Papers by Author: Oguzhan Gunduz

Abstract: This study is combined a 3D printing and Electrohydrodynamic (EHD) methods to fabricate a 3D PCL scaffolds for tissue engineering. Various kV values were applied to the different PCL solutions to investigate the effect of the voltage on scaffolds. The morphology of 3D-EHD printed PCL scaffolds were characterized by an Optical Microscope. 10 wt.% PCL up to 3 kV was obtained best sample to use for tissue engineering scaffolds.

Abstract: In current study the electrical properties of clinoptilolite/aluminium oxide/bovine hydroxyapatite composites (Cp/Al₂O₃/BHA) were analysed. Different concentrations of Cp and Al₂O₃ (5 and 15 wt% for both Cp and Al₂O₃) were added to BHA (70 and 90 wt% BHA) and studied after being sintered at 1000, 1100, 1200, and 1300°C for 4 hours under ambient conditions. The dielectric constant (ɛ'), theoretical dielectric constant (ɛ"), dielectric loss factor (tanδ), capacity and conductivity properties were measured on the frequency of 0.1Hz to 10MHz. As the experiment indicates the electrical capacity, loss factor and dielectric values of BHA, CSHA and Al₂O₃ are high at lower frequencies. While the composite materials, especially the 5wt% Cp and Al₂O₃ exhibits high stability, smaller amount of change and better conductive properties than pure substances.

Abstract: In this study, whey protein concentrate (WPC) and poly (ε-caprolactone) (PCL) composite nanofibers were prepared by electrospinning in the diameter of 50-350nm. Characterization tests of the polymer solutions such as density, viscosity, conductivity was studied. Fourier-transformed infrared spectroscopy (IR) results confirmed that the processed fibers were composed of both PCL and WPC constituents. Morphology of nanofibers composite was observed using scanning electron microscopy (SEM). Moreover the PCL/WPC nanofibers with high WPC content exhibited the maximum tensile strength (about 1.40 MPa).

Abstract: In this present work, an original 3D bioprinting method has been developed by modifying an exceptional 3D printer. Using a composite material, bioprinting was carried out to create the ideal scaffold material to contribute regeneration of the certain amount of tissue types in humans. After bypassing the extruder and heating system of the 3D printer, instead of using solid filaments, polymer-ceramic composite was dissolved using an organic agent and bioprinting was conducted. During the bioprinting, dissolving agent was evaporated quickly and solidification process was completed. Despite of the traditional 3D printing, which benefits from the glass transition temperature of the materials, regardless of the temperature, rapid prototyping technology has been merged with controlled flow rate of the composite solution and evaporation of the solvents were adjusted meticulously for proper solidification and layer by layer bioprinting of the scaffolds.

Abstract: Nowadays hydroxyapatite (HA) bioceramics are very important because increasing traffic accidents and ageing of the population. They can be produced from synthetic or natural sources with different production methods. The biggest negative issue of HA is being very brittle and unstable under pressure. Various materials are added for restoring these weaknesses, but there is not so much studies adding nano-ingredients for restoring the mechanical properties of HA. In this study, 5-10% nano-yittria-oxide is added to bovine derived HA (BHA) and to commercial synthetic (CSHA) as a control group. Physical and mechanical properties are examined. Results show that adding of nano-ingredients are really helping to mechanical properties of HA.

Abstract: Hydroxyapatite (HA) is one of the most widely used bioceramics to reconstruct most parts of the skeleton. HA biomaterials are nontoxic and biocompatible with bony tissues. It can be derived from natural sources like bovine bone and other original sources. Also it can be produced synthetically from reagent materials. Due to the fact that HA is not able to be used in biomedical applications cause of bear loadings. It has to be reinforced with materials such as whiskers, metallic oxides, glasses and others. In this study, sintering effects on physical and mechanical properties, such as density (gr/cm³), compression strength (MPa) and Vickers microhardness (HV) of the commercial inert glass (CIG) added human dentine HA (DHA) composite investigated. HA source material is dentine material which is obtained from extracted human teeth. After calcinations enamel and dentine parts were separated (850°C - 4 hours). DHA particles were ball milled and sieved through 100µm sieve. DHA is mixed with 5 and 10 % CIG. Then, this composite material is pressed with a steel mould and sintered in the temperature range of 1000°C to 1300°C with 100°C increments. After scanning electron microscope (SEM) and x-ray diffraction (XRD) studies, both physical and mechanical characterization for DHA – CIG composites are completed by performing density, micro and macro-mechanical test procedures, i.e., HV and compression testing. Briefly, density measurements are conducted corresponding to the Archimedes principle. HV measurements are obtained under a 200g load. Compression test is performed at a rate of 2 mm/min. Here the densest structure was obtained as 2.48 gr/cm³ at 1300°C with 5 wt.% CIG addition. The HV values are increasing with temperature (1082 HV at 1300°C with 10 wt.% CIG addition). The toughest MPa value is 118MPa with 10%CIG addition, sintered at 1300°C. Inert glass addition to dentine HA sounds promising with increasing values of microhardness and compression properties. It can be described as a very hard and a strong biomaterial.

Abstract: Hydroxyapatite (HA) is produced from animal sources like bovine-sheep bones and from human sources with different techniques. Nowadays, it is very crucial utilizing higher valued products from waste materials. Especially, fish bones become major sources for HA production. We have used the waste bone of "Atlantic Bonito" (Sarda sarda), which is a very characteristic fish species. It lives through Atlantic Ocean, the Mediterranean Sea and up to the Black Sea, where it is regarded as a point commercial fish. In this study, the fish bones of "Atlantic Bonito" (Sarda sarda) were collected and cleaned from flesh and greasy parts with distilled boiling water. It was washed again with distilled water, dried and calcinated for 4 hours at 850 °C. Afterwards the material was analysed by X-ray diffraction (XRD) and scanning electron microscope (SEM). XRD analysis revealed the obtained bioceramic material is made of 66.7% HA and 33.3% TCP. The fish bone of “Atlantic Bonito” (Sarda sarda) can be easily trandformed to bioceramic material and it can be used in applications where partly resorbable and economic biomaterials with low carbon footprint needed.

Abstract: Tissue engineering applications have opened a different future-promising era for critical injuries, defects and diseases. Bone tissue engineering is the part of tissue engineering which aims to stir up new practical bone re-formation via the interactive combination of biomaterials and cells. Poly (e-caprolactone) (PCL) is a unique semi crystalline polymer material which handles several important features such as biocompatibility, high biomedical durability and degradation properties. Bovine hydroxyapatite (BHA) is another biocompatible material which provides to get ultimate mechanical behavior in composite designs. Because of their high biocompatibility, PCL and BHA were integrated the electrospinning system together. The system was revised for multi-feeding needle equipment. Eight dissimilar tissue scaffolds were produced and investigated for this recent work.

Abstract: Bioceramics are commonly used biomaterials for orthopedic and dental applications. Among these bioceramics, hydroxyapatite (HA) and tricalcium phosphate (TCP) are of interest and are used in various biomedical applications. Production of bioceramics from natural materials such as bovine and sheep bones with calcination method, is possible. Lately, fish scales become an alternative biological source for bioceramic production. The present study proposes an approach to obtain HA bone-scaffolds from European Sea Bass (Dicentrarchus labrax) scales aiming to provide nano-biomaterials via calcination method. Untreated fish scales are obtained and are carefully cleaned from their meat and grease. They are washed with alkaline water several times and calcinated at 850°C for 4 hours. Energy Dispersive Spectroscopy (EDS), X-ray diffraction analysis, Scanning Electron Microscopy (SEM) studies are performed. Various calcium phosphate species (HA, TCP) are identified in the study. SEM images prove the presence of the nano-scale structures. This study indicates calcination as a simple way of nano-scale bioceramic production for drug delivery and tissue engineering applications. Being produced from wastes of a sustainable and cheap source, these bioceramics can be good candidates for future clinical applications.

Abstract: Calcium phosphates are very important biomaterials for orthopaedic and dental applications. Hydroxyapatite (HA) is one of the important phases used for grafting. Those are produced from synthetic and natural sources with various methods. Especially nano-bioceramics can be produced through calcitic and aragonitic structures (i.e. mussel shells, sea snail shells, land snail shells and sea urchin shells). The plate limpet shells were used. The plate limpet is a gastropod, a soft-bodied invertebrate (an animal without a backbone) that is protected by a very hard, flattened conical shell. In this study the Plate Limpet (Tectura scutum) shells were obtained from a local gift store in Istanbul. The habitation of these limpets broadens from south Alaska down to California - Mexico. First the exact CaCO₃ content was measured with thermal analysis (DTA/TGA). Here in this study agitation was carried out on a hot-plate (i.e. mechano-chemical processing). First the temperature was set at 80 °C for 15 min. Then equivalent amount to CaO H₃PO₄ was added dropwise for HA phase formation and the reaction was set on a hotplate for 8 hours. The dried sediments HA part was divided into 2 groups. One group was sintered to 835 °C and second group to 855 °C. Here x-ray diffraction and scanning electron microscope (SEM) studies were performed. From the study various HA phases and TCP phases were obtained. A previous study done with Atlantic Deer Cowrie encourages nanobioceramic production from natural sources. This study proposes that mechanochemical agitation with very simple way for producing nano-sized calcium phosphates for future bioengineering scaffold applications.