Chitosan-ImH@γ-CD: a pH-sensitive smart bio-coating to enhance the corrosion resistance of magnesium alloys in bio-implants

Abstract

Magnesium alloys hold promise as bio-implants but are hindered by poor corrosion resistance. To overcome this, a pH-sensitive smart anti-corrosion bio-coating was developed using a layer-by-layer technique. The first layer consists of Imidazol@waterproofed γ-Cyclodextrin metal organic framework (ImH@waterproofed γ-CD MOF), which encapsulates ImH, a green inhibitor, in waterproofed γ-CD MOF. The second layer is composed of 1% w/v chitosan. ImH@waterproofed γ-CD MOF was characterized by SEM, FTIR, and XRD. The corrosion parameters of the smart bio-coating were investigated through potentiodynamic polarization (Tafel) plots and electrochemical impedance spectroscopy (EIS) in simulated body fluid (SBF). The results indicate that when the magnesium alloy coated with the chitosan-ImH@γ-CD composite is placed in the SBF solution, the pH near the corrosion site increases over time. This increase in pH leads to the release of imidazole as a corrosion inhibitor, effectively preventing surface corrosion by forming a protective layer on the alloy's surface. The chitosan-ImH@γ-CD composite exhibits an inhibition efficiency of 97.27% after 5 days of immersion in SBF. Additionally, the cell viability on the chitosan-ImH@γ-CD composite surface is significantly higher than on uncoated Mg alloy, promoting MC3T3-E1 cell proliferation. Alkaline phosphatase results also indicate improved differentiation of MC3T3-E1 cells with the chitosan-ImH@γ-CD composite.