Coating of bismuth and carbonate doped hydroxyapatite on acid etched Ti6Al4V via biomimetic method; investigation of mechanical, structural and biological properties

Hacıoğlu, Tuğçe
Titanium and its alloys are used in both engineering and dental applications. Ti6Al4V alloy is one of the most commonly preferred titanium alloy used in medical industry. Ti6Al4V with hydroxyapatite (HAp) coating has been frequently used material combinations. Though coating Ti6Al4V with HAp does not provide the desired amount of biocompatibility, it is significant to coat doped HAp on titanium alloy with antibacterial properties. In this thesis, first of all best experimental conditions for pre-treatment and coating process were determined. To prepare a new generation and high quality Ti6Al4V implant coating, bismuth + carbonate co-doped and pure HAps were coated on rough surfaces of Ti6Al4V plates by biomimetic method. After that, the coated plates were examined by SEM, EDS, AFM, FTIR, XRD, ICP and XPS. Furthermore, mechanical profilometer tests, scratch tests and in vitro cell studies were carried out. To investigate the antibacterial property of the coating, the survival of the Staphylococcus epidermidis on the surface of the implant was determined. Optimum pretreatment procedure was found to be three steps (sandblasted + acid etched + preheated) pretreatment. AFM results proved that the surface roughness increased by sandblasting, acid etching and preheating, respectively. By applying three steps method, substrate’s surface became much rougher which enabled advanced mechanical interlocking between the substrate surface and precipitated coating. Structural analysis performed for pure and co-doped coatings proved that HAp nucleation started 4 days after immersion, nucleation increased with the incubation time and co-dopants had great effect on surface characteristics. Furthermore the pretreatment procedure and dopants had significant influence on mechanical properties of the coatings. The resulting coatings had very high critical loads and surface adhesion. The critical load values obtained for coating failure were found to be above 100 mN for all type of coatings. Co-doped coatings, especially 0.3 mM co-doped coatings, had much higher critical loads than pure coatings. The proliferation of fibroblast (L929) and cancerous bone cells (SaOS-2) on pure and co-doped HAp coatings were evaluated in terms of biological properties. For L929 cell line, low concentrations of bismuth ion slightly improved cell viability. In case of SaOS-2 cell line, 0.1-C7 and 0.3-C7 exhibited highest reduction percentage among all co-doped samples. The higher stability and coherence of 0.3 mM co-doped coatings were also verified by mechanical test results. Further increase in dopants concentrations up to 0.5 mM lead to increase in toxicity and decrease in cell proliferation. The adherences of SaOS-2 cells onto the coatings were also investigated by the SEM analysis. In order to study antibacterial property of coating S.epidermidis bacteria was used. Antibacterial test results showed the most antibacterial samples were 0.1-C7 and 0.3-C7, the results were consistent with cell culture study. 


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Citation Formats
T. Hacıoğlu, “Coating of bismuth and carbonate doped hydroxyapatite on acid etched Ti6Al4V via biomimetic method; investigation of mechanical, structural and biological properties,” Ph.D. - Doctoral Program, Middle East Technical University, 2018.