Complete characterization of sol–gel silver-fluoride-hydroxyapatite coatings on external fixators for orthopedic surgery applications: structural, biological, and in vitro evaluations

External fixator pins (EF) have many applications in orthopedic surgeries in the field of trauma. Infection is a well-known problem associated with EF pins. The infection, occur by creating a biofilm on the surface of EF pins due to planktonic bacteria adhere to EF and therefore, loosening of the EF embedded in the bone. Coating the surfaces of EF pins with antibacterial materials has been identified as the most effective method for improving the interface between the bone and EF to prevent the formation of biofilms and reduce the risk of infection. Accordingly, the current study has been centered on the creation of a coating of Silver-Fluoride-Hydroxyapatite (Ag-FHA) on Stainless Steel Substrates through the sol-gel method. The FESEM images and Mapping analysis have confirmed the nano-scale size and homogeneous dispersion of particles in the Ag-FHA structure, respectively. The FTIR results indicate the hydroxyapatite formation in obtained structure. A comprehensive antibacterial study was conduct on the synthesized powders. The results indicated that Ag 0.4-FHA exhibits significant inhibitory effects on the growth of both Staphylococcus aureus and Escherichia coli. In Ag 0.4-FHA structure, the minimum inhibitory concentration (MIC) was determined to be 2000 mg/ml against Staphylococcus aureus bacteria and 500 mg/ml against Escherichia coli bacteria. The effectiveness of 0.3 and 0.4% by weight was confirmed against the growth inhibition of the investigated microorganisms through the agar well diffusion method. The cytotoxicity test results confirmed that the synthesized structures had no toxic effect. Also, the morphology of NIH/3T3 cells showed the normal morphology of the cells with intact membranes. The obtained results of this project demonstrate that structures containing 0.3 and 0.4 Ag are highly effective in preventing the growth of both bacterial strains. These structures can be suitable candidates for covering orthopedic implant to reduce the risk of infection in surgery. Graphical Abstract