Characterization of Silver Doped Hydroxyapatite Prepared by EDTA Chelate Decomposition Method
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Characterization of Silver Doped Hydroxyapatite Prepared by EDTA Chelate Decomposition Method Kubra Celik1, Celaletdin Ergun2, Huseyin Kizil1 1 Materials Science and Engineering, Istanbul Technical University, 34469 Istanbul, Turkey. 2 Mechanical Engineering, Istanbul Technical University, 34437 Istanbul, Turkey.
ABSTRACT In this study, Ag doped hydroxyapatite (HA) samples prepared by EDTA chelate decomposition method were characterized with X-Ray Diffraction Spectroscopy (XRD), Scanning Electron Microscopy (SEM) and antimicrobial sensitivity test. Hydroxyapatite (Ca10(PO)6(OH)2) and NaCaPO4 (rhenanite) phases were observed while Ag was present in the form of Ag2O. Results showed that microstructurally controlled HA-based composites with NaCaPO4 interphase can be prepared, which significantly enhances sinterability of hydroxyapatite at 1100° C without formation of any undesired second phases, such as tricalcium phosphate (TCP) known to decrease the stability of HA. The antibacterial sensitivity was tested with E.Coli gram-negative bacteria. The radius of circle enclosing the sample increases with increasing Ag content in the structure as an indication of the region of non-bacterial activity. INTRODUCTION Among calcium phosphates, hydroxyapatite (HA), (Ca10(PO)6(OH)2) is known to be the major constituent (69%) of the bones. It is an attractive material for hard tissue implants [1] and deserves particular interest due to its bioresorbability [2]. It was found that changes in powder formulation and processing routes have significant effects on the characteristic properties of HA [3]. With its lattice arrangement, HA can be considered as a loosely packed hexagonal structure. A great variety of cationic and anionic species can be substituted into HA structure due to its high flexibility, specifically considered as an effective method to modify the properties of HA [4]. Silver (Ag) has long been known as a medical agent effective on a wide range of bacteria and used on many medical devices [5-6]. Into the HA structure the substitution of Ag+ (1.28 Å) ions takes place as an ion exchange with Ca2+ (0.99 Å) preferentially in the Ca(1) site of HA, which leads to an increase in the lattice parameters linearly with the amount of silver added in the range of atomic ratio Ag/(Ag+Ca) between 0 and 0.055 [7]. The silver containing HA coating prepared through ion exchange reaction in solution also exhibited excellent antimicrobial activity [7-9]. The present study shows the preparation steps of Ag-doped hydroxyapatite (Ag-HA) by EDTA chelate decomposition method and their characterization by SEM, AFM, and antimicrobial sensitivity tests. The aim is to precipitate Ag-doped hydroxyapatite powders from
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aqueous solutions of the Ca(NO3)2 and (NH4)H2PO4 with EDTA chelate solutions at a ratio of Ca/P:1,667. EXPERIMENTAL DETAILS EDTA chelate decomposition technique was used to prepare Ag-doped HA powder [10]. 200 ml 0.5 M Ca(NO3)2íAgNO3 solution was prepared using 0.095 mol Ca(NO3)2 and 0.005 mol AgNO3. 38 gr EDTA chelate with 120 m
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