Magnesium alloys are candidates to be used as biodegradable biomaterials for producing medical device. Their use is restricted due to the high degradation rate in physiological media. To contribute to solving this problem, a polydopamine (PDOPA) layer could be used to increase adhesion between the metallic substrate and external organic coating. In this paper, the corrosion behaviour of samples was investigated to determine their performance during the long-term exposure in simulated body fluid. Electrochemical methods including Open Circuit Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) were used to investigate the corrosion resistance of samples. The results demonstrated a decreasing of the substrate degradation rate when PDOPA was used as interlayer supposing a synergistic effect when it was used together with the organic coating.

Titania nanotubes are widely studied for their potential applications in several fields. In this paper, the electrochemical characterization of a dental implant, made of commercially pure titanium grade 2, covered by titania nanotubes, when immersed in Hank’s solution, is proposed. Few papers were found in the scientific literature regarding this topic, so a brief review is reported, concerning the use of some equivalent circuits to model experimental data. The analysis of results, obtained by using Electrochemical Impedance Spectroscopy, showed that: (i) a good correlation exists between the variation of E_corr and the estimated values of the charge transfer resistance for both the bare- and the nanotube-covered samples, (ii) the nanostructured surface seems to possess a more active behaviour, while the effect could be over-estimated due to the real extent of the surface covered by nanotubes, (iii) the analysis of the “n” parameter, used to fit the experimental data, confirms the complex nature of nanostructured layer as well as that the nanotubes are partially filled by compounds containing Ca, P and Mg, when immersed in Hank’s solution. The results obtained in this work give a better understanding of the electrochemical behaviour of the nanotubes layer when immersed in Hank’s solution and could help to design a surface able to improve the implant osseointegration.

Anodic oxidation is an easy and cheap surface treatment to form nanostructures on the surface of titanium items for improving the interaction between metallic implants and the biological environment. The long-term success of the devices is related to their stability. In this work, titanium nanotubes were formed on a dental screw, made of titanium CP2, through an anodization process using an “organic” solution based on ethylene glycol containing ammonium fluoride and water. Then, the electrochemical stability in the Hank’s solution of these “organic” nanotubes has been investigated for 15 days and compared to that of titanium nanotubes on a similar type of sample grown in an inorganic solution, containing phosphoric and hydrofluoridric acids. Morphological and crystallographic analysis were performed by using scanning electron microscopy (SEM) and X-Ray diffractometry (XRD) tests. Electrochemical measurements were carried out to study the stability of the nanotubes when are in contact with the biological environment. The morphological measurements revealed long nanotubes, small diameters, smooth side walls, and a high density of “organic” nanotubes if compared to the “inorganic” ones. XRD analysis demonstrated the presence of rutile form. An appreciable electrochemical stability has been revealed by Electrochemical Impedance Spectroscopy (EIS) analysis, suggesting that the “organic” nanotubes are more suitable for biomedical devices.

Self-organized TiO₂ nanotube layer has been formed on titanium screws with complex geometry, which are used as dental implants. TiO₂ nanotubes film was grown by potentiostatic anodizing in H₃PO₄ and HF aqueous solution. During anodizing, the titanium screws were mounted on a rotating apparatus to produce a uniform structure both on the peaks and on the valleys of the threads. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX) and electrochemical characterization were used to evaluate the layer, chemical composition and electrochemical properties of the samples. Aging in Hank’s solution of both untreated and nanotubes covered screw, showed that: (i) samples are covered by an amorphous oxide layer, (ii) the nanotubes increases the corrosion resistance of the implant, and (iii) the presence of the nanotubes catalyses the formation of chemical compounds containing Ca and P.

Epoxy based coatings are susceptible to ultra violet (UV) damage and their durability can be significantly reduced in outdoor environments. This paper highlights a relevant property of graphene-based nanoparticles: Graphene Nanoplatelets (GNPs) incorporated in an epoxy-based free-standing film determine a strong decrease of the mechanical damages caused by UV irradiation. The effects of UV light on the morphology and mechanical properties of the solidified nanocharged epoxy films are investigated by Atomic Force Microscopy (AFM), in the acquisition mode “HarmoniX.” Nanometric-resolved maps of the mechanical properties of the multi-phase material evidence that the incorporation of low percentages, between 0.1% and 1.0% by weight, of graphene nanoplatelets (GNPs) in the polymeric film causes a relevant enhancement in the mechanical stability of the irradiated films. The beneficial effect progressively increases with increasing GNP percentage. The paper also highlights the potentiality of AFM microscopy, in the acquisition mode “HarmoniX” for studying multiphase polymeric systems.

Magnesium alloys are candidates as biodegradable medical materials due to their biocompatibility and favorable mechanical properties. Unfortunately, the high corrosion rate in physiological media and the release of hydrogen, limit their widespread use in biomedical applications. In this work, an intermediate coating based on polydopamine (PDOPA), between Mg substrate and an organic coating, was used to decreasing the degradation rate of AZ31 magnesium alloy, during the long-term exposure in simulated body fluid. Electrochemical Impedance Spectroscopy measurements were carried out to study the corrosion resistance of samples. Results demonstrated that the PDOPA interlayer determined the reduction of the substrate degradation rate. The results were interpreted supposing a synergistic effect which occurred when PDOPA and the organic coating were used together.