Biomedical subjects

M Kiremitçi

Publications and source records attributed to M Kiremitçi.

9 recordsLinked to original sources

PubMed1994

Protein adsorption behaviour of ionogenic poly(HEMA) membranes: a fluorescence study.

A series of ionogenic poly(HEMA) membranes which were prepared by bulk copolymerization of 2-hydroxyethylmethacrylate (HEMA) and anionic or cationic comonomers, acrylic acid (AA), and dimethylaminoethylmethacrylate (DMAEMA), were characterized by equilibrium swelling measurements, surface free energies, and protein adsorption studies. It was found that their equilibrium water content (EWC) values are greater than 40% which increases with increasing comonomer concentration. That is why the surface free energy is approximately the same (approximately 60 erg cm-2) for all surfaces and does not depend mainly on the composition of the polymer matrix. The adsorption of two plasma proteins that have received much attention, i.e. BSA and fibrinogen, on these membranes was followed by fluorimetric measurements as a function of time. The uptake of proteins from dilute solutions appeared to be directly related to the type and density of surface charge, and also structural properties of the proteins.

Adsorption↗

PubMed1993

Relationship of surface characteristics to cellular attachment in PU and PHEMA.

Adhesion characteristics of fibroblastic baby hamster kidney (BHK) cells and epithelial Madine Darby kidney (MDBK) cells on polyurethane (PU) and polyhydroxyethylmethacrylate (PHEMA) based surfaces have been studied. PU surfaces were prepared by a classical solvent-casting procedure of Pellethane solution that contains different types of solvents, i.e., THF, dioxane and their compositions. PHEMA based surfaces were obtained by bulk polymerization of respective comonomers (HEMA, acrylic acid, AA, and dimethylaminoethylmethacrylate, DMAEMA) in the presence of the crosslinker. Thus, a number of polymeric surfaces were obtained with different surface charges (COO- and NH+4) and with different surface free energies in a range between 60-82 ergs/cm2. Surface properties of these membranes were characterized by equilibrium water contents, air and octane contact angles, surface free energies, SEM photographs and ATR-FTIR spectra. Interactions of BHK and MDBK cells with the surfaces were examined in stationary culture conditions which were carried out in MEM supplemented with fetal calf serum. The observations strongly suggested that the chemical and/or physical properties of membrane surface and morphology of the cell control the degree of cell adhesion to the PU and PHEMA based membranes.

Animals↗

PubMed1993

Nonspecific adsorption and covalent coupling of heparin on polyacrylate based microbeads.

Polyacrylate based microbeads were prepared by copolymerization of four different acrylate monomers, namely 2-hydroxyethylmethacrylate (HEMA), ethyleneglycoldimethacrylate (EGDMA), methylmethacrylate (MMA) and dimethylaminoethylmethacrylate (DMEAMA). These beads were further activated with CNBr at alkaline pH. The extend of nonspecific adsorption and covalent coupling of heparin on these beads were investigated in a batch reactors at different temperatures. The effects of initial concentrations of activation agent and heparin were also studied. Nonspecific heparin adsorption on the microbeads containing DMAEMA was significantly higher than the others. Nonspecific adsorption decreased with increasing temperature. Heparin was covalently coupled on CNBr activated microbeads. The amount of coupled heparin increased by increasing concentration of CNBr.

Acrylates↗

PubMed1991

Cell-culturing characteristics of newly developed PHEMA microcarriers: their use with BHK21 cells.

Baby hamster kidney (BHK) fibroblasts, as model cells, have been proliferated on acrylic based microcarriers. Microcarriers were prepared by a novel suspension polymerization of acrylic monomers. Hydroxyethyl methacrylate was the basic monomer. Ethylene glycol dimethacrylate was used as the cross-linker. A hydrophobic comonomer, namely, methyl methacrylate, was included in order to adjust the hydrophilicity of the resultant matrix. An acrylic comonomer with positively charged tertiary amine groups, i.e., dimethylaminoethyl methacrylate, was also added in order to optimize the surface charge of the carriers. The adhesion, spreading, and growth characteristics of BHK cells on these novel beads were studied either in stationary or in submerged culture conditions. The results demonstrate that the cell attachment and growth can be controlled by changing the degree of charge and the hydrophilicity of the poly(hydroxyethyl methacrylate) matrix.

Animals↗

PubMed1990

Structural and cellular characterization of solvent-casted polyurethane membranes.

Fibroblastic cell attachment and growth characteristics of different polyurethane (PU) films were tested. These films were prepared by a classical solvent-casting procedure. By changing the composition and the type of casting solution (i.e. tetrahydrofurane, dioxane, dimethyl formamide-tetrahydrofurane, tetrahydrofurane-dioxane, etc.) PU films with different physical and chemical bulk and surface structures were obtained. Structural properties of these films were investigated by scanning electron microscopy, equilibrium swelling experiments and contact-angle studies. In stationary cell culture tests, a model cell-line, i.e. baby hamster kidney (BHK) were used. Thus the effects of structural properties on the cell behaviour were investigated. The results demonstrate that it is possible to achieve different cell responses by changing the preparation conditions of the films. While the cell attachment is excellent on porous PU surfaces, the others showed similar adhesion. Better proliferation of BHK cells was obtained with PU films prepared from dioxane solution.

Animals↗

PubMed1990

Swelling of PHEMA based membranes in ethanol and their nitroglycerin permeabilities.

The aim of this study is to prepare PHEMA based polymeric membranes for a transdermal delivery system, which includes a skin permeation enhancer (i.e. ethanol) for nitroglycerin. Membranes were prepared by bulk polymerization of HEMA monomer. Polymerization was achieved in the presence of EGDMA, as the cross-linker, and AIBN as the initiator. MMA was used as a comonomer to improve the mechanical properties and to adjust the permeabilities of the resulting membranes. Water was also included in the polymerization mixture to control the matrix structure. Membranes with different chemical and physical structures were prepared. Swelling behaviour of these matrices in ethanol were observed. Nitroglycerin diffusion through swollen membranes (in ethanol) were investigated. It was obtained that the relative amounts of ingredients (i.e., HEMA, MMA, EGDMA and water) in the casting solutions affect both the equilibrium swelling values and the permeabilities. By increasing the water content and by decreasing the amounts of MMA and EGDMA both parameters can be increased. AIBN does not affect these parameters significantly.

Ethanol↗

PubMed1990

Cell adhesion to the surfaces of polymeric beads.

The main goal of this study is to determine the relationship between the surface properties of polymeric materials and fibroblastic cell adhesion. Therefore, two series of polymeric beads, PHEMA and PS, were tested in microcarrier-facilitated cell culture systems. The crosslinked PHEMA beads were prepared by suspension polymerization of HEMA monomer in the presence of various acrylic monomers (i.e. MMA, EGDMA, DMAEMA). The hydrophobic PS beads were used after coated with different alkylamine monomers (i.e. EDA, ALAM, TEA) by plasma polymerization process. The cell culturing studies were performed with BHK cells in stationary culture conditions and the cell adhesion characteristics were determined by the common methods. Attachment of the BHK cells on these microcarriers were satisfactorily modeled by surface saturation type of mathematical expression. The results demonstrated that, there were finite number of sites on the microcarrier surfaces available for adhesion. Number of these sites depends on the surface charge density which was supplied by amine groups and surface wettability. It is possible to achieve desired cell adhesion and also growth, by changing the chemical structure of beads with suitable modification methods.

Allylamine↗

PubMed1988

Subcutaneous polymeric matrix system p(HEMA-BGA) for controlled release of an anticancer drug (5-fluorouracil). II: Release kinetics.

A subcutaneous polymeric drug delivery system, which consists of a polymeric matrix of poly(hydroxyethyl methacrylate-bisglycol acrylate), was developed. 5-fluorouracil was used as the model anticancer drug. Polymer-drug beads with a diameter of 3 mm were prepared by low-temperature radiation polymerization. In order to modify the release rate, polymeric beads with different composition, drug loading and crosslinking density were obtained. The kinetics of drug release were described by the expression Mt/M infinity = ktn. The diffusional release exponent 'n', which was calculated from the release curves, indicated that the mechanism of drug release from the polymeric matrix is due to the anomalous (non-Fickian) type of diffusion.

Acrylates↗

PubMed1988

Subcutaneous polymeric matrix system poly(HEMA-BGA) for controlled release of an anticancer drug (5-fluorouracil). I. Synthesis and structure.

The present study was an attempt to design a new polymer-drug composite system for local chemotherapy. Poly(hydroxyethylmethacrylate-bisglycolacrylate) carriers containing an anticancer drug, 5-fluorouracil, were prepared by low temperature radiation polymerization technique. By changing the relative amounts and the types of ingredients, drug loading and radiation dosage, polymer-drug composites with different structural properties were obtained. This paper presents the preparation procedure and analyses some of the structural properties of these novel composites.

Acrylates↗