Browsing by Author "Dogan, I."

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    Formation of silicon nanocrystals in sapphire by ion implantation and the origin of visible photoluminescence
    (AIP Publishing, 2006) Yerli, S.; Serincan, U.; Dogan, I.; Tokay, S.; Genisel, M.; Aydınlı, Atilla; Turan, R.
    Silicon nanocrystals, average sizes ranging between 3 and 7 nm, were formed in sapphire matrix by ion implantation and subsequent annealing. Evolution of the nanocrystals was detected by Raman spectroscopy and x-ray diffraction (XRD). Raman spectra display that clusters in the matrix start to form nanocrystalline structures at annealing temperatures as low as 800 degrees C in samples with high dose Si implantation. The onset temperature of crystallization increases with decreasing dose. Raman spectroscopy and XRD reveal gradual transformation of Si clusters into crystalline form. Visible photoluminescence band appears following implantation and its intensity increases with subsequent annealing process. While the center of the peak does not shift, the intensity of the peak decreases with increasing dose. The origin of the observed photoluminescence is discussed in terms of radiation induced defects in the sapphire matrix.
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    Neuroactive peptide nanofibers for regeneration of spinal cord after injury
    (Wiley-VCH Verlag GmbH & Co. KGaA, 2020-10-11) Sever-Bahçekapılı, Melike; Yılmaz, Canelif; Demirel, A.; Kilinc, M. C.; Dogan, I.; Caglar, Y. S.; Guler, M. O.; Tekinay, Ayşe Begüm
    The highly complex nature of spinal cord injuries (SCIs) requires design of novel biomaterials that can stimulate cellular regeneration and functional recovery. Promising SCI treatments use biomaterial scaffolds, which provide bioactive cues to the cells in order to trigger neural regeneration in the spinal cord. In this work, the use of peptide nanofibers is demonstrated, presenting protein binding and cellular adhesion epitopes in a rat model of SCI. The self-assembling peptide molecules are designed to form nanofibers, which display heparan sulfate mimetic and laminin mimetic epitopes to the cells in the spinal cord. These neuroactive nanofibers are found to support adhesion and viability of dorsal root ganglion neurons as well as neurite outgrowth in vitro and enhance tissue integrity after 6 weeks of injury in vivo. Treatment with the peptide nanofiber scaffolds also show significant behavioral improvement. These results demonstrate that it is possible to facilitate regeneration especially in the white matter of the spinal cord, which is usually damaged during the accidents using bioactive 3D nanostructures displaying high densities of laminin and heparan sulfate-mimetic epitopes on their surfaces.