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In vivo application of poly-3-hydroxyoctanoate as peripheral nerve graft

Hazer, Derya Burcu | Bal, Ercan | Nurlu, Gülay | Benli, Kemal | Balcı, Serdar | Öztürk, Feral | Hazer, Baki

Article | 2013 | Journal of Zhejiang University: Science B14 ( 11 ) , pp.993 - 1003

Objective: This study aims to investigate the degree of biocompatibility and neuroregeneration of a polymer tube, poly-3-hydroxyoctanoate (PHO) in nerve gap repair. Methods: Forty Wistar Albino male rats were randomized into two groups: autologous nerve gap repair group and PHO tube repair group. In each group, a 10-mm right sciatic nerve defect was created and reconstructed accordingly. Neuroregeneration was studied by sciatic function index (SFI), electromyography, and immunohistochemical studies on Days 7, 21, 45 and 60 of implantation. Biocompatibility was analyzed by the capsule formation around the conduit. Biodegradation was . . .analyzed by the molecular weight loss in vivo. Results: Electrophysiological and histomorphometric assessments demonstrated neuroregeneration in both groups over time. In the experimental group, a straight alignment of the Schwann cells parallel to the axons was detected. However, autologous nerve graft seems to have a superior neuroregeneration compared to PHO grafts. Minor biodegradation was observed in PHO conduit at the end of 60 d. Conclusions: Although neuroregeneration is detected in PHO grafts with minor degradation in 60 d, autologous nerve graft is found to be superior in axonal regeneration compared to PHO nerve tube grafts. PHO conduits were found to create minor inflammatory reaction in vivo, resulting in good soft tissue response. © 2013 Zhejiang University and Springer-Verlag Berlin Heidelberg Daha fazlası Daha az

Synthesis and characterization of poly[(RS)-3-hydroxybutyrate] telechelics and their use in the synthesis of poly(methyl methacrylate)-b-poly(3-hydroxybutyrate) block copolymers

Arslan, Hülya | Hazer, Baki | Kowalczuk, Marek

Article | 2002 | JOURNAL OF APPLIED POLYMER SCIENCE85 ( 5 ) , pp.965 - 973

Poly [(R, S)-3-hydroxybutyratel oligomers containing dihyroxyl (PHB-diol), dicarboxylic acid (PHB-diacid) and hydroxyl-carboxylic acid (a-PHB) end functionalities were obtained by the anionic polymerization of beta-butyrolacton (beta-BL). Ring opening anionic polymerization of beta-BL was initiated by a complex of 18-Crown-6 with gamma-bydroxybutyric acid sodium salts (for PHB-diol and a-PHB) or succinic acid disodium salt (for PHB-diacid). Dihydroxyl functionalization was formed by the termination of polymerization with bromo-ethanol or bromo-decanol while the others were done by protonation. Hydroxyl and/or carboxylic acid functio . . .nalized PHB oligomers with eerie salts were used to initiate the polymerization of methylmethacrylate (MXIA). PHB-b-PMMA block copolymers obtained by this way were purified by fractional precipitation and characterized using H-1-NMR and C-13-NMR, gel permeation chromatography (GPC), and thermal analysis (DSC and TGA) techniques. (C) 2002 Wiley Periodicals, Inc. J Appl Polyra Sci 85: 965-973, 2002 Daha fazlası Daha az

Reactions of anionic living polymers with bromomethyl-functionalized benzoyl peroxides

Hazer, Baki | Hirao, Akira | Volga, Cüneyt

Article | 1999 | Macromolecular Chemistry and Physics200 ( 1 ) , pp.71 - 76

In order to synthesize benzoyl peroxide functionalized polystyrene (PSt), polyisoprene (PI) and poly(methyl methacrylate) (PMMA), anionic living PSt, PI, and PMMA were allowed to react with an excess amount of 4-(bromomethyl)benzoyl tert-butyl peroxide (BMtB) or bis[3,5-bis(bromomethyl)benzoyl] peroxide (BDBP) in tetrahydrofuran (THF) at -78°C. The results indicate that coupling reactions leading to dimers are significant during the reaction. Dimer formation was avoided when the living polystyrene was modified to the alcoholate anion by reaction with ethylene oxide (EO). © Wiley-VCH Verlag GmbH, 1999.

Deactivation models for sulfur dioxide adsorption on silica gel

Kopaç, Türkan | Kocabaş, Sefa

Article | 2004 | Advances in Environmental Research8 ( 03.Apr ) , pp.417 - 424

In this work, experimental breakthrough curves for sulfur dioxide adsorption on silica gel were analysed with deactivation models proposed by 'Can. J. Chem. Eng. 60 (1982) 314' and 'Ind. Eng. Chem. Res. 40 (2001) 5206'. The deactivation model of 'Ind. Eng. Chem. Res. 40 (2001) 5206' taking into account the concentration dependence of the deactivation process along the reactor gave the best fit to the experimental breakthrough data for sulfur dioxide adsorption on silica gel. Deactivation rate constant k d values were determined from adsorption experiments done at 473 K temperature with a sulfur dioxide inlet concentration in the ran . . .ge of 0.0443-0.3504 mol/m3. © 2002 Elsevier Science Ltd. All rights reserved Daha fazlası Daha az

Redox polymerization of N-isopropylacrylamide by using hydroxylated soya oil polymer

Allı, Abdulkadir | Şanal, Timur | Hazer, Baki

Article | 2015 | Turkish Journal of Chemistry39 ( 2 ) , pp.382 - 394

Abstract: Water soluble hydroxylated soya oil polymer was used in the redox polymerization of N-isopropylacrylamide (NIPAM) in order to obtain water-based hydroxylated-soya oil polymer-g-PNIPAM graft copolymer. For this purpose, soya oil was exposed to air under sunlight to obtain autoxidized soya oil polymer (PSy-ox). PSy-ox was allowed to react with diethanol amine to obtain hydroxylated soya oil polymer (hydroxylated-PSy). An ammonium persulfate with hydroxylated-PSy redox initiating system was used in the polymerization of NIPAM in order to obtain thermo-responsive hydroxylated-PSy-g-PNIPAM water-based graft copolymers. The graf . . .t copolymers were characterized using proton nuclear magnetic resonance, Fourier transform infrared~spectroscopy, gel permeation chromatography, thermal gravimetric analysis, and differential scanning calorimetry techniques. The effects of hydroxylated-PSy on the thermal response rate of PNIPAM and the percentage of transmittance in the water of graft copolymers were studied by means of observing UV transmittance behaviors in response to changing temperature. This showed the temperature-responsive property, and exhibited a volume phase transition from 22 °C to 29 °C, while that of PNIPAM was 32 °C. Abstract: Water soluble hydroxylated soya oil polymer was used in the redox polymerization of N-isopropylacrylamide (NIPAM) in order to obtain water-based hydroxylated-soya oil polymer-g-PNIPAM graft copolymer. For this purpose, soya oil was exposed to air under sunlight to obtain autoxidized soya oil polymer (PSy-ox). PSy-ox was allowed to react with diethanol amine to obtain hydroxylated soya oil polymer (hydroxylated-PSy). An ammonium persulfate with hydroxylated-PSy redox initiating system was used in the polymerization of NIPAM in order to obtain thermo-responsive hydroxylated-PSy-g-PNIPAM water-based graft copolymers. The graft copolymers were characterized using proton nuclear magnetic resonance, Fourier transform infrared~spectroscopy, gel permeation chromatography, thermal gravimetric analysis, and differential scanning calorimetry techniques. The effects of hydroxylated-PSy on the thermal response rate of PNIPAM and the percentage of transmittance in the water of graft copolymers were studied by means of observing UV transmittance behaviors in response to changing temperature. This showed the temperature-responsive property, and exhibited a volume phase transition from 22 °C to 29 °C, while that of PNIPAM was 32 °C Daha fazlası Daha az

Grafting on polybutadiene with polytetrahydrofuran macroperoxyinitiators. Postpolymerization studies

Macit, Hülya | Hazer, Baki

Article | 2007 | European Polymer Journal43 ( 9 ) , pp.3865 - 3872

Grafting reactions of polybutadiene with macro peroxy initiators and postpolymerization were studied. The cationic polymerization of tetrahydrofuran (THF) initiated by the cationic species derived from bis-(4-bromomethylbenzoyl) peroxide (BBP) or bis-(3,5-dibromomethylbenzoyl) peroxide (BDBP) gave the PTHF macroperoxy initiator (MPI). PTHF-b-PMMA macroperoxy initiator (MPIb) was also obtained by the redox polymerization of methyl methacrylate initiated with the hydroxyl ends of PTHF and Ce(IV) salts without decomposing the peroxide groups in the middle. Macroperoxy initiators thermally grafted on cis-polybutadiene (PBD) with thermal . . . curing to yield graft copolymers containing crosslinked and soluble parts, which were separated by the sol-gel analysis. FTIR spectra of the crosslinked samples indicated the characteristic signals of the PTHF, PBD and PMMA blocks. The crosslinked copolymers decomposed at around 470 °C. Postpolymerization of the crosslinked products indicated the increase in crosslinking density which has been followed by measuring the gradual increase of swelling values. Postpolymerization crosslinking was estimated as a first order reaction rate. © 2007 Elsevier Ltd. All rights reserved Daha fazlası Daha az

Electrospray ionisation tandem mass spectrometry of poly [(R,S)-3-hydroxybutanoic acid] telechelics containing primary hydroxy end groups

Arslan, Hülya | Adamus, Grażyna | Hazer, Baki | Kowalczuk, Marek

Article | 1999 | Rapid Communications in Mass Spectrometry13 ( 24 ) , pp.2433 - 2438

Evaluation of polymer end-capping reactions with the aid of electrospray ionisation tandem mass spectrometry techniques (ESI-MS(n)) allows characterisation of novel poly[(R,S)-3-hydroxybutanoic acid] (a-PHB) telechelics, containing primary hydroxyl groups at both polymer chain ends. The chemical structures of individual mass-selected macromolecules of the well-defined a-PHB telechelics haze been defined in this way, and fragmentation mechanisms have been proposed.

A molecular mechanics and semiempirical molecular orbital study on the conformation of polynorbornene chains

Yilmaz-Savaşkan, Sevil | Abbasoğlu, Rza | Hazer, Baki

Article | 2003 | Journal of Molecular Modeling9 ( 4 ) , pp.230 - 234

The conformational analysis of polynorbornene (PNB) chains was investigated with the AM1, MM2, AMBER and OPLS methods taking into consideration the possibility of binding of norbornene monomers to each other at various positions, i.e. exo-exo, exo-endo, endo-endo. The chain that is formed by connecting exo-endo positions of the monomers has lower torsional barrier energy than those formed with bonds at other positions and has more flexibility. It is determined that the thredisyndiotactic chain formed by exo-endo addition adopts a helix structure and has a coil shape. The disyndiotactic chain formed by connecting norbornene monomers . . .in mixed type has a linear structure. It is found that the repeat unit conformations of thredisyndiotactic and disyndiotactic chains of PNB are TGTG- and (TGTG-)2, respectively Daha fazlası Daha az

Biodegradable and biocompatible radiopaque iodinated poly-3-hydroxy butyrate: synthesis, characterization and in vitro/in vivo X-ray visibility

Erol, Arzu | Rosberg, Derya B. Hazer | Hazer, Baki | Göncü, Beyza S.

Article | 2019 | Polymer Bulletin , pp.230 - 234

Some novel radiopaque biodegradable and biocompatible iodinated polymers based on poly-3-hydroxy butyrate (PHB) were obtained. Following the attachment of diethanol amine to PHB, the hydroxyl ends were capped with 4-iodobenzoic acid and 2,3,5-tri-iodobenzoic acid. In this manner, tri-novel radiopaque polymers were obtained. The resulting polymers were structurally characterized by NMR technique. They were evaluated with respect to their possible use as radiopaque implant biomaterials indicating X-ray visibility in a noninvasive manner using routine X-ray absorption imaging techniques. These polymers exhibited good radiopacity with c . . .onventional imaging X-ray techniques in vivo. Additionally, biocompatibility of these iodinated polymers was also evaluated. There were no signs of infection or abscess formation on the surgical area. These novel radiopaque PHBs should be promising biomaterials for a new-generation radiopaque materials. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature Daha fazlası Daha az

Synthesis of a novel macromonomer initiator for atom transfer radical polymerization: Self condensing and graft copolymerization

Allı, Abdulkadir | Hazer, Baki

Article | 2009 | Hacettepe Journal of Biology and Chemistry37 ( 1 ) , pp.23 - 31

A new macromonomer initiator for atom transfer radical polymerization (ATRP-MIM) based on polyethylene glycol (Mn= 660 Da) (PEG) was synthesized by the reaction of hydroxyl end of the mono-methacryloyl polyethylene glycol with 2-bromopropanoyl chloride leading to methacryloyl polyethylene glycol 2-bromopropanoyl ester (v-PEG-Br). Poly(ethylene glycol) functionalized with methacrylate at one end was reacted with 2-bromopropionyl chloride to form a macromonomeric initiator for ATRP. Self condensing ATRP-MIM polymerization yielded branched PEG with low cross-linked fraction (3-29 wt%). In the same polymerization condition, self condens . . .ing ATRP-MIM polymerization was found faster than that of conventional free radical macromonomer initiators which behave as macro crosslinker, macro initiator and macromonomer. Besides the PEG obtained has still unreacted double bonds and halides leading to the further branching. In the second step, ATRP of methyl methacrylate was initiated by the MIM-ATRP using the copper coordination complex CuBr / N,N,N’,N’,N’’-pentamethyl diethylenetriamine (PMDETA). The ATRP-MIM and the chloroform soluble branched polymers obtained were characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC). Variation of gel polymer content, molecular weight of the soluble parts and conversion of the monomers with the changing polymerization conditions were also discussed. A new macromonomer initiator for atom transfer radical polymerization (ATRP-MIM) based on polyethylene glycol (Mn= 660 Da) (PEG) was synthesized by the reaction of hydroxyl end of the mono-methacryloyl polyethylene glycol with 2-bromopropanoyl chloride leading to methacryloyl polyethylene glycol 2-bromopropanoyl ester (v-PEG-Br). Poly(ethylene glycol) functionalized with methacrylate at one end was reacted with 2-bromopropionyl chloride to form a macromonomeric initiator for ATRP. Self condensing ATRP-MIM polymerization yielded branched PEG with low cross-linked fraction (3-29 wt%). In the same polymerization condition, self condensing ATRP-MIM polymerization was found faster than that of conventional free radical macromonomer initiators which behave as macro crosslinker, macro initiator and macromonomer. Besides the PEG obtained has still unreacted double bonds and halides leading to the further branching. In the second step, ATRP of methyl methacrylate was initiated by the MIM-ATRP using the copper coordination complex CuBr / N,N,N’,N’,N’’-pentamethyl diethylenetriamine (PMDETA). The ATRP-MIM and the chloroform soluble branched polymers obtained were characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC). Variation of gel polymer content, molecular weight of the soluble parts and conversion of the monomers with the changing polymerization conditions were also discussed Daha fazlası Daha az

Initiation system effects in the cationic copolymerization of tetrahydrofuran (THF)

Kul, Dilek | Volga, Cüneyt | Yılmaz-Savaşkan, Sevil | Hazer, Baki

Article | 2002 | POLYMER BULLETIN49 ( 1 ) , pp.25 - 32

https://dx.doi.org/10.1007/s00289-002-0067-2 https://hdl.handle.net/20.500.12628/2787

Polymeric linoleic acid-polyolefin conjugates: Cell adhesion and biocompatibility

Çakmaklı, Birten | Hazer, Baki | Tekin, İshak Özel | Açıkgöz, Şerefden | Can, Murat

Article | 2007 | JAOCS, Journal of the American Oil Chemists' Society84 ( 1 ) , pp.73 - 81

To diversify edible-oil polymer composite, polymeric linoleic acid (PLina) peroxide was obtained by the auto-oxidation of linoleic acid in a simple way for use as a macroinitiator in free radical polymerization of vinyl monomers. Peroxidation, epoxidation, and/or perepoxidation reactions of linoleic acid under air at room temperature resulted in PLina, having soluble fraction more than 91 weight percent (wt%), with molecular weight ranging from 1,644 to 2,763 Da, and containing up to 1.0 wt% of peroxide. PLina initiated the free radical polymerization of ether styrene (S), methyl methacrylate (MMA), or n-butyl methacrylate (nBMA) to . . . give PLina-g-polystyrene (PS), PLina-g-poly-MMA (PMMA), and PLina-g-poly- nBMA (PnBMA) graft copolymers. The polymers obtained were characterized by proton nuclear magnetic resonance (1H NMR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and gel permeation chromatography (GPC) techniques. Microstructure of the graft copolymers was observed by using scanning electron microscope (SEM). Graft copolymers obtained contained polymeric linoleic acid in a range between 8.5 and 19.3 mol percent (mol%). PLina-g-PS, PLina-g-PMMA and PLina-g-PnBMA graft copolymer samples were also used in cell culture studies. Fibroblast and macrophage cells were strongly adhered and spread on the copolymer film surfaces. These newly synthesized copolymers were tested for their effects on human blood protein adsorption compared with PMMA graft copolymers containing polymeric soybean oil and polymeric linseed oil; interestingly we observed a dramatic decrease in the protein adsorption on the linoleic acid graft copolymer, which is important in tissue engineering. © AOCS 2007 Daha fazlası Daha az

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