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Biomedical subjects

A Tuncel

Publications and source records attributed to A Tuncel.

17 recordsLinked to original sources
PubMed2002

Nucleotide adsorption-desorption behaviour of boronic acid functionalized uniform-porous particles.

In this study, nucleotide adsorption-desorption behaviour of boronic acid-carrying uniform, porous particles was investigated. The particles were produced by a "multi-step microsuspension polymerization" in the form of poly(styrene-vinylphenyl boronic acid-divinylbenzene) terpolymer. In the first step of the production method, uniform polystyrene latex particles (6.2 microm in size) were obtained by dispersion polymerization. These particles were first swollen by a low molecular mass organic agent (i.e. dibutylphthalate, DBP) and then by a monomer mixture including styrene (S), 4-vinylphenyl boronic acid (VPBA) and divinylbenzene (DVB). The particle uniformity was protected in both swelling stages by adjusting DBP/polystyrene latex and monomer mixture/polystyrene latex ratios. Polymerization of the monomer mixture in the swollen seed particles provided boronic acid-carrying uniform, porous particles 11-12 microm in size. To have uniform particles with different porosities and boronic acid contents, the feed concentration of boronic acid-carrying monomer and the monomer/seed latex ratio were changed. The particles were tried as sorbent for the adsorption of a model nucleotide (i.e., beta-nicotinamide adenine dinucleotide, beta-NAD). In the beta-NAD adsorption experiments, the maximum equilibrium adsorption was obtained at pH 8.5 which was very close to pKa of boronic acid. The incorporation of boronic acid functionality provided a significant increase in the beta-NAD adsorption. In contrast to plain poly(styrene-co-divinylbenzene) particles, four-fold higher beta-NAD adsorption was obtained with the boronic acid functionalized particles. Beta-NAD was desorbed from the particles with the yields higher than 90% by weight.

Adsorption↗
PubMed2000

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.

Adsorption↗
PubMed2000

Cartilage shaping using the Er:YAG laser: preliminary report.

Cartilage grafts have been widely used for reconstruction of congenital or acquired deformities. Reshaping and preserving the new shape of the cartilage grafts have been a problem. In this in vitro experimental study the authors studied the effect of the Er:YAG laser on cartilage reshaping in comparison with scalpel stripping and suture holding. The study consisted four groups (n = 9): group I, untouched cartilage; group II, the short edges of the cartilage were sutured to each other; group III, cartilage was incised using a scalpel; and group IV, Er:YAG laser stripping was applied to the cartilage. Changes in the shape of cartilage were evaluated at 15 minutes, and days 1, 4, and 10. The majority of cartilage in the scalpel-stripped group returned to the initial shape by day 10, whereas the laser-stripped cartilage showed progressive warping day by day, and almost all cartilage formed a circle by day 10. The Er:YAG laser enhanced cartilage warping by a mechanical effect of stripping and a thermal effect of laser radiation resulting in ultrastructural changes.

Animals↗
PubMed2000

Thermally reversible VPBA-NIPAM copolymer gels for nucleotide adsorption.

A thermosensitive gel matrix was prepared by free radical copolymerization of N-isopropylacrylamide (NIPAM) with a boronic acid-carrying monomer (i.e. 4-vinylphenylboronic acid, VPBA). The synthesis of the gel was performed at 70 degrees C in an alcohol-water mixture, using azobisisobutyronitrile and methylenebisacrylamide as the initiator and the crosslinker, respectively. To produce thermosensitive gels with a higher diol-binding affinity, an amino-containing comonomer, N-[3-(dimethylamino)propyl]methacrylamide (DMAPM) was included in the gel formation recipe. Thermally reversible VPBA-NIPAM and VPBA-DMAPM-NIPAM gels with different swelling properties were obtained by changing the feed concentrations of VPBA and DMAPM. To test the usability of the produced gels as sorbents in nucleotide adsorption, beta-nicotinamide adenine dinucleotide (beta-NAD) was selected as a model biomolecule. Then the adsorption isotherm for beta-NAD was obtained at +4 degrees C in HEPES buffer medium with a pH of 8.5. The support material was in a highly swollen form under these conditions, due to its thermosensitive character. This property was then used to enhance beta-NAD adsorption onto the gel matrix. Equilibrium adsorption capacities up to 70 mg beta-NAD/g dry gel could be achieved with the thermosensitive support prepared with the 12.9 mol% VPBA feed. The gels produced with higher VPBA and DMAPM feed concentrations exhibited higher equilibrium adsorption capacities for beta-NAD.

Acrylamides↗
PubMed2000

The value of percent free prostate specific antigen, prostate specific antigen density of the whole prostate and of the transition zone in Turkish men.

INTRODUCTION: This study was undertaken to evaluate the value of percent free prostate specific antigen (PSA), PSA density of the whole prostate (PSAD) and of the transition zone (TZPSAD) in reducing unnecessary biopsies in Turkish men with serum PSA levels between 2.5 and 20 ng/mL. MATERIALS AND METHODS: A total of 105 patients referred for early prostate cancer detection or lower urinary tract symptoms participated in the study. All patients had serum total PSA level, PSAD, total prostate volume, and rectal examination, 43 patients had serum free PSA level, and 65 patients had TZPSAD. Using transrectal ultrasound, sextant biopsy and two additional transitional zone biopsies were performed. The value of percent PSA, PSAD, and TZPSAD in reducing unnecessary biopsies was evaluated. RESULTS: Prostate carcinoma was detected in 25 of 105 patients (23.8%). Overall, areas under the ROC curves for percent free PSA, PSAD, and TZPSAD were 0.553, 0.595, and 0.550, respectively. In patients with a benign rectal examination, the value of percent free PSA slightly increased. On the other hand, in patients with prostate volume smaller than 50 cc, the value of percent free PSA and TZPSAD was encouraging. Areas under the ROC curves for percent free PSA, and TZPSAD were 0.615 and 0.642 respectively. CONCLUSION: In Turkish men with intermediate serum PSA concentrations, percent free PSA, PSAD, and TZPSAD are poor predictors of biopsy outcome, whereas in the prostate smaller than 50 cc, percent free PSA and TZPSAD provide additional information. This may reflect ethnic differences between this population and those reported in other series.

Adenocarcinoma↗
PubMed1999

Cibacron blue F3G-A-attached uniform and macroporous poly(styrene-co-divinylbenzene) particles for specific albumin adsorption.

Cibacron blue F3G-A-carrying uniform macroporous particles were proposed as an alternative sorbent for specific albumin adsorption. These particles were produced by a multistep polymerization procedure. In the first step of production, the uniform polystyrene seed particles were prepared by a dispersion polymerization method. Next. the polystyrene seed particles were first swollen by dibutylphthalate and then by styrene-divinylbenzene mixture in an aqueous emulsion medium. In the last step (i.e. repolymerization), styrene-divinylbenzene mixture was copolymerized within the swollen seed particles in the absence or presence of a stabilizer (e.g. poly(vinyl alcohol)). Although a considerable amount of non-specific BSA adsorption was observed on the surface of the particles produced in the absence of PVA, zero non-specific albumin adsorption could be achieved with the uniform macroporous particles produced in the presence of PVA. The stabilizer on the particle surface was also used as a ligand in the further derivatization of macroporous particles for specific albumin adsorption. Cibacron blue F3G-A was then covalently attached onto the surface of uniform macroporous particles. Specific albumin adsorption capacities up to 93 mg g(-1) could be achieved with the cibacron blue F3G-A-carrying macroporous particles of 6.25 microm in size.

Adsorption↗
PubMed1996

A study on the effect and tolerance of lisuride on Parkinson's disease.

Seventeen idiopathic parkinsonian patients ranging between 47 and 75 years of age were included in this study to investigate the effect and tolerance of lisuride on PD. The duration of this simple clinical study, which had no control group was 12 weeks. There was 50% relief in disability scores and ADL in 13 patients in the first group in the combined therapy for 12 weeks with lisuride added to L-DOPA plus benserazide (p < 0.01). Optimal lisuride doses added to L-DOPA plus benserazide varied between 0.1 and 0.8 mg (mean 0.5 +/- 0.2 mg). With the addition of lisuride to treatment, the L-DOPA plus benserazide dose was reduced in 6 of 13 by 38%. Monotherapy with lisuride resulted in 56% to 57% improvement in disability scores and 47% in relief in ADL. Dry mouth, nausea, weakness, postural hypotension, and headache were the most frequently encountered side effects of lisuride. These adverse effects disappeared in 3 or 4 days, depending on a slight decrease and following increase in the dose of lisuride and/or the development of tolerance. Not only will such a combined therapy contribute to the reduction of the end-of-dose inadequacies, on-off phenomena, wearing off, peak-dose dyskinesias, and similar motor fluctuations, it may also play a prophylactic role in their prevention or delay.

Age of Onset↗
PubMed1995

Monosize poly(ethylcyanoacrylate) microspheres: preparation and degradation properties.

Monosize, biodegradable poly(ethylcyanoacrylate) (PECA) microspheres in the size range of 0.5-2.5 microns were prepared by a relatively new polymerization technique, the so-called dispersion polymerization. The polymerizations were performed by using a stabilizer system containing a poly(ethyleneoxide)/poly(propyleneoxide) (PEO/PPO) copolymer and dextran in the aqueous HCl solution as a dispersion medium. Phosphoric acid was used as a catalyst, stabilizer, monomer concentrations, and the pH of dispersion medium on the monomer conversion, average size, and size distribution of the PECA microspheres were studied. The resultant microsphere size was mainly controlled by PEO/PPO copolymer and HCl concentrations. To explain the degradation mechanism, the degradation of monosize PECA microspheres was studied in in vitro conditions. The partially degraded beads were observed by electron microscopy. The results indicated that the degradation of monosize PECA microspheres occurred mainly by surface erosion.

Biodegradation, Environmental↗
PubMed1995

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

Rifampicin-loaded poly(D,L-lactide) (PDLLA) microspheres in the size range of 0.8-8.0 microns were prepared by a modified solvent evaporation method. Rifampicin loading was changed by using different types of solvents (i.e. methylene chloride, chloroform, and carbon tetrachloride) with different solvent/polymer ratios and different emulsifiers (i.e. methyl cellulose, gelatin, and Tween-20), and by changing the initial drug/polymer ratio. These rifampicin-loaded PDLLA microspheres degraded much faster in the medium at basic pH (9.8) and at high temperatures (55 degrees C). Rifampicin release was also high under these conditions. It was concluded that rifampicin release was both degradation- and diffusion-controlled.

Biocompatible Materials↗
PubMed1995

Degradation and drug release characteristics of monosize polyethylcyanoacrylate microspheres.

Monosize, biodegradable poly(ethylcyanoacrylate) (PECA) microspheres with a diameter of 1.3 microns were prepared by a relatively new polymerization method, the so-called phase inversion polymerization. The effects of pH and temperature on the degradation behavior of PECA particles were investigated. PECA microspheres were degraded mainly by surface erosion. The degradation rate increased with increasing pH temperature. A model drug, i.e. 2,4-dinitrophenylhydrazine (DNPH) was loaded into the monosize PECA microspheres during polymerization. The drug incorporation into the PECA microspheres increased with increasing initial drug concentration in the monomer phase. Drug release from the PECA microspheres was investigated at different pH. Higher drug release rates were observed in the neutral and alkaline media as compared with the acidic medium.

Biodegradation, Environmental↗
PubMed1995

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.

Animals↗
PubMed1994

Monosize microbeads based on polystyrene and their modified forms for some selected medical and biological applications.

Polymeric particles are produced by different polymerization techniques. Phase inversion (dispersion) polymerization is one of the recent techniques to obtain monosize polymeric microbeads in the size range of 1-50 microns. The size and monodispersity of these microbeads can be adjusted by using several solvent systems (e.g., alcohol-water mixtures) with different polarities and by changing the type and amount of monomer, initiator and stabilizer. Surfaces of these microbeads can be further modified by different techniques including coating with different copolymers. Monosize polymeric microbeads are widely used in medical and biological applications as carriers, such as in immunoassays and cell separation, in site-specific drug delivery systems, in nuclear medicine for diagnostic imaging, in studying the phagocytic process, in affinity separation of biological entities, etc. Here, some important aspects of the production of monosize microbeads based on polystyrene and their modified forms are briefly discussed, and some selected medical and biological applications are summarized.

Biopolymers↗
PubMed1992

Biologically modified PHEMA beads for hemoperfusion: preliminary studies.

Polyhydroxyethylmethacrylate (PHEMA) beads were prepared by phase separation polymerization. Hydroxyl groups on PHEMA beads were activated with CNBr at alkaline pH. Adsorption of heparin, blood proteins (i.e. albumin, fibrinogen and gamma-globulin), protein A, HIgG and DNA on these beads were studied. Preparation and activation procedures are given here. The preliminary results of these studies are also reported.

Adsorption↗