS, SDBS, AOT, and DTM-12) and then used for the adsorption and removal of an anionic dye (congo red) from aqueous solutions were described. The effect of surfactant concentration, surfactant ionic head-group, and surfactant hydrophobic tail were investigated in detail. The result revealed the modified CS beads all had the obviously higher adsorption capacity than CS beads. Compared to the ionic head-group, the hydrophobic tail of the surfactant plays more important role in the adsorption, and a high adsorption capacity was observed for CS/AOT beads and CS/DTM-12 beads (both with two hydrophobic tails). The Sips isotherm model showed a good fit with the equilibrium experimental data, and the values of the heterogeneity factor (n) indicated heterogeneous adsorption. The adsorption kinetics analysis indicated that the pseudo-second-order rate model could better describe the adsorption process than the pseudo-first-order rate model.     

Adsorption of chromium from aqueous solution using chitosan beads

A basic investigation on the removal of Cr(III) and Cr(VI) ions from aqueous solution by chitosan beads was conducted in a batch adsorption system. The chitosan beads were prepared by casting an acidic chitosan solution into an alkaline solution. The influence of different experimental parameters; pH, agitation period and different concentration of Cr(III) and Cr(VI) ions was evaluated. A pH 5.0 was found to be an optimum pH for Cr(III) adsorption, and meanwhile pH 3.0 was the optimum pH for the adsorption of Cr(VI) onto chitosan beads. The Langmuir and Freundlich adsorption isotherm models were applied to describe the isotherms and isotherm constants for the adsorption of Cr(III) and Cr(VI) onto chitosan beads. Results indicated that Cr(III) and Cr(VI) uptake could be described by the Langmuir adsorption model. The maximum adsorption capacities of Cr(III) and Cr(VI) ions onto chitosan beads were 30.03 and 76.92 mg g⁻¹, respectively. Results showed that chitosan beads are favourable adsorbents. The Cr(III) and Cr(VI) ions can be removed from the chitosan beads by treatment with an aqueous EDTA solution.     

Conjugating a cyanine dye to a polymer surface. In search of a monomeric dye in apolar media

Solution and solid-phase syntheses of a cyanine dye conjugated to polystyrene beads (desired for potentially interesting electronic properties) are described.     

An immobilized immuno-stirrer for the determination of creatine kinase-mb isoenzyme in blood serum

An immobilized immuno-stirrer is described for the determination of creatine kinase-MB isoenzyme in blood serum. The IgG antibodies are immobilized on alkylamine glass beads using glutaraldehyde as cross-linking reagent, and the beads are packed into a rotating porous cell. After incubation with stirring, the CK-M isoenzymes in the blood serum sample are inhibited and are bound to the antibodies inside the stirrer. The residual CK-B isoenzyme activity is then determined spectrophotometrically or electrochemically. The binding capacity of the immuno-stirrer to CK-M isoenzyme was estimated to be 800 Ul^-1 with an average inhibitory efficiency of 97.8%. The within-day and day-to-day coefficients of variation were 5% and 4%, respectively, over a period of 52 days. An immuno-stirrer loaded with antibodies attached to cyanogen bromide-activated cellulose beads was also characterized, but the antibodies were not as stable as on glass beads.     

Array-based split-pool combinatorial screening of potential catalysts

A new method for screening split-pool combinatorial libraries for catalytic activity is described. Site-selective detection of catalytic activity for solution-based reactions was made possible without cofunctionalizing beads or adding diffusion-limiting matrixes. This was done by spatially separating resin-bound catalysts on an adhesive array on a microscope slide and introducing the reacting liquid to the top of the slide. Convective mixing and evaporation was controlled using a cover slide and imaging both the formation of products within active beads and the diffusion of products out of the beads. Colored reaction products and pH-sensitive indicators were used to visually detect catalytically active beads in the presence of inactive ones. Quantitative analyses of the images support the assumption that color intensities can be used to assess the quality of hits from a combinatorial screen. The Knoevenagel condensation reaction catalysis as well as esterase screening using methyl red were used to validate the approach. Using the esterase data, it was shown that some information on activity could also be extracted from the colored plume surrounding individual beads although the precision is not as good as that from direct measurement of absorbance through the bead. It was also found that the distribution of products within a single bead can also be gleaned from the absorbance data for different-sized beads.     

Immobilization of penicillin acylase in porous beads of polyacrylamide gel

A procedure is described for the immobilization of benzylpenicillin acylase from Escherichia coli within uniformly spherical, porous polyacrylamide gel beads. Aqueous solutions of the enzyme and sodium alginate and of acrylamide monomer, N,N'-methylene-bis-acrylamide, N,N,N,N'-tetramethylethylenediamine (TEMED) and sodium alginate are cooled separately, mixed, and dropped immediately into ice-cold, buffered calcium formate solution, pH 8.5, to give calcium alginate-coated beads. The beads are left for 30-60 min in the cold calcium formate solution for polyacrylamide gel formation. The beads are then treated with a solution of glutaraldehyde and the calcium alginate subsequently leached out with a solution of potassium phosphate. Modification of the native enzyme with glutaraldehyde results in a slight enhancement in the rate of hydrolysis of benzylpenicillin at pH 7.8 and 0.05M substrate concentration. The enzyme entrapped in porous polyacrylamide gel beads shows no measurable diffusional limitation in stirred reactors, catalyzing the hydrolysis of the substrate at a rate comparable to that of the glutaraldehyde-modified native enzyme. The immobilized enzyme preparation has been used in batch mode over 90 cycles without any apparent loss in hydrolytic activity.     

Prussian Blue Dispersed Sphere Catalytic Labels for Amplified Electronic Detection of DNA

A highly sensitive electrochemical DNA hybridization assay using Prussian blue (PB)-modified polymeric spheres as the oligonculeotide labeling tag is described. The sandwich assay relies on a secondary nucleic-acid probe functionalized with polystyrene beads loaded with numerous Prussian blue nanoparticles. The very strong catalytic activity of the captured PB 'artificial peroxidase' tag towards the reduction of hydrogen peroxide, along with the encapsulation of numerous catalytic particles onto polymeric beads, allows amperometric detection of the DNA target down to the 50 fM level (2.5 amol). Imaging and spectroscopic measurements are used to characterize the PB-tagged polystyrene beads. Such coupling of PB catalytic labels with polymeric carrier beads offers great promise for amplified transduction of different biomolecular interactions.     

Adsorption of humic acid from aqueous solutions on crosslinked chitosan-epichlorohydrin beads: kinetics and isotherm studies

The adsorption of humic acid on crosslinked chitosan-epichlorohydrin (chitosan-ECH) beads was investigated. Chitosan-ECH beads were characterized by Fourier transform infrared spectroscopy (FTIR), surface area and pore size analyses, and scanning electron microscopy (SEM). Batch adsorption experiments were carried out and optimum humic acid adsorption on chitosan-ECH beads occurred at pH 6.0, agitation rate of 300 rpm and contact time of 50 min. Adsorption equilibrium isotherms were analyzed by Langmuir and Freundlich models. Freundlich model was found to show the best fit for experimental data while the maximum adsorption capacity determined from Langmuir model was 44.84 mg g(-1). The adsorption of humic acid on chitosan-ECH beads was best described with pseudo-first-order kinetic model. For desorption study, more than 60% of humic acid could be desorbed from the adsorbent using 1.0M HCl for 180 min.