Influence of the Microstructure and Silver Content on Degradation, Cytocompatibility, and Antibacterial Properties of Magnesium‐Silver Alloys In Vitro

Abstract

Implantation is a frequent procedure in orthopedic surgery, particularly in the aging population. However, it possesses the risk of infection and biofilm formation at the surgical site. This can cause unnecessary suffering to patients and burden on the healthcare system. Pure Mg, as a promising metal for biodegradable orthopedic implants, exhibits some antibacterial effects due to the alkaline pH produced during degradation. However, this antibacterial effect may not be sufficient in a dynamic environment, for example, the human body. The aim of this study was to increase the antibacterial properties under harsh and dynamic conditions by alloying silver metal with pure Mg as much as possible. Meanwhile, the Mg-Ag alloys should not show obvious cytotoxicity to human primary osteoblasts. Therefore, we studied the influence of the microstructure and the silver content on the degradation behavior, cytocompatibility, and antibacterial properties of Mg-Ag alloys in vitro. The results indicated that a higher silver content can increase the degradation rate of Mg-Ag alloys. However, the degradation rate could be reduced by eliminating the precipitates in the Mg-Ag alloys via T4 treatment. By controlling the microstructure and increasing the silver content, Mg-Ag alloys obtained good antibacterial properties in harsh and dynamic conditions but had almost equivalent cytocompatibility to human primary osteoblasts as pure Mg.

Microstructure, mechanical and corrosion properties of novel quaternary biodegradable extruded Mg–1Zn–0.2Ca-xAg alloys

“…An investigation also described that the mixing enthalpy of Mg-Zn (−4 kJ mol −1 ) and Mg-Ca (−6 kJ mol −1 ) is less than that of Mg-Ag (−10 kJ mol −1 ) [36], thus manifesting that the Mg atoms bond more easily with the Ag than the Zn and Ca atoms. Son et al [37] concludes that the addition of Ag in Mg-6Zn-2Sn-0.4Mn-based alloy can lead to the precipitation of the Ag 17 Mg 54 phase, which was also found in Liu's study [30]. In this paper, Ag 17 Mg 54 phase (a=14.240 Å, b=14.209 Å c=14.663 Å, α=β=γ=90°) is also the main strengthening second phase in the Ag-containing alloys after analyzing the XRD and TEM results shown in figures 3 and 4.…”

“…The Volta potential of the second phase is about −30∼−50 mV, which is obviously lower than that of the matrix. As illustrated in figure 10, the corrosion potential of the Ag 17 Mg 54 phase moves to a positive electrode due to the Ag addition [30,46]. Therefore, the surface microgalvanic corrosion is shifted to a circumstance which could lead to faster homogeneous corrosion and minimize pitting corrosion [29,46].…”

“…With the content up to 6 wt%, the UTS was doubled from pure magnesium(from 108.3 to 215.9 MPa) [29]. It was lately revealed the addition of 8wt% Ag in magnesium alloy accelerated the speed of the alloy degradation both in vitro and in vivo [30]. Moreover, the Ag element, which is noted for superior antibacterial property in the form of ion, is generally applied in the medical devices and products with its promising biosafety in the human body [31].…”

“…Moreover, the Ag element, which is noted for superior antibacterial property in the form of ion, is generally applied in the medical devices and products with its promising biosafety in the human body [31]. Nevertheless, the researchers pour more attention into binary or ternary Ag-contained magnesium alloy while little investigations have been focused on the multicomponent degradable extrusion magnesium alloy [25][26][27][28][29][30]. Considering the effect of the Ag element on strengthening mechanical properties and accelerating the corrosion rate, it is suitable to solve the above-mentioned problems faced by Mg-2Zn alloys as the anastomotic surgery materials.…”

Advances and Challenges of Biodegradable Implant Materials with a Focus on Magnesium-Alloys and Bacterial Infections

“…Even though magnesium implants could not curb bacterial infections in mice, clinical data is needed before a final conclusion can be drawn. In addition, several alternative strategies are presently investigated, such as antibioticreleasing coatings for magnesium-based implants or the addition of antibacterial acting alloy metals like silver, copper, or zinc that release cytotoxic ions [119][120][121][122][123][124][125]. The major challenge for such an approach is to maintain the balance of achieving efficacious bactericidal ion concentrations in vivo without damaging the host tissue.…”