Antimicrobial performance of novel glutathione-conjugated silver nanoclusters (GSH@AgNCs) against Escherichia coli and Staphylococcus aureus by membrane-damage and biofilm-inhibition mechanisms

Bacterial infection has become an important factor affecting human health, and the increasing antibiotic resistance has seriously hindered the treatment of infectious diseases. This study aimed to explore a novel nanotechnology that combines silver with glutathione (GSH) to form antibacterial nanoclusters, GSH@AgNCs. The composite was characterized using a UV fluorescence spectrophotometer, high-resolution transmission electron microscopy (HR-TEM), particle size-zeta potential, fourier transform infrared (FTIR), X-ray photoelectron spectrometer (XPS), thermal gravimetric analysis (TGA), and X-ray diffraction analysis (XRD). This study examined the inhibitory effect of GSH@AgNCs on the bacterial growth and biofilm formation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), as well as its antibacterial mechanisms. The results indicated that GSH@AgNCs were more successful in restricting E. coli than S. aureus. The bacterial membrane exposed to GSH@AgNCs was damaged irreversibly, presenting cytoplasm leakage, membrane depolarization, ATPase activity decline, and cell degeneration. In addition, at low concentration (1/8 MIC), GSH@AgNCs significantly inhibited the formation of biofilms and damaged mature biofilms, reducing the viable cells. This study demonstrated that GSH@AgNCs effectively hindered the proliferation of foodborne Gram-positive bacteria (S. aureus) and Gram-negative bacteria (E. coli), providing new feasibility for applying organic composite nanomaterials and nanotechnology in the food industry.