Yu-Hong Zou

Self-assembled silane film and silver nanoparticles coating on magnesium alloys for corrosion resistance and antibacterial applications

Contamination resulting from microbial adhesion on magnesium alloys is very common in many applications. Self-assembly technology was employed to prepare an antibacterial composite coating by fixing silver nanoparticles (AgNPs) onto the surface of magnesium alloys. The AgNPs were immobilized on the surface of 3-aminopropyltrimethoxysilane (APTMS)-modified magnesium alloy AZ31 (APTMS/Mg) through electrostatic inter-attraction between partially protonated amino groups and negatively charged citrate-capped AgNPs, resulting in the AgNPs attached APTMS/Mg (AgNPs/APTMS/Mg) substrate. The prepared Ag colloid and functionalized AZ31 alloy were characterized by ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and electrochemical methods. Finally, the bactericidal activity of AgNPs/APTMS/Mg substrate against Escherichia coli was assessed by the inhibition zone. The results demonstrated that Si-O-Si covalent bonds existed on the substrate with the formation of inorganic Si-O-Mg bonds. AgNPs were immobilized and well-dispersed, forming a uniform submonolayer on the silane film in two dimensions. The AgNPs/APTMS-pretreated AZ31 alloys exhibited better corrosion resistance and excellent antibacterial performance.

In vitro corrosion resistance and antibacterial properties of layer-by-layer assembled chitosan/poly-L-glutamic acid coating on AZ31 magnesium alloys

Abstract Surface functionalization of magnesium (Mg) alloys is desired to obtain the surfaces with both improved corrosion resistance and antibacterial property. A corrosion-resistant and antimicrobial coating was prepared on Mg alloy surface by layer-by-layer (LbL) assembly of chitosan (CHI) and poly-L-glutamic acid (PGA) by electrostatic attraction. The functionalized surfaces of the Mg alloys were characterized by field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy and electrochemical tests. The bactericidal activity of the samples against Staphylococcus aureus was assessed by the zone of plate-counting method. The obtained coating on the Mg alloy substrates exhibits good corrosion resistance and antibacterial performance.

In vitro corrosion and antibacterial properties of layer-by-layer assembled GS/PSS coating on AZ31 magnesium alloys

Abstract To enhance the corrosion resistance of magnesium (Mg) alloy and to impart its surface with antibacterial functionality for inhibiting biofilm formation and biocorrosion, Mg(OH) 2 films were fabricated on AZ31 magnesium alloy substrates by an in-situ hydrothermal method and well-defined multilayer coatings, consisting of gentamicin sulfate (GS) and poly(sodium 4-styrene sulfonate) (PSS), were prepared via layer-by-layer (LbL) assembly. The morphologies, chemical compositions and corrosion resistance of the obtained (PSS/GS) n /Mg sample were investigated using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, electrochemical methods and immersion tests. Finally, the bactericidal activity of (PSS/GS) n /Mg samples against Staphylococcus aureus was assessed by the zone of inhibition methods and plate-counting method. The so-synthesized composite coating on the Mg alloy substrates exhibits good corrosion resistance and antibacterial performance, which make them attractive as coatings for medical implanted devices.

In Vitro Degradation of Pure Magnesium―The Effects of Glucose and/or Amino Acid

The influences of glucose and amino acid (L-cysteine) on the degradation of pure magnesium have been investigated using SEM, XRD, Fourier transformed infrared (FTIR), X-ray photoelectron spectroscopy (XPS), polarization and electrochemical impedance spectroscopy and immersion tests. The results demonstrate that both amino acid and glucose inhibit the corrosion of pure magnesium in saline solution, whereas the presence of both amino acid and glucose accelerates the corrosion rate of pure magnesium. This may be due to the formation of -C=N- bonding (a functional group of Schiff bases) between amino acid and glucose, which restricts the formation of the protective Mg(OH)2 precipitates.

Blood compatibility of zinc–calcium phosphate conversion coating on Mg–1.33Li–0.6Ca alloy

Magnesium alloys as a new class of biomaterials possess biodegradability and biocompatibility in comparison with currently used metal implants. However, their rapid corrosion rates are necessary to be manipulated by appropriate coatings. In this paper, a new attempt was used to develop a zinc-calcium phosphate (Zn-Ca-P) conversion coating on Mg-1.33Li-0.6Ca alloys to increase the biocompatibility and improve the corrosion resistance. In vitro blood biocompatibility of the alloy with and without the Zn-Ca-P coating was investigated to determine its suitability as a degradable medical biomaterial. Blood biocompatibility was assessed from the hemolysis test, the dynamic cruor time test, blood cell count and SEM observation of the platelet adhesion to membrane surface. The results showed that the Zn-Ca-P coating on Mg-1.33Li-0.6Ca alloys had good blood compatibility, which is in accordance with the requirements for medical biomaterials.

In vitro corrosion of magnesium alloy AZ31 — a synergetic influence of glucose and Tris

Biodegradable Mg alloys have generated great interest for biomedical applications. Accurate predictions of in vivo degradation of Mg alloys through cost-effective in vivo evaluations require the latter to be conducted in an environment close to that of physiological scenarios. However, the roles of glucose and buffering agents in regulating the in vivo degradation performance of Mg alloys has not been elucidated. Herein, degradation behavior of AZ31 alloy is investigated by hydrogen evolution measurements, pH monitoring and electrochemical tests. Results indicate that glucose plays a content-dependent role in degradation of AZ31 alloy in buffer-free saline solution. The presence of a low concentration of glucose, i.e. 1.0 g/L, decreases the corrosion rate of Mg alloy AZ31, whereas the presence of 2.0 and 3.0 g/L glucose accelerates the corrosion rate during long term immersion in saline solution. In terms of Tris-buffered saline solution, the addition of glucose increases pH value and promotes pitting corrosion or general corrosion of AZ31 alloy. This study provides a novel perspective to understand the bio-corrosion of Mg alloys in buffering agents and glucose containing solutions.

Corrosion resistance of a novel SnO2-doped dicalcium phosphate coating on AZ31 magnesium alloy

A SnO2-doped dicalcium phosphate coating was prepared on AZ31 alloy by means of hydrothermal deposition. The results showed that the coating possessed a globular morphology with a long lamellar crystalline structure and a thickness of approximately 40 μm. The surface of the coating became smooth with an increase additive amount of the SnO2 nanoparticles. The corrosion current density and hydrogen evolution rate of the coating prepared in presence of SnO2 were reduced compared to the coating without SnO2 and the bare AZ31 substrate, indicating an improvement in the corrosion resistance of the SnO2-doped coating.