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

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.

Model Protein BSA Adsorption and Covalent Coupling onto Methyl Methacrylate Based Latex Particles with Different Surface Properties

The adsorption and covalent coupling of bovine serum albumin (BSA) onto methylmethacrylate (MMA) based monodisperse latex particles with different hydrophylic surfaces were investigated. P(MMA) and P(MMA/HEMA) microbeads in the size range of 1.5–2.0 mm were prepared by a dispersion homopolymerization method in the presence of poly(vinylpyrrolidone) (PVP) and poly(vinyl alcohol) (PVA) as steric stabilizer and by copolymerization of MMA and 2-hydroxethyl methacrylate (HEMA) where PVP was used as steric stabilizers. Surface properties of these particles were characterized in terms of contact angle measurements and FTIR-DRS spectra. Additionally, hydroxyl groups of PMMAPVA and P(MMA/HEMA) particles were activated to provide aldehyde groups on surfaces. Adsorption of the BSA onto these five types of latex particles was examined as a function of initial albumin concentration, pH and ionic strength of the various cations (Na+,Ca+ and Mg− and anions (Cl− and SCN−). The maximum adsorption capacities for all latex particles were obtained in solutions with 0.01μ m ionic strength and 1 mg/mL BSA concentration. When using PMMAPVA, P(MMA/HEMA) and PMMAPVP, the adsorption increased as hydrophobicity increased. Aldehyde activation of the two most hydrophobic particles elevated the coupling (immobilization) significantly in ionic strength of 0.01μ m. The adsorption and/or immobilization were maximum in the presence of monovalent cation, Na+ or anion, Cl−B for all types of latex particles.

Surface Modification and Covalent Coupling of Concanavalin A onto Poly(EGDMA/HEMA) Microbeads for Cell Affinity Applications

The surfaces of nonporous and porous Poly(EGDMA/HEMA) microbeads were modified by the reaction of sodium periodate, hexamethylenediamine and glutaraldehyde. Covalent immobilization of Concanavalin A (Con A) was optimized for maximum loading at various Con A concentrations, pH, temperatures, and ionic strengths. The optimal Con A immobilized concentration was determined as 0.37 and 0.75 mg/g microbeads for the nonporous and porous microbeads, respectively. Covalent coupling was achieved at 37 C, with 0.5 mg/mL of Con A at pH 7.4 and ionic strength of 0.01. The specific activity of Con A immobilized microbeads to carbohydrate structure was tested for affinity for myeloma HeLa cells. The data indicates that Con A may play a role in myeloma cell adhesion.

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.

Protein A Immobilized Poly(Methylmethacrylate-Co-Hydroxyethylmethacrylate) Microbeads for IgG Adsorption

Poly(methylmethacrylate- co-2-hydroxyethylmethacrylate) microbeads in the size range of 1.5-2.0μm were prepared by a phase inversion polymerization. The hydroxyl groups were activated by periodate oxidation, and the active ligand, i.e., protein A was immobilized via a spacer-arm, i.e., hexamethylene diamine (HDMA) by using a cross-linker, i.e., glutaraldehyde and protein A. The optimal concentration obtained for modifications are as follows: sodium periodate concentration: 0.467 × 10−2mmol/mL; HMDA concentration: 3.5 × 10−2mmol/mL; and glutaraldehyde concentration: 0.7 × 10−6mmol/mL. Yields of immobilization of protein A onto the plain and periodate oxidized microbeads were found very close, and were in the range of 0.01-0.02 mg protein A/g microbeads. The optimal conditions for immobilization are as follows: the initial protein A concentration: 0.1 mg/mL; temperature: 25°C; pH: 9.5; and immobilization time:120 min. Incorporation of protein A at these conditions resulted in 0.825 mg protein A/g microbeads. The HIgG adsorption onto these protein A incorporated microbeads was 41 mg HIgG/g microbeads.

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.

Adding Functions to Biomaterial Surfaces through Protein Incorporation

The concept of biomaterials has evolved from one of inert mechanical supports with a long-term, biologically inactive role in the body into complex matrices that exhibit selective cell binding, promote proliferation and matrix production, and may ultimately become replaced by newly generated tissues in vivo. Functionalization of material surfaces with biomolecules is critical to their ability to evade immunorecognition, interact productively with surrounding tissues and extracellular matrix, and avoid bacterial colonization. Antibody molecules and their derived fragments are commonly immobilized on materials to mediate coating with specific cell types in fields such as stent endothelialization and drug delivery. The incorporation of growth factors into biomaterials has found application in promoting and accelerating bone formation in osteogenerative and related applications. Peptides and extracellular matrix proteins can impart biomolecule- and cell-specificities to materials while antimicrobial peptides have found roles in preventing biofilm formation on devices and implants. In this progress report, we detail developments in the use of diverse proteins and peptides to modify the surfaces of hard biomaterials in vivo and in vitro. Chemical approaches to immobilizing active biomolecules are presented, as well as platform technologies for isolation or generation of natural or synthetic molecules suitable for biomaterial functionalization.

Protein A immobilization and HIgG adsorption onto porous/nonporous and swellable HEMA-incorporated polyEGDMA microspheres

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 protein A. The optimal values for modifications were as follows: sodium periodate concentration, 1.0 mgml(-1); HMDA concentration, 4 mgml(-1); and glutaraldehyde concentration, 0.070 microgml(-1). Adsorption of protein A onto the plain and periodate oxidized poly(EGDMA/HEMA) microbeads were very close to each other, and were 0.01-0.02 mg protein A on the 1-g Microbeads I and II, respectively. Protein A immobilization on poly(EGDMA/HEMA) microbeads were studied at different temperatures, times, and pHs using single protein solution containing different amounts of proteins. The optimal values for immobilization were as follows: the initial protein A concentration, 0.1 mgml(-1); temperature, 25 degrees C; pH, 9.5; and immobilization time, 120 min. Incorporation of protein A resulted in 1.420 and 1.825 mg protein A on the 1-g Microbeads I and II, respectively. HIgG adsorption capacity on the protein A-incorporated poly(EGDMA/HEMA) microbeads is 27 and 35 mg HIgGg(-1) polymer for Microbeads I and II, respectively.