Monosize and non-porous p(HEMA-co-MMA) microparticles designed as dye- and metal-chelate affinity sorbents

Removal of DDE by exploiting the alcoho-phobic interactions

DDE (1,1-bis-(4-chlorophenyl)-2,2-dichloroethene), which is a commonly used pesticides in agriculture, has harmful effects on human health. Therefore, the removal of this substance from the drinking water and the soil is essential. Since DDT (1,1″-(2,2,2-Trichloroethane-1,1-diyl) bis(4-chlorobenzene)) is derivation of DDE, the presence of DDT can be monitored by the detection of DDE present in the environment. Herein, we report on the development of aspartic acid-incorporated poly(2-hydroxyethyl methacrylate-L-aspartic acid) [poly(HEMA-MAsp)] cryogel for the removal of DDE from aqueous solutions for the first time in the literature. The synthesized cryogels were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), an N₂ adsorption method, elemental analysis, and swelling test. The separation experiments were carried out via a batch system to get the optimum adsorption conditions including pH, interaction time, initial DDE concentration, and temperature. The desorption and the reusability results revealed that there was no significant decrease in the DDE adsorption capacity of the cryogels after five adsorption-desorption cycles. The maximum DDE adsorption capacity of poly(HEMA-MAsp) cryogels was found to be 31.51 mg DDE/g polymer for 50 mg DDE/L solution.

Enhancement of crystallization with nucleotide ligands identified by dye-ligand affinity chromatography

Ligands interacting with Mycobacterium tuberculosis recombinant proteins were identified through use of the ability of Cibacron Blue F3GA dye to interact with nucleoside/nucleotide binding proteins, and the effects of these ligands on crystallization were examined. Co-crystallization with ligands enhanced crystallization and enabled X-ray diffraction data to be collected to a resolution of atleast 2.7 Å for 5 of 10 proteins tested. Additionally, clues about individual proteins’ functions were obtained from their interactions with each of a panel of ligands.

Enhancement of stability of glucose oxidase by immobilization onto metal ion-chelated poly(N-vinyl imidazole) hydrogels

Poly(N-vinylimidazole), PVIm, gels were prepared by gamma-irradiation polymerization of N-vinylimidazole in aqueous solutions as an affinity gel for glucose oxidase (GOx). These affinity gels with a water swelling ratio of 1800% for plain polymeric gel and between 30-80% for Cu(II) and Co(II)-chelated gels at pH 6.0 in phosphate buffer were used in the GOx adsorption studies. Maximum metal ion adsorption capacity of these hydrogels was found to be 3.64 mmol/g dry gel for Cu(II) and 1.72 mmol/g dry gel for Co(II) leading to GOx adsorption capacities of 343 and 528 mg enzyme/g dry gel, respectively, as compared to 228 mg for the plain dry PVIm gel. Activity studies were carried out using plain and the metal ion-chelated form of this hydrogel to investigate the stability and retained activity of the GOx in different buffer solutions and at different temperatures. Activity of the enzyme, either in free or immobilized form on the gel, decreased dramatically in acetate buffer solutions. In phosphate buffer solution, however, stability of enzyme has been found to be significantly high reaching 90% retained activity at the end of a 40-day period at 4 degrees C for Co(II) chelated systems. After immobilization of the enzyme onto metal-chelated hydrogel, the thermal stability of enzyme was enhanced significantly showing 23% activity, even at 75 degrees C.

Preparation and evaluation of thiolated chitosan scaffolds for tissue engineering

Thiolated chitosan (TCS) was proposed as a promising candidate as scaffold material for tissue engineering. However, a continuous exploration of such material as a three-dimensional (3D) scaffold with controllable design of microstructure as well as mechanical strength was necessitated. The current study was thus carried out to substantiate such potential of TCS. Thioglycolic acid (TGA) was first introduced on the side chain of chitosan (CS) via the amide bond formation between COOH groups of TGA and NH(2) groups of CS. Composite TCS/CS scaffolds with different ratios were prepared via freeze-drying under different temperatures to optimize the structural properties. The microstructure of the scaffolds was observed by scanning electron microscopy (SEM), and tensile strength of scaffolds was measured. Both the TCS/CS proportion and freezing temperature affected the microstructure and mechanical property of scaffolds, which in turn rendered effects on the growth of cultured fibroblasts. Scaffolds obtained from the TCS/CS proportion of 7:3 and a freezing temperature of -20 degrees C had the maximum tensile strength with a pore distribution ranging from a few to several hundred micrometers. The preferential growth of fibroblasts on this scaffold was also demonstrated. Hence, results in this study would offer valuable information on the preparation of suitable TCS scaffolds for tissue engineering.

Monodisperse polystyrene microspheres by dispersion copolymerization of styrene and other vinyl comonomers: characterization and protein adsorption properties

Dispersion polymerization is a very attractive method for preparing micron-size monodisperse polymeric microspheres. The applications of microspheres have been greatly extended by using comonomers. In the present study, five kinds of polystyrene microspheres of 4-6 microm in diameters bearing different surface functional groups were synthesized by copolymerization of styrene and various vinyl comonomers. Their surface physicochemical characteristics were examined, including average particle size and size distribution, concentration of surface functional groups, as well as hydrophobicity. Concentration of FT-IR spectra of different samples were also discussed. The effects of microspheres' surface physicochemical properties on the isotherms of adsorption and chemisorption of BSA were determined. The results show that microspheres bearing different surface function groups have different capacity of protein adsorption. Besides, since the protein adsorption behaviors were more complex than the ideal adsorption model, the isotherms could not fit Freundlich model very well. Possible reasons were discussed. Knowledge gained from these results may be utilized for rational design of carriers of receptors and antibodies used in solid-phase immunoassay, especially Scintillation proximity assay in High-throughput Screening.

Methacrylate-based chromatographic media

This review summarizes the preparation and application of chromatographic separation media based on methacrylate monomers with a major focus on highly crosslinked macroporous beads prepared from 2-hydroxyethyl methacrylate and glycidyl methacrylate, respectively. The effects of process variables such as composition of the polymerization mixture that includes monomers, porogenic solvents, and free radical initiator, suspension stabilizer, reaction temperature, and stirring are detailed for both classical and templated suspension polymerization. In addition, specific features of the preparation of monodisperse beads are also discussed. The performance of methacrylate-based separation media is demonstrated on numerous separations in a variety of chromatographic modes.

Expanded bed adsorption for purification of alcohol dehydrogenase using a dye-iminodiacetic acid matrix

Expanded bed adsorption (EBA) was successfully applied for the purification of alcohol dehydrogenase (ADH) from unclarified bakers' yeast homogenate using a new dye-iminodiacetic acid (IDA) matrix carrying immobilized metal ions. The existence of cells and cell debris do not have a significant effect on the adsorption of ADH on the matrix. The presence of imidazole in adsorption buffer was found to be an important factor in reducing the level of the adsorbed contaminant proteins. The optimal imidazole concentration was 5 mM. The dynamic binding capacity of the dye-IDA matrix in EBA was found to be 569 U/ml matrix. A chromatography of one-step elution with imidazole was developed, in which ADH was successfully adsorbed in the presence of 5 mM imidazole; subsequently, the column was washed with 5 mM imidazole containing 1 M NaCl and eluted with 150 mM imidazole containing 1.5 M NaCl. The purification factor and ADH recovery were 8.8 and 93.5%, respectively.

Development of new dye-metal agarose-coated alumina matrix and elution strategy for purification of alcohol dehydrogenase

A high-density matrix was prepared by coating an alumina particle with agarose using an emulsion technique. Iminodiacetic acid and Cibacron Blue 3GA were immobilized onto this matrix. Charging this matrix with zinc created a useful chromatography matrix for purification of yeast alcohol dehydrogenase. The elution strategy was then investigated to obtain a high recovery of this enzyme and a high purification factor. One-step elution using 4 mM EDTA containing 0.5 M NaCl resulted in 66% enzyme recovery and a purification factor of 4.7. Two-step elution using imidazole containing NaCl resulted in a higher purification factor. The first-step elution using 5 mM imidazole containing 1 M NaCl released most contaminant proteins. The second-step elution using 150 mM imidazole containing 1.5 M NaCl resulted in high-performance purification with a purification factor of 6.5 and an enzyme recovery of 40.7%. Equilibration of the matrix with imidazole prior to sample application increased the purification factor and the enzyme recovery to 8.4 and 76.8%, respectively.

Purification of the specific immunoglobulin G1 by immobilized metal ion affinity chromatography using nickel complexes of chelating porous and nonporous polymeric sorbents based on poly(methacrylic esters). Effect of polymer structure

Ni2+ complexes of the chelating nonporous and porous bead sorbents based on methacrylic esters crosslinked with ethylene dimethacrylate were used in isolation of the horseradish peroxidase-specific immunoglobulin IgG1 from the crude mouse ascitic fluid by immobilized metal ion affinity chromatography (IMAC). Iminodiacetic and aspartic acids were attached to porous poly(glycidyl methacrylate) beads differing in size, morphology and chemical composition. Ethylenediaminetriacetic acid and quinolin-8-ol chelating groups were attached mainly to the surface hydroxyl groups in nonporous poly(diethylene glycol methacrylate) beads through spacers. The latter sorbents exhibited better kinetic characteristics than the former but a very low IgG1 sorption capacity. In a single-step IMAC procedure, the best efficiency in the specific IgG1 purification was obtained with porous sorbents (recovery 92%, purity 73%). Differences in IMAC separations are discussed from the point of view of morphology of polymer beads as well as of the type and concentration of chelating ligands.

Dye-ligand affinity systems

Dye-ligands have been considered as one of the important alternatives to natural counterparts for specific affinity chromatography. Dye-ligands are able to bind most types of proteins, in some cases in a remarkably specific manner. They are commercially available, inexpensive, and can easily be immobilized, especially on matrices bearing hydroxyl groups. Although dyes are all synthetic in nature, they are still classified as affinity ligands because they interact with the active sites of many proteins mimicking the structure of the substrates, cofactors, or binding agents for those proteins. A number of textile dyes, known as reactive dyes, have been used for protein purification. Most of these reactive dyes consist of a chromophore (either azo dyes, anthraquinone, or phathalocyanine), linked to a reactive group (often a mono- or dichlorotriazine ring). The interaction between the dye ligand and proteins can be by complex combination of electrostatic, hydrophobic, hydrogen bonding. Selection of the supporting matrix is the first important consideration in dye-affinity systems. There are several methods for immobilization of dye molecules onto the support matrix, in which usually several intermediate steps are followed. Both the adsorption and elution steps should carefully be optimized/designed for a successful separation. Dye-affinity systems in the form of spherical sorbents or as affinity membranes have been used in protein separation.