Review:Fabrication and Application of Zwitterion-based Functional Coatings

Zwitterion-based materials by virtue of their special physical and chemical characteristics have attracted researchers to utilize them for fabricating functional coatings. The simultaneous presence of positive and negative charges renders the zwitterion-based materials with electrostatically induced hydration properties, which enables a high resistance towards oily pollutants, nonspecific protein adsorption, bacterial adhesion and biofilm formation. This review starts from the working mechanism of zwitterions and covers the fabrication strategies of zwitterion-based functional coatings, namely the zwitterion-bearing binder route, the zwitterion-bearing additive route and the post-generation of coatings containing zwitterionic precursors. The applications of zwitterion-based functional coatings are discussed, including medical implants, marine antifouling and oil-resistant coatings, with focus on the relevant mechanisms of the zwitterion-containing coatings for a specific performance. Finally, some comments and perspectives on the current situation and future development of zwitterion-based functional coatings are given.

Fabrication and Evaluation of a Bioactive Sr–Ca–P Contained Micro-Arc Oxidation Coating on Magnesium Strontium Alloy for Bone Repair Application

Considering the compatibility between degradation and bioactivity of magnesium-based implants for bone repair, micro-arc oxidation is used to modify the magnesium alloy surface in aqueous electrolytes, allowing strontium, calcium, and phosphorus to be incorporated into the coating. The thickness, composition, morphology and phase of this Sr-Ca-P containing coating are characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer and X-ray diffraction. The in vitro and in vivo degradation of the coating is evaluated by immersion test, electrochemical test and implantation test. Moreover, the cytocompatibility is tested with osteoblast cell according to ISO 10993. The results show that St, Ca and P elements are incorporated into the oxide coating, and a refined structure with tiny discharging micro-pores is observed on the surface of the coating. The Sr-Ca-P coating possesses a better corrosion resistance in vitro and retards the degradation in vivo. Such coating is expected to have significant medical applications on orthopedic implants and bone repair materials.

Improving the radiopacity of Fe-Mn biodegradable metals by magnetron-sputtered W-Fe-Mn-C coatings:Application for thinner stents

In this exploratory work,micrometric radiopaque W-Fe-Mn-C coatings were produced by magnetron sputtering plasma deposition,for the first time,with the aim to make very thin Fe-Mn stents trackable by fluoroscopy.The power of Fe-13Mn-1.2C target was kept constant at 400 W while that of W target varied from 100 to 400 W producing three different coatings referred to as P100,P200,P400.The effect of the increased W power on coatings thickness,roughness,structure,corrosion behavior and radiopacity was investigated.The coatings showed a power-dependent thickness and W concentration,different roughness values while a similar and uniform columnar structure.An amorphous phase was detected for both P100 and P200 coatings while γ-Fe,bcc-W and W_(3)C phases found for P400.Moreover,P200 and P400 showed a significantly higher corrosion rate(CR)compared to P100.The presence of W,W_(3)C as well as the Fe amount variation determined two different micro-galvanic corrosion mechanisms significantly changing the CR of coatings,0.26±0.02,59.68±1.21 and 59.06±1.16μm/year for P100,P200 and P400,respectively.Sample P200 with its most uniform morphology,lowest roughness(RMS=3.9±0.4 nm)and good radiopacity(~6%)appeared the most suitable radiopaque biodegradable coating investigated in this study.