Biodegradation mechanisms of pure Mg in presence of glucose, vitamin C, and citric acid

Abstract

The physiological environment of the human body is an extremely complex system, containing not only inorganic ions but also organic molecules; thus it is necessary to understand the influences of the different functional groups of three six-carbon small organic molecules (glucose (Glu), vitamin C (Vc), and citric acid (CA)) on the degradation mechanisms of pure magnesium (Mg). Electrochemical polarization and impedance spectroscopy, hydrogen evolution rates, and pH monitoring tests were used to characterize the degradation behaviors of pure Mg in 0.9 ​wt% NaCl and phosphate-buffered saline (PBS) solutions. Using scanning electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, the compositions, phase structures, and morphologies of the degradation products were investigated. Results indicated that Glu enhanced the biodegradation rate of pure Mg in 0.9 ​wt% NaCl solution, whereas Vc and CA slowed down their biodegradation rate. In the PBS solution, both Glu and Vc reduced the biodegradation rate of pure Mg, while CA accelerated its initial biodegradation and retarded its long-term biodegradation. In addition, Raman spectroscopy demonstrated the formation of Mg-(gluconate, l-threonic acid, oxalate, and citrate) on the pure Mg. Plausible biodegradation mechanisms of pure Mg are proposed regarding the influences of Glu, Vc, and CA.