The Substantial Role of Cell and NanoparticleSurface Properties in the Antibacterial Potential of Spherical Silver Nanoparticles [Letter]

Dear editor

I am delighted to express my interest in the work published in Nanotechnology, Science and Applications regarding the relationship between nanoparticle charge and antimicrobial effect.¹ These findings challenged the existing views on the antibacterial mechanisms of silver nanoparticles (AgNPs) and their interactions with bacterial cells.

AgNPs have long been regarded as broad-spectrum bactericidal agents.^2,3 However, the relationship between nanoparticle properties, such as size and shape, and their antibacterial efficacy is rather intricate. The antibacterial effect of AgNPs depends not only on their inherent characteristics but also on the resistance levels of diverse bacteria. The authors themselves reported that there is a difference in the susceptibility of Gram-positive bacteria and most Gram-negative bacteria to AgNPs carrying either a highly negative or positive charge. Their findings were similar to a published work about a Gram-selective antibacterial based on charge-tunable modified MoS₂.⁴ Niu et al reported that the citraconic anhydride-modified PEI-MoS₂, which carry a negative charge, exhibited stronger bactericidal properties Gram-positive bacteria, S. aureus, when compared with PEI (positive charge) modified nanoparticles.

I would like to mention the importance of lipophilic groups. They can interact with the lipophilic parts of the phospholipid bilayer of cell membranes, affecting the composition and structure of the membranes, transmembrane transport of substances, and the permeability and fluidity of cell membranes. Krychowiak-Maśnicka et al used AgNPs coated with sodium citrate as a highly negatively charged nanoparticles.¹ However, compared the other four modified AgNPs, AgNPs-Cit seems lack of lipophilic groups (or perhaps more details about this nanomaterial should be provided), which may result in a relatively low bactericidal ability. Instead, well-designed compounds like the citraconic anhydride-modified PEI-MoS₂ mentioned above should be employed.⁴

And according to literatures such as references 14–20 they cited in this article, I think the conclusion that moderate charge of silver nanoparticles is crucial for their bactericidal performance requires more evidence to support.