Systematic review of metal-based alloys with autogenous antibacterial capability

Pathogenic bacterial infection, especially in surgical and nosocomial settings, is an outstanding and long-lasting challenge due to the ability of microorganisms to evolve and develop mechanisms to become drug-resistant (i.e., superbugs). Considerable efforts have been made in recent years to develop metal-based alloys with autogenous antibacterial capability and to comprehend their mechanism of action, which are systematically reviewed in this work. To comprehensively understand current developments, antibacterial mechanisms (e.g., cell wall/membrane disruption), resistance mechanisms (e.g., permeability barrier), and the primary standardized techniques used to assess the antibacterial response (e.g., plate-count method) are initially introduced. Subsequently, metallic elements with intrinsic antibacterial response are presented alongside a brief discussion of the effects that manufacturing methods have on the ability to achieve metal-based alloys with autogenous antibacterial properties. The several antibacterial metal-based alloys currently being developed, which include Co-, Fe-, Mg-, Ti-, and Zn-based alloys, and some few other metal-based alloy systems, were analyzed in detail, and an effort to comparatively evaluate the antibacterial and mechanical response of the different alloys developed so far was made. Generally, the incorporation of Cu or Ag, which are well-known antibacterial metallic elements, shows remarkable effectiveness against both Gram-positive and Gram-negative bacteria. Additionally, some few other elements like Ca, Ce, and rare earths have been investigated, and some of them show antibacterial capability. The work is complemented with some challenges to be addressed and opportunities to be taken.