CERAMICS INTERNATIONAL Available online at www.sciencedirect.com Ceramics International 40 (2014) 15479–15487 Carbonated hydroxyapatite deposition at physiological temperature on ordered titanium oxide nanotubes using pulsed electrochemistry F.S. Utku a,n , E. Seckin b , G. Goller b , C. Tamerler c , M. Urgen b a Yeditepe University, Department of Biomedical Engineering, Istanbul, Turkey b Department of Metallurgical & Materials Engineering, Istanbul Technical University, Istanbul 06800, Turkey c Department of Mechanical Engineering and Bioengineering Research Center, The University of Kansas, Lawrence, KS 66045, USA Received 14 September 2012; received in revised form 7 February 2014; accepted 1 July 2014 Available online 17 July 2014 Abstract The effect of temperature and nanotubular surface morphology on calcium phosphate deposition was investigated using a modified simulated body fluid and electrochemistry. Ordered nanotubular titanium oxide plates were coated by pulsed electrochemical deposition process, while titanium oxide and pure titanium surfaces were used as controls at 80 1C and 37 1C. The calcium phosphate deposit was characterized using XRD, FT-IR and FE-SEM. Carbonated hydroxyapatite was deposited at the physiological temperature of 37 1C on nanotubular surfaces, which provided a large surface area for hydroxide ion generation and a small volume for the confinement and concentration of hydroxide ions. Compounds containing carbonates and hydrogen phosphates were deposited on porous titanium oxide surfaces and flat titanium surfaces as the control group. This study demonstrates deposition of hydroxyapatite at physiological temperatures, which is essential for codeposition of organic bioceramics for medical use. & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: Anodization; Cathodic deposition; HA/CHA; Nanotubular titania; Pulsed electrochemical deposition 1. Introduction Biomineralization organizes the mineral, the organic mate- rial and the tissue fluid hierarchically to form a natural composite material. Biomimicking biomineralization has enabled the design and production of innovative nanomaterials and systems that contain a bioactive, biocompatible and osteoconductive calcium phosphate (Ca-P) layer, produced using an appropriate deposition method [1–11]. Coating methods can be grossly classified as wet chemistry, high temperature processes and electrochemical methods. The wet chemistry methods produce Ca-P by immersing the surface to be coated in a fluid consisting of anions found in the body and subsequently adding calcium, which results in dense coatings with good biological performance [12]. The high temperature processes are as follows: plasma spray method, producing thick, inhomogeneous coatings; the ion-beam method, producing thin coatings; the laser method, producing thin coatings with diverse compositions, crystallinities and high fatigue strength; RF sputtering, producing thin, but dense and adhesive coatings; and hot-isostatic pressing of uniform Ca-P granules on titanium surface [13]. Electrochemical methods for depositing Ca-P coatings on implant surfaces are electrophoresis, i.e. deposition of negatively charged Ca-P particles migrating towards the cathodically polarized surfaces [14], and electrochemical deposition (ECD), or cathodic deposition as used here, enabling Ca-P coating of implant materials of any size and shape from an electrolyte solution containing calcium and phosphorus. The method involves vari- ous controllable factors, which determine the chemistry of Ca- P coating, e.g. current density, potential, length of cathodic and anodic deposition cycles, temperature and type of solution used [13,15–24]. www.elsevier.com/locate/ceramint http://dx.doi.org/10.1016/j.ceramint.2014.07.004 0272-8842/& 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved. n Correspondence to: Yeditepe University, Department of Biomedical Engineering, Kayısdagi, Atasehir, Istanbul, Turkiye.Tel.: þ90 216 578 0433; fax: þ90 216 578 0400. E-mail address: sermin.utku@yeditepe.edu.tr (F.S. Utku).