Biomedical subjects

E Pişkin

Publications and source records attributed to E Pişkin.

At least 37 records · Page 2Linked to original sources

PubMed1998

Cadmium removal from human plasma by Cibacron Blue F3GA and thionein incorporated into polymeric microspheres.

Poly(2-hydroxyethylmethacrylate-ethyleneglycoldimethacrylate) [poly(HEMA-EGDMA)] microspheres carrying Cibacron Blue F3GA and/or thionein were prepared and used for the removal of cadmium ions Cd(II) from human plasma. The poly(HEMA-EGDMA) microspheres, in the size range of 150-200 microm in diameter, were produced by a modified suspension copolymerization of HEMA and EGDMA. The reactive triazinyl dye-ligand Cibacron Blue F3GA was then covalently incorporated into the microspheres. The maximum dye incorporation was 16.5 micromol/g. Then, thionein was bound onto the Cibacron Blue F3GA-incorporated microspheres under different conditions. The maximum amount of thionein bound was 14.3 mg/g. The maximum amounts of Cd(II) ions removed from human plasma by poly(HEMA-EGDMA)-Cibacron Blue F3GA and poly(HEMA-EGDMA)-Cibacron Blue F3GA-thionein were of 17.5 mg/g and 38.0 mg/g, respectively. Cd(II) ions could be repeatedly adsorbed and desorbed with both types of microspheres without significant loss in their adsorption capacity.

Cadmium↗

PubMed1998

Adhesion of different bacterial strains to low-temperature plasma-treated sutures.

In this study, five different bacteria with their different strains were isolated and characterized. Contact angles were measured by a captive-bubble technique. Surface-free energies were calculated from the contact angles. Hydrophobicities also were evaluated by rho-xylene adhesion. The zeta potentials and surface charges of the bacteria were obtained. The contact angles of the gram-positive bacteria and gram-negative bacteria were within the range of 48 degrees-69 degrees and 43.5 degrees-55 degrees, respectively, while corresponding surface-free energies were in the limits of 45.4-51.6 erg/cm-2 and 51.7-61.8 erg/cm-2, respectively. The rho-xylene adhesions were parallel to hydrophobicities defined by contact angles, and 32.2-80.3% and 2.3-36.6% for the gram-positive bacteria and gram-negative bacteria, respectively. The zeta potentials for these bacteria were from -650.2 to +17.5 mV and from -159.6 to -6.0 mV, respectively. Most of the bacteria were negatively charged, except the CNS-2 and CPS-1 strains. In the second part of the study, attachment of these bacteria to Vicryl sutures and their DMAEMA and AAc plasma-treated forms were investigated. Hydrophobic bacteria attached more to hydrophobic Vicryl sutures. Both plasma treatments caused significant drops in bacterial attachment in most cases. Effects of AAc plasma treatment were more pronounced.

Bacterial Adhesion↗

PubMed1998

Bilirubin removal from human plasma in a packed-bed column system with dye-affinity microbeads.

A dye-ligand. Cibacron Blue F3GA. was covalently coupled with the poly(EGDMA-HEMA) microbeads. The affinity sorbent carrying 16.5 micromol Cibacron Blue F3GA per gram polymer was then used to remove bilirubin from human plasma in a packed-bed column system. Bilirubin adsorption from human plasma on the unmodified poly(EGDMA-HEMA) microbeads was 0.32 mg/g, while much higher adsorption values, up to 24.2 mg/g, were obtained with the dye-attached microbeads. The bilirubin adsorption capacity of the microbeads decreased with an increase in the recirculation rate of plasma. Bilirubin adsorption increased with increasing temperature, and the maximum adsorption achieved at 37 degrees C (32.5 mg bilirubin/g polymer). Bilirubin molecules interacted directly with the immobilized Cibacron Blue F3GA molecules. Contribution of albumin adsorption on bilirubin adsorption was also significant.

Absorption↗

PubMed1998

Interactions of DNA with fluorescent dyes: by scanning tunneling microscopy.

Genomic DNA was obtained from peripheral blood samples of healthy volunteers and interacted with two fluorescent dyes (i.e. Hoechst 33,258 and ethidium bromide) in aqueous media. These media containing DNA-dye complexes deposited on the gold coated mica surfaces. Then, STM images were obtained in which the STM was operated in air at atmospheric pressure with a tip-to-substrate bias voltage of 250-1000 mV (sample positive) and the tunneling currents in the range of 10-20 pA by using etched tips of Pt/Ir, in constant current mode. Both dyes from molecular clusters on DNA. While, the Hoechst molecules were observed on the DNA chains at regular distances, the ethidium bromide molecular clusters did not.

Bisbenzimidazole↗

PubMed1998

In vivo degradation and release kinetics of chloramphenicol-loaded poly(D,L)-lactide sponges.

Poly(d,l)-lactide (PDLLA) homopolymer, with an average molecular weight of 20,000 daltons, was produced by the ring-opening polymerization of d,l-lactide in the presence of SnCl(2).2H(2)O as the catalyst. The PDLLA sponges loaded with chloramphenicol were prepared by a solvent evaporation technique. The drug loadings achieved were 14.84 and 25.23 mg for the PDLLA sponges with 35 and 70 mg total weights, respectively. These sponges were implanted in Wistar rats, and in vivo degradation, drug release, and tissue reactions were followed. The PDLLA sponges carrying no drug degraded with time linearly. Almost 80% of the sponges were degraded in about 180 days. While the drug-loaded PDLLA sponges were degraded much faster in 4 weeks (about 35% of the matrix was degraded), then the degradation slowed down significantly. Drug release from the sponges was parallel to the degradation. Almost 60% of the loaded drug released in 4 weeks. There were no acute inflammatory reactions in the initial period, either for the plain or for the drug-loaded PDLLA sponges. Macrophages and multinuclear giant cells start to appear after 7 days of implantation. The fibroblastic activity also started after the same period. After that, there were decreases in the number of some cells (neutrophils, lymphocytes, and macrophages), while multinuclear giant cells and fibroblastic activities gradually increased. Granulation tissue started at about 1 month, and new connective tissue was gradually formed until 180 days of implantation. There were significant numbers of inflammatory cells after 60 days, which were replaced by fibroblasts after 180 days. There was almost no significant neovascularization after 180 days, but implant fragmentation gradually increased (which slows the degradation) with time. It was concluded that this novel drug release sponge may be safely and effectively used as an active soft tissue-filling material.

Animals↗

PubMed1998

Adhesion of different bacterial strains to low-temperature plasma treated biomedical PVC catheter surfaces.

In this study, firstly five different bacteria (i.e. Coagulase positive and negative staphylococcus, Streptococcus pyogenes, Escherichia coli, Pseudomonas aeruginosa) with their different strains were isolated and used. The contact angle, surface free energy, p-xylene adhesion, and zeta potential of these bacteria were in the range of 43-69 deg, 45.4-61.8 erg cm(-2), 2.3-80.3%, and from -650.2 to + 17.5 mV, respectively. Most of the bacteria were negatively charged. Attachment of these bacteria to PVC catheter and its DMAEMA- and AAc-plasma treated forms were investigated. Bacterial attachment to the hydrophobic PVC catheter was high. Both plasma treatments caused significant drops in bacterial attachment in most of the cases. The effects of AAc-plasma treatment was more significant.

Acrylates↗

PubMed1997

Dye-incorporated poly(EGDMA-HEMA) microspheres as specific sorbents for aluminum removal.

Aluminum [Al(III)] adsorption onto dye-incorporated poly(ethylene glycol dimethacrylate-hydroxyethyl methacrylate) [poly(EGDMA-HEMA)] microspheres was investigated. Poly(EGDMA-HEMA) microspheres, in the size range of 150-200 microm, were produced by a modified suspension polymerization of EGDMA and HEMA. The reactive dyes (i.e., Congo Red, Cibacron Blue F3GA and Alkali Blue 6B) were covalently incorporated to the microspheres. The maximum dye load was 14.5 micromol Congo Red/g, 16.5 micromol Cibacron Blue F3GA/g and 23.7 micromol Alkali Blue 6B/g polymer. The maximum Al(III) adsorption on the dye microspheres from aqueous solutions containing different amounts of Al(III) ions were 27.9 mg/g, 17.3 mg/g and 12.2 mg/g polymer for the Congo Red, Cibacron Blue F3GA and Alkali Blue 6B, respectively. The maximum Al(III) adsorption was observed at pH 7.0 in all cases. Non-specific Al(III) adsorption was about 0.84 mg/g polymer under the same conditions. High desorption ratios (95%) were achieved in all cases by using 0.1 M HNO3. It was possible to reuse these dye-incorporated poly(EGDMA-HEMA) microspheres without significant losses in the Al(III) adsorption capacities.

Adsorption↗

PubMed1997

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

Cibacron Blue F3GA-immobilized poly(EGDMA-HEMA) microbeads were investigated as a specific sorbent for bilirubin removal from human plasma. The poly(EGDMA-HEMA) microbeads were prepared by a modified suspension copolymerization technique. Cibacron Blue F3GA was covalently coupled to the poly(EGDMA-HEMA) microbeads via the nucleophilic reaction between the chloride of its triazine ring and the hydroxyl groups of the HEMA molecule, under alkaline conditions. Bilirubin adsorption was investigated from hyperbilirubinemic human plasma on the poly(EGDMA-HEMA) microbeads containing different amounts of immobilized Cibacron Blue F3GA, (between 5.0-16.5 micromol/g). The non-specific bilirubin adsorption on the unmodified poly(EGDMA-HEMA) microbeads were 0.32 mg/g from human plasma. Higher bilirubin adsorption values, up to 14.8 mg/g, were obtained with the Cibacron Blue F3GA-immobilized microbeads. Bilirubin molecules interacted with these sorbents directly. Contribution of albumin adsorption on the bilirubin adsorption was pronounced. Bilirubin adsorption increased with increasing temperature.

Adsorption↗

PubMed1997

Coating of silicone-based impression materials in a glow-discharge system by acrylic acid plasma.

OBJECTIVES: The main purpose of this study was to demonstrate an increase in the wettability of silicone-based impression materials after coating them with a hydrophilic film in a glow-discharge system. METHODS: Two vinyl polysiloxane impression materials, Extrude (Kerr) and Accuflex (GC America Inc.) were used. Impression specimens were treated in a glow-discharge reactor at a radio frequency of 13.56 MHz at different discharge powers (5-20 W) and exposure times (5-60 min). Surface analysis of the specimens was done by FTIR. Surface contact angles were obtained by a captive-bubble method. These results were analyzed by ANOVA and Duncan's Multiple Range test (p < 0.05). The total number of voids on the die stone casts was observed microscopically. Linear dimensional accuracy, detail reproducibility, and surface hardness of the die stone casts were also determined. A Student t-test was performed for statistical analysis of these parameters (p > 0.05). RESULTS: FTIR spectra indicated that the number of hydroxyl groups on the surfaces increased (p > 0.05) because of the glow-discharge treatment. Contact angle measurements showed an increase (p < 0.05) in surface hydrophilicity. Total void formation in the stone casts decreased. There were no significant differences in the linear dimensional accuracy, detail reproducibility, and hardness, before and after glow-discharge treatment (p > 0.05). SIGNIFICANCE: It was concluded that the surface wettability of the impression materials may be increased by plasma deposition, and therefore, the formation of voids was reduced in the stone casts.

Acrylates↗

PubMed1997

Rifampicin carrying polyhydroxybutyrate microspheres as a potential chemoembolization agent.

In this study, we attempted to prepare microspheres from a microbial biodegradable polyester, i.e. polyhydroxybutyrate (PHB) as a potential chemoembolization agent. The drug loaded PHB microspheres were prepared by a solvent evaporation technique, in which methylene chloride, distilled water, and polyvinyl alcohol were utilized as the solvent, dispersion medium, and emulsifier, respectively. Microspheres were obtained within a size range of 5-100 microns by changing the initial polymer/solvent ratio, emulsifier concentration, stirring rate, and initial drug concentration. It was possible to obtain PHB with very narrow size distributions by applying gravity field-flow fractionation technique. Very high drug loadings of up to 407.6 mg rifampicin/g PHB were achieved. Drug release rates were very rapid. Almost 90% of the drug loaded was released in about 24 h. Both the size and drug content of PHB microspheres were found to be effective in controlling the drug release from these microspheres.

Antibiotics, Antitubercular↗

PubMed1997

Comparison of albumin binding capacities of three different reactive dye-derivatized poly(ethylene glycol dimethacrylate-hydroxyethyl methacrylate) microbeads.

Bovine serum albumin (BSA) adsorption onto dye-derivatized poly(ethylene glycol dimethacrylate-hydroxyethyl methacrylate) [poly(EGDMA-HEMA)] microbeads carrying three different reactive dye ligands (i.e. Congo Red. Cibacron Blue F3GA, and Alkali Blue 6B) was investigated. Swellable poly(EGDMA-HEMA) microbeads, in the size range of 150-200 microns, were produced by a modified suspension copolymerization of EGDMA and HEMA. The dyes were covalently attached to the microbeads. The maximum amounts of dye loadings were 14.5, 16.5, and 23.7 mumol g-1 for Congo Red, Cibacron Blue F3GA, and Alkali Blue 6B, respectively. The maximum BSA adsorption on the dye-derivatized microbeads from aqueous solutions containing different amounts of BSA were 90, 60.5, and 40 mg g-1 for the Congo Red, Cibacron Blue F3GA, and Alkali Blue 6B carrying microbeads, respectively. The maximum BSA adsorptions were observed at pH 6.0 in all cases. Desorption of albumin molecules were achieved by using 1.0 M NaSCN (pH 8.0). High desorption ratios (more than 85% of the adsorbed BSA) were observed in all cases. It was possible to reuse these novel sorbents without significant losses in the adsorption capacities.

Adsorption↗

PubMed1997

Protein A carrying PMMA microbeads: adsorption of cholesterol and HlgG from human plasma.

Cholesterol and HIgG adsorbed from human plasma obtained from a hypercholesterolemic patient, onto protein A-immobilized polymethyl-methacrylate uniform microbeads carrying different amounts of protein A (0.264-1.682 mg protein A/g PMMA, or 0.66-4.2 mg protein A/m2 PMMA) were investigated in batchwise experiments. There was no interaction between protein A molecules and cholesterol when cholesterol aqueous solutions were used. However, there was significant cholesterol and HIgG adsorption from the plasma obtained from a patient with hypercholesterolemia. The maximum amounts of cholesterol and HIgG adsorbed were 3.96 micromol cholesterol/g PMMA (5.4 mg cholesterol/g PMMA) and 0.242 micromol IgG/g PMMA (35.4 mg IgG/g PMMA).

Cholesterol↗

PubMed1997

Interaction of activated leukocytes with polymeric microspheres.

Three types of polymeric particles with different surface wettabilities, i.e., poly(methylmethacrylate) (PMMA), poly(methylmethacrylate-hydroxyethylmethacrylate) (P(MMA/HEMA)) and poly(methylmethacrylate)/poly(vinyl alcohol) PMMA/PVAL with a diameter of 1.5 microm were produced in this study These particles were incubated with blood samples obtained both from three patients undergoing cardiopulmonary bypass. In the blood samples taken before the bypass operations, there was considerable phagocytosis and/or adhesion of the PMMA particles, i.e., 14+/-4 particles per monocyte and 11+/-3 particles per neutrophil. While there was almost no phagocytosis and/or adhesion of the P(MMA/HEMA) and PMMA/PVAL particles. In the blood samples which were taken during bypass operations, phagocytosis and/or adhesion of PMMA microspheres increased significantly. The P(MMA/HEMA) and/or PMMA/PVAL particles adhered, or were even phagocytosed by the activated leukocytes in this case. Leukocytes activated during the bypass operations gradually returned to normal in about 24 h.

Cardiopulmonary Bypass↗

PubMed1996

Glow-discharge-modified activated carbon cloths as skin substitutes.

In this study, activated carbon cloths (ACCs) were modified in a glow-discharge apparatus by using 2-hydroxyethyl-methacrylate (HEMA), dimethyl-aminoethyl methacrylate (DMAEMA), and hydroxymethyldisiloxane (HMDS) plasmas. Scanning electron micrographs exhibited the formation of the polymeric films on the ACCs after glow-discharge modification. The adsorption experiments were performed using model solutes, i.e., creatinine, vitamin B-12, and trypsin. No significant change was observed in the adsorption capacities of the ACC/PHEMA and ACC/PDMAEMA composites compared with the original ACC adsorption capacity. However, there was a pronounced decrease in the case of the ACC/PHMDS. Oxygen permeabilities of both the original and modified ACCs were measured in a flow-through gas chamber. The oxygen permeabilities of the original and modified forms were 817 and 3.5-5 cm3/s.cm2.cm Hg x 10(-7), respectively. Water-vapor permeabilities of the composites were obtained by using a standard water-cup assembly. Permeabilities varying between 921 and 10,300 g/m2.day were found. Microorganism impermeabilities of the ACCs were demonstrated by using model PS monosize polymeric particles with a diameter of 0.2 micron. The particle permeability of the original ACC was 65.6 mg/m2.day. Almost no particle permission was observed through the modified ACCs.

Adsorption↗

PubMed1996

Investigation of ascorbate-Cu (II) induced cleavage of DNA by scanning tunneling microscopy.

Scanning Tunneling Microscopy (STM) was used for the investigation of oxidative DNA damage. A PCR amplified fragment of human beta-globin gene was used as a model for time dependent cleavage reaction by ascorbate and copper. Cleavage reactions were carried out in a medium containing 0.5 microgram/20 microliters DNA, 20 nM Tris-HC1 pH, 7.8 and ascorbate-Cu (II) in the final concentrations of 1 mM and 30 microM, respectively. The mixtures were incubated at 37 degrees C for 5, 15 and 30 min. For STM studies, 3 pg/5 microliters DNA samples were deposited on the gold coated mica and dried in a water flow vacuum drier. The STM was operated in air at atmospheric pressure with a tip-to-substrate bias of 100 mV and tunneling currents of < 10 pA. Etched tips of Pt/Ir wires were used in a constant current mode. The degradated DNA structure can be distinguished from the intact DNA and the sizes of the degradation products can be identified in the STM micrographs. The size of fragments decreased from approximately 3000 A to 34 A in ascorbate-Cu (II) medium, after 30 min of incubation.

Ascorbic Acid↗

PubMed1996

Rifampicin carrying poly (D,L-lactide)/poly(ethylene glycol) microspheres: loading and release.

The aim of this study is to prepare rifampicin-loaded poly (D,L-lactide)/poly(ethylene golycol) (PDLLA/ PEG) copolymer microspheres as an injectable drug delivery system. PDLLA homopolymers with three different molecular weights (9,760, 14,540, and 23,050 daltons) were synthesized and then transesterified with PEG (with a molecular weight of approximately 3,300-4,000 daltons). By changing the ratio of PEG to PDLLA, block copolymers with different chain structures were synthesized. PDLLA and PDLLA/PEG microspheres in the size range of 2-10 microns were prepared by a modified solvent evaporation technique with the use of methylene chloride as the solvent and methyl cellulose as the emulsifier within the aqueous dispersion medium. Rifampicin was loaded within the microspheres during particle formation. Effects of the solvent/polymer and drug/polymer ratios, PDLLA molecular weight, and PEG content on drug loading and release were investigated. High drug loadings up to 100 mg rifampicin/g polymer were achieved. Both size and drug loadings were decreased by an increase in the solvent/polymer ratio and PEG content and by a decrease in the drug/polymer ratio and PDLLA molecular weight. High release rates were observed in the first 5 days after which constant and slow release rates were noted. Drug release was decreased by a decrease in the solvent/polymer ratio and PEG content and by an increase in the drug/polymer ratio and PDLLA molecular weight.

Delayed-Action Preparations↗

PubMed1996

Imaging of liposomes by scanning tunneling microscopy.

In this study, unilamellar and multilamellar liposomes consisting of dipalmitoylphosphatidylcholine, cholesterol and dicetylphosphate were prepared. Scanning tunneling microscopy images of these liposomes on highly oriented pyrolytic graphite surfaces were obtained. It was observed that scanning tunnelling microscopy can be successfully used for high-resolution, three-dimensional structure analysis of liposomes under very mild conditions.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1996

Protein A carrying monosize PMMA microbeads for the removal of HIgG from human plasma.

Protein A-incorporated polymethylmethacrylate (PMMA) microbeads were investigated for specific removal of HIgG from human plasma. The microbeads were prepared by a phase inversion polymerization, and activated by periodate oxidation. Protein A was then incorporated by covalent binding onto these microbeads through hydroxyl groups coming from the stabilizer. The amount of incorporated protein A was controlled by the initial concentrations of protein A in the immobilization medium and pH. The maximum protein A immobilization of 0.615 mg protein A/g PMMA, was observed at a pH of 9.5 corresponding to an initial protein A concentration of 0.1 mg/ml. There was no HIgG adsorption onto the plain PMMA microbeads, while high HIgG adsorptions of up to 32 mg HIgG/g PMMA were achieved with human plasma.

Adsorption↗