Yazar "Balcik, Ozlem S." seçeneğine göre listele

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    Bone-Like Mineral Nucleating Peptide Nanofibers Induce Differentiation of Human Mesenchymal Stem Cells into Mature Osteoblasts
    (Amer Chemical Soc, 2014) Ceylan, Hakan; Kocabey, Samet; Gulsuner, Hilal Unal; Balcik, Ozlem S.; Guler, Mustafa O.; Tekinay, Ayse B.
    A bone implant should integrate to the tissue through a bone-like mineralized interface, which requires increased osteoblast activity at the implant tissue boundary. Modification of the implant surface with synthetic bioinstructive cues facilitates on-site differentiation of progenitor stem cells to functional mature osteoblasts and results in subsequent mineralization. Inspired by the bioactive domains of the bone extracellular matrix proteins and the mussel adhesive proteins, we synthesized peptide nanofibers to promote bone-like mineralization on the implant surface. Nanofibers functionalized with osteoinductive collagen I derived Asp-Gly-Glu-Ala (DGEA) peptide sequence provide an advantage in initial adhesion, spreading, and early commitment to osteogenic differentiation for mesenchymal stem cells (hMSCs). In this study, we demonstrated that this early osteogenic commitment, however, does not necessarily guarantee a priority for maturation into functional osteoblasts. Similar to natural biological cascades, early commitment should be further supported with additional signals to provide a long-term effect on differentiation. Here, we showed that peptide nanofibers functionalized with Glu-Glu-Glu (EEE) sequence enhanced mineralization abilities due to osteoinductive properties for late-stage differentiation of hMSCs. Mussel-inspired functionalization not only enables robust immobilization on metal surfaces, but also improves bone-like mineralization under physiologically simulated conditions. The multifunctional osteoinductive peptide nanofiber biointerfaces presented here facilitate osseointegration for long-term clinical stability.
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    The Comparison of Standard and Salvage Chemotherapy Regimens Regarding to CD34(+) Peripheric Stem Cell Harvesting Success
    (Akad Doktorlar Yayinevi, 2013) Balcik, Ozlem S.; Aksoy, Cafer; Akdeniz, Derya; Akkaya, Cigdem; Guvenc, Birol; Dincer, Suleyman
    Although regimens of harvesting peripheric stem cell vary from one center to another, the most common ones are chemotherapy plus growth factor or growth factor alone. We aimed to determine which variables of harvesting peripheral stem cells are effective on the number of harvested CD34+ cells and successfull mobilisation defined as the collection of >2.0 x 106 CD34+ cells/kg b.w. with a maximum of three leukaphereres. From August 2008 to January 2011, the documents of 56 patients included in the autologous peripheral stem cell harvesting program were retrieved retrospectively. Regarding harvesting regimens, 28 patients (50.0%) were administered filgrastim 10 mu g/kg/day (filgrastim group), 18 patients (32.1%) were administered a standard regime with ifosphamide + etoposide + epirubicin + filgrastim 5 mu g/kg/day or cyclophosphamide + etoposide + filgrastim 5 mu g/kg/day (standard group), and 10 patients (17.9%) were administered a salvage regime + filgrastim 5 mu g/kg/day (salvage group). Rituximab was added if the disease was CD20 positive. The median number of CD34+ cells and the number of inadequate collection did not differ between these 3 groups. Transplantation before mobilization was found to have a negative effect on the harvesting success. The transplantated patients had a lower number of harvested CD34+ cells than the patients without transplantation history. But no clear relationship was seen between harvest success and the diagnosis of the patients, pretransplant response, radiotherapy history before mobilization, or mobilization with a standard regimen. Finally, the number of standard CT cycles before mobilization were found to have a borderline negative effect on the harvested CD34+ cells.