Person: EKREN, NAZMİ
Loading...
Email Address
Birth Date
Research Projects
Organizational Units
Job Title
Last Name
EKREN
First Name
NAZMİ
Name
18 results
Search Results
Now showing 1 - 10 of 18
Publication Open Access Bioinspired scaffold induced regeneration of neural tissue(PERGAMON-ELSEVIER SCIENCE LTD, 2019-05) EKREN, NAZMİ; Altun, Esra; Aydogdu, Mehmet O.; Togay, Sine O.; Sengil, Ahmet Z.; Ekren, Nazmi; Haskoylu, Merve E.; Oner, Ebru T.; Altuncu, Nese A.; Ozturk, Gurkan; Crabbe-Mann, Maryam; Ahmed, Jubair; Gunduz, Oguzhan; Edirisinghe, MohanIn the last decade, nerve tissue engineering has attracted much attention due to the incapability of self-regeneration. Nerve tissue regeneration is mainly based on scaffold induced nanofibrous structures using both bio and synthetic polymers. The produced nanofibrous scaffolds have to be similar to the natural extracellular matrix and should provide an appropriate environment for cells to attach onto. Nanofibrous scaffolds can support or regenerate cells of tissue. Electrospinning is an ideal method for producing the nanofibrous scaffolds. In this study, Bacterial cellulose (BC)/Poly (epsilon-caprolactone) (PCL) blend nanofibrous scaffolds were successfully prepared by electrospinning for nerve tissue induced repair. The produced nanofibrous scaffolds contain well defined interconnected nanofiber networks with hollow micro/nanobeads. Firstly, in-vitro biocompatibilities of nanofibrous scaffolds were tested with L2929 murine fibroblasts and improved cell adhesion and proliferation was observed with polymer blends compared with PCL only. The primary cell culture was performed with dorsal root ganglia (DRG) cells on nanofibrous samples and the samples were found suitable for enhancing neural growth and neurite outgrowth. Based on these results, the BC/PCL (50:50 wt.%) nanofibrous scaffolds exhibited nerve-like branching and are excellent candidate for potential biomimetic applications in nerve tissue engineering regeneration.Publication Open Access A drug-eluting nanofibrous hyaluronic acid-keratin mat for diabetic wound dressing(2022-01-01) EKREN, NAZMİ; GÜNDÜZ, OĞUZHAN; Su S., Bedir T., KALKANDELEN C., Sasmazel H. T. , Basar A. O. , Chen J., EKREN N., GÜNDÜZ O.© 2022, Qatar University and Springer Nature Switzerland AG.Diabetes mellitus is a chronic metabolic disease associated with long-term multisystem complications, among which are non-healing diabetic foot ulcers (DFUs). Electrospinning is a sophisticated technique for the preparation of polymeric nanofibers impregnated with drugs for wound healing, burns, and diabetic ulcers. This study describes the fabrication and characterization of a novel drug-eluting dressing made of core–shell structured hyaluronic acid (HA)–keratin (KR)-polyethylene oxide (PEO) and polycaprolactone (PCL) nanofibers to treat diabetic wounds. The core–shell nanofibers produced by the emulsion electrospinning technique provide loading of metformin hydrochloride (MH), HA, and KR in the core of nanofibers, which in return improves the sustained long term release of the drug and prolongs the bioactivity. Morphological and chemical properties of the fibers were examined by SEM, FTIR, and XRD studies. It was observed that the fibers which contain HA and KR showed thin fiber structure, greater swelling capacity, fast degradation and increased cumulative drug release amount than neat emulsion fibers due to the hydrophilic nature of HA and KR. MH showed a sustained release from all fiber samples over 20 days and followed the first-order and Higuchi model kinetics and Fickian diffusion mechanism according to kinetic analysis results. In vitro cell culture studies showed that the developed mats exhibited enhanced biocompatibility performance with HA and KR incorporation. The results show that HA and KR-based emulsion electrospun fiber mats are potentially useful new nanofiber-based biomaterials in their use as drug carriers to treat diabetic wounds.Publication Open Access Marine-derived bioceramics for orthopedic, reconstructive and dental surgery applications(2022-11-01) OKTAR, FAİK NÜZHET; ÜNAL YILDIRIM, SEMRA; GÜNDÜZ, OĞUZHAN; EKREN, NAZMİ; ALTAN, ERAY; OKTAR F. N. , Unal S., GÜNDÜZ O., Ben Nissan B., Macha I. J. , Akyol S., Duta L., EKREN N., ALTAN E., YETMEZ M.Bioceramics are a fast-growing materials group, which are widely used in orthopedics, maxillofacial, dental, and reconstructive surgeries. They are produced using raw materials either from synthetic or natural sources. As naturally originated resources, the bones of sheep and cows are used after converting to calcium phosphates. Human-originated sources in the past were obtained from human cadaver bones, however now-a-days this has been discontinued. On the other hand, the \"golden standard\" in the reconstruction surgery has been using patients own bones, -i.e., autogenous bones, which heal better than other alternatives. Besides natural products, synthetic materials are produced from a range of inorganic raw and natural materials based on marine sources, such as corals, and other marine-derived materials (i.e., seashells, nacre). These are used to produce bioceramics and hence implants, devices, and bone grafts. Although during the last four decades a number of excellent books and book chapters have been published, no comprehensive review has been yet reported to cover the available marine materials and to indicate the related work and corresponding references to allow for both medical and ceramic scientists to access directly and open new avenues for further research on marine structures and their applications in orthopedic, maxillofacial, and reconstructive surgery areas. Hence, this review covers the general marine structures, their locations and availability in different countries and, current research on production methods of these unique structures that are difficult to fabricate synthetically. The authors are confident that this comprehensive review will be an excellent source not only for the ceramists, but also for the medical scientists.Publication Open Access Levodopa-Loaded 3D-Printed Poly (Lactic) Acid/Chitosan Neural Tissue Scaffold as a Promising Drug Delivery System for the Treatment of Parkinson's Disease(MDPI, 2021-11-13) ŞAHİN, ALİ; Saylam, Ezgi; Akkaya, Yigit; Ilhan, Elif; Cesur, Sumeyye; Guler, Ece; Sahin, Ali; Cam, Muhammmet Emin; Ekren, Nazmi; Oktar, Faik Nuzhet; Gunduz, Oguzhan; Ficai, Denisa; Ficai, AntonParkinson's disease, the second most common neurodegenerative disease in the world, develops due to decreased dopamine levels in the basal ganglia. Levodopa, a dopamine precursor used in the treatment of Parkinson's disease, can be used as a drug delivery system. This study presents an approach to the use of 3D-printed levodopa-loaded neural tissue scaffolds produced with polylactic acid (PLA) and chitosan (CS) for the treatment of Parkinson's disease. Surface morphology and pore sizes were examined by scanning electron microscopy (SEM). Average pore sizes of 100-200 mu m were found to be ideal for tissue engineering scaffolds, allowing cell penetration but not drastically altering the mechanical properties. It was observed that the swelling and weight loss behaviors of the scaffolds increased after the addition of CS to the PLA. Levodopa was released from the 3D-printed scaffolds in a controlled manner for 14 days, according to a Fickian diffusion mechanism. Mesenchymal stem cells (hAD-MSCs) derived from human adipose tissue were used in MTT analysis, fluorescence microscopy and SEM studies and confirmed adequate biocompatibility. Overall, the obtained results show that PLA/CS 3D-printed scaffolds have an alternative use for the levodopa delivery system for Parkinson's disease in neural tissue engineering applications.Publication Open Access Fabrication of naturel pumice/hydroxyapatite composite for biomedical engineering(BMC, 2016-12) OKTAR, FAİK NÜZHET; Komur, Baran; Lohse, Tim; Can, Hatice Merve; Khalilova, Gulnar; Gecimli, Zeynep Nur; Aydogdu, Mehmet Onur; Kalkandelen, Cevriye; Stan, George E.; Sahin, Yesim Muge; Sengil, Ahmed Zeki; Suleymanoglu, Mediha; Kuruca, Serap Erdem; Oktar, Faik Nuzhet; Salman, Serdar; Ekren, Nazmi; Ficai, Anton; Gunduz, OguzhanBackground: We evaluated the Bovine hydroxyapatite (BHA) structure. BHA powder was admixed with 5 and 10 wt% natural pumice (NP). Compression strength, Vickers micro hardness, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction studies were performed on the final NP-BHA composite products. The cells proliferation was investigated by MTT assay and SEM. Furthermore, the antimicrobial activity of NP-BHA samples was interrogated. Results: Variances in the sintering temperature (for 5 wt% NP composites) between 1000 and 1300 degrees C, reveal about 700 % increase in the microhardness (similar to 100 and 775 HV, respectively). Composites prepared at 1300 degrees C demonstrate the greatest compression strength with comparable result for 5 wt% NP content (87 MPa), which are significantly better than those for 10 wt% and those that do not include any NP (below 60 MPa, respectively). Conclusion: The results suggested the optimal parameters for the preparation of NP-BHA composites with increased mechanical properties and biocompatibility. Changes in micro-hardness and compression strength can be tailored by the tuning the NP concentration and sintering temperature. NP-BHA composites have demonstrated a remarkable potential for biomedical engineering applications such as bone graft and implant.Publication Open Access Starch/PCL composite nanofibers by co-axial electrospinning technique for biomedical applications(BMC, 2017-12) OKTAR, FAİK NÜZHET; Komur, B.; Bayrak, F.; Ekren, N.; Eroglu, M. S.; Oktar, F. N.; Sinirlioglu, Z. A.; Yucel, S.; Guler, O.; Gunduz, O.Background: In this study, starch and polycaprolactone (PCL), composite nanofibers were fabricated by co- axial needle electrospinning technique. Processing parameters such as polymer concentration, flow rate and voltage had a marked influence on the composite fiber diameter. Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), mechanical and physical properties (such as density, viscosity and electrical conductivity) of the composite fibres were evaluated. Moreover, a cell culture test was performed in order to determine their cytotoxicity for wound dressing application. Results: The effect of starch ratio in the solution on the properties and morphological structure of the fibers produced was presented. With lower starch concentration values, the fibers have greater ultimate tensile strength characteristic (mostly 4 and 5 wt%). According to SEM results, it can be figured out that the nanofibers fabricated have good spinnability and morphology. The mean diameter of the fibers is about 150 nm. According to results of cell culture study, the finding can be determined that the increase of starch in the fiber also increases the cell viability. Conclusions: Composite nanofibers of starch/ PCL have been prepared using a coaxial needle electrospinning technique. PCL was successfully encapsulated within starch. Fiber formation was observed for different ratio of starch. With several test, analysis and measurement performed, some important parameters such as quality and effectuality of each fiber obtained for wound dressing applications were discussed in detail.Publication Open Access A Hydrophobic antireflective and antidust coating with $\text{SiO}_2$ and $\text{TiO}_2$ nanoparticles using a new 3-D printing method for photovoltaic panels(2022-07-01) EKREN, NAZMİ; SAĞLAM, ŞAFAK; Ekren N., Sarkin A. S., Sağlam Ş.The main outdoor factors that reduce the efficiency of the photovoltaic (PV) panel are the reflection and refraction of light, dirt, dust, and organic waste accumulating on the panel surface. In this article, an antireflection, self-cleaning coating was applied on the PV panel cover glass with a new method. With the coating, the surface has been given a hydrophobic feature. As a coating method, a 3-D printer has not been seen in the literature and used as a new method. The electrospinning method has also been tried as an alternative method. Solutions in different combinations were developed using polylactic acid or polymethylmethacrylate polymer, chloroform ($\text{CHCl}_3$) as a solvent, and silicon dioxide ($\text{SiO}_2$) and titanium dioxide ($\text{TiO}_2$) nanoparticles as primary materials in a modified 3-D printer for bioprinting. Five PV panels were obtained by applying different 3-D parameters from three solutions, which have the best results. Coating thicknesses are in the range of 3.12-8.47 mu m. Coated and uncoated PV panels were tested in outdoor conditions for ten-day periods. The power outputs of the PV panels were measured, and their ten-day average efficiency was presented. According to the results, the highest efficiency increase is 8.7%. The highest light transmittance is 88.2% at 550 nm. In addition, hydrophobic properties were observed on all surfaces and the water contact angle was measured as 96.18 degrees.Publication Open Access 3D printing of PVA/hexagonal boron nitride/bacterial cellulose composite scaffolds for bone tissue engineering(ELSEVIER SCI LTD, 2020-11) ŞENGÖR, MUSTAFA; Aki, Deniz; Ulag, Songul; Unal, Semra; Sengor, Mustafa; Ekren, Nazmi; Lin, Chi-Chang; Yilmazer, Hakan; Ustundag, Cem Bulent; Kalaskar, Deepak M.; Gunduz, OguzhanIn this study, a novel Polyvinyl Alcohol (PVA)/Hexagonal Boron Nitride (hBN)/Bacterial Cellulose (BC) composite, bone tissue scaffolds were fabricated using 3D printing technology. The printed scaffolds were characterized by fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), tensile testing, swelling behaviour, differential scanning calorimetry (DSC), and in vitro cell culture assay. Results demonstrated that bacterial cellulose addition affected the characteristic properties of the blends. Morphological studies revealed the homogenous dispersion of the bacterial cellulose within the 12 wt%PVA/0.25 wt%hBN matrix. Tensile strength of the scaffolds was decreased with the incorporation of BC and 12 wt%PVA/0.25 wt%hBN/0.5 wt%BC had the highest elongation at break value (93%). A significant increase in human osteoblast cell viability on 3D scaffolds was observed for 12 wt%PVA/0.25 wt%hBN/0.5 wt%BC. Cell morphology on composite scaffolds showed that bacterial cellulose doped scaffolds appeared to adhere to the cells. The present work deduced that bacterial cellulose doped 3D printed scaffolds with well-defined porous structures have considerable potential as a suitable tissue scaffold for bone tissue engineering (BTE). (c) 2020 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).Publication Open Access Next Generation Student Centricity in Higher Education: The Concept and Ranking of the University that Educates Entrepreneur Students(2022-04-01) EKREN, NAZMİ; Ekren N., PARLAR H., EKREN N.Students are the most important component of national human capital stock/assets that should never be wasted. The concept of demographic window of opportunity underscores the importance of timely acquisition of knowledge and skills. Student-centricity should be considered as matching the preferences and priorities of the students with the demands and expectations of the society in a way that produces a quality distinction. Higher education organizations act as an interface in this matching process. Such an approach will make a significant contribution to strengthening individual competencies, and increasing national capacities and performances. Entrepreneurship should be considered as an individual\"s making a difference by showing his/her ability to produce innovative ideas and applications by using his/her knowledge and experiences during the process of fulfilling duties and responsibilities, and to offer new solutions and alternatives to problems. Therefore, every field of higher education (university, faculty, and department, institute and program) should be restructured to align with this perspective. The process should be designed to enable the students to be aware of the universal data, knowledge level and application models in the field of study, to learn the philosophy of the field, and to receive the training that will improve their abilities. In this new architecture, higher education organizations\" unique structures, decisions and practices have a critical role and function. However, higher education public authorities should ensure that the new generation student-centered approach is handled as a high-priority strategic target in all higher education organizations, in terms of capacities and performances. Ranking universities in this respect will positively affect the results of the structural change as well.Publication Open Access Manufacturing of a portable electrospinning gun for biomedical applications(2022-01-01) EKREN, NAZMİ; EKREN N., Karacan C. E.Electrospun patches have attracted interest in different biomedical fields, including tissue engineering and drug delivery. Portable electrospinning guns promise faster and more practical interventions in these areas. In this article, the design, construction and testing of a portable electrospinning gun are described to produce fiber and particle products. Results were discussed depending on the electrospinning gun\"s working system and properties of the products. The electrospinning gun system could have a high voltage of up to 30 kV. Also, no heating problems were encountered during high voltage values. Due to the uniformity, reproducibility and tunability of the produced PCL and PMSQ fibers, it can be said that electrospinning gun can be used in nanotechnology, drug delivery systems and wound dressing applications.