Evaluation of Antimicrobial and Antidiabetic Activities of Ag@SiO2 Core–Shell Nanoparticles Synthesized with Diverse Shell Thicknesses

Abstract

Ag@SiO2 core–shell nanoparticles with different shell thicknesses were synthesized by Stober method and characterized. The shell thicknesses was appropriately controlled by changing the concentration of silica source (TEOS) as evidenced by the DRS-UV spectra, which exhibited change in surface plasmon resonance absorption with change in silica thicknesses. X-ray diffraction analysis confirmed the fcc structure of silver metal as the crystalline phase within the nanocomposite. SEM results revealed the spherical shape of the synthesized Ag@SiO2 core–shell nanoparticles and EDX analysis established the presence of silica along with silver nanoparticles. TEM micrographs evidenced the successful formation of Ag@SiO2 core–shell nanoparticles with uniformly encapsulated silica shell over silver core nanoparticles. The porous features of the Ag@SiO2 core–shell nanoparticles were confirmed by N2 adsorption–desorption studies, which revealed the typical type IV isotherms. Silver release rates and bactericidal efficacy against bacterial and fungi strains were investigated, in which the Ag@SiO2 core–shell nanoparticles obtained with 25 µg/mL concentration of TEOS shows excellent microbial activity compared to the rest of the core–shell nanoparticles. The present study also intends to examine α-amylase and α-glucosidase activity of Ag@SiO2 core–shell nanoparticles, and again found the core–shell nanoparticles synthesized using 25 µg/mL of TEOS displayed highest antidiabetic activity.