Surface Minimal Bactericidal Concentration: A comparative study of active glasses functionalized with different-sized...

Area of Science:

• Materials Science
• Nanotechnology
• Microbiology

Background:

• Silver nanoparticles (AgNPs) exhibit antimicrobial properties.
• Understanding the impact of AgNP size and immobilization on antibacterial efficacy is crucial for material development.
• Previous studies often focus on colloidal AgNPs, with less emphasis on immobilized systems.

Purpose of the Study:

• To quantify the antimicrobial properties of differently sized AgNPs immobilized on a surface.
• To investigate the relationship between AgNP size, immobilization, and antibacterial efficacy against *Escherichia coli*.
• To establish a Surface Minimal Bactericidal Concentration (SMBC) for immobilized AgNPs.

Main Methods:

• Synthesis and characterization of 6, 30, and 52 nm spheroidal AgNPs using UV-vis, SEM, TEM, and ICP-MS.
• Determination of Minimal Inhibitory Concentration (MIC) and Minimal Bactericidal Concentration (MBC) against *E. coli*.
• Quantification of antibacterial efficacy (R) using an adapted ISO 22196 protocol for immobilized AgNPs on amino-silanized glass.

Main Results:

• Immobilized AgNPs showed significantly higher antibacterial efficacy compared to colloidal AgNPs.
• Surface MBC (SMBC) values were determined for each AgNP size: 0.023 μg/cm² (6 nm), 0.026 μg/cm² (30 nm), and 0.034 μg/cm² (52 nm).
• Antibacterial surfaces achieving ≥ 99.9999% bacterial reduction were developed using approximately 100 times less silver than the MBC of colloidal AgNPs.

Conclusions:

• Immobilization of AgNPs reduces aggregation and maximizes surface area, enhancing direct contact with bacterial cells.
• This approach allows for the development of highly effective antibacterial materials using minimal silver content.
• The findings support the safe application of these materials in biomedical and food packaging industries.