Influence Of Glucose On Degradation And Interface Properties Of Biomedical Magnesium And Its Alloys

Magnesium(Mg)and its alloys are receiving immense attention as promising biodegradable implants owing to their excellent degradability,biocompatibility,bioactivity and comparable mechanical properties to bone.The principal drawback of Mg based implants is their poor corrosion resistance in physiological environments.The degradation of biomedical magnesium and coating depends on the dynamics at the interface between the material and its environment and the interaction between the materials and chemicals.In patients with diabetes,biomedical magnesium as a implant material will face a more specific hyperglycemic environment.Thus,it is of vital necessity to study the influence of glucose on degradation behavior of Mg alloys in physiological environments.On the basis of degradation behavior,calcium-phosphorus(Ca-P)coating was fabricated via molecular recognition of glucose,displaying good protection to substrate.Glucose-induced composite coatings containing crystalline calcium phosphate were prepared on pure Mg substrate through hydrothermal deposition in order to improve the corrosion resistance.In this work,influence of glucose on degradation behaviors of AZ31 alloy in vitro(0.9%NaCl)were detailed studied.The synergetic influence of glucose and Tris on corrosion of AZ31 alloy was elucidated in 0.9%NaCl solution.Moreover,Ca-P composite coating was fabricated with an aid of glucose,which enhanced the corrosion resistance of pure Mg.The corrosion resistance of magnesium in different solutions and Ca-P composite coating on pure Mg were investigated using hydrogen evolution and potentiodynamic electrochemical testing technology.The characteristics of the samples and corrosion products formed on sample surface were analyzed by scanning electron microscope(SEM)、Energy dispersive spectrum(EDS)、X-ray diffraction analysis(XRD)、Fourier Transform Infrared spectrum(FT-IR)and X-ray photoelectron spectroscopy(XPS).The results showed different corrosion behaviors of magnesium in various solutions.Firstly,it presented AZ31 alloy exhibiting different corrosion responses to 0.9%NaCl solutions with glucose.1 g/L of glucose decreases the corrosion rate of Mg alloy AZ3 1,whereas the presence of 2.0 and 3.0 g/L glucose accelerates the degradation rate during long term immersion in saline solution.A low content(1 g/L)of glucose can decrease the corrosion rate of AZ31 alloy due to complexing with Mg2+ ions and thus impede further aggression of Cl-ions;whereas high concentrations(2 and 3 g/L)of glucose accelerate the degradation progress,which is attributed to the transformation of glucose into gluconic acid and thus destroyed the protective corrosion product of Mg(OH)2.In terms of Tris-buffered saline solution,the addition of glucose accelerates corrosion of AZ31 alloy due to hydrolysis of Tris that promoted the transformation of glucose into gluconic acid.Glucose has an excellent molecular recognition function.In the hydrothermal system,glucose can rapid transformed into gluconic acid and appeal to the substrate surface.Gluconic acid attracted the Ca2+ ions to sample surface and thus reacted to PO43-and HPO4-ions,fabricated Ca-P coating on pure Mg substrate.Moreover,this reaction occurs in alkaline environment,forming protective film of magnesium hydroxide on the substrate.In a word,glucose-induced Ca-P coating exhibits good corrosion resistance and adhesion strength,which provided Mg and its alloys with the potential application in biomedical filed.