Endowing biodegradable Zinc implants with dual-function of antibacterial ability and osteogenic activity by micro-addition of Mg and Ag (≤ 0.1 wt.%)

Infection remains the devastating complications associated with surgical fixation of bones fractured dur -ing trauma. In this study, we report a low-alloyed Zn-Mg-Ag that simultaneously has optimized strength degeneration profiles during degradation, outstanding antibacterial efficacy and osteogenic activity. Our results showed that Zn-0.05Mg-0.1Ag alloy had favorable mechanical properties (UTS: 247.8 +/- 1.6 MPa, Elong.: 35 +/- 2.2 %) and presented a better hold of mechanical integrity than pure Zn during 28 days corrosion, 2.6 % vs. 18.7 % reduction. After one-year of natural aging, the alloy still preserved an elon-gation of 24.07 +/- 3.84 %. As verified by microbial cultures, Zn-0.05Mg-0.1Ag alloy demonstrated high antibacterial performance against Gram-positive and Gram-negative strains, as well as antibiotic-resistant strains (MRSA) in vitro and in vivo due to the synergistic antibacterial actions of Zn2+ and Ag +. Mean-while, Zn-Mg-Ag alloy also exhibited enhanced viability, osteogenic differentiation, and gene expressions of osteoblasts in vitro , as well as promoted osteogenic activity than pure Zn in the femoral condyle defect repair model. The co-releasing of Zn, Mg and Ag ions did not induce toxic side effects. Collectively, low alloyed Zn-0.05Mg-0.1Ag indicated long-lasting mechanical integrity during degradation, and presented the ability to synergistically inhibit bacteria and promote osteogenesis, possessing tremendous potential in treating implant-associated infections.Statement of significance Infection after fracture fixation (IAFF) remains the most common and serious side effects of orthopedic surgery. Additionally, widespread antibiotic use contributes to the development of multi-drug resistant bacteria such as methicillin-resistant staphylococcus aureus (MRSA), which exacerbates IAFF treatment and prevention. IAFF treatment and prevention remain clinically challenging, so implants with dual antibac-terial and osteogenic functions are in high demand. The antibacterial efficacy and osteogenic activity of low-alloyed Zn-Mg-Ag ( <= 0.1 wt.% Mg, Ag) alloys were investigated in vitro and in vivo. The results showed that micro addition of Mg and Ag could significantly improve osseointegration function, mechanical prop-erties, and antibacterial performance. These quantification findings shed new light on the development and understanding of dual functional Zn-based orthopedic implants.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study reports a low-alloyed Zn-Mg-Ag material with optimized strength degeneration profiles, excellent antibacterial efficacy, and osteogenic activity. The Zn-0.05Mg-0.1Ag alloy showed favorable mechanical properties, high antibacterial performance, and promoted osteogenesis.