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    Calcified and mechanically debilitated three-dimensional hydrogel environment induces hypertrophic trend in chondrocytes
    (Sage Publications Ltd, 2016) Celik, Ekin; Bayram, Cem; Akcapinar, Rumeysa; Turk, Mustafa; Denkbas, Emir Baki
    Currently, the main focus on tissue engineering strategies is to mimic the extracellular matrix of the related tissues. Many studies accomplished to build tissue scaffolds to act as the natural surroundings of the specific interest, which can be established to behave like either healthy or unhealthy tissues. The latter one of these conditions is a quite new approach and crucial for the design of three-dimensional in vitro disease models. This study investigates the potential of a composite scaffold consisting hydroxyapatite-integrated fluorenyl-9-methoxycarbonyl diphenylalanine hydrogels by focusing on the optimization of this hybrid scaffold for the development of an in vitro model of degenerative cartilage. Cell growth, chondrocyte proliferation, extracellular matrix production, hypertrophy marker monitoring, scaffold mechanical properties, and morphological analysis were evaluated. Fluorenyl-9-methoxycarbonyl diphenylalanine dipeptides were dissolved in null cell culture media and pH decreased sequentially to compel peptides to self-organize into fibrous hydrogel scaffolds. Nano-hydroxyapatite crystals were incorporated into fluorenyl-9-methoxycarbonyl diphenylalanine hydrogels during the gelation to investigate the effect on chondrocytes. It is observed that hydroxyapatite incorporation into peptide hydrogels significantly increased the alkaline phosphatase activity and assymetrical cell divisions, which is appraised as an outcome of chondrocyte hypertrophy. It is concluded that chondrocytes develop a hypertrophic potential when they are cultured in a media with nano-hydroxyapatites in a three-dimensional cell culture matrix mimicking the extracellular matrix conditions of degenerative cartilage.
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    Dual delivery of platelet-derived growth factor and bone morphogenetic factor-6 on titanium surface to enhance the early period of implant osseointegration
    (WILEY, 2020) Keceli, H. Gencay; Bayram, Cem; Celik, Ekin; Ercan, Nuray; Demirbilek, Murat; Nohutcu, Rahime Meral
    Objective To test the surface properties and in vitro effects of a new sequential release system on MC3T3-E1 cells for improved osseointegration. Background BMP6-loaded anodized titanium coated with PDGF containing silk fibroin (SF) may improve osseointegration. Methods Titanium surfaces were electrochemically anodized, and SF layer was covered via electrospinning. Five experimental groups (unanodized Ti (Ti), anodized Ti (AnTi), anodized + BMP6-loaded Ti (AnTi-BMP6), anodized + BMP6 loaded + silk fibroin-coated Ti (AnTi-BMP6-SF), and anodized + BMP6-loaded + silk fibroin with PDGF-coated Ti (AnTi-BMP6-PDGF-SF)) were tested. After SEM characterization, contact angle analysis, and FTIR analysis, the amount of released PDGF and BMP6 was detected using ELISA. Cell proliferation (XTT), mineralization, and gene expression (RUNX2andALPL) were also evaluated. Results After successful anodization and loading of PDGF and BMP6, contact angle measurements showed hydrophobicity for TiO(2)and hydrophilicity for protein-adsorbed surfaces. In FTIR, protein-containing surfaces exhibited amide-I, amide-II, and amide-III bands at 1600 cm(-1)-1700 cm(-1), 1520 cm(-1)-1540 cm(-1), and 1220 cm(-1)-1300 cm(-1)spectrum levels with a significant peak in BMP6- and/or SF-loaded groups at 1100 cm(-1). PDGF release and BMP6 release were delayed, and relatively slower release was detected in SF-coated surfaces. Higher MC3T3-E1 proliferation and mineralization and lower gene expression ofRUNX2andALPLwere detected in AnTi-BMP6-PDGF-SF toward day 28. Conclusion The new system revealed a high potential for an improved early osseointegration period by means of a better factor release curve and contribution to the osteoblastic cell proliferation, mineralization, and associated gene expression.
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    The effect of calcium chloride concentration on alginate/Fmoc-diphenylalanine hydrogel networks
    (Elsevier Science Bv, 2016) Celik, Ekin; Bayram, Cem; Akcapinar, Rumeysaa; Turk, Mustafa; Denkbas, Emir Baki
    Peptide based hydrogels gained a vast interest in the tissue engineering studies thanks to great superiorities such as biocompatibility, supramolecular organization without any need of additional crosslinker, injectability and tunable nature. Fmoc-diphenylalanine (FmocFF) is one of the earliest and widely used example of these small molecule gelators that have been utilized in biomedical studies. However, Fmoc-peptides are not feasible for long term use due to low stability and weak mechanical properties at neutral pH. In this study, Fmoc-FF dipeptides were mechanically enhanced by incorporation of alginate, a biocompatible and absorbable polysaccharide. The binary hydrogel is obtained via molecular self-assembly of FmocFF dipeptide in alginate solution followed by ionic crosslinldng of alginate moieties with varying concentrations of calcium chloride. Hydrogel characterization was evaluated in terms of morphology, viscoelastic moduli and diffusional phenomena and the structures were tested as 3D scaffolds for bovine chondrocytes. In vitro evaluation of scaffolds lasted up to 14 days and cell viability, sulphated glycosaminoglycan (sGAG) levels, collagen type II synthesis were determined. Our results showed that alginate incorporation into FmocFF hydrogels leads to better mechanical properties and higher stability with good biocompatibility. (C) 2016 Elsevier B.V. All rights reserved.
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    The effect of thymoquinone coating on adhesive properties of polypropylene mesh
    (Bmc, 2017) Aydin, Oktay; Aydinuraz, Kuzey; Agalar, Fatih; Sahiner, I. Tayfun; Agalar, Canan; Bayram, Cem; Atasoy, Pinar
    Background: An incisional hernia is a common complication following abdominal surgery. Polypropylene mesh is frequently used in the repair of such defects and has nearly become the standard surgical treatment modality. Though they are very effective in reducing recurrence, mesh materials exhibit a strong stimulating effect for intraabdominal adhesion. The thymoquinone (TQ) extracted from Nigella sativa seeds has potential medical properties. TQ has antiinflammatory, antioxidant and antibacterial properties. The aim of this study is to coat polypropylene mesh with TQ in order to investigate the effect of surface modification on intraabdominal adhesions. Methods: TQ-coated polypropylene mesh material was tested for cytotoxicity, contact angle, surface spectroscopy, TQ content, sterility, and electron microscopic surface properties. An experimental incisional hernia model was created in study groups, each consisting of 12 female Wistar rats. The defect was closed with uncoated mesh in control group, with polylactic acid (PLA)coated mesh and PLA-TQ coated mesh in study groups. Adhesion scores and histopathologic properties were evaluated after sacrifice on postoperative 21th day. Results: Granuloma formation, lymphocyte and polymorphonuclear leukocyte infiltration, histiocyte fibroblast and giant cell formation, capillary infiltration, collagen content were significantly reduced in the PLA-TQ coated mesh group (p < 0.05). Though not statistically significant, likely due to the limited number of study animals, adhesion formation was also reduced in the PLA-TQ coated mesh group (p: 0.067). Conclusion: TQ coated mesh is shown to reduce adhesion formation and TQ is a promising coating material for mesh surface modification.
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    Proliferation Of Mc3t3-E1 Osteoblastic Cells After Sequential Release Of Pdgf And Bmp-6. An In Vitro Study
    (2017) Keçeli, H. Gencay; Bayram, Cem; Ercan, Nuray; Türk, Mustafa; Arat, Esra; Nohutçu, Rahime M.
    Background and Aim: To evaluate the release kinetics of bone morphogenetic protein (BMP)-6 or -7 loaded nanoparticles (NPs) that located inside the microparticles (MPs) carrying platelet-derived growth factor (PDGF), and test this NP-in-MP system with MC3T3-E1 osteoblastic cells. Materials and Methods: Poly-lactic acid-co-glycolic acid (PLGA) NPs was loaded with BMP-6 or -7 and inserted in sodium alginate MPs loaded with PDGF. To evaluate the osteoblastic effect; proliferation of MC3T3-E1 cells that were treated with BMP-6, -7 and PDGF free solutions (FS) or within the particles (BMP-6 or -7 loaded PLGA NP alone and BMP-6 or -7 loaded PLGA NP in PDGF loaded alginate MP) were assessed at 2, 4, 7, 14 and 21 days. Results: It was shown that while both NP and NP-in-MP systems showed similar burst release at first time periods; especially in 24-72 h time period, NP-in-MP system exhibited a sustained release profile till 14th day. According to proliferation experiments, till the 7th day, both particle and FS groups exhibited similar profiles, but after that time particle groups, especially BMP-7 NP in PDGF MP, reached to statistically higher cell numbers than FS groups. NP-in-MP system exhibited a gradually longer time factor release resulting with delayed but elongated cell proliferation period. Conclusion: Findings indicate that NP-in-MP system might be promising in future for mimicking the natural bone formation process by providing sequential release of PDGF and BMPs, for bone tissue engineering. More comprehensive experiments evaluating mineralization and gene expression profile is necessary to verify these results