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Biomedical subjects

E Piskin

Publications and source records attributed to E Piskin.

At least 19 recordsLinked to original sources
PubMed2005

Treatment of segmental bone defects in rats by the stimulation of bone marrow osteo-progenitor cells with prostaglandin E2.

An alternative to bone grafting is engineered osteo-conductive material that carries osteo-progenitor cells with osteo-stimulant factors impregnated on a malleable osteo-conductive material. We used bone marrow stem cells as the source of osteo-progenitor cells and stimulated them with prostaglandin E2 using demineralised bone matrix as a carrier. We treated 35 skeletally mature male Wistar albino rats with segmentary radial bone defects using five different treatment groups. Group I received no treatment; the remaining four groups all received a mixture of bone marrow and demineralised bone matrix. In group III, a copolymer was added. In group IV, prostaglandin E2 and in group V prostaglandin E2 within a copolymer was added to the mixture. Eight weeks after the surgical procedure, the rats were sacrificed. Radiological and histological evaluation of the radial bone showed that while there was no significant healing in groups I, II and III, there was a significant healing response in groups IV and V.

Animals↗
PubMed2005

Nano- and micro-fiber combined scaffolds: a new architecture for bone tissue engineering.

One possible interesting way of designing a scaffold for bone tissue engineering is to base it on trying to mimic the biophysical structure of natural extracellular matrix (ECM). This work was developed in order to produce scaffolds for supporting bone cells. Nano and micro fiber combined scaffolds were originally produced from starch based biomaterials by means of a fiber bonding and a electrospinning, two step methodology. The cell culture studies with SaOs-2 human osteoblast-like cell line and rat bone marrow stromal cells demonstrated that presence of nanofibers influenced cell shape and cytoskeletal organization of the cells on the nano/micro combined scaffolds. Moreover, cell viability and Alkaline Phosphatase (ALP) activity for both cell types was found to be higher in nano/micro combined scaffolds than in control scaffolds based on fiber meshes without nanofibers. Consequently, the developed structures are believed have a great potential on the 3D organization and guidance of cells that is provided for engineering of 3-dimensional bone tissues.

Alkaline Phosphatase↗
PubMed2000

Poly(D,L-lactide/epsilon-caprolactone)/hydroxyapatite composites.

In this study, elastomeric D,L-lactide and epsilon-caprolactone copolymers with two different molecular weights (Mn: 108.000 and 40.000) were synthesized by ring-opening polymerization of the respective dimers by using stannous octoate as the catalyst, as a potential bone-filling material. The final ratio of D,L-lactide to epsilon-caprolactone obtained by 1NMR was 60/40 (comparing to the initial ratio of 50/50). Both copolymers were amorphous having Tg at around -21 degrees C. Different amounts of hydroxyapatite (HA) powder were loaded within the copolymers. These composites were easily shaped by hand. Mechanical properties of the composites changed with the HA loading and the molecular weight of the copolymer. The percent elongation decreased, while both the Young's modulus and yield point (stress) increased with the HA content. The copolymers were degraded within the Ringer solutions in about 6 weeks. The molecular weight distribution became broader during degradation. Incorporation of HA reduced the degradation rate.

Biodegradation, Environmental↗
PubMed1998

New chelate-forming polymer microspheres carrying dyes as chelators for iron overload.

Dye-incorporated [poly(EGDMA-HEMA)] microspheres were investigated as a new chelate-forming polymer for iron overload. 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 dye-ligands (i.e. Cibacron Blue F3GA, Alkali Blue 6B and Congo Red) were covalently incorporated to the microspheres. The maximum dye incorporations were 16.5 micromol Cibacron Blue F3GA g(-1), 23.7 micromol Alkali Blue 6B g(-1), and 14.5 micromol Congo Red g(-1). The maximum Fe(III) adsorptions on the dye-incorporated microspheres from aqueous solutions containing different amounts of Fe(III) ions were 51.0, 37.3, and 25.1 mg g(-1) for the Cibacron Blue F3GA, Alkali Blue 6B, and Congo Red carrying microspheres, respectively. The maximum Fe(III) adsorptions were observed at pH 4.0 in all cases. Fe(III) removal from human plasma was also investigated. The maximum adsorption capacities of Fe(III) ions from human plasma for Cibacron Blue F3GA, Alkali Blue 6B, and Congo Red, were of 12.0, 7.5, and 3.8 mg g(-1) polymer, respectively. It was observed that Fe(III) could be repeatedly adsorbed and desorbed without significant loss in adsorption capacity.

Adsorption↗
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↗
PubMed1993

STM of glow-discharge treated surfaces.

As a model surface, graphite slides were treated by pure nitrogen gas plasma for different periods (15 sec-5 min). These samples were kept in air or under argon atmosphere in sealed holders. STM images were obtained at constant current mode. Results showed that both the number and the size of clusters formed by plasma deposition increased with exposure time.

Air↗
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↗
PubMed1992

Biologically modified polymeric biomaterial surfaces: introduction.

Synthetic polymers are the most diverse class of biomaterials. As with all other biomaterials, they must meet certain criteria depending on the intended medical application. Biocompatibility is one of the basic criteria for selection of a particular biomaterial. Biomaterial surfaces are believed to play an important role in determining their biocompatibilities. The study of the surface properties of biomaterials, and also interactions between the biomaterial and the living system interface are fundamental to define the behavior of the biomaterial in the biological environment, and therefore to evaluate accurately the biocompatibility of a new biomaterial. Surfaces of polymeric biomaterials may be modified by using a variety of biological entities (e.g. proteins and cells) not only to increase their biocompatibilities but also to add a functionality to the respective surfaces. I intended to highlight the topics which are discussed in depth in the other chapters of this volume.

Albumins↗
PubMed1992

Hepatocyte immobilization on PHEMA microcarriers and its biologically modified forms.

Polyhydroxyethylmethacrylate (PHEMA) based microcarriers with different bulk structures were prepared by a phase inversion polymerization technique. PHEMA surfaces were further modified chemically by glow-discharge treatment, and biologically by covalent attachment of fibrinogen and collagen. Hepatocytes were isolated from young male Wistar rats using an in situ portal vein collagenase perfusion technique. Freshly isolated hepatocytes were seeded at 6 x 10(5) cells/mL and microcarrier concentration was 10 g/L. Stationary microcarrier cultures were carried out in standard (nontissue culture) polystyrene petri dishes in a humidified 5% CO2 incubator at 37 +/- 0.5 degrees C. Cell attachment was followed by light microscopy by taking samples from the culture medium every 30 min. Urea and protein syntheses by microcarrier-attached hepatocytes were determined by standard techniques. Nonswellable (highly cross-linked) hydrophilic PHEMA microcarriers did not support cell attachment and viability. However, swellable (low cross-linked) PHEMA microcarriers (pretreated in FBS) allowed high attachment and cell spreading. PHEMA microcarriers treated in dimethylaminoethylmethacrylate (DMAEMA) glow-discharge plasma also improved the cell attachment characteristics of the PHEMA microcarriers. The highest attachment efficiencies (immobilization yields) were observed with the biologically modified PHEMA microcarriers, especially modified with fibronectin. Metabolic activity, as estimated by urea and protein syntheses, was also higher in these microcarriers.

Animals↗
PubMed1992

Plasma processing of biomaterials.

Surface properties of biomaterials can easily be modified by glow-discharge plasma processing for very diverse biomedical applications. Activated carbon granules can be coated with a very thin polymeric membrane by plasma polymerization to improve their blood compatibilities without changing their adsorption capabilities. The problems associated with the microporous polypropylene oxygenator membranes can be eliminated by coating with a nonporous thin polymeric film in a glow-discharge reactor. Cell attachment and growth on polystyrene microcarriers can significantly be increased by alkylamine plasma treatment. Physical and chemical properties of polyurethane biomaterials can be tailor-made by plasma modification.

Animals↗
PubMed1991

Functional assessment of human gastrointestinal tract using 99Tcm-latex particles.

99Tcm-latex particles (LP) is a newly developed radiopharmaceutical for the evaluation of the gastrointestinal (GI) tract. Following oral ingestion, it passes through the entire GI tract undissolved. The purpose of the present investigation was to introduce the clinical application of 99Tcm-LP. A group of 11 healthy volunteers was studied. Following a 12 h fast, the subjects were given 150 ml of water containing 37 MBq of 99Tcm-LP orally. Dynamic images up to 2 h were recorded to document temporal progression of radioactivity. Static images of the abdomen and whole body were taken at intervals. In normal subjects the tracer arrival times at the caecum and sigmoid colon were 3.2 +/- 0.9 and 11.2 +/- 3.2 h, respectively. The average t1/2 value for gastric emptying, 50% colonic filling and small bowel transit time were found to be 21.6 +/- 5.6, 233 +/- 72 and 211 +/- 66.4 min, respectively. In conclusion, 99Tcm-LP has the potential of providing functional information of the GI tract.

Adult↗
PubMed1986

Technical aspects of hemoperfusion.

A review of the different types of adsorbents being used in hemoperfusion. The different types of polymers used in coating charcoal are also reviewed.

Adsorption↗
PubMed1984

Preparation of polyethyleneglycol (PEG) coatings for microencapsulation of charcoal.

Polyethyleneglycols (PEGs) with their high solubility in water cannot normally be used as a coating material in aqueous solutions such as blood. A gamma-radiation procedure was therefore applied after coating charcoal granules with PEG in a non-aqueous phase, and an 80-90% insoluble polymer matrix on charcoal was obtained. PEGs with different molecular weights from 4000 to 300,000 were used for coating. The performance of this system was determined by using several test solutes, namely creatinine, uric acid, and vitamin B-12. It was observed that the pore size and structure of these membranes can be adjusted by changing the irradiation time and by using PEGs with different molecular weights. Thus, very high mass transfer rates can be achieved.

Adsorption↗