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Biodegradation Evaluation of Magnesium Alloys Corrosion Via Hydrogen Evolution Measurements
Self-assembled monolayers (SAMs) as a form of nanotechnology has being gaining a lot of attention for its potential medical applications due to the ease of modification of surface properties through the selection of the appropriate terminal functional group in the monolayer (6). SAMs have been also been reported for surface modification of metallic biomaterials (7). Our laboratory has recently reported the formation of (SAMs) of octadecylphosphonic acid (ODPA) on the native oxide layer of magnesium alloy (8).
In this manuscript we report the biodegradation evaluation of phosphonic SAMs coated magnesium alloys using hydrogen evolution measurements. 18-octadecylphosphonic acid (ODPA) and 16-Phosphonohexadecanoic acid (16-PA) SAMs were formed on magnesium alloy (1 x 1 cm) using protocols developed in our laboratory (6). After SAM formation the bio-corrosion behavior of the magnesium and SAM coated magnesium was evaluated using hydrogen evolution method.
Figure 1: Hydrogen Evolution Setup
Figure 1 schematically illustrates the hydrogen evolution setup. Test samples were soaked in phosphate buffer saline (PBS) test solution at 37oC for a preset time (1, 3, 7, 14, 21 and 28 days. The emitted hydrogen volume was measured as a function of immersion time. Figure 2 shows the volume of hydrogen evolved over time for magnesium and magnesium coated samples. Figure 3 shows the magnesium hydroxide that was formed as a byproduct of the corrosion.
Figure 2:Hydrogen Evolution of ODPA, 16PA and Uncoated Mg alloy in PBS solution
Figure 3: Magnesium hydroxide formation as result of biodegradation in PBS
Figure 2 showed that magnesium and magnesium coated substrates had similar hydrogen evolution profiles with the differences found to be statistically insignificant. The coatings on magnesium alloy did not significantly change the corrosion behavior of the underlying magnesium. Thus these SAM coatings could be used for surface modification of the magnesium for biomedical applications.
Reference:
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