Aggregation and interaction of cationic nanoparticles on bacterial surfaces

Area of Science:

• Nanotechnology
• Microbiology
• Surface Chemistry

Background:

• Gold nanoparticles (AuNPs) are increasingly explored for biomedical applications.
• Understanding nanoparticle-cell membrane interactions is crucial for targeted delivery and efficacy.
• Bacterial cell envelopes differ significantly between Gram-negative and Gram-positive species.

Purpose of the Study:

• To investigate the size-dependent interaction of cationic monolayer-protected gold nanoparticles (AuNPs) with bacterial cell membranes.
• To elucidate the distinct aggregation patterns and effects on bacterial viability (lysis) of different-sized AuNPs.
• To determine the role of bacterial surface proteins in mediating these interactions.

Main Methods:

• Synthesis and characterization of cationic AuNPs (6 nm and 2 nm).
• Incubation of AuNPs with Escherichia coli (Gram-) and Bacillus subtilis (Gram+).
• Analysis of AuNP-bacteria interactions using transmission electron microscopy (TEM) and UV-vis spectroscopy.
• Assessment of bacterial lysis and the effect of proteolytic treatment.

Main Results:

• Distinct AuNP surface aggregation patterns were observed on E. coli and B. subtilis.
• The size of the AuNPs influenced the aggregation patterns and the extent of bacterial lysis.
• Proteolytic treatment of bacteria abolished the observed distinct aggregation patterns, indicating protein involvement.
• Smaller 2 nm AuNPs showed more pronounced effects compared to 6 nm AuNPs.

Conclusions:

• Cationic AuNP interactions with bacterial membranes are size-dependent and species-specific.
• Bacterial surface proteins play a critical role in mediating AuNP aggregation and subsequent cellular effects.
• These findings provide insights into the mechanism of nanoparticle-bacterial interactions, relevant for antimicrobial strategies.