7/27/2019 Resumen HA San Diego

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Adherent hydroxiapatite coating on 316L SSsubstrate using electrochemical deposition

L. E. Gil*, L. A. Hernandez*, J. Alvarez**, E. Mundaray*

*Universidad Nacional Experimental Politecnica (UNEXPO), Centro de Estudios de Corrosiony Biomateriales, Puerto Ordaz, Venezuela. Email:lindaegil@gmail.com**Fundacin IDEAS. Ministerio de Poder Popular para la Ciencia y la Tecnologa, Valle deSartenejas, Caracas, Venezuela, email: jalvarreto@gmail.com* e-mail de autor de correspondencia: LUIS COLOCA TU MAIL ACA

To improve the biocompatibility with the osseous tissue of 316lSS titanium and its

alloys, which are generally used as implant materials in orthopedic and maxillofacial

surgery, are coated with calcium phosphate (CP) biomaterials such as hydroxyapatite

(HA). On commercial orthopedic and dental implants, the HA coating is generally

prepared by the plasma spray technique, where the HA powder is projected at very high

temperatures. However, the major drawback for this process is the decomposition andphase transformation of HA during spraying, owing to the high temperature involved.

Other techniques such as electrochemical deposition (ECD) has recently attracted

considerable attention because of a considerable number of advantages over other

conventional coating methods such as low process temperature, the ability to deposit on

porous or complex shapes of substrate, easy control of microstructure and the simple

control of deposit thickness. The present research evaluates the influence of processing

parameters on the microstructure, adhesion and corrosion resistance of an ECD-HA

coating. The HA coating deposition was performed by employing a galvanostatic

electrochemical deposition technique, varying the current density to values of 0.5, 2, 5

and 10 mA/cm2, using CaCl2.2H20 and NH4H2PO4 as precursors, under constant

conditions of temperature and acid pH on 316L stainless steel samples. The thickness,

morphology, composition and the structure of the coatings were investigated by X-ray

diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy

(SEM) techniques. Impedance spectroscopy (EIS) was used to determine the corrosion

resistance of hydroxyapatite (HA) coatings and its dependence on the deposition

parameters. The adhesion of the coatings on the substrate was assessed using a CSEM

scratch tester fitted with a Rockwell C 200m-radius diamond stylus. Thebiocompatibility was evaluated in vitro through cultivation of mesenchymal stem cells

(MSCs) on the coated surface and the determination of these metabolic activities.

Osteo-inductive capacity was evaluated through the osteogenic differentiation of MSCs,

analyzing their proliferation and secretion or deposition of various markers of bone ascalcium deposition, alkaline phosphatase activity, among others. The results showed

that the hexagonal HA is the main phase present for all electrodepositing current

densities evaluated. The morphology of the coating changes with the electrodeposited

current density and exhibits a needle like structure at low current densities (0.5 mA

/cm2), meanwhile compact spherical crystals agglomerate at high current densities (10

mA /cm2). The coating thickness was dependent on both time of deposition and the

applied deposition current density parameters. The potential-time curves showed that

the CP deposition progress is conditioned by the initial reduction of alloy surface oxide

layer, after which a substantial reduction of nitrate ions takes place on the active free

surface sites.