Applied Methods to Assess the Antimicrobial Activity of Metallic-Based Nanoparticles.

Area of Science:

• Antimicrobial resistance research
• Nanomaterial safety and efficacy
• In vitro diagnostics

Background:

• Antibiotic resistance necessitates novel antimicrobial discovery and standardized testing.
• Existing methods for aqueous reagents are established, but testing particle-based suspensions like nanomaterials remains challenging.
• ISO standard validations for nanomaterial testing have faced scrutiny, requiring corrective actions.

Purpose of the Study:

• To evaluate five in vitro assays for testing antimicrobial activities of metallic-based nanomaterials.
• To assess the reliability and limitations of each assay method.
• To identify optimal methods for confirming antimicrobial activity and determining minimum inhibitory concentration (MIC) of nanomaterials.

Main Methods:

• Serial analysis of 10 metallic-based nanomaterials against 10 pathogens using five different in vitro assays.
• Evaluation of technique, limitations, and robustness of each assay.
• Comparison of agar well diffusion and resazurin broth dilution methods for efficacy and MIC determination.

Main Results:

• At least two methods are required to confirm antimicrobial activities of metallic-based nanomaterial suspensions.
• The agar well diffusion method is the most reliable, providing data on efficacy, ions, and synergistic effects.
• Resazurin broth dilution is recommended for determining MIC, offering visual results and overcoming detection issues.
• Bimetallic AgCu demonstrated the highest antimicrobial effectiveness (MIC 7 µg/mL for bacteria, 62.5 µg/mL for fungi).

Conclusions:

• Standardized and validated in vitro assays are essential for assessing antimicrobial nanomaterials.
• A combination of agar well diffusion and resazurin broth dilution provides comprehensive evaluation.
• AgCu bimetallic nanoparticles show significant potential as antimicrobial agents.