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Biomedical subjects

E Pişkin

Publications and source records attributed to E Pişkin.

65 records · Page 4Linked to original sources
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↗
PubMed1985

Properties of new sorbents containing activated carbon-PHEMA-PEG.

A new immobilized powder activated carbon system was developed. In this approach, highly biocompatible hydrophilic polymer gels, namely polyHEMA and PEG, were used as support. The sorbents were produced by radiation-induced polymerization of HEMA in super-cooled media. The polymer composites obtained by using different ratios of ingredients (HEMA, PEG and AC) and by changing the radiation dose period, were in the form of, almost, spherical black gels having different elasticities. Equilibrium adsorption studies were carried out to evaluate the sorption capacities of both powder and immobilized activated carbon. The comparative performance characteristics of the hemoperfusion columns filled with either granules or immobilized carbons were obtained for creatinine. Fresh human blood was used to study the biocompatibility of immobilized carbon samples. The surface morphology and the pore structure of the gels were evaluated by means of Scanning Electron Microphotography and Optical Microphotography. According to the experimental results, it was concluded that this new type of immobilized activated carbon system seems to be more attractive for hemoperfusion applications due to having comparatively higher adsorption rates and very good blood compatibility as well as simple and uniformly reproducible method of production.

Adsorption↗
PubMed1981

Effects of temperature on the removal of urea as ammonia by enzymatic conversion and by gas absorption using an oxygenator.

Urea in dialysate solution was converted by urease into ammonium and bicarbonate. Ammonium and bicarbonate can be removed using a gas absorption unit (e.g. oxygenator) to remove ammonia gas and carbon dioxide. The times for the total ammonium levels in the dialysate to be lowered by 50% were 95 minutes at 25 degree C and 15 minutes at 60 degree C. Increasing the dialysate temperature alone was effective in increasing the removal of ammonium, without the need to add NaOH.

Absorption↗
PubMed1981

The best coating material for hemoperfusion: comparation of cellulose nitrate with cellulose acetate and derivatives.

In this study the clearance characteristics of the two most widely used membrane systems (cellulose nitrate and cellulose acetate) were compared in order to obtain the best coating material for hemoperfusion. The columns containing uncoated or coated charcoal granules were tested using creatinine, uric acid and vitamin B-12. The platelet loss were also analyzed using bovine blood. The membrane thickness was kept constant (0.5% by weight) in all membrane systems. Due to the simple coating procedure, cellulose nitrate coating, which also has good biocompatibility and high removal rates for toxins, was found to be preferable.

Adsorption↗
PubMed1980

Effects of air and fluid flow rates on removing different concentrations of urea and ammonia from fluid by gas absorption in a capillary hemodialyzer.

Urease converts urea into ammonium and bicarbonate. Alkalinization converts ammonium into free ammonia which can be removed as a gas. Our approach is to use a capillary hemodialysis as a gas absorption unit with liquid moving through the blood compartment and air through the dialysate compartment to extract ammonia gas. This paper examines the effects of air flow rate, fluid flow rate, and concentrations of ammonia (and urea) in the fluid. It was observed that increasing air flow rate or dialysate flow rate increases the mass transfer rate for ammonia especially at low ammonia concentration levels. Ammonia removal rate increases with air flow rate linearly. Ammonia removal rate increases with increasing fluid flow rate, but reaches a plateau when flow rate was above 500 ml/mn.

Air↗
PubMed1980

Effects of pH and urea concentration on urea removal from dialysate by enzymatic conversion and gas absorption using a capillary hemodialyzer.

This paper reports the effects of initial urea concentrations and pH values on the performance of a capillary hemodialyzer for the removal of free ammonia (NH3) formed by enzymatic hydrolysis of urea. Air was chosen as the gas phase. NaOH was used for alkalinization of dialysate. It was shown that one of the most important parameters was free ammonia concentration. The degrees of alkalinization and the initial urea concentration, were also important. Although even without the addition of NaOH, about 42% of the initial urea can be removed in one hour.

Absorption↗
PubMed1979

Dialysis of middle molecules at pulsatile flow.

Pulsatile flow was used in a continuous flow flat-plate dialyzer in order to achieve the more efficient removal of middle molecules. The solutes ranged in the molecular weights from 342 (sucrose) to 1355 (vitamin B-12). The permeability of Cuprophane membrane to sucrose, raffinose and vitamin B-12 were calculated both for pulseless and pulsatile flows. It was found that pulsatile flow is more favorable than steady flow with regard to increase of membrane permeability. However, as the solute molecular weight increases, fluid-phase resistances become relatively less important and the transport rate becomes dominated by the membrane properties.

Dialysis↗
PubMedDate not supplied

5-fluorouracil loaded chitosan microspheres for chemoembolization.

In this study, chitosan microspheres were prepared by a suspension cross-linking technique. A petroleum ether/mineral oil mixture was used as the suspension medium which includes an emulsifier, e.g. Tween-80. Glutaraldehyde was used as the cross-linker. 5-Fluorouracil was incorporated in the matrix for the possible use of the microspheres in chemoembolization. The size and size distribution of the chitosan microspheres varied in the size range of 100-200 microns, by changing the emulsifier concentration, stirring rate, chitosan/solvent ratio and drug/chitosan solution ratio. In summary, the size and size distribution of the microspheres decreased when the emulsifier concentration and stirring rate were increased. Smaller microspheres with narrower size distributions were obtained when the chitosan/solvent ratio and drug/chitosan ratio were lower. It was possible to load the chitosan microspheres with 5-FU to a concentration of 10.4 mg 5-FU/g chitosan. Around 60% of the loaded drug was released within the first 24 h, then the release rate became much slower.

Chemoembolization, Therapeutic↗
PubMedDate not supplied

99mTc-labelled monodisperse latex particles coated with amino or carboxyl groups for studies of GI function.

Latex particles coated with either amino or carboxyl groups were labelled with 99mTc. Two labelling methods were used: (1) direct labelling with tin reduction and (2) ligand exchange with tin pyrophosphate. Labelling efficiency and the radiochemical impurities were determined by thin-layer chromatography. Effect of [Sn2+] and pH on labelling yield was investigated to find the optimum labelling conditions. 99mTc-labelled latexes were administered orally to six normal subjects, and scintigrams from the abdomen were obtained at 1, 3, 6, and 24 h. Whole-body scintigrams were also taken by a gamma-camera. The first method was found to be efficient for carboxyl coated latexes and the second method for both types, giving > 98 per cent labelling efficiency. Labelled latexes were stable up to 24 h of testing at RT (> 99 per cent labelled). Scintigraphic studies showed that the labelled particles remained in GIT (98.11 +/- 0.92 per cent at 6 h) without dissociation of the label. No radioactivity was observed in the thyroid, stomach (at late images) and urinary bladder. This study demonstrated that latex particles coated with either amino or carboxyl groups can be efficiently labelled with 99mTc and used in the studies of GI function.

Acrylates↗