New sorbent for bilirubin removal from human plasma: Cibacron Blue F3GA-immobilized poly(EGDMA-HEMA) microbeads

Fabrication of chitin/graphene oxide composite sponges with higher bilirubin adsorption capacity

Chitin/graphene oxide (Ch/GO) composite sponges had been synthesized in 11 wt% NaOH/4 wt% urea aqueous solution by a simple method. The structure, thermal stability and mechanical properties of the composite sponges were investigated by scanning electron microscopy, Fourier-transform infrared spectroscopy, wide-angle X-ray diffraction, thermogravimetric analysis, and compressive strength measurements. The results revealed that chitin and GO were mixed homogeneously. Interestingly, the composite sponges showed meso-macroporous structure, which played an important role in improving their adsorption properties. Besides, thermal stability and mechanical properties were significantly improved compared with pure chitin sponges. Taking advantages of these fantastic characteristics, the maximum adsorption capacity of composite sponges for bilirubin was up to 422.9 mg/g under the optimized condition, which was not only significantly higher than the adsorption capacities of pure chitin sponges, but also superior to those of many reported adsorbents for removal of bilirubin. Furthermore, blood compatibility evaluations confirmed that this blended sponges had negligible hemolysis and coagulation. Therefore, this work provided a potential possibility to offer Ch/GO composite sponges for removal of bilirubin.

Construction of blood compatible lysine-immobilized chitin/carbon nanotube microspheres and potential applications for blood purified therapy

Novel lysine-immobilized chitin/carbon nanotube microspheres are prepared with excellent bilirubin adsorption properties and good blood compatibility for blood purified therapy.

A New Embolization Agent: Embolization of the Kidneys with Ethylene Glycol Dimethacrylate-Hydroxyethyl Methacrylate Copolymer Microbeads

Ethylene glycol dimethacrylate (EGDMA)-hydroxyethyl methacrylate (HEMA) copolymer microbeads (125-150,jm in diameter) were produced by suspension polymerization. The percent of HEMA incorporated and the swelling ratio of the non-porous microbeads produced were 12% and 22.7%, respectively. Microbeads, sterilized with ethylene oxide, were used in the embolization of the kidneys of three adult mongrel dogs by angiography. The effectiveness of the embolization was examined by angiographs after each step. In the first step of the embolization, the microbeads reached the pre-capillaries and blood flow was successfully blocked, which was confirmed by accumulation of the contrast agent within the kidneys. In angiograms after another injection, as the second step, again there were neither contrast agent movement toward the kidneys nor distribution through the paranchyme. The embolized kidneys were subjected to histopathologic examinations where pathological changes were observed.

Attachment of 3T3 and MDBK Cells onto PHEMA-Based Microbeads and their Biologically Modified Forms

Polyhydroxyethylmethacrylate (PHEMA) microbeads in a size range of 150-250 μm were prepared by suspension polymerization in an aqueous phase containing magnesium oxide. Hydroxyl groups were oxidized with NaIO4 and cell adhesive proteins, namely collagen and fibronectin, were immobilized using glutaraldehyde. A spacer-arm, hexamethylene diamine, was used in some cases. Higher amounts of collagen were immobilized, than in fibronectin. The attachment of two cell lines (i.e., 3T3 and MDBK cell lines) on these microbeads with a wide variety of surface properties was studied in vitro culture media. The attachments of both cells, even onto plain microbeads, were significant. Introducing both fibronectin and collagen onto the microbeads caused significant increases in the cell attachment. More cells attached to the microbeads carrying fibronectin covalently attached onto the microbeads through the spacer-arm molecules. Fibronectin was better than collagen for high attachment values. The mathematical model proposed successfully simulated attachment kinetics.

Collagen and Fibronectin Carrying PHEMA Microbeads as Cell Affinity Sorbents

PHEMA microbeads, produced by suspension polymerization, were modified by the immobilization of a spacer (hexamethylene diamine, HMDA), and two proteins, collagen or fibronectin. Adsorption of collagen and fibronectin onto the plain and periodate oxidized PHEMA microbeads were similar; 0.05-0.1 mg of collagen and 0.04-0.05 mg of fibronectin per g of polymer, respectively. Collagen and fibronectin immobilization on PHEMA microbeads were studied at different temperatures, time and pH. The optimal values for immobilization were 0.1 mg/mL for fibronectin; and 0.25 mg/mL for collagen at 25°C for fibronectin and 4°C for collagen; pH 7 in 120 min. Both fibroblastic 3T3 and epithelial MDBK cells were attached to unmodified and modified microbeads. The attachments of both 3T3 and MDBK cells, to the fibronectin and collagen immobilized microbeads were more than 2000 cells per mg of polymer.

Collagen Immobilization onto P(EGDMA/HEMA) Microbeads for Cell Affinity Systems

Both nonswellable and swellable poly(EGDMA/HEMA) microbeads were produced by suspension copolymerization. These microbeads were modified by immobilization of a spacer-arm (hexamethylene diamine, HMDA) and collagen. The optimal values for modifications were as follows: sodium periodate concentration: 0.467 × 10-2 mmol/mL; HMDA concentration: 3.5 × 10-2 mmol/mL; and glutaraldehyde concentration: 0.70 × 106 mmol/mL. Adsorption of collagen onto plain and periodate oxidized poly(EGDMA/HEMA) microbeads were similar, 0.25 and 0.50 mg collagen/g polymer, respectively. Collagen immobilization on poly(EGDMA/HEMA) microbeads was studied at various temperatures, times, and pH by using protein solution containing various amounts of proteins. The optimal values for immobilizations were as follows: the initial collagen concentration: 0.25 mg/mL; temperature: 4°C; pH 7; and the immobilization time; 120 min. Both fibroblastic 3T3 and epithelial MDBK cells were attached to these unmodified and modified microbeads. The attachments of 3T3 and MDBK cells, especially to the collagen immobilized swellable microbeads were very high. Almost 96% of the 3T3 cells available in the cell culture medium became attached to these microbeads (2297 ± 122 cells per mg of polymer). There was no significant effect by swelling on cell attachment.

Cell Growth on Poly(EGDMA/HEMA) Based Microbeads

Poly(EGDMA/HEMA) copolymeric microbeads were prepared by suspension polymerization. A comonomer, i.e., HEMA, was included in the formula in order to provide functional hydroxyl groups on the microbead surfaces. Toluene was used in the polymerization formulations to introduce porosity into the matrix. Hydroxyl groups were first oxidized with NaIO4, and then two biological molecules, namely collagen and fibronectin were immobilized by using glutaraldehyde. A spacer-arm, i.e., hexamethylene diamine, was also used in some cases. More protein molecules were immobilized onto more swellable microbeads using spacer-arm. Higher amounts of collagen were immobilized, more than fibronectin immobilization. Growth of two cell lines, 3T3 and MDBK, on these microbeads with a wide variety of surface properties was studied in vitro culture media. Growths of both cells even onto the plain microbeads were significant. More cell proliferation occurred with the more swellable microbeads. More cells proliferated on the microbeads carrying fibronectin covalently attached onto the microbeads through spacer-arm molecules. Fibronectin was better than collagen for promoting high proliferation. The mathematical model proposed successfully simulated the growth kinetics.

Macroporous PHEMA-based cryogel discs for bilirubin removal

A novel N-methacryloyl-L-tryptophan methyl ester (MATrp) containing poly (hydroxyethyl methacrylate) cryogel (PHEMATrp) disc was prepared for removal of bilirubin (BR) out of human plasma. PHEMATrp cryogel disc was produced by bulk polymerization, with high gelation yield up to 92% and characterized by swelling tests, scanning electron microscopy (SEM), elemental analysis, Brunauer- Emmett-Teller (BET) analysis, contact angle measurements and surface energy calculations. BR adsorption studies were performed in a batch system, and the maximum BR adsorption capacity was found as 22.2 mg/g cryogel disc.

Bilirubin removal performance of immobilized albumin in a magnetically stabilized fluidized bed

Human serum albumin (HSA)-immobilised magnetic poly(2-hydroxyethyl methacrylate) (mPHEMA) particles were investigated as an adsorbent for selective bilirubin removal from human plasma in a magnetically stabilized fluidized bed system. mPHEMA particles were prepared by suspension polymerization in the presence of Fe3O4 particles. mPHEMA particles were characterized by scanning electron microscopy (SEM), surface area and pore size measurements. The mPHEMA beads have a spherical shape and porous structure. The specific surface area of the mPHEMA particles was found to be 50 m2/g with a size range of 80-120 microm in diameter and the swelling ratio was 45%. Then, HSA was covalently coupled to the cyanogen bromide (CNBr)-activated mPHEMA particles. The amount of coupled HSA was arranged by changing the activation degree of particles (i.e., CNBr concentration). In vitro bilirubin removal was investigated from hyperbilirubinemic human plasma on the mPHEMA particles containing different amounts of immobilised HSA (between 11 and 100 mg/g). The non-specific bilirubin adsorption on the bare mPHEMA particles was 0.47 mg/g. Higher bilirubin adsorption capacities, up to 88.3 mg/g, were obtained with the HSA-immobilised magnetic particles. Bilirubin capacity decreased significantly from 75.0 mg/g to 40.0 mg/g polymer with the increase of the flow-velocity from 0.5 ml/min to 4.0 ml/min. Bilirubin adsorption increased with increasing temperature. Adsorption behavior of bilirubin could be modelled using the Langmuir isotherm.

[Preparation of bovine serum albumin immobilized adsorbent for specific adsorption of bilirubin]

Serum bilirubin concentration is greatly elevated in certain diseases such as hyperbilirubinemia and severe hepatitis. Lowering the level of bilirubin is one of the major targets of many therapies such as plasma exchange and hemoperfusion. In this study, a bilirubin specific adsorbent was prepared by covalently immobilizing bovine serum albumin (BSA) onto macroporous poly (glycidyl methacrylate-co-trimethylolpropane trimethacrylate) microspheres. The resulting BSA immobilized adsorbent (BIA) demonstrated good performance in adsorption of bilirubin with an adsorption capacity of 48.7 mg/g. Presence of BSA in bilirubin solution significantly lowered the adsorption capacity of the adsorbent due to the tight binding of bilirubin onto BSA. Adsorption performance of the adsorbent for bilirubin was improved with the elevation of temperature. The adsorbent demonstrated good stability even after 31 d of storage at - 80 degrees C in that there was almost no change in adsorption capacity for bilirubin. These results indicated that the prepared BSA immobilized adsorbent could be an alternative choice for specific adsorption of bilirubin.

A microfluidic approach to fabricate monodisperse hollow or porous poly(HEMA-MMA) microspheres using single emulsions as templates

We have successfully developed a novel and simple method to controllably prepare monodisperse poly(hydroxyethyl methacrylate-methyl methacrylate) (poly(HEMA-MMA)) microspheres with two distinct structures using single emulsions as templates. By employing a microfluidic emulsification approach to fabricate monomer-contained oil-in-water (O/W) emulsions as templates, and introducing proper initiators and different types of porogens, poly(HEMA-MMA) microspheres with hollow or porous structure are prepared in a controllable way. The shell thickness of hollow microspheres or the porosity of porous microspheres is controllably achieved by simply adjusting the porogen concentration. The prepared poly(HEMA-MMA) microspheres with controllable hollow or porous structures are favored for various potential applications. Furthermore, by using the simple preparation methodology proposed in this study, fabrication of monodisperse porous microspheres or hollow microcapsules with other materials can also be easily achieved.

Bilirubin removal from human plasma by Cibacron Blue F3GA using immobilized microporous affinity membranous capillary method

A novel affinity sorbent system for direct bilirubin removal from human plasma was developed. These new adsorbents comprise Cibacron Blue F3GA as the specific ligand, and microporous membranous poly(tetrafluoroethylene) capillary (modified by coating with a hydrophilic layer of poly(vinyl alcohol) after activation) as the carrier matrix. The affinity adsorbents carrying 126.5 micromol Cibacron Blue F3GA/g polymer was then used to remove bilirubin in a flow-injection system. Non-specific adsorption on the poly(vinyl alcohol) coated capillary remains low, and higher affinity adsorption capacity, of up to 76.2 mg/g polymer was obtained after dye immobilization. The bilirubin adsorption capacity of the affinity capillary decreased with increase in the recirculation rate of plasma. The adsorption capacity increased with increase the temperature while decreased with increase the ionic strength. The maximum adsorption was only observed in neutral solution (pH 6-7). The adsorption isotherm fitted the Langmuir model well. These new adsorbents have higher velocity of mass transfer, better adsorption capacity, less fouling, longer service life and good reusability. The results of blood tests suggested the dye affinity capillary has good blood compatibility.

Adsorptive membranes for bilirubin removal

In this study, we employed ethylene vinyl alcohol (EVAL) adsorptive membranes with bovine serum albumin (BSA) as bioligand for affinity supports for bilirubin (BR) retention. Microfiltration membranes were prepared from ternary or quaternary water/(1-octanol)/DMSO/EVAL systems. To obtain active binding sites for BSA, the EVAL membranes were either chemically functionalized in aqueous and organic medium and by plasma dischargement or physically activated by entrapping of active particles. Static BR removal was determined for all EVAL-BSA membranes. BR retentions relevant for human plasma were gained for the mixed adsorber membranes and additionally investigated in the dynamic mode.

Synthesis and characterization of a biospecific adsorbent containing bovine serum albumin as a ligand and its use for bilirubin retention

Epoxy-activated gels from cross-linked polybutadiene-hydroxyethylmethacrylate (PB-HEMA) copolymer and epichlorohydrin (ECH) were prepared and characterized. Albumin was covalently bonded to the matrix and used as support of affinity chromatography in bilirubin (BR) retention experiments. PB-HEMA-ECH with different amounts of immobilized albumin (between 5.20 and 6.80 mg/g dry gel) were obtained. Bilirubin retention of 3.10 mg/g of these beads was observed at 5 degrees C.

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.

Attachment of 3T3 and MDBK cells onto poly(EGDMA/HEMA) based microbeads and their biologically modified forms

Poly(EGDMA/HEMA) based microbeads were prepared by suspension polymerization. A comonomer, i.e., 2-hydroxyethylmethacrylate (HEMA) was included in the recipe in order to have functional hydroxyl groups on the microbead surfaces. Toluene was used in the polymerization formulations to introduce porosity into the matrix. Hydroxyl groups were first oxidized with NaIO4, and then two biological molecules, namely collagen and fibronectin were immobilized by using glutaraldehyde. A spacer-arm, i.e., hexamethylene diamine, was also used in some cases. More protein molecules were immobilized onto more swellable microbeads using spacer-arm. Higher amounts of collagen were immobilized, more than fibronectin immobilization. Attachment of two cell lines (i.e., 3T3 and MDBK cell lines) on these microbeads with a wide variety of surface properties was studied in vitro culture media. Attachments of both cells even onto the plain microbeads were significant. More cells did attach to more swellable microbeads. Introducing both fibronectin and collagen onto the microbeads caused significant increase in the cell attachment. More cells attached to the microbeads carrying fibronectin covalently attached onto the microbeads through the spacer-arm molecules. Fibronectine was better than collagen for high attachment values. The mathematical model proposed successfully simulated attachment kinetics.

A potential cell affinity sorbent: fibronectin carrying poly(EGDMA/HEMA) microbeads

Both non-swellable and swellable poly(EGDMA/HEMA) microbeads were produced by suspension copolymerization. These microbeads were modified by immobilization of a spacer-arm (hexamethylene diamine, HMDA) and fibronectin. The optimal values for modifications were as follows: the sodium periodate concentration 1.0 mg ml(-1); the HMDA concentration 4 mg ml(-1); and the glutaraldehyde concentration 0.070 microg ml(-1). Adsorption of fibronectin onto the plain and periodate-oxidized poly(EGDMA/HEMA) microbeads were very similar, and were 0.025-0.035 mg fibronectin per g polymer, respectively. Fibronectin immobilization on poly(EGDMA/HEMA) microbeads were studied at different temperature, time and pH using single protein solution containing different amount of proteins. The optimal values for immobilizations were as follows: the initial fibronectin concentration 0.1 mg ml; temperature + 25 degrees C; pH 7; the immobilization time 120 min. Both fibroblastic 3T3 and epithelial MDBK cells were attached to these unmodified and modified microbeads. The attachments of both 3T3 and MDBK cells, especially to the fibronectin-immobilized swellable microbeads, were very high. Almost 96% of the 3T3 cells available in the cell culture medium did attach to these microbeads (2345 +/- 98 cells per mg of polymer).