The porosity and roughness of electrodeposited calcium phosphate coatings in simulated body fluid

Abstract

Calcium phosphate coatings were electrochemically deposited on titanium from an aqueous solution of Ca(NO 3 ) 2 and NH 4 H 2 PO 4 at a current density of 10 mA cm -2 for a deposition time of 15 min. The obtained brushite coatings (CaHPO 4 ·2H 2 O), were converted to hydroxyapatite (HA) by soaking in simulated body fluid (SBF) for 2, 7 and 14 days. The brushite and hydroxyapatite coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was shown that increasing the soaking time increased the porosity, roughness and crystallite domain size of the HA coatings and decreased the unit cell parameters and unit cell volume, while the mean pore area of HA was unaffected. The calcium and phosphorus ions concentrations in SBF were determined by atomic absorption spectroscopy (AAS) and UV-Vis spectroscopy, respectively, and a mechanism of HA growth based on dissolution-precipitation was proposed.Available on line at www.shd.org.rs/JSCS/ DJOŠIĆ, MITRIĆ and MIŠKOVIĆ-STANKOVIĆThe main constituents of human bone are calcium orthophosphates, collagen and water. Hydroxyapatite (HA, Ca 10 (PO 4 ) 6 (OH) 2 ), constitutes the majority of the inorganic component. HA is the only compound among calcium phosphatebased ceramics that is stable in a physiological environment and is biologically active. Applications of HA bioceramics are based on its excellent bioactivity, biocompatibility and porous structure. Both the micro-and macro-porosity of HA coatings are important. The macroporosity controls access of tissue and biological fluids to HA coatings. The microporosity controls protein adsorption, body fluid circulation and the resorption rate of calcium phosphate. The porous structure of HA improves the mechanical interlock between the cells and the surface of an implant, promotes osteoconductivity and enhances the adhesion between natural bone and an implant by the formation of an apatite layer. 3-5 Besides the coating porosity, a very important characteristic is the roughness of a coating, because the biocompatibility and corrosion resistance of implants are, also, determined by surface microstructural properties, such as surface roughness and grain size, which influence cell attachment, proliferation and differentiation. 6,7 There are a great number of methods for HA preparation, 8-12 including transformation of more soluble metastable phosphates, as precursors, e.g., brushite, monetite and octacalcium phosphate, in an aqueous environment. [13][14][15][16][17][18][19][20] The application of HA coatings depends on its crystallite size. It is possible to improve the characteristics of HA by controlling the particle size, particle distribution and agglomeration of precursors. Nanocrystalline HA exhibits a greater surface area and has better bioactivity than coarser crystals. [21][22][23][24] Brushite, CaHPO 4 ·2H 2 O, is a metastable compound, known as mineral brushite. It can be observed when calcium phosphate is precipitated at low pH values and low temperatures. 2...

In vitro investigation of electrophoretically deposited bioactive hydroxyapatite/chitosan coatings reinforced by graphene

“…At the same time HAP dissolves, increasing the concentration of calcium and phosphate ions in solution and leading to the precipitation of HAP. The dissolution and precipitation of calcium phosphates in SBF is a reversible reaction [37]. Graphene promotes the deposition of HAP by attracting calcium ions, due to its negative surface charge arising from the large number of p electrons in sp2 hybrid orbitals [33].…”

Gentamicin-Loaded Bioactive Hydroxyapatite/Chitosan Composite Coating Electrodeposited on Titanium

“…One of the most employed ceramic coatings for the improvement of the metal surface biocompatibility is hydroxyapatite (HAP). HAP coating is biocompatible (i.e., has the ability to induce the growth of the new layer of so-called bone apatite in the body environment) . Coatings, deposited on the metal implants, can be made of pure HAP or composite material, predominantly HAP and a polymer. , However, pure HAP is brittle, and so its application is limited.…”

“…HAP coating is biocompatible (i.e., has the ability to induce the growth of the new layer of so-called bone apatite in the body environment) . Coatings, deposited on the metal implants, can be made of pure HAP or composite material, predominantly HAP and a polymer. , However, pure HAP is brittle, and so its application is limited. Ceramic/polymer composite material improves mechanical properties of HAP, while mimicking the natural bone composition (HAP and collagen). , Because it is biocompatible, biodegradable, nontoxic, with low allergenic effect and good antimicrobial activity, chitosan (CS) is an attractive natural polymer for biomedical application .…”

Properties Investigation of GO/HA/Pt Composite Thin Film

“…The formation of the carbonated hydroxyapatite is favorable as it characterizes the mineral phase in human bone. The availability of the functional groups in the biomimetic synthetic serum can help the growth of the hydroxyapatite on the electrodeposited surface [32]. The hydroxyapatite surface charges negatively and thus attracts ions of Ca+2 by the exposure of the phosphate and hydroxyl ions in hydroxyapatite to the biomimetic synthetic serum.…”