Silver nanoparticles composited co-dopped polypyrrole/zinc coating for enhancing anti-corrosion and antibacterial properties of ZK60 magnesium alloy in Hank’s solution

Abstract

For the biodegradable implant applications, silver nanoparticles (Ag NPs) are incorporated in polypyrrole (PPy) co-dopped with tartrate (TA) and salicylate (SA) anions to obtain multi-functional Ag NPs-PPy(TA + SA)/Zn bilayer coating on ZK60 magnesium alloy with high protective and antibacterial properties. The effects of Ag NPs on the composition, structure, and antibacterial and protective properties of Ag NPs-PPy(TA + SA)/Zn bilayer coating are studied. Incorporating Ag NPs influences the electrochemical growth conditions of PPy(TA + SA), possibly increasing the defects in PPy chains. Its surface morphology and film thickness are similar to PPy(TA + SA). However, Ag species (Ag+/Ag0 ≈ 0.1) are only distributed in the PPy surface layer (hundreds of nm), containing some adsorbed and agglomerated Ag NPs on its surface. In Hank’s solution at 37 °C, Ag NPs-PPy(TA + SA) experiences slow degradation, and the Ag content loses slowly to zero. Its protection time is significantly improved to 113 ± 2.6 days, much more prolonged than PPy(TA + SA) (54 ± 1.5 d), suggesting the crucial role of Ag NPs. After Ag NPs-PPy(TA + SA) is broken due to its local destruction, ZK60 displays typical local corrosion. Ag NPs-PPy(TA + SA) exhibited excellent cytocompatibility and antibacterial properties. The corresponding mechanism involved is thoroughly discussed.