Zinc-doped hydroxyapatite-zeolite/polycaprolactone composites coating on magnesium substrate for enhancing in-vitro corrosion and antibacterial performance

This work is focused on developing zinc-doped hydroxyapatite-zeolite(Zn HA-Zeo)and polycaprolactone(PCL)composite coatings on magnesium(Mg)substrate to improve the corrosion resistance and antimicrobial properties.Dip-coating technique was used to coat Zn HA-Zeo/PCL on the Mg substrate at room temperature.The samples were subjected to field emission scanning electron microscopy(FESEM),X-ray diffraction(XRD),Fourier transform infrared(FTIR),energy dispersive X-ray spectroscopy(EDX)and antimicrobial potential.Results demonstrated that composite coatings consist of HA,scholzite,zeolite,and PCL phases.EDX spectra indicated the presence of calcium(Ca),silicon(Si),aluminum(Al),zinc(Zn),phosphorus(P)and oxygen(O).The composite surface appeared in spherical-like microstructure on coating with thickness ranging 226-260μm.Zinc-doped HA-Zeo composite coating had a high corrosion resistance and provided sufficient protection to the Mg surface against galvanic corrosion.Doped Zn HA-Zeo coating samples exhibited superior disc inhibition by confirming antimicrobial activity against the E.coli as compared to HA-Zeo sample.Altogether these results showed that the Zn HA-Zeo coatings not only improved the corrosion resistance,but also enhanced the antimicrobial property and hence they can be used as suitable candidates for implant applications.

Potential bioactive coating system for high-performance absorbable magnesium bone implants

Magnesium alloys are considered the most suitable absorbable metals for bone fracture fixation implants.The main challenge in absorbable magnesium alloys is their high corrosion/degradation rate that needs to be controlled.Various coatings have been applied to magnesium alloys to slow down their corrosion rates to match their corrosion rate to the regeneration rate of the bone fracture.In this review,a bioactive coating is proposed to slow down the corrosion rate of magnesium alloys and accelerate the bone fracture healing process.The main aim of the bioactive coatings is to enhance the direct attachment of living tissues and thereby facilitate osteoconduction.Hydroxyapatite,collagen type I,recombinant human bone morphogenetic proteins 2,simvastatin,zoledronate,and strontium are six bioactive agents that show high potential for developing a bioactive coating system for high-performance absorbable magnesium bone implants.In addition to coating,the substrate itself can be made bioactive by alloying magnesium with calcium,zinc,copper,and manganese that were found to promote bone regeneration.