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

Makale | 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

Hazer, Derya Burcu | Kılıçay, Ebru | Hazer, Baki

Gözden Geçirme | 2012 | Materials Science and Engineering C32 ( 4 ) , pp.637 - 647

Biomaterials have played an important role in the treatment of disease and the improvement of health care. Synthetic and naturally occurring biodegradable and biocompatible polymers have been used as biomaterials. Polyhydroxyalkanoates (PHAs) are promising materials for biomedical applications because they are biodegradable, non-toxic and biocompatible. We will shortly summarize the modification reactions, which include functionalization and grafting reactions, to improve the mechanical, thermal and hydrophilic properties of PHAs. The use of the modified PHAs in numerous biomedical applications, such as sutures, cardiovascular patch . . .es, wound dressings, scaffolds in tissue engineering, tissue repair/regeneration devices, drug carriers will be discussed in this review. © 2012 Elsevier B.V. All rights reserved Daha fazlası Daha az

Acar, Merve | Çoban, Selim | Hazer, Baki

Makale | 2013 | Journal of Macromolecular Science, Part A: Pure and Applied Chemistry50 ( 3 ) , pp.287 - 296

A cold water soluble, biobased polymer derived from autoxidized soya oil has been described. Oxidized soya oil polymer was obtained by exposure to air under daylight at room temperature. The thickness of the soya oil at the beginning of the reaction and the oxidation time adversely influenced the molecular weight of the soya oil polymer obtained. The oxidized soya oil polymer obtained was then reacted with diethanol amine to obtain a hydroxylated soya oil polymer. The cold water soluble hydroxylated soya oil polymer was characterized by viscosity measurements, elemental analysis, FT-IR, 1H-NMR, 13C-NMR and cosy-NMR. © 2013 Copyright . . . Taylor and Francis Group, LLC Daha fazlası Daha az

Yanpar, Tuğba | Hazer, Baki | Arslan, Ali

Makale | 2006 | İnönü Üniversitesi Eğitim Fakültesi Dergisi7 ( 11 ) , pp.113 - 122

Bu çalışmanın amacı, oluşturmacı yaklaşıma dayalı grup aktivitelerinin etkilerini göstermektir. Bu araştırma 2001- 2002 öğretim yılı, güz döneminde Kdz. Ereğli Anadolu Lisesinde okuyan 58 öğrenci üzerinde yapılan deneysel çalışmadır. Deney grubunda oluşturmacılık temelli grup aktiviteleri, kontrol grubunda geleneksel yöntem kullanılmıştır. Veri toplama aracı olarak, bilişsel becerilerini ölçebilmek için ön ve son testler, duyuşsal algılamalarını belirlemek için açık uçlu sorular sorulmuştur. Bu çalışma grup çalışmalarının kullanıldığı sınıftaki öğrenci başarısının, geleneksel öğretim yönteminin kullanıldığı gruptaki öğrenci başarısı . . .ndan daha yüksek olduğunu göstermiştir. Ayrıca öğrencilerin oluşturmacılık temelli grup aktivitelerini algılamalarının olumlu olduğu sonucuna ulaşılmıştır. The purpose of this research was to demonstrate the effectiveness of group activities based on constructivism in chemistry course for High School. The study was carried on with 58 high school students at the beginning of the spring semester of 2001-2002. Group activities based on constructivism were performed with the experimental group while the traditional teaching style (teacher active) was performed with the control group. An achievement test and an open-ended questionnaire were used to gather the data. This study indicated that the success of the students in the experimental group in which constructivist learning approach was employed was higher than those in the control group. Therefore, it was found that the students in the experimental group perceived the group activities, based on constructivism, positively Daha fazlası Daha az

Savaşkan, Sevil | Volga, Cüneyt | Hazer, Baki

Makale | 1998 | Designed Monomers and Polymers1 ( 1 ) , pp.111 - 119

Polytetrahydrofuran macromonomeric initiators (poly-THF-inimer) were synthesized via cationic polymerization of THF, initiated by the combination of AgSbFe 6 and mono-, di-, or tetra-bromomethyl benzoyl peroxides, followed by termination with methacrylate anion. The macroinimers were characterized by 1 H-NMR and GPC techniques. Copolymerization of poly-THF-inimers with methyl methacrylate (MMA) gave crosslinked block copolymers. Sol-gel analysis and swelling measurements of the crosslinked product are also reported.

Yıldız, Ufuk | Hazer, Baki | Tauer, Klaus

Gözden Geçirme | 2012 | Polymer Chemistry3 ( 5 ) , pp.1107 - 1118

Hazer, Baki | Savaşkan, Sevil

Makale | 1998 | European Polymer Journal34 ( 05.Jun ) , pp.863 - 870

Macromonomer peroxy initiator, MMPI, was synthesized by the reaction of polytetrahydrofurandiol (Mw 1000g/mol) with isophoran diisocyanate (IPDI), 2,5-dimethyl-2,5-dihydroperoxyhexane (Luperox 2,5-2,5) and isocyanato ethyl methacrylate (IEM). Copolymerization of methyl methacrylate, (MMA), with MMPI gave poly(THF-b-MMA) cross-linked block copolymers. The overall polymerization rate constant, k, was calculated to be 2.46 × 10-4 (mol/L)1/2 sec-1. The cross-linked copolymer samples showed the peroxide decomposition at 175°C and glass transition at approximately 54°C. Poly(THF-b-MMA) cross-linked block copolymers containing undecomposed . . . peroxide groups initiated the thermal polymerization of styrene; S. Poly(THF-b-MMA-b-S) cross-linked block copolymers with a Tg of 80°C were obtained. By measuring the degrees of swelling of the polymer networks, the mechanism of crosslinking polymerization has been investigated. © 1998 Elsevier Science Ltd. All rights reserved Daha fazlası Daha az

Yalçın, Barış | Çakmak, Mukerrem | Arkın, Ali Hakan | Hazer, Baki | Erman, Burak

Makale | 2006 | Polymer47 ( 24 ) , pp.8183 - 8193

There is a continuing need to produce polymer films with high optical clarity with ability to dial in the optical properties including refractive indices and optical anisotropies. In this research, we investigated the mechano-optical behavior of PMMA/PHB-Cl blend films during uniaxial deformation and mapped out the composition-birefringence-processing relationships. The results indicate the presence of a broad glass transition for the composition range investigated that indicates the development of micro-heterogeneities particularly at the higher concentration of PHB-Cl. However, this did not detrimentally influence the optical tran . . .sparency of the solvent cast films as the size of these micro-heterogeneities remains well below the size range to affect the transparency. Optical retardation behavior of the films can be altered from negative to positive by increasing the PHB-Cl concentration from 0 to 20 wt%. The films with 18 wt% PHB-Cl are predicted to exhibit zero birefringence even when they are stretched to large deformations. This dialability of optical properties makes these materials suitable for optical device applications such as CD and DVDs as well as optical retarder films for liquid-crystal display applications. © 2006 Elsevier Ltd. All rights reserved Daha fazlası Daha az

İlter, Songun | Hazer, Baki | Borcaklı, Mehlika | Atıcı, Oya

Makale | 2001 | Macromolecular Chemistry and Physics202 ( 11 ) , pp.2281 - 2286

Poly(3-hydroxy alkanoate) containing unsaturated side chains was produced by feeding Pseudomonas oleovorans with soybean-oil acid (PHA-soybean). The composition of PHA-soybean were found to be 10 mol-% of unsaturated side chains with the saturated hexanoate, octanoate and decanoate units. Methyl methacrylate (MMA) was thermally grafted on PHA-soybean in the presence of benzoyl peroxide. Fractional precipitation was used to isolate the graft copolymer from related homopolymers. PHA content in copolymer samples was between 15 to 30 mol-%. Graft copolymer samples were kept in hydroquinone to prevent post polymerization leading to cross . . .linking in a day under laboratory atmospheric conditions. Copolymer characterization was performed using GPC and NMR techniques. Thermal analysis of the graft copolymer indicated the decomposition and glass transition temperatures of the PHA and PMMA segments of the graft copolymers. They also showed elongation at break in the range 10 to 21 related to the plasticizer effect of the biopolyester segments Daha fazlası Daha az

Hazer, Derya Burcu | Hazer, Baki | Kaymaz, Figen

Makale | 2009 | Biomedical Materials4 ( 3 ) , pp.2281 - 2286

Biocompatibility studies of the autoxidized and unoxidized unsaturated medium-long chain length (m-lcl) co-poly-3-hydroxyalkanoates (m-lclPHAs) derived from soya oily acids have been reported. Pseudomonas oleovorans was grown on a series of mixtures of octanoic acid (OA) and soya oily acids (Sy) with weight ratios of 20:80, 28:72 and 50:50 in order to obtain unsaturated m-lcl copolyesters coded PHO-Sy-2080, PHO-Sy-2872 and PHO-Sy-5050, respectively. The PHA films were obtained by solvent cast from CHCl3. They were all originally sticky and waxy except PHO-Sy-5050. Autoxidation of the unsaturated copolyester films was carried out on . . .exposure to air at room temperature in order to obtain crosslinked polymers. They became a highly flexible elastomer after being autoxidized (about 40 days of autoxidation). The in vivo tissue reactions of the autoxidized PHAs were evaluated by subcutaneous implantation in rats. The rats appeared to be healthy throughout the implantation period. No symptom such as necrosis, abscess or tumorigenesis was observed in the vicinity of the implants. Retrieved materials varied in their physical appearance after 6 weeks of implantation. In vivo biocompatibility studies of the medical applications indicated that the microbial copolyesters obtained were all biocompatible and especially the PHOSy series of copolyesters had the highest biocompatibility among them. © 2009 IOP Publishing Ltd Daha fazlası Daha az

Erduranlı, Haydar | Hazer, Baki | Borcaklı, Mehlika

Konferans nesnesi | 2008 | Macromolecular Symposia269 ( 1 ) , pp.161 - 169

Chemical modification is useful to diversify poly(3-hydroxyalkanoate)s, for medical and industrial applications. In this manner, transesterification reactions of poly(3-hydroxy butyrate) were carried out under reflux condition of 1,2-dichlorobenzene in the presence of 1,4-butane diol, poly(ethyleneglycol) bis(2-aminopropyl ether) with molecular weights of 1000 and 2000, poly(ethylene glycol)methacrylate or glycerol at 180°C. Addition reactions of bromine and -SH groups of 3-mercaptopropionic acid to the double bond of poly(3-hydroxy-io-undecenoate) were also carried out. Functionalized poly(3-hydroxyalkanoate)s were characterized us . . .ing 1H NMR, FTIR, GPC and thermal analysis techniques. Copyright © 2008 WILEY-VCH Verlag GmbH & Co. KGaA Daha fazlası Daha az

Kılıçay, Ebru | Demirbilek, Murat | Türk, Mustafa | Güven, Eylem | Hazer, Baki | Denkbaş, Emir Baki

Makale | 2011 | EUROPEAN JOURNAL OF PHARMACEUTICAL SCIENCES44 ( 3 ) , pp.310 - 320

Targeted drug delivery systems are one of the most promising alternatives for the cancer therapy. Rapid developments on nanomedicine facilitated the creation of novel nanotherapeutics by using different nanomaterials. Especially polymer based nanoparticles are convenient for this purpose. In this study; a natural polymer (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), PHBHHX) was used as a base matrix for the production of a novel nanotherapeutic including antineoplastic agent, Etoposide and attached folic acid as a ligand on the nanoparticles. Modified solvent evaporation technique was used for the production of PHBHHX nanoparticle . . .s and the average size of the obtained PHBHHX nanoparticles were observed in the range of 180 nm and 1.5 mu m by the change in experimental conditions (i.e., homogenization rate, surfactant concentration and polymer/solvent ratio). By the increase in homogenization rate and surfactant concentration, size of the nanoparticles was decreased, while the size was increased by the increase in polymer/solvent ratio. Drug loading ratio was also found to be highly affected by polymer/drug ratio. Surface charge of the prepared nanoparticles was also investigated by zeta potential measurements. In the cytotoxicity tests; Etoposide loaded and folic acid attached PHBHHX nanoparticles were observed as more effective on HeLa cells than Etoposide loaded PHBHHX nanoparticles without attached folic acid. The cytotoxicity of folic acid conjugated PHBHHX nanoparticles to cancer cells was found to be much higher than that of normal fibroblast cells, demonstrating that the folate conjugated nanoparticles has the ability to selectively target to cancer cells. In addition, apoptotic/necrotic activities were evaluated for all formulations of the PHBHHX nanoparticles and parallel results with cytotoxicity tests were obtained. These studies demonstrate that the folic acid attached and Etoposide loaded PHBHHX nanoparticles seem as promising for the targeted cancer therapy. (C) 2011 Elsevier B.V. All rights reserved Daha fazlası Daha az