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Table 1 Overview of metals with respect to their antibacterial effects, immunomodulatory effects, advantages and limitations

From: Immunomodulatory biomaterials for implant-associated infections: from conventional to advanced therapeutic strategies

 

Antibacterial effects

Immunomodulatory effects

Advantages

Limitations

Ref

Ag

· Disrupt membranes by binding to sulfhydryl groups

· Damage DNA and protein by oxidative stress

· Bind directly to nucleic acid molecules and hinder cell growth and reproduction

· Induce M1 polarization of macrophages and exacerbate the inflammatory response

· Promote M2 polarization of macrophages, ROS scavenging, and new bone formation (in very low doses)

· Induce death of host cells

· Direct and broad-range antibacterial effects

· High stability

· Mature techniques available for incorporation in implants

· Toxicity for eukaryotic cells

[124,125,126, 135, 136]

Ga

· Replace iron in bacterial metabolism

· Aggregate at the site of inflammation

· Inhibit bone resorption by inhibiting osteoclast activity

· Promote osteogenic gene expression in MG63 cells

· Reduce the inflammatory response of the wound

· Unique antibacterial mechanism

· Inhibit bone resorption

· Aggregate spontaneously to the site of infection

· Unstable antibacterial effect influenced by iron concentration

· Fewer molecular mechanism studies currently

· High cost

[140, 141] [143, 144, 195]

Zn

· Damage DNA and protein by oxidative stress

· Disrupt the cell walls/membranes

· Enhance phagocytosis and chemotaxis of macrophages

· Mediate PGRPs exert antibacterial activity

· Promote immune cell maturation

· Anti-inflammatory effects by deregulating NF-κB pathway activity

· Pro-osteogenic effects described

· Significant immune regulation function

· Essential trace elements

· Weak direct antibacterial effects

[149,150,151, 154,155,156] [157, 158]

Cu

· Disrupt membranes by binding to sulfhydryl groups Generate ROS through Fenton reactions

· Disrupt helix structure of DNA

· Facilitate M1 macrophage switch and bacteria phagocytosis to resist infection

· Induce a proper immune environment for bone regeneration

· Induce angiogenesis

· Direct and broad-range antibacterial effects

· Fenton reaction catalyst

· High stability

· Essential trace elements

· Significant angiogenic and osteogenic abilities

· Toxicity at supraphysiologic concentration

[159, 196, 197]

Mg

· Inhibit bacterial adhesion and biofilm formation due to Elevated pH by Mg degradation

· Inhibit biofilm-forming genes and protein expression in the outer membrane of bacteria

· Stimulate M2 macrophage switch and inhibit osteoclastogenesis and osteolysis

· Downregulate pro-inflammatory cytokines and induce osseointegration

· Protect neutrophils from endogenous oxidative stress

· Essential element for bone tissue

· Excellent anti-inflammatory and pro-osteogenic activity

· Poor corrosion resistance

· Poor inherent antibacterial properties

[198,199,200]