In vitro antibacterial activity of a coating with silver nanoparticles and amikacin on a PEEK cranial implant model

Abstract

Infections associated with cranial implants represent a large medical problem for surgery, driving the creation of innovative coatings to prevent bacterial colonization. The main objective of this thesis is to develop a coating based on silver nanoparticles (AgNPs) and amikacin and assess in vitro its antibacterial activity. AgNPs were synthesized by the chemical reduction method, using sodium citrate (1% w/v) as reduction agent and carboxymethylcellulose (CMC, 1.5% w/v) as a matrix controlling the nanoparticles release. To evaluate its activity, the AgNPs–amikacin formulations were applied as a thin coating on a PEEK model substrate. We evaluated antimicrobial efficacy against Escherichia coli ATCC 35218 and Staphylococcus aureus ATCC 25923 in two stages. First, the broth microdilution assay demonstrated that at the minimum inhibitory concentration (MIC) of 10 mM AgNO₃, CFUs were suppressed by over 90 %. Next, biofilm formation was assessed via the crystal violet viability assay, which likewise showed a greater than 90 % reduction in biofilm biomass at the same MIC. Even at sub‑MIC levels (½× and ¼×), AgNO₃ coatings maintained substantial activity, producing more than 75 % inhibition in both bacterial growth and biofilm development, indicative of a clear dose–response effect. The agar diffusion method achieved inhibition halos of 16 mm using the MIC. These results show that AgNPs–amikacin-CMC stabilized coating can suppress bacterial growth and biofilm formation of key pathogens in vitro effectively, plus the synthesis and application process is simple suggesting scalability for later biomedical use. To validate this dual-action coating as a preventative strategy for infection in cranial implant procedures, researchers should investigate in vivo, assay biocompatibility, and test durability further.