Characterization and bioactive properties of zirconia based polymeric hybrid for orthopedic applications

Hydroxyapatite and β-TCP modified PMMA-TiO2 and PMMA-ZrO2 coatings for bioactive corrosion protection of Ti6Al4V implants

Organic-inorganic hybrid coatings deposited on different types of metallic alloys have shown outstanding anticorrosive performance. The incorporation of osteoconductive additives such as hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) into organic-inorganic hybrid coatings is promising to improve the osseointegration and corrosion resistance of Ti6Al4V alloys, which are the most widely used metallic orthopedic and dental implant materials today. Therefore, this study evaluated the capability of poly(methyl methacrylate) (PMMA)-TiO₂ and PMMA-ZrO₂ hybrid coatings modified with HA and β-TCP to act as bioactive and corrosion protection coatings for Ti6Al4V alloys. In terms of cell growth and mineralization, osteoblast viability, Ca⁺² deposition and alkaline phosphatase assays revealed a significant improvement for the HA and β-TCP modified coatings, compared to the bare alloy. This can be explained by an increase in nanoscale roughness and associated higher surface free energy, which lead to enhanced protein adsorption to promote osteoblast attachment and functions on the coatings. The effect of HA and β-TCP additives on the anticorrosive efficiency was studied by electrochemical impedance spectroscopy (EIS) in a simulated body fluid (SBF) solution. The coatings presented a low-frequency impedance modulus of up to 430 GΩ cm², 5 decades higher than the bare Ti6Al4V alloy. These findings provide clear evidence of the beneficial role of HA and β-TCP modified hybrid coatings, improving both the biocompatibility and corrosion resistance of the Ti6Al4V alloy.

Immobilization of Antimicrobial Silver and Antioxidant Flavonoid as a Coating for Wound Dressing Materials

Purpose

The aim of this study is to develop a new coating for wound dressings that is comprised of antimicrobial silver (Ag) and antioxidant flavonoid quercetin (Q).

Methods

Dip-coating was used to apply the coating on cotton gauge as a model dressing. Ag was immobilised using polydopamine as a priming and catalytic layer followed by coating of quercetin that was incorporated in a functionalized polydimethylsiloxane. The coating was investigated using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and release assay. The antimicrobial activity of quercetin and Ag was tested against Staphylococcus aureus (S. aureus). A surgical wound model on mice was used to evaluate the effects of the coated dressing on wound healing rates and tissue histology.

Results

Ag and quercetin showed enhanced antimicrobial activity against S. aureus when used in combination. Ag and quercetin were successfully immobilized onto the fibre of the dressing using the dip-coating process. The coating released Ag and quercetin over 8 days and showed strong antioxidant activity. In the wound healing model, complete wound closure was achieved in 12 days in the group receiving coated dressing and was associated with an enhancement in tissue remodelling and neo-angiogenesis and the reduction in tissue inflammation.

Conclusion

These new antimicrobial-antioxidant coatings may be promising in the development of advanced wound care therapies.