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    Hydroxyapatite-based nanoparticles as a coating material for the dentine surface: An antibacterial and toxicological effect
    (Elsevier Sci Ltd, 2020) Erdem, Umit; Dogan, Mustafa; Metin, Aysegul U.; Baglar, Serdar; Turkoz, Mustafa B.; Turk, Mustafa; Nezir, Saffet
    In this study, nano sized hydroxyapatite (nHAp) and Ag(I) doped hydroxyapatite (Ag-nHAp) particles were synthesized by the precipitation method and used as a coating material for remineralization on caries-affected dentine samples. Characterization studies of both the synthesized hydroxyapatite-based particles and the coated dentine samples were performed using instrumental techniques such as SEM and FFIR, and then toxicity and antibacterial properties were also evaluated. It was observed that dentine samples were effectively coated by both nHAp and Ag center dot nHAp particles which have no toxic effects. Furthermore, the costing of nano-hydroxyapatite on dentine samples positively contributed to the viability of L929 fibroblast cells and also provided an antibacterial effect against to bacteria such as S. mutants, C. albicans and E. coli bacteria that are most frequently caused caries in the teeth. While all type of bacteria was eliminated by the nHAp coated dentine samples at 24th, Ag-nHAp coated dentine samples removed to all bacteria type at 1st.
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    Refinement of fundamental characteristic properties with homovalent Er/Y partial replacement of YBa2Cu3O7-y ceramic matrix
    (Elsevier Science Sa, 2021) Erdem, Umit; Turkoz, Mustafa B.; Yildirim, Gurcan; Zalaoglu, Yusuf; Nezir, Saffet
    In the current work, the effect of partial substitution of Er-sites for the Y-sites in the bulk YBa2Cu3O7-y (YBCO) crystal system on the fundamental superconducting, electrical, crystallinity and structural morphology features is examined together with the reasons by means of powder X-ray diffraction (XRD), temperature-dependent electrical resistivity (rho-T), scanning electron microscopy (SEM), electron dispersive X-ray (EDX) investigations and deduced calculation parameters. All the experimental test results show that the erbium impurities are suc-cessfully substituted by the yttrium sites in the bulk Y-123 crystal system, confirmed by sensitively the EDX and rho-T measurement results. Moreover, it is found that all the fundamental characteristic quantities improve with the increment in the Er/Y partial substitution level up to the value of x = 0.03 beyond which the features tend to degrade dramatically. In this respect, the bulk Y1-xErxBa2Cu3O7-y ceramic compound prepared within the molar ratio of x = 0.03 crystallizes in the orthorhombic space group P-4/ mmm with a little distortion due to the refinement in the crystallinity quality, crystallite growth, oxygen ordering degree, scattering mechanism, intra and intergrain boundary couplings, grain alignment distributions and orientations. The XRD results show that the optimum erbium content enables to develop seriously the fundamental crystallographic features (lattice strain, lattice cell constants, crystallite size distribution, dislocation density ratio, oxygen concentrations in the unit cells) of Y-123 crystal structure. However, the excess Er/Y substitution leads to enhance considerably the systematic structural problems and inhomogeneous distribution of strains (formed by the structural defects) in the YBCO crystal structure. Thus, the phase transition from orthorhombic to tetragonal (structural O-T transition) crystal structure is observed. In fact, the XRD result displays that the trivalent Er3+ particles may partially be replaced by the divalent Cu2+ host atoms in the bulk Y-123 crystal structure after the critic substitution level of x = 0.03. The optimum Er concentration causes to form more thermodynamically activated super-electrons in the homogeneous superconducting cluster percentages in the paths due to the induced polaronic effect, and accordingly the intrinsic overdoped nature of Y-123 ceramic system transits into optimally doped state. Similarly, the erbium ions enable to increase the mobile hole carrier concentration and homogeneities in the oxidation state of superconducting grains. Namely, the amplitude of pair wave function (Psi=Psi(0)e(-i phi)) is strength enough to form bipolarons in the polarizable lattices and localize of densities of electronic states (DOS) at Fermi level. SEM investigations picture that the surface morphology view and crystallinity quality develop remarkably with the increment in the erbium content up to the critical dopant level of x = 0.03 where the sample exhibits the best grain alignment orientations, densest and smoothest surface morphology with the combination of lowest porous and largest particle distributions well linked each other. All in all, this comprehensive work based on the analysis of Er/Y partial replacement mechanism along the YBa2Cu3O7- y ceramic matrix may open up a newly/novel and feasible area for the advanced engineering, heavy-industrial technology and large-scale applications of type-II superconducting materials. (C) 2021 Elsevier B.V. All rights reserved.
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    Spectral analysis and biological activity assessment of silver doped hydroxyapatite
    (Taylor & Francis Ltd, 2021) Erdem, Umit; Bozer, Busra Moran; Turkoz, Mustafa B.; Metin, Aysegul U.; Yildirim, Gurcan; Turk, Mustafa; Nezir, Saffet
    In this study, the hydroxyapatite biomaterials are produced by the precipitation method and the role of silver doping within the different molar ratios of 2.0, 5.0, and 10.0% are investigated with some fundamental analysis, including powder XRD, SEM, EDS, FTIR, Raman, and material densities. In vitro biocompatibility assessment is conducted with cytotoxicity and agar diffusion tests. Moreover, genotoxicity tests determine whether the biomaterials produced cause the mutations or not. In addition, a hemolytic effect test examines the variation of hemolytic behavior of compounds. Also, the cell migration experiments inspect the influence of silver ion levels in biomaterials on many biological processes. The experimental results reveal that the honeycomb-patterned morphological structures are obtained for all the products. FTIR and Raman analyses reveal that the dramatic changes in the characteristic functional group peaks are obtained with the increment in the amount of silver ions. The experimental parts related to the biocompatibility assessment of the study show that there seems to be deterioration in biocompatibility as the silver ion-doping level increases in the system. To sum up, the ideal doping value for bone tissue engineering applications is found to be 2%.