Harnessing Stabilized Nanoparticles to Combat Antimicrobial Resistance

Antimicrobial resistance (AMR) is a grave global health threat that demands immediate attention and multisectoral action. The misuse and overuse of antimicrobials, coupled with limited access to quality antimicrobials, clean water, sanitation, and infection prevention and control measures, are the primary drivers of AMR. This phenomenon occurs when bacteria, viruses, fungi, and parasites evolve over time, rendering medicines ineffective in treating infections. AMR undermines the effectiveness of treatments for common infections, major surgery, and cancer chemotherapy, posing a significant challenge to modern medicine.

To address AMR, novel antimicrobial agents are being explored, and nanoparticles have emerged as promising candidates due to their unique physical and chemical properties. Nanoparticles, defined as materials with at least one dimension between 1 and 100 nanometers, can interact with biological systems at the molecular level. Among the various types of nanoparticles, metal nanoparticles such as silver and copper have been extensively studied for their potential antibacterial properties. These nanoparticles release metal ions that disrupt bacterial cell membranes, metabolism, and DNA, making them potential weapons against AMR. Indeed, nanoparticles can penetrate microbial biofilms, which are notorious for promoting antibiotic resistance, and effectively eradicate the bacteria within.

In a new study published in the peer-reviewed journal Frontiers in Microbiology by Dr. Thelma Ameh, Dr.  Kusy Zarzosa, Dr.  Jake Dickinson, Dr.  Christie Sayes, and Dr.  W. Evan Braswell from Baylor University, in collaboration with the United States Department of Agriculture, delves into the antibacterial properties of silver and copper nanoparticles with different surface stabilizing agents. The researchers investigated how the surface charge and functionality of nanoparticles influenced their antibacterial activity and mechanism of action against three bacterial strains: Escherichia coli, Staphylococcus aureus, and Sphingobacterium multivorum.

The research team synthesized silver and copper nanoparticles with two types of surface stabilizing agents: cetyltrimethylammonium bromide (CTAB) and polyvinyl pyrrolidone (PVP). CTAB conferred a positive surface charge to the nanoparticles, while PVP conferred a neutral surface charge. The authors fully characterized the nanoparticles using techniques such as dynamic light scattering, transmission electron microscopy, and zeta potential measurement. They discovered that CTAB-stabilized nanoparticles were smaller and more positively charged than PVP-stabilized nanoparticles.

The authors evaluated the antibacterial activity of the nanoparticles using various methods, including broth microdilution, viable plate count, live/dead staining, reactive oxygen species generation, DNA fragmentation, and scanning electron microscopy. The study revealed that CTAB-stabilized silver and copper nanoparticles exhibited higher antibacterial activity than their PVP-stabilized counterparts. These CTAB-stabilized nanoparticles had lower minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values, indicating their greater potency.

Furthermore, the researchers observed that CTAB-stabilized nanoparticles caused extensive membrane damage, cell lysis, oxidative stress, and DNA fragmentation in the bacteria, while PVP-stabilized nanoparticles inhibited bacterial growth with minimal membrane damage and cell lysis. CTAB-stabilized nanoparticles also attached more abundantly and uniformly to the bacterial cell surface. This comprehensive investigation demonstrated that the surface stabilizing agents of metal nanoparticles significantly influenced their antibacterial properties and mechanisms of action.

The findings of this study suggest that CTAB-stabilized silver and copper nanoparticles could serve as highly effective antibacterial agents at low doses to combat AMR. By understanding how surface stabilizing agents influence the interaction between metal nanoparticles and bacteria, researchers and pharmaceutical companies can design innovative strategies to combat AMR and more targeted nanoparticles with enhanced antibacterial activity.