Ali Tuncel

Cibacron Blue F3G-A-attached monosize poly(vinyl alcohol)-coated polystyrene microspheres for specific albumin adsorption

Abstract Monosize polystyrene (PS) microbeads (4 μm in diameter) were produced by phase inversion polymerization of styrene in ethanol-methoxyethanol medium. They were coated with poly(vinyl alcohol) (PVAL) by adsorption and chemical cross-linking to decrease the non-specific protein adsorption. Cibacron Blue F3G-A was then attached for specific protein adsorption. The adsorption conditions were optimized to increase the amount of PVAL by changing the initial concentration of PVAL, and using different types of salts at different ionic strengths. Higher amounts of PVAL (up to 19 mg PVAL/g PS) were loaded by increasing the PVAL initial concentration and by using NA 2 SO 4 at a higher ionic strength (0.2). Bovine serum albumin (BSA) adsorption and desorption on these PS-based microbeads were also investigated under different conditions. PVAL coating prevented the non-specific BSA adsorption. A higher amount of BSA (up to 60 mg BSA/g dye-attached PS/PVAL) was specifically adsorbed on dye-attached PS microbeads, especially around pH 5 and lower ionic strengths (0.01). About 90% of the adsorbed BSA was desorbed in 1 h by using 0.5 M NaSCN.

Swellable ethylene glycol dimethacrylate-hydroxyethylmethacrylate copolymer beads

Abstract In this study, Swellable poly(EGDMA/HEMA) beads in the size range of 30–170 μm with different size distributions were produced by suspension copolymerization of ethylene glycol dimethacrylate (EGDMA) and hydroxyethylmethacrylate (HEMA) in aqueous media. Poly(vinyl alcohol) and benzoyl peroxide were used as the stabilizer and the initiator. The diluent, i.e. toluene was included in the recipe of the second group of copolymerizations. The beads were characterized by optical microscopy, FTIR and FTIR-DRS. Crosslinked, transparent, nonporous and Swellable (up to a swelling ratio of 31.2%) poly(EGDMA/HEMA) beads were obtained in which there was no toluene in the recipe. While copolymerizations with toluene provided Swellable (up to a swelling ratio of 57.1%), opaque, porous and crosslinked copolymer beads. In the polymerization (without toluene) HEMA is mainly incorporated on the outer layers (near surface) of the beads. In this case, increase in the EGDMA/HEMA ratio resulted larger beads with wider size distributions, and with lower swellabilities. The porosity of the dry copolymer beads were studied with mercury pycnometric method. Incorporation of toluene within the recipe (in the modified polymerization) caused pronounced effects both on bead size and swellability. Larger beads with broader size distributions, with higher swellabilities were obtained when the relative amount of toluene increased.

Preparation and characterization of thermoresponsive isopropylacrylamide - hydroxyethylmethacrylate copolymer gels

A random copolymer of N-isopropylacrylamide and 2-hydroxyethylmeth-acrylate, poly(NIPAM-co-HEMA), having thermoresponsive character was prepared bya redox copolymerization method. Poly(ethylene glycol), PEG 4000 was included in the copolymerization recipe to increase the thermoresponsivity of copolymeric structure. Poly(NIPAM-co-HEMA) copolymer gels having more elastic character and higher mechanical strength relative to poly(NIPAM) gel could be achieved by the proposed copolymerization procedure. The equilibrium and dynamic response against the temperature were investigated for the gel matrices produced by changing the initial NIPAM/HEMA mol ratio and PEG 4000 concentration in the copolymerization mixture. The effective diffusion coefficient of water within the gel matrix was estimated for either swollen or shrunken states by applying an unsteady-state diffusion model on the dynamic swelling and shrinking behaviors of gel matrix prepared in the cylindrical form.

Phagocytosis of monosize polystyrene-based microspheres having different size and surface properties

In this study, nondegradable monosize polystyrene (PS) based polymeric microspheres with different size and surface chemistries were prepared by different polymerization techniques. Surfaces of the plain microspheres were further modified biologically by albumin (BSA) or fibronectin (Fn) preadsorption. Phagocytosis of these polymeric microspheres by leukocytes and macrophages were investigated. The phagocytic response of both leukocytes and macrophages decreased by increasing size of the particles. More hydrophilic particles phagocytosed less. Positive charges increased the uptake while negative charges oppositely reduced the uptake. BSA on the surface almost prevented the uptake, while Fn caused opsonization.

Nonswellable and swellable poly(EGDMA) microspheres

In this study, nonswellable and swellable poly(ethylene glycol-dimethacrylate) microspheres, in the size range of 20–177 μm, were produced by conventional and modified suspension polymerizations of ethylene glycol-dimethacrylate (EGDMA) in an aqueous medium. Poly(vinyl alcohol) and benzoyl peroxide were used as the stabilizer and the initiator. A diluent, i.e., toluene, was included in the polymerization recipe of the modified suspension polymerization. The microspheres were characterized by optical microscopy, FTIR, and FTIR-DRS. Highly crosslinked, transparent, and nonswellable poly(EGDMA) microspheres were obtained with the conventional suspension polymerization procedure. While the modified suspension polymerization provided swellable, opaque, and crosslinked copolymer microspheres.

DNA adsorption onto polyethylenimine-attached poly( p-chloromethylstyrene) beads

In this study, DNA adsorption properties of polyethylenimine (PEI)-attached poly(p-chloromethylstyrene) (PCMS) beads were investigated. Spherical beads with an average size of 186 microm were obtained by the suspension polymerization of p-chloromethylstyrene conducted in an aqueous dispersion medium. Owing to the reasonably rough character of the bead surface, PCMS beads had a specific surface area of 14.1 m2/g. PEI chains could be covalently attached onto the PCMS beads with equilibrium binding capacities up to 208 mg PEI/g beads, via a direct chemical reaction between the amine and chloromethyl groups. After PEI adsorption with 10% (w/w) initial PEI concentration, free amino content of PEI-attached PCMS beads was determined as 0.91 mequiv./g. PEI-attached PCMS beads were utilized as sorbents in DNA adsorption experiments conducted at +4 degrees C in a phosphate buffer medium of pH 7.4. DNA immobilization capacities up to 290 mg DNA/g beads could be achieved with the tried sorbents. This value was approximately 50-times higher relative to the adsorption capacities of previously examined sorbents.

Immobilization of α-chymotrypsin in thermally reversible isopropylacrylamide-hydroxyethylmethacrylate copolymer gel

In this study, α-chymotrypsin was immobilized via physical entrapment within thermally reversible poly(isopropylacrylamide-co-hydroxyethylmethacrylate), poly(NIPAM-co-HEMA)copolymer gels. The thermoresponsive gel matrices in cylindrical geometry were prepared in an aqueous buffer medium by a redox polymerization method. The kinetic behavior of enzyme-gel cylinders was investigated in a batch reactor. The results indicated that the overall reaction rate was controlled by the substrate diffusion through the gel matrix. Due to the thermoresponsive character of the carrier gel, the maximum activity was achieved at 30°C with the enzyme-gel system while the free enzyme exhibited maximum activity at 40°C.

Acrylic-based high internal phase emulsion polymeric monolith for capillary electrochromatography

The use of high internal phase emulsion polymers (polyHIPEs) for CEC applications has remained relatively unexplored. A few reports exist in the literature for the preparation of similar structures. In this study, polyHIPEs having high porosity, and interconnected open-cell structure, were introduced and evaluated as stationary phase for CEC. The polyHIPE monolithic columns were prepared by the in situ polymerization of isodecylacrylate (IDA) and divinylbenzene (DVB) in the continuous phase of a high internal phase emulsion (HIPE). Due to its well-defined polyHIPE structure with interconnected micron size spherical voids, the columns synthesized with different initiator concentrations were successfully used for the separation of alkylbenzenes. Furthermore, the columns indicated a strong electroosmotic flow (EOF) without any additional EOF generating monomer probably due to the presence of ionizable sulfate groups coming from the water-soluble initiator used in the preparation of polyHIPE matrix. The best chromatographic performance in the separation of alkylbenzenes was achieved by using 70% ACN in the mobile phase with high column efficiency (up to 200,000 plates/m).

Electron microscopic observation of uniform macroporous particles. I. Effect of seed latex type and diluent

Uniform and macroporous polymer particles in the size range of 5–21 μm were prepared by a multistep seeded polymerization method. The uniform polystyrene particles in the size range of 1.9–7.5 μm were used as the seed particles in the preparation of macroporous beads. The seed particles with different sizes and molecular weights were produced by dispersion polymerization, by changing the type of dispersion medium and the initiator concentration. In the synthesis of macroporous particles, a two-step swelling procedure was employed. The seed latexes were first swollen by a low molecular-weight organic agent (i.e., dibutyl phthalate, DBP), then by a divinylbenzene–ethylvinylbenzene isomer mixture including an oil phase soluble initiator (i.e., benzoyl peroxide). The porous structure in the final beads was achieved by the polymerization of the monomer phase within the swollen seed particles including a mixture of linear polystyrene and DBP. The initiator concentration in the repolymerization step, the seed latex type (i.e., the diameter and the molecular weight of seed latex), DBP/seed latex, and the monomer/seed latex ratios were changed to achieve uniform polymer beads with different average sizes and pore structures. The average size, the size distribution, and the surface morphology of final beads were analyzed by Scanning Electron Microscopy. The internal structure of the beads were analyzed by Transmission Electron Microscopy. The results indicated that the average size of the final particles increased with increasing the seed latex diameter, DBP/seed latex, and monomer/seed latex ratios. The average pore size decreased with decreasing the molecular weight of the seed latex and increasing the DBP/seed latex and monomer/seed latex ratios. These tendencies were explained by the viscosity change of the porogen solution used in the repolymerization step.

Cibacron blue F3G-A attached poly(vinyl alcohol) particles for specific albumin adsorption

Abstract Poly(vinyl alcohol) (PVAL) particles (average size: 50 μm) were prepared in the present study by chemical crosslinking of PVAL with glutaraldehyde in an organic dispersion oil phase. Cibacron Blue F3G-A was attached to these hydrophilic PVAL particles. Bovine serum albumin (BSA) adsorption onto these dye-attached PVAL particles from aqueous solutions containing different amounts of BSA in three different salts (i.e., NaCl, CaCl2, and NaSCN) at different pH and ionic strengths was investigated in batch reactors. The maximum adsorption capacity (about 35 mg BSA/g dye-attached PVAL) was observed around pH 6.0 in a medium containing NaCl with an ionic strength of 0.01. Nonspecific BSA adsorption on plain PVAL particles was almost zero. About 90% of the adsorbed BSA was desorbed by using a 0.5 M NaSCN desorption medium for 1 hour.