Evaluating Antibacterial Effects of Bio-synthesized Silver-coated Silica Nanoparticles on Staphylococcus aureus and Acinetobacter baumannii

Healthcare-associated infections (HAIs) cause economic and social burden by affecting millions of patients annually, especially in low-income countries. The treatment of HAIs with antibiotics can lead to their increased resistance and subsequently increased mortality. As an alternative solution, nanomaterials combined with inorganic metals (silver ions and silver-based compounds) have been proposed. In this study, after extraction of sodium silicate from rice husk ash, silver-coated silica nanoparticles (SiO₂@Ag-NPs) were synthesized by sol-gel method and evaluated the antibacterial activity against hospital-acquired infections. SiO₂@Ag-NPs were analyzed by transmission electron microscopy (TEM). The antibacterial activity of SiO₂@Ag-NPs against two clinical isolated bacterial strains, including methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii, was assessed using minimum inhibitory concentrations (MICs) and using scanning electron microscopy (SEM). TEM images showed that SiO₂ nanoparticles had a uniform shape with a size of around 50 nm SiO₂@Ag-NPs’ surface area and homogeneous pores are 78 m²/g and 2.71 nm, respectively, with purity over 98%. Silver nanoparticles attached to SiO₂ surface have uniform shapes with size smaller than 5 nm. The MIC results were determined from 25 to 400 ppm depending on the concentration and bacterial strain tested. SEM images showed that SiO2@Ag-NPs inhibited established biofilms in both bacterial strains, discrete bacterial cells, and fewer clusters. There was no or little extracellular matrix observed, the cells were distorted, shrank, ruptured, and appeared to have indentation or perforation in the cell wall. The results showed that SiO₂@Ag-NPs were an attractive nanomaterial for commercial applications and in treating diseases associated with microbial infections.