Antibacterial Effect and Cytotoxic Evaluation of Mg alloy Functionalised by Sol-Gel Magnesium Hydroxide and Copper doped

Introduction: Biodegradable alloys are promising candidates for implants that offer stability during healing and controlled degradation after healing, eliminating the need for second surgery and reducing the risk of chronic inflammation or allergic reactions. In particular, Mg alloys have a high capacity for bone regeneration and mechanical properties similar to natural bone, making them very promising for biomedical applications. However, there is a growing need to find new treatments with antimicrobial properties while slowing and controlling the dissolution kinetics of Mg alloys. This study aims to evaluate the antibacterial properties of a coating doped with magnesium hydroxide (Mg(OH)2). Materials and Methods: MgAZ31 magnesium alloy discs produced by the superplastic forming (SPF) process were coated by sol-gel technique with Mg(OH)2 doped with copper (Cu) ions. Microbiological testing assessed the antibacterial properties of the material through growth inhibition (viable count) and biofilm formation (SEM analysis) using Staphylococcus aureus strains (ATCC 25923). The WST-1 viability assay is performed on fibroblast and pre-osteoblast mouse cell lines to assess the toxicity of the Sol Gel-Cu doped coating. Results: The antibacterial data reported on MgAZ31 SPF-SolGel-Cu doped alloys show that the doping reduces bacterial growth of S.aureus strain and also inhibits bacterial biofilm formation. The effect on cell viability was different in the two lines analysed. No change in viability was observed in the L929 cell line, whereas viability decreased in the more differentiated pre-osteoblast MC3T3. Conclusion: Despite inconsistent data on cell viability, preosteoblasts and osteoblastic cells, encouraging antibacterial data reported on MgAZ31-Sol-Gel-Cu doped alloys show that doping reduces bacterial growth of two S.aureus strains and also inhibits bacterial biofilm formation. These promising data should encourage research to evaluate the effects of doped coatings more broadly, assessing immunotoxic effects and osteointegration capabilities.