Electrophoretic deposition and characterization of chitosan/silica/bioactive glass composite coatings on magnesium WE43 alloy

Abstract

Magnesium (Mg) and its alloys have been extensively explored as potential biodegradable implant materials for orthopedic and dental applications. However, the rapid degradation corrosion of Mg based alloys in physiological conditions has delayed their introduction for therapeutic applications. Electrophoretic deposition (EPD) of chitosan/silica/ bioactive glass (45S5 composition) composite coating on magnesium alloy (WE43) substrates was investigated. The present project has the aim to reduce and control the substrate corrosion rate and augment the initial bioactivity. The surface morphology, hydrophilic character, adhesion and surface topography of the coated sample were investigated by means of optical microscopy, SEM images, contact angle, roughness and tape test. The in vitro test consisted on immersion of the coated samples in Simulated Body Fluid (SBF) at 37°C during 2h, 1, 2, 3 and 7 days with following characterization through optical microscopy, SEM, Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy and X-Ray Diffraction (XRD) in order to identify hydroxycarbonate apatite (HCA) formation on the surface. HCA indicates the degree of bioactivity of the sample, because it leads to strong bond between the biomaterial and the living tissue. Characterization of the corrosion behavior was achieved by electrochemical impedance spectroscopy (EIS) and by potentiodynamic polarization in 0.1 M NaCl at ambient temperature. Surface analysis of the coated sample showed to be beneficial for bone regeneration. HCA formation was confirmed after 7 days of immersion in SBF, providing a bioactive behavior to the Mg WE43 alloy. Regarding the degradation behavior, results showed that the coating did not provided improvements on protection against corrosion at least during the 30 minutes that the samples were immersed in 0.1M NaCl at ambient temperature.