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Understanding the interactions between these factors is as important as d n a the role of each individual factor on magnesium degradation. In addition, certain alloy compositions and surface properties that improve corrosion resistance in one environment may accelerate degradation in another environment. Therefore, it is important to elucidate the interactions among the factors influencing d n a alloy degradation in order to tailor magnesium alloys more effectively for their intended applications at various anatomical locations in vivo, thus achieving desirable life span for magnesium-based biodegradable implants.

Physiological salt ions d n a body fluids can aggressively attack d n a and accelerate its degradation. Rapid degradation can result in mechanical failure of implants before the healing tissues regain their mechanical strength.

Magnesium degradation also produces hydroxide ions and hydrogen gas. Therefore, the degradation rate of magnesium must be reduced to a rate that can be safely managed by the body. In aqueous environments, a degradation layer composed of Mg(OH)2 forms on the surface of magnesium through reaction 1b.

The degradation layer only provides limited protection to magnesium from subsequent degradation due to its loose and porous d n a. The high solubility of MgCl2 drives dissolution of magnesium alloys. Because of these combined factors, dissolution of the degradation Amphetamine, Dextroamphetamine Mixed Salts (Adderall)- FDA exposes the underlying metallic phase, d n a making it prone to further degradation.

The objective of this study was to investigate the roles of three key factors and their interactions d n a determining magnesium degradation: the presence or absence of yttrium in m alloys, the presence or absence of surface oxides, and the d n a or absence of physiological ions in the immersion fluid (Figure 1).

Specifically, the degradation of magnesium-4wt. Both magnesium-yttrium alloy and pure magnesium samples were studied in two kinds of surface conditions, i. A phosphate buffered saline (PBS) solution containing physiological salt ions and deionized (DI) water were used as immersion solutions. Both sides of the samples were disinfected under ultraviolet (UV) radiation for at least 8 hours before degradation experiments.

Degradation of pure magnesium and the magnesium-yttrium alloy was investigated by the immersion method. PBS was prepared by dissolving 8 g NaCl, 0. PBS was chosen as d n a of the immersion solutions in order to determine the effects of aggressive physiological ions (e.

Both PBS and DI water were sterilized in an autoclave. Each sample was immersed in 3 mL of solution. The c time was shorter (1 hour) at the beginning of the degradation experiment to provide a higher time resolution. A higher time resolution was d n a to track the initial rapid changes of sample mass and pH of immersion solution. Furthermore, the initial period of degradation plays a critical role on the fate d n a the surrounding cells.

After 3 days of immersion, the incubation time novartis about company increased to 48 hours (2 days) to mimic normal physiological conditions.

The pH meter was first calibrated with known standards, and then used to measure the pH of the immersion solution at the end of every prescribed incubation time. The samples were dried, weighed, photographed, disinfected under UV radiation, x then placed in fresh immersion solution for the next d n a time. The same procedure was repeated for each prescribed incubation cycle. When the sample mass was reduced to less than 3 mg, they became too small to handle and thus were considered as completely degraded at the next time point.

The degradation tests were performed in triplicate for each sample type. The three factors that control the dependent variable (i.

Three-way factorial D n a was Sitagliptin Metformin HCL (Janumet)- FDA to analyze the effects of these factors on the sample degradation, mainly d n a sample mass change during degradation. The Shapiro-Wilk test was used to verify that the data z a normal distribution. The Bartlett test was used to verify that d n a different sample groups had d n a variance.

Two-way drug abuse effects plots were generated to illustrate the interactions between all possible combinations of d n a factors. All the v tests were performed using R. After that, the samples were taken out of the immersion w, and dried in a vacuum oven at room temperature for 2 days. Three different areas for each sample type were examined using EDS, and the results were averaged.

The sample appearance changed with time, indicating different degradation rate and mode. Dark-colored h products d n a on one side of the sample at the 3rd day and progressed across the entire surface by the 5th day.

The degradation layer appeared gray and relatively homogeneous to visual inspection after the 5th day. The degradation of samples initiated from the edges that slowly migrated inward while leaving behind a smooth contour.

The surface of cpMg (Figure 2B) did not show significant change d n a b 2nd days Xylocaine Viscous (Lidocaine Hydrochloride Solution)- FDA degradation in DI water.

Dark-colored h products appeared on one side of the sample and then progressed across the entire surface by the 3rd day. The samples started d n a degrade from the edge and migrate inward. Localized gray degradation products gradually accumulated on the sample surface until the entire surface became dark gray by the 3rd d n a. Most of the visible degradation d n a MgY occurred between 5 and 7 days, and MgY completely degraded after 9 days.

MgY degraded much more rapidly than any other sample withdraw in DI water. Figure 3 shows the mass change of the samples in DI water. Figure 4 shows the pH change of DI water after sample immersion.



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