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Öğe In vitro biocompatibility of plasma-aided surface-modified 316L stainless steel for intracoronary stents(IOP Publishing LTD, 2010) Bayram, Cem; Mızrak, Alpay Koray; Aktürk, Selçuk; Kurşaklıoğlu, Hürkan; İyisoy, Atila; İfran, Ahmet; Denkbaş, Emir Baki316L-type stainless steel is a raw material mostly used for manufacturing metallic coronary stents. The purpose of this study was to examine the chemical, wettability, cytotoxic and haemocompatibility properties of 316L stainless steel stents which were modified by plasma polymerization. Six different polymeric compounds, polyethylene glycol, 2-hydroxyethyl methacrylate, ethylenediamine, acrylic acid, hexamethyldisilane and hexamethyldisiloxane, were used in a radio frequency glow discharge plasma polymerization system. As a model antiproliferative drug, mitomycin-C was chosen for covalent coupling onto the stent surface. Modified SS 316L stents were characterized by water contact angle measurements (goniometer) and x-ray photoelectron spectroscopy. C1s binding energies showed a good correlation with the literature. Haemocompatibility tests of coated SS 316L stents showed significant latency (t-test, p < 0.05) with respect to SS 316L and control groups in each test.Öğe Osteoblast activity on anodized titania nanotubes: Effect of simulated body fluid soaking time(American Scientific Publishers, 2012) Bayram, Cem; Demirbilek, Murat; Çalışkan, Nazlı; Demirbilek, Melike Erol; Denkbaş, Emir BakiEarly phase osseointegration is crucial for orthopedic implants. For the improvement of osseointegrative properties of orthopedic implants several surface modification methods such as acid etching, hydroxyapatite (HA) coating and sandblasting can be applied. In this article titanium implants were anodized to possess nanotubular titania structures on the surface. Titania nanotube structures with a 45-50 nm of average inner diameter were obtained and to enhance bioactivity, samples were soaked in 10X simulated body fluid (SBF) for apatite deposition on surface for different time periods (1, 2, 3, 5, 8 hours). Apatitic calcium phosphate deposited surfaces were analyzed with infrared spectrometry and wettability studies. Effect of soaking time on osteoblast cell was investigated by cell viability, alkaline phosphatase activity tests and morphological evaluations. As a result, 3 hours of soaking time was found as the optimum time period (p < 0.005). This in vitro study indicated that soaking in 10X SBF can be a rapid and economical technique to enhance osseointegration of anodized titanium implants however excess and/or uncontrolled HA coating of titania layer limits the bioactive potential of the implant.Öğe Osteoblast response on co-modified titanium surfaces via anodization and electrospinning(ELSEVIER SCIENCE BV, 2014) Bayram, Cem; Demirbilek, Murat; Yalçın, Eda; Bozkurt, Murat; Doğan, Metin; Denkbaş, Emir BakiTopography plays a key role in osseointegration and surface modifications at the subcellular level, increasing initial cell attachment in the early period. In the past decade, nanosized texture on metal like a nanotube layer and also more recently extracellular matrix like surface modifications - such as polymeric nanofibrils - have been proposed for a better osseointegration in the literature. Here, we investigate two types of nanoscaled modifications alone and together for the first time. We characterized different types of surface modifications morphologically and investigated how they affected osteoblast cells in vitro, in terms of cell adhesion, proliferation, alkaline phosphatase activity and calcium content. We anodized titanium samples with a thickness of 0.127 mm to obtain a nanotubular titania layer and the silk fibroin (SF), as a biocompatible polymeric material, was electrospun onto both anodized and unanodized samples to acquire 4 sample groups. We analyzed the resulting samples morphologically by scanning electron microscopy (SEM). Cell adhesion, proliferation, alkaline phosphatase (ALP) activity and calcium content were evaluated at 3,7 and 14 days. We found that cell proliferation increased by 70% on the groups having two modifications respect to unmodified titanium and after 7 days, ALP activity and calcium content were 110% and 150%, respectively, higher on surfaces having both surface treatments than that of unmodified group. In conclusion, a nanotube layer and SF nanofibers on a titanium surface enhanced cell attachment and proliferation most. Comodification of titanium surfaces by anodization and SF electrospinning may be useful to enhance osseointegration but it requires in vivo confirmationÖğe Porous polyurethane film fabricated via the breath figure approach for sustained drug release(Wiley, 2019) Daban, Gizem; Bayram, Cem; Bozdoğan, Betül; Denkbaş, Emir BakiThe breath figure (BF) method is an effective process for fabricating porous polymeric films. In this study, we fabricated porous polymer films from thermoplastic polyurethane (PU) through static BF with CHCl3 as a solvent under 55-80% relative humidity. The porous PU films were prepared within various pore structures and sizes, which were adjustable, depending on the fabrication conditions. The humidity and exposure time were examined as variable parameters affecting the surface morphology, wettability, and cytotoxicity. Atorvastatin calcium, a hyperlipidemic agent, was loaded into the porous films during the casting process, and the drug-loading and drug-releasing behaviors of the porous PU membranes were evaluated. Approximately 60-80% of the drug was released in 14 days. The films exhibited sustained drug-release performances because of the hydrophobicity and nonbiodegradable nature of PU for perivascular drug administration.Öğe Preparation and characterization of papaverine-loaded poly[(R)-3- hydroxybutyrate] membranes to be used in the prevention of vasospasm(2010) Güven, Eylem; Güven, Eşref Oğuz; Bayram, Cem; Kazak, Osman Nuri; Denkbaş, Emir BakiThe objective of this study is the preparation and characterization of poly[(R)-3-hydroxybutyrate] (PHB) membrane loaded with a vasodialative agent (i.e., papaverine hydrochloride) as a blood vessel coverage strip to be used in the prevention of undesired vascular vasospasm. Papaverine-loaded PHB membranes were especially designed to act locally and provide an efficient, long term, and sustained prevention of vasospasm at the site of the newly created vascular anastomosis without any systemic vasodilation effect of the papaverine, which may be life-threatening for the patient. The membranes were prepared by gelation of PHB followed by solvent casting. PHB membranes were characterized in terms of morphology, chemical structure, swelling behavior, in vitro drug release, degradation, and blood compatibility studies as in vitro coagulation tests. Activated partial thromboplastin time, prothrombin time, and fibrinogen concentration were measured by blood coagulation assays. Investigated and evaluated parameters for in vitro drug release, degradation, and in vitro coagulation studies were the concentration of PHB and drug content. Similar effective parameters were used for swelling behavior studies (i.e., concentration of PHB and drug content). Drug release, swelling behavior, degradation, and in vitro coagulation of the membranes were found to be influenced by these parameters. Obtained results showed that papaverine-loaded PHB membranes provide an efficient and advantegous means for the prevention of vasospasm during vascular anastomosis as a local application. ©PDA, Inc. 2010.Öğe Preparation and characterization of polyhydroxybutyrate scaffolds to be used in tissue engineering applications(Hacettepe Üniversitesi, 2008) Güven, Öztürk Eylem; Demirbilek, Murat; Sağlam, Necdet; Karahaliloğlu, Zeynep; Erdal, Ebru; Bayram, Cem; Denkbaş, Emir BakiPolyhydroxyalkanoates (PHA) are good alternatives on account of biocompatible and biodegradable properties to produce materials as scaffolds for engineered tissues. Polyhydroxybutyrate (PHB) which is a member of polyhydroxyalkanoate family have been widely used as a biomaterial for in vitro and in vivo studies due to its unique properties such as improved flexibility and processability. In this study polyhydroxybutyrate scaffolds were prepared for tissue engineering applications. In order to improve cell attachment on the scaffolds they were modified. During the modification three different immunologically inactive compounds, polyetyhylene glycol (PEG), 2-hydroxyethyl methacrylate (HEMA) and ethylenediamine (EDA) were used in radio frequency glow discharge (RFGD) plasma polymerization system. Morphological evaluations were obtained by using scanning electron microscopy. Obtained results showed high and interconnected porosity. In vitro weight loss profiles of the scaffolds were investigated by using gravimetric method and found to be influenced by PHB concentration used in the preparation of scaffolds. Their biological promotion of activities including cell attachment, morphology and proliferation on L929 mouse fibroblast cells were examined and cytotoxicity tests were performed at the last part of the study.Öğe Silk fibroin/nylon-6 blend nanofilter matrix for copper removal from aqueous solution(SPRINGER, 2015) Yalçın, Eda; Gedikli, Serap; Çabuk, Ahmet; Karahaliloğlu, Zeynep; Demirbilek, Murat; Bayram, Cem; Şam, Mesut; Sağlam, Necdet; Denkbaş, Emir BakiHeavy metal pollution has become a serious problem for living organisms. In this study, silk fibroin (SF)/nylon-6 nanofiber matrices were formed by electrospinning and their surface was modified with calcium phosphate (CaP) crystals to increase the affinity of divalent heavy metals. The properties of matrices were evaluated as a filter matrix for copper adsorption from aqueous solution. Attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDXS), X-ray photoelectron spectroscopy (XPS), and alizarin red staining method were used for characterization. Adsorption studies were performed by batch and continuous system. The various parameters regarding adsorption process such as pH of solution, surface area, initial copper concentration, and flow rate were optimized. Toxicity values were assessed before and after the Cu(II) adsorption studies. The resultant SF/nylon-6 nanofiber matrices indicate an excellent fibrous structure without beads (fiber diameter at 250 +/- A 50 nm) and modified successfully with CaP crystals. Adsorption results showed that the removal efficiency of copper could reach 32 % by continuous flow system whereas 77 % by batch system. Acute toxicity bioassays using Vibrio fischeri showed that the toxicity decreased after continuous and batch flow systems. For desorption study, different concentrations of various desorption solutions were used and the percentage of Cu(II) desorption was determined as 11 %, approximately.
