Antimicrobial Bioresorbable Mg–Zn–Ca Alloy for Bone Repair in a Comparison Study with Mg–Zn–Sr Alloy and Pure Mg

Abstract

Magnesium–zinc–calcium (Mg–Zn–Ca) alloys have attracted increasing attention for biomedical implant applications, especially for bone repair, because of their biocompatibility, biodegradability, and similar mechanical properties to human bone. The objectives of this study were to characterize Mg–2 wt % Zn–0.5 wt % Ca (named ZC21) alloy pins microstructurally and mechanically, and determine their degradation and interactions with host cells and pathogenic bacteria in vitro and in vivo in comparison with the previously studied Mg–4 wt % Zn–1 wt % strontium (named ZSr41) alloy and Mg control. Specifically, the in vitro degradation and cytocompatibility of ZC21 pins with bone marrow derived mesenchymal stem cells (BMSCs) were investigated using both direct culture and direct exposure culture methods. The adhesion density of BMSCs on ZC21 pins (i.e., direct contact) was significantly higher than on pure Mg pins in both in vitro culture methods; the cell adhesion density around ZC21 pins (i.e., indirect contact) was similar to the cell-only positive control in both in vitro culture methods. Interestingly, ZC21 showed a higher daily degradation rate, crack width and crack area ratio in the direct exposure culture than in the direct culture, suggesting different culture methods did affect its in vitro degradation behaviors. When cultured with Gram-positive bacteria methicillin-resistant Staphylococcus aureus (MRSA), ZC21 reduced bacterial adhesion on the surface more significantly than that of ZSr41 and Mg. The in vivo degradation and biocompatibility of the ZC21 pins for bone regeneration were studied in a mouse femoral defect model. The in vivo degradation rate of ZC21 pins was much slower than that of ZSr41 alloy and Mg control pins. After 12 weeks of implantation in vivo, the ZC21 group showed the shortest gap at the femoral defect, indicating that ZC21 pins promoted osteogenesis and bone healing more than ZSr41 and Mg control pins. Overall, the ZC21 alloy is promising for bone repair, while providing antibacterial activities, and should be further studied toward clinical translation.

In vivo urinary compatibility of Mg-Sr-Ag alloy in swine model

“…Like the other two commonly studied biodegradable metallic materials, iron and zinc, magnesium and its alloys also have inherent antimicrobial activities [ 8 , 19 , 20 ]. Lock et al [ 21 ] identified a significant decrease in bacterial proliferation when magnesium alloys degraded in artificial urine, and similar phenomena were also reported by Zhang et al [ 22 ]. Thus, the evident antibacterial activity makes magnesium alloy a very favorable candidate as biodegradable ureteral implant material.…”

“…Lock et al [ 21 ] identified a significant decrease in bacterial proliferation when magnesium alloys degraded in artificial urine. Zhang et al [ 22 ] determined that magnesium alloy degradation produced a more significant reduction in the proliferation of Methicillin-resistant Staphylococcus aureus (MRSA) when the bacteria were in direct contact with alloy surfaces. In our study, apart from the contribution to antibacterial process from the a rise in pH and the Mg 2+ ion release, the Ag + ion release during the degradation of JQ also played very an important role due to its strong antibacterial activity ( Fig.…”

Sequence Does Not Matter: The Biomedical Applications of DNA-Based Coatings and Cores

“…Magnesium (Mg) alloys are currently regarded as a material of choice for making biodegradable bone implants [ 60 ] because Mg is involved in the regulation of osteogenesis [ 61 ] and the Mg alloy elastic modulus is close to that of natural bones [ 62 ]. The Mg-based implant should provide mechanical support and promote tissue healing, and eventually degrade in the organism when it is no longer needed [ 63 ].…”

Rationale for Processing of a Mg-Zn-Ca Alloy by Equal-Channel Angular Pressing for Use in Biodegradable Implants for Osteoreconstruction

“…It was found that an optimal Ca content in a Mg alloy is in the range of 0.5-1.0 wt.%, while further increase in its content raises the biocorrosion rate of the alloy [31]. Zhang et al [32] studied plates made from Mg-2 wt.% Zn-0.5 wt.% Ca (ZC21) and showed that the biodegradation rate of the alloy was sufficiently low for the intended application as an implant material. Furthermore, the alloy exhibited a good compatibility with mesenchymal stem cells of the bone marrow.…”