Mesoporous silica decorated with silver nanoparticles - an investigation of the radiolytic synthesis parameters through factorial experiments

Resistant infectious microorganisms are causing a worldwide emerging problem, called antimicrobial resistance. To avoid this outbreak, new antimicrobial technologies are necessary. Silver nanoparticles (AgNPs) are known for their antibacterial properties and several studies have focused on their synthesis, characterization, and biological assays. One possibility to synthesize AgNPs is through gamma radiation, known as radiolytic synthesis. This work focuses on the radiolytic synthesis of AgNPs capped into a mesoporous silica nanoparticle aiming at an antimicrobial application. The variants of the radiolytic synthesis, which may influence the AgNPs formation, were studied and statistically compared by Design of Experiments Factorial Design in Minitab Software. The Ag content is statically dependent on dose, volume, and pH, as well as on two parameters interaction: [Ag+]-pH and [Ag+]-volume-pH interaction. Transmission electron microscopy and nitrogen adsorption analyses indicated the presence of subnanometric AgNPS located inside the mesopores. Silver nanoagglomerates were also found by transmission electron microscopy, which could be formed by silver oxides, as shown in X-ray photoelectron spectroscopy. AgNPs reduce the specific surface area of the silica nanoparticle, while the matrix morphology remains. The nanocomposites presented preliminary biocompatibility observed in in vitro biological assay using fibroblasts, which support their application in biological systems as antimicrobial substitutes.