Browsing by Subject "Scaffolds"
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Item Open Access 97 percent light absorption in an ultrabroadband frequency range utilizing an ultrathin metal layer: randomly oriented, densely packed dielectric nanowires as an excellent light trapping scaffold(Royal Society of Chemistry, 2017) Ghobadi, A.; Dereshgi, S. A.; Hajian, H.; Birant, G.; Butun, B.; Bek, A.; Özbay, EkmelIn this paper, we propose a facile and large scale compatible design to obtain perfect ultrabroadband light absorption using metal-dielectric core-shell nanowires. The design consists of atomic layer deposited (ALD) Pt metal uniformly wrapped around hydrothermally grown titanium dioxide (TiO2) nanowires. It is found that the randomly oriented dense TiO2 nanowires can impose excellent light trapping properties where the existence of an ultrathin Pt layer (with a thickness of 10 nm) can absorb the light in an ultrabroadband frequency range with an amount near unity. Throughout this study, we first investigate the formation of resonant modes in the metallic nanowires. Our findings prove that a nanowire structure can support multiple longitudinal localized surface plasmons (LSPs) along its axis together with transverse resonance modes. Our investigations showed that the spectral position of these resonance peaks can be tuned with the length, radius, and orientation of the nanowire. Therefore, TiO2 random nanowires can contain all of these features simultaneously in which the superposition of responses for these different geometries leads to a flat perfect light absorption. The obtained results demonstrate that taking unique advantages of the ALD method, together with excellent light trapping of chemically synthesized nanowires, a perfect, bifacial, wide angle, and large scale compatible absorber can be made where an excellent performance is achieved while using less materials.Item Open Access Development of peptide nanomaterials for neural regeneration(Bilkent University, 2015-05) Mammadov, BüşraNervous system consists of a dense network of cells and their connections and exhibits a high level of complexity. This complexity arises from the high variety of cell types with very specific functions, the high number of cells along with the abundance of connections between these cells. When combined with the nonproliferative nature of neural cells and inhibitory nature of the pathological extracellular matrix (ECM), this complexity leads to a very limited regenerative potential. Thus neurodegenerative disorders and traumatic injuries of neural tissues lead to lifelong disabilities due to the poor success of current therapies. Novel therapeutic approaches which can overcome barriers that impede neural regeneration are therefore required to be developed. Smartly designed nanomaterials that can direct cells towards desired functions can improve the regeneration of neural tissues. Herein, I have described my work on development of peptide nanofibers for neuroregeneration and biological applications of these nanomaterials. To achieve the regeneration of the nervous system, the composition of the neural ECM under healthy conditions and during early development was mimicked through structural resemblance and bioactive epitope presentation using nanofibers. Laminin derived IKVAV peptide sequence and glycosaminoglycan mimicking, growth factor-binding sulfonated peptide sequence were presented on peptide nanofiber scaffolds. Differentiation of PC-12 cells, a model cell system for neuroregenerative studies, was found to be improved on these nanofiber scaffolds when compared to the cells on epitope free control scaffolds. Cells could even extend neurites on these scaffolds in the presence of inhibitory chondroitin sulfate proteoglycans. These nanofibers also proved to be efficient in sciatic nerve regeneration after injury. When injected into the lumen of polymeric nerve guidance channels, this bioactive nanofiber system provided guidance to the elongating axons and resulted in better axonal regeneration that was evident both from histological analysis and electromyography results. Results of in vitro and in vivo experiments were correlated and indicated the neuroregenerative potential of these peptide nanofibers. In addition, semiconductive oligothiophene was encapsulated in peptide nanofibers without compromising the biocompatibility. These hybrid nanofiber scaffolds can potentially be used for electrical stimulation of neurons that can further boost regeneration.Item Open Access Extracellular matrix mimetic peptide scaffolds for neural stem cell culture and differentiation(Humana Press, 2014) Mammadov, Busra; Güler, Mustafa O.; Tekinay, Ayşe B.Self-assembled peptide nanofibers form three-dimensional networks that are quite similar to fibrous extracellular matrix (ECM) in their physical structure. By incorporating short peptide sequences derived from ECM proteins, these nanofibers provide bioactive platforms for cell culture studies. This protocol provides information about preparation and characterization of self-assembled peptide nanofiber scaffolds, culturing of neural stem cells (NSCs) on these scaffolds, and analysis of cell behavior. As cell behavior analyses, viability and proliferation of NSCs as well as investigation of differentiation by immunocytochemistry, qRT-PCR, western blot, and morphological analysis on ECM mimetic peptide nanofiber scaffolds are described.Item Open Access Materials for articular cartilage regeneration(Bentham Science Publishers B.V., 2012) Tombuloglu, Ayşegül; Tekinay, Ayşe B.; Güler, Mustafa O.Many health problems remaining to be untreatable throughout the human history can be overcome by utilizing new biomedical materials. Healing cartilage defects is one of the problems causing significant health issue due to low regeneration capacity of the cartilage tissue. Scaffolds as three-dimensional functional networks provide promising tools for complete regeneration of the cartilage tissue. Diversity of materials and fabrication methods give rise to many forms of scaffolds including injectable and mechanically stable ones. Various approaches can be considered depending on the condition of cartilage defect. A scaffold should maintain tissue function within a short time, and should be easily applied in order to minimally harm the body. This review will cover several patents and other publications on materials for cartilage regeneration with an outlook on essential characteristics of materials and scaffolds.Item Open Access Self-assembled proteins and peptides as scaffolds for tissue regeneration(Wiley-VCH Verlag, 2015) Loo, Y.; Goktas, M.; Tekinay, A. B.; Güler, Mustafa O.; Hauser, C. A. E.; Mitraki, A.Self-assembling proteins and peptides are increasingly gaining interest for potential use as scaffolds in tissue engineering applications. They self-organize from basic building blocks under mild conditions into supramolecular structures, mimicking the native extracellular matrix. Their properties can be easily tuned through changes at the sequence level. Moreover, they can be produced in sufficient quantities with chemical synthesis or recombinant technologies to allow them to address homogeneity and standardization issues required for applications. Here. recent advances in self-assembling proteins, peptides, and peptide amphiphiles that form scaffolds suitable for tissue engineering are reviewed. The focus is on a variety of motifs, ranging from minimalistic dipeptides, simplistic ultrashort aliphatic peptides, and peptide amphiphiles to large "recombinamer" proteins. Special emphasis is placed on the rational design of self-assembling motifs and biofunctionalization strategies to influence cell behavior and modulate scaffold stability. Perspectives for combination of these "bottom-up" designer strategies with traditional "top-down" biofabrication techniques for new generations of tissue engineering scaffolds are highlighted. Recent advances in self-assembling proteins, peptides, and peptide amphiphiles that form scaffolds suitable for tissue engineering are discussed. Rational design and biofunctionalization strategies for a variety of motifs ranging from minimalistic dipeptides, ultrashort aliphatic peptides, and peptide amphiphiles to large "recombinamer" proteins are reviewed and challenges and perspectives for their widespread adoption in applications are highlighted.Item Open Access A versatile bio-inspired material platform for catalytic applications: Micron-sized "buckyball-shaped" TiO2 structures(Royal Society of Chemistry, 2015) Erdogan, D. A.; Solouki, T.; Ozensoy, E.A simple sol-gel synthesis method is presented for the production of micron-sized buckyball-like TiO2 architectures using naturally occurring Lycopodium clavatum (LC) spores as biotemplates. We demonstrate that by simply altering the calcination temperature and titanium(iv) isopropoxide : ethanol volume ratio, the crystal structure and surface composition of the buckyball-like TiO2 overlayer can be readily fine-tuned. After the removal of the biological scaffold, the unique surface morphology and pore structure of the LC biotemplate can be successfully transferred to the inorganic TiO2 overlayer. We also utilize photocatalytic degradation of Rhodamine B dye samples to demonstrate the photocatalytic functionality of these micron-sized buckyball-like TiO2 architectures. Moreover, we show that the photocatalytic activity of TiO2 overlayers can be modified in a controlled manner by varying the relative surface coverages of anatase and rutile domains. These results open a potential gateway for the synthesis of a variety of bio-inspired materials with unique surface properties and shapes comprised of reducible metal oxides, metal sulfides, mixed-metal oxides, and/or perovskites.