Yazar "Demirbilek, Murat" seçeneğine göre listele
Listeleniyor 1 - 15 / 15
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe A comparative study of receptor-targeted magnetosome and HSA-coated iron oxide nanoparticles as MRI contrast-enhancing agent in animal cancer model(Humana Press, 2018) Erdal, Ebru; Demirbilek, Murat; Yeh, Yasan; Akbal, Öznur; Ruff, Laura; Bozkurt, Damla; Çabuk, Ahmet; Senel, Yasin; Gümüşkaya, Berrak; Algın, Oktay; Çolak, Şeyda; Esener, Sadık; Denkbaş, Emir BakiMagnetosomes are specialized organelles arranged in intracellular chains in magnetotactic bacteria. The superparamagnetic property of these magnetite crystals provides potential applications as contrast-enhancing agents for magnetic resonance imaging. In this study, we compared two different nanoparticles that are bacterial magnetosome and HSA-coated iron oxide nanoparticles for targeting breast cancer. Both magnetosomes and HSA-coated iron oxide nanoparticles were chemically conjugated to fluorescent-labeled anti-EGFR antibodies. Antibody-conjugated nanoparticles were able to bind the MDA-MB-231 cell line, as assessed by flow cytometry. To compare the cytotoxic effect of nanoparticles, MTT assay was used, and according to the results, HSA-coated iron oxide nanoparticles were less cytotoxic to breast cancer cells than magnetosomes. Magnetosomes were bound with higher rate to breast cancer cells than HSA-coated iron oxide nanoparticles. While 250 mu g/ml of magnetosomes was bound 92 +/- 0.2%, 250 mu g/ml of HSA-coated iron oxide nanoparticles was bound with a rate of 65 +/- 5%. In vivo efficiencies of these nanoparticles on breast cancer generated in nude mice were assessed by MRI imaging. Anti-EGFR-modified nanoparticles provide higher resolution images than unmodified nanoparticles. Also, magnetosome with anti-EGFR produced darker image of the tumor tissue in T2-weighted MRI than HSA-coated iron oxide nanoparticles with anti-EGFR. In vivo MR imaging in a mouse breast cancer model shows effective intratumoral distribution of both nanoparticles in the tumor tissue. However, magnetosome demonstrated higher distribution than HSA-coated iron oxide nanoparticles according to fluorescence microscopy evaluation. According to the results of in vitro and in vivo study results, magnetosomes are promising for targeting and therapy applications of the breast cancer cells.Öğe Active nano/microbilayer hemostatic agents for diabetic rat bleeding model(Wiley, 2017) Karahaliloğlu, Zeynep; Demirbilek, Murat; Ulusoy, İbrahim; Gümşkaya, Berrak; Denkbaş, Emir BakiPatients with diabetes mellitus have an increased cardiovascular risk due to the abnormality of hemostatic system components. Therefore, hemostasis is an important concept when considering that diabetics are under risk due to potential bleeding complications during surgical operation. The aim of our study was to examine the efficiency of a fabricated nano/microbilayer hemostatic dressing for bleeding control in diabetic patients. For this purpose, we prepared a nano/microbilayer hemostatic dressing that has a porous sublayer, including chitosan (CTS), bacterial cellulose (BC) as basement and active agents in coagulation cascade, such as vitamin K (Vit K), protamine sulfate (PS), and kaolin (Kao) as a filler and an upper layer consisting of silk fibroin (SF) or SF/phosphatidylcholine (PC) blend to achieve complete hemostasis in diabetic rats. Coagulative performances of the prepared hemostatic dressings were examined by the determination of bleeding time, blood loss, and mortality rate through diabetic rat femoral artery injury model. The percent of diabetic rat blood absorption was found to be 247 +/- 5% for gauze as opposed to 2214 +/- 56% for SF-coated PS/BC/CTS. Vit K-reinforced within 138 s and SF-coated BC/CTS hemostatic dressings within 144 s showed a rapid coagulation time. In vivo coagulation studies demonstrated that hemostatic agent-reinforced BC/CTS hemostatic dressing, especially PS/BC/CTS showed a significant hemostatic plug formation. This study suggests that the high positive charge and porosity give to these hemostatic agents reinforced hemostatic dressings the ability to rapidly swell and to promote the accumulation of red blood cells and platelets through electrostatic interactions. (C) 2016 Wiley Periodicals, Inc.Öğe Aligned bacterial PHBV nanofibrous conduit for peripheral nerve regeneration(Taylor & Francis Ltd, 2015) Demirbilek, Murat; Sakar, Mustafa; Karahaliloğlu, Zeynep; Erdal, Ebru; Yalçın, Eda; Bozkurt, Gökhan; Korkusuz, Petek; Bilgiç, Elif; Temuçin, Çağri Mesut; Denkbaş, Emir BakiThe conventional method of peripheral nerve gap treatment is autografting. This method is limited. In this study, an aligned nanofibrous graft was formed using microbial polyester, Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). The regenerative effect of the graft was compared with that of autografting in vivo. To determine the regenerative effect, rats were assessed with sciatic nerve functional index, electromyographic evaluation, and histological evaluation. Results found in this study include PHBV grafts stimulated progressive nerve regeneration, although regeneration was not comparable with that of autografting. We conclude that the study results were promising for aligned bacterial polymeric grafts for peripheral nerve regeneration.Öğe Characterization and optimization of poly(3-hydroxybutyrate) produced by bacteria isolated from hydrocarbon polluted soil(Elsevier Science Bv, 2012) Güngörmedi, Gökhan; Demirbilek, Murat; Çabuk, Ahmet; Mutlu, Mehmet Burçin; Şam, Mesut; Denkbaş, Emir Baki[Abstract Not Available]Öğe Hemostatic activities of nano/microporous bilayer dressings in a femoral artery bleeding rat model(Wiley-Blackwell, 2016) Karahaliloğu, Zeynep; Demirbilek, Murat; Ulusoy, İbrahim; Gümüşkaya, Berrak; Denkbaş, Emir BakiRecently, an effective hemostatic dressing requirement has become a major problem in both the military and civilian world. Available hemostatic agents are too expensive, ineffective, unsafe, or complicated to use. Here, we evaluated the hemostatic efficacy of a nano/micro bilayer hemostatic dressing including a porous sublayer from chitosan (CTS) and bacterial cellulose (BC) and a nanofibrillar upper layer from silk fibroin (SF). In addition, several active agents rolled in coagulation cascade [vitamin K (Vit K), protamine sulfate (PS), kaolin (Kao), etc.] were doped to the sublayer of bilayer hemostatic agent and their activities were compared via in vivo and in vitro tests. Lactate dehydrogenase (LDH) activity test results demonstrated that BC/CTS, SF-coated BC/CTS, and Vit K K/BC/CTS, SF/phosphatidylcholine (PC)-coated BC/CTS showed higher LDH activity compared to standard gauze (p<0.005). In a femoral artery bleeding rat model, SF-coated PS/BC/CTS significantly reduced bleeding time (80 +/- 0.3 s) compared to standard gauze and kaolin-doped group (p<0.005). Blood loss and mortality rate with 2.3 g and 37.5% SF-coated BC/CTS and SF-coated PS/BC/CTS showed increased efficacy in achieving hemostasis compared to standard gauze. All the prepared hemostatic dressings except for kaolin-doped BC/CTS and standard gauze induced no inflammatory reaction in the tissue. All these data suggest that active agent-doped BC/CTS/SF-based bilayer hemostatic dressings have a great influence on the resulting hemostatic action. (c) 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43657.Öğe Magnetic silk fibroin e-gel scaffolds for bone tissue engineering applications(SAGE PUBLICATIONS, 2017) Karahaliloğlu, Zeynep; Yalçın, Eda; Demirbilek, Murat; Denkbaş, Emir BakiRecently, the incorporation of magnetic nanoparticles into standard scaffolds has emerged as a promising approach for tissue engineering applications. This strategy can promote not only tissue regeneration but also reloading of scaffolds through an external supervising center that adsorbs growth factors, preserving their stability and biological activity. In this study, novel magnetic silk fibroin e-gel scaffolds were prepared by the electrogelation process of concentrated Bombyx mori silk fibroin (8 wt%) aqueous solution. In addition, basic fibroblast growth factor was conjugated physically to human serum albumin=Fe3O4 nanoparticles (71.52 +/- 2.3nm in size) with 97.5% binding yield. Scanning electron microscopy images of the prepared human serum albumin=Fe3O4-basic fibroblast growth factor-loaded silk fibroin e-gel scaffolds showed a three-dimensional porous morphology. In terms of water uptake, basic fibroblast growth factor-conjugated scaffolds had the highest water absorbability among all groups. In vitro cell culture studies showed that both the human serum albumin coating of Fe3O4 nanoparticle surface and basic fibroblast growth factor conjugation had an inductive effect on cell viability. One of the most used markers of bone formation and osteoblast differentiation is alkaline phosphatase activity; human serum albumin=Fe3O4-basic fibroblast growth factor-loaded silk fibroin e-gels showed significantly enhanced alkaline phosphatase activity (p<0.05). SaOS-2 cells cultured on human serum albumin=Fe3O4-basic fibroblast growth factor-loaded silk fibroin e-gels deposited more calcium compared with those cultured on bare silk fibroin e-gels. These results indicated that the proposed e-gel scaffolds are valuable candidates for magnetic guiding in bone tissue regeneration, and they will present new perspectives for magnetic field application in regenerative medicine.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 Oxidative stress parameters of L929 cells cultured on plasma-modified PDLLA scaffolds(Humana Press, 2011) Demirbilek, Melike Erol; Demirbilek, Murat; Karahaliloğlu, Zeynep; Erdal, Ebru; Vural, Tayfun; Yalçın, Eda; Sağlam, Necdet; Denkbaş, Emir BakiOxidative stress may produce high level of reactive oxygen species (ROS) following cell exposure to endogenous and exogenous factors. Recent experiments implicate oxidative stress as playing an essential role in cytotoxicity of many materials. The aim of this study was to measure intracellular malondialdehyde (MDA), advanced oxidation protein product (AOPP) levels, and superoxide dismutase (SOD) activities of L929 fibroblasts cultured on PDLLA, polyethylene glycol (PEG), or ethylenediamine (EDA) grafted PDLLA by plasma polymerization method. Cell proliferation on these scaffolds was studied by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. The study showed that MDA, AOPP levels, and SOD activities in L929 fibroblast cells cultured on all scaffolds were significantly different compared to the control group and each other. The highest MDA (0.42 +/- 0.76 nmol/mg protein), AOPP (14.99 +/- 4.67 nmol/mg protein) levels, and SOD activities (7.49 +/- 3.74 U/mg protein) were observed in cells cultured on non-modified scaffolds; meanwhile, the most cell proliferation was obtained in EDA-modified scaffolds (MDA 0.15 +/- 0.14 nmol/mg protein, AOPP 13.12 +/- 3.86 nmol/mg protein, SOD 4.82 +/- 2.64 U/mg protein). According to our finding, EDA- or PEG-modified scaffolds are potentially useful as suitable biomaterials in tissue engineering.Öğe Plasma polymerization-modified bacterial polyhydroxybutyrate nanofibrillar scaffolds(Wiley-Blackwell, 2013) Karahaliloğlu, Zeynep; Demirbilek, Murat; Şam, Mesut; Erol-Demirbilek, Melike; Sağlam, Necdet; Denkbaş, Emir BakiThe design and the development of novel scaffold materials for tissue engineering have attracted much interest in recent years. Especially, the prepared nanofibrillar scaffold materials from biocompatible and biodegradable polymers by electrospinning are promising materials to be used in biomedical applications. In this study, we propose to produce low-cost and cell-friendly bacterial electrospun PHB polymeric scaffolds by using Alcaligenes eutrophus DSM 545 strain to PHB production. The produced PHB was characterized by Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Nanofibrous scaffolds were fabricated via electrospinning method that has a fiber diameter approximately 700800 nm. To investigate cell attachment, cell growth, and antioxidant enzyme activity on positively and negatively charged PHB scaffold, PHB surface was modified by plasma polymerization technique using polyethylene glycol (PEG) and ethylenediamine (EDA). According to the results of superoxide dismutase (SOD) activity study, PEG-modified nanofibrillar scaffolds indicated more cellular resistance against oxidative stress compared to the EDA modification. As can be seen in cell proliferation results, EDA modification enhanced the cell proliferation more than PEG modification, while PEG modification is better as compared with nonmodified scaffolds. In general, through plasma polymerization technique, surface modified nanofibrillar structures are effective substrates for cell attachment and outgrowth. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013Öğe Preparation and characterization of magnetically responsive bacterial polyester based nanospheres for cancer therapy(Amer Scientific Publishers, 2012) Erdal, Ebru; Kavaz, Doğa; Şam, Mesut; Demirbilek, Murat; Demirbilek, Melike Erol; Sağlam, Necdet; Denkbaş, Emir BakiPolyhydroxyalkanoates (PHA) are natural, thermoplastic polyesters and due to their biocompatible and biodegradable properties they are good alternatives for the production of scaffolds for engineered tissues or nanoparticles for drug delivery. As a member of polyhydroxyalkanoate family, polyhydroxybutyrates (PHB) have been widely used as a biomaterial for in vitro and in vivo studies since their mechanical properties are very similar to conventional plastics. By using multi-emulsion technique, iron oxide particles were coated with polyhydroxybutyrate (PHB) polymer synthesized from Alcaligenes eutrophus bacteria and the magnetic carrier system was prepared accordingly. The bare nanoparticles and magnetic nanoparticles were morphologically, structurally and magnetically characterized by using Scanning electron microscope (SEM) and Atomic force microscope (AFM); Fourier Transform Infrared Spectrometry (FTIR), and Electron Spin Resonance (ESR) and Vibrating Sample Magnetometer (VSM) techniques, respectively. Particle size of PHB nanoparticles was determined by Zeta Sizer. It was found that the smallest particles were in the range of 239,43+/-5,25 nm in diameter. Concanavalin-A (Con-A) was used for targeting the Cancer cells while etoposide was used as drug. Con-A and etoposide were loaded onto the particles. Release studies of etoposide were evaluated and the system was optimized for the further in vivo applications. Finally different formulation magnetic PHB nanoparticles cytotoxicity were evaluated in cell culture studies and used He La cell line (cervical cancer cells) as a cancer cells and L929 cells (mouse fibroblast cells) as a non-cancer cell line.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.Öğe Surface-modified bacterial nanofibrillar PHB scaffolds for bladder tissue repair(Taylor & Francis, 2016) Karahaliloğlu, Zeynep; Demirbilek, Murat; Şam, Mesut; Sağlam, Necdet; Mızrak, Alpay Koray; Denkbaş, Emir BakiThe aim of the study is in vitro investigation of the feasibility of surface-modified bacterial nanofibrous poly [(R)-3-hydroxybutyrate] (PHB) graft for bladder reconstruction. In this study, the surface of electrospun bacterial PHB was modified with PEG- or EDA via radio frequency glow discharge method. After plasma modification, contact angle of EDA-modified PHB scaffolds decreased from 110 +/- 1.50 to 23 +/- 0.5 degree. Interestingly, less calcium oxalate stone deposition was observed on modified PHB scaffolds compared to that of non-modified group. Results of this study show that surface-modified scaffolds not only inhibited calcium oxalate growth but also enhanced the uroepithelial cell viability and proliferation.Öğe Targeted delivery of etoposide to osteosarcoma cells using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanoparticles(TÜBİTAK, 2017) Alp, Esma; Çırak, Tamer; Demirbilek, Murat; Türk, Mustafa; Güven, EylemFolic acid (FA)-functionalized poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanoparticles were prepared to enhance the delivery efficiency of the anticancer drug etoposide for the clinical treatment of osteosarcoma. PHBV nanoparticles were synthesized by emulsification/solvent evaporation technique and obtained in the size range of 200–250 nm and zeta potential range of –21 and –27 mV. Encapsulation efficiency and in vitro drug release were studied. The cytotoxic, apoptotic, and necrotic effects of PHBV nanoparticles were also investigated using Saos-2 osteosarcoma cells. The results obtained in this study demonstrate that etoposideloaded and FA-functionalized PHBV nanoparticles can be successfully used for targeted treatment of osteosarcoma.
