Dual-functional superhydrophobic coatings on biodegradable Mg alloys via nano-SiO2 particles assisted surface modification

In the exploration of next-generation biocompatible implant materials, magnesium (Mg) alloys have great potential due to their inherent biodegradability. The current study delineates the development of dual-functional coatings for Mg alloys, incorporating zinc (Zn) and calcium (Ca), characterized by both anti-bacterial and anti-corrosion attributes. These coatings were synthesized by integrating surface groups of magnesium hydroxide/magnesium oxide with surface atoms of nano‑silicon dioxide (nano-SiO2) particles, leading to the formation of magnesium silicate junctions. Subsequently, these interfacial surfaces were functionalized using organofluorosilanes. With the application of the coating, a notable enhancement in the static contact angle of water from 43.7° ± 1.1° to 158.4° ± 1.3° was observed. The anti-adhesive properties of the coating against bacteria were assessed through inoculation assays with Staphylococcus aureus, a predominant agent of implant-associated infections. No bacterial colonization on the Mg4Zn0.5Ca alloy surface was detected when the dual-functional coatings were applied. While a hydrogen evolution (HE) of 4.78 mL/cm2 was measured on uncoated surfaces, the HE reduced significantly to 0.35 mL/cm2 for coated alloy surfaces. Analysis using Nyquist plots unveiled a polarization resistance of coated surfaces that was an order of magnitude higher than uncoated surfaces. As a result, Mg alloys covered with a dual-functional nanocoating layer demonstrate favorable characteristics, such as diminished corrosion rates and enhanced resistance against bacterial adhesion. Such coatings negate the necessity for subsequent surgical removal of bone implants, consequently mitigating potential bacterial infections and the concomitant medical expenses.