Silver nanoparticle-ionic silsesquioxane: a new system proposed as an antibacterial agent

Area of Science:

• Nanotechnology
• Materials Science
• Microbiology

Background:

• Silver nanoparticles (AgNPs) are recognized for their antimicrobial properties.
• Developing stable and effective AgNPs requires precise control over size and surface charge.
• Existing AgNP formulations often face challenges with stability and require higher concentrations for efficacy.

Purpose of the Study:

• To synthesize and characterize novel spherical silver nanoparticles (AgNPs) using a charged silsesquioxane stabilizer.
• To evaluate the antibacterial efficacy of the synthesized AgNPs against common bacterial pathogens.
• To assess the stability and cytotoxicity of the AgNPs for potential therapeutic applications.

Main Methods:

• Synthesis of ~5 nm spherical AgNPs in aqueous medium utilizing a quaternary ammonium-containing silsesquioxane as a stabilizer and size controller.
• Characterization of AgNP stability using UV-Vis spectroscopy over one year and zeta potential measurements.
• In vitro antibacterial assays against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus.
• Cytotoxicity assessment on mammalian cells.

Main Results:

• Successfully synthesized stable, positively charged (~5 nm) spherical AgNPs with a zeta potential of +24.7 mV.
• Demonstrated high stability of AgNPs, evidenced by unchanged UV-Vis spectra after one year.
• Achieved potent in vitro antibacterial activity with low minimum inhibitory concentrations (MICs): 0.60 μg mL⁻¹ for E. coli, 1.1 μg mL⁻¹ for P. aeruginosa, and 2.0 μg mL⁻¹ for S. aureus.
• Confirmed safety of AgNPs for mammalian cells at effective antibacterial concentrations.

Conclusions:

• The novel silsesquioxane-stabilized AgNPs represent a highly stable and effective antibacterial agent.
• The low MIC values and excellent safety profile make these AgNPs promising for various antimicrobial applications.
• This study introduces a new, efficient method for AgNP synthesis with significant potential in combating bacterial infections.