In an earnest pursuit of scientific advancement in this era of rapid progress in science and medicine, there remains a dark side that we cannot overlook. This dark side poses a significant threat to health, engulfing us with worry and fear about our future well-being. This concern revolves around the resurgence of drug-resistant pathogens, such as multidrug-resistant bacterial strains, fungi, and parasites. This looming fear has compelled scientists to urgently delve into the minutiae to find radical solutions. Their aim is to develop new, effective compounds against microbes or sustain studies and modify existing substances to prevent the spread of diseases and shield humanity from threats invisible to the naked eye.
Nanotechnology presents an innovative solution, allowing for the modification of key properties of materials, including metallic nanoparticles obtained through various methods. Among the best of these methods, biogenic synthesis stands out as a reliable approach in manufacturing metallic nanoparticles. Moreover, this method is considered environmentally friendly compared to other chemical and physical methods, making it an intriguing option for research and development in the field of nanotechnology, medicine, and industry.
Silver is one of these vital substances known for thousands of years for its effectiveness in combating infections such as burn infections, bone infections, urinary tract infections, and central venous catheter-related infections. Recently, silver nanoparticles have gained prominence for their potent antimicrobial activity, making silver-based antimicrobial materials a common choice. Current studies aim to understand their mechanisms of action more precisely, further enhancing their effectiveness and specificity, thus making them a powerful tool in our ongoing battle against drug-resistant diseases.
The Impact of Silver Nanoparticles on Bacterial Behavior and Growth
Small particles carry significant effects While silver ions may not be able to eradicate all types of bacteria, they can indeed achieve remarkable results in eliminating many bacterial strains. With ongoing research and innovation, silver nanoparticles are expected to remain at the forefront of infection and disease control, making them one of the most suitable and effective solutions to the health challenges we face. Several scientific studies have shown that silver nanoparticles, with an average size of 16 nanometers, were highly toxic to Escherichia coli cells at a low concentration (60 mg/L). It was observed that silver nanoparticles adhered completely to the cell wall and were found inside the bacteria. In another study, silver nanoparticles produced by a specific fungus were also found to be toxic to bacteria and led to faster bacterial cell membrane disruption. Furthermore, another study demonstrated that silver nanoparticles, approximately 20 nanometers in size, had a toxic effect on Escherichia coli cells, with transmission electron microscopy (TEM) analysis showing complete bacterial cell membrane disruption shortly after exposure to silver nanoparticles. All these tests and results indicate the effectiveness of silver nanoparticles due to their large surface area, which allows for greater interactions with bacteria. The effect of silver ions on bacteria includes:
- Destruction of bacterial cell structure: Silver ions react with bacterial proteins (the structure of bacterial cells) inside the bacteria, leading to their damage and disruption of their functions, thereby limiting their growth and spread.
- Inhibition of respiration within bacteria: Silver ions disrupt electron transport within bacteria, leading to the inhibition of the cellular membrane’s function, reducing their ability to produce energy and ultimately causing their death.
- DNA damage: Silver ions significantly contribute to damaging bacterial DNA, reducing their ability to spread and reproduce due to the changes they induce in the cell’s structure itself.
- Significant changes in bacterial cell structure: Silver ions cause noticeable changes in the structure of bacterial cells, resulting in the separation of the cytoplasmic membrane from the cell walls.
Silver Nanoparticles and Silver Ions in Confronting Harmful Bacteria
And scientists continue their meticulous research to better understand the mechanisms of silver resistance at a molecular level, aiming to identify the genes and proteins responsible for this process and to determine how bacteria respond to both silver ions and silver nanoparticles. This endeavor seeks to develop new strategies to combat silver-resistant bacteria and enhance our understanding of how to effectively use silver as an antibacterial agent. The main difference between silver nanoparticles and silver ions lies in their effectiveness against bacteria:
- A detailed study by a team of researchers revealed that the impact of silver nanoparticles differs significantly from that of silver ions, which are typically present in nanomolar concentrations in the case of nanoparticles and in micromolar ranges in the case of silver ions.
- Protein analysis showed that even brief exposure to silver nanoparticles caused changes in the expression of envelope and heat shock proteins in Escherichia coli cells, and silver nanoparticles significantly disrupted bacterial cells, leading to massive potassium loss and decreased ATP levels, ultimately impairing the cell’s ability to survive.
- As for potential resistance to silver ions, the use of silver as an antiseptic is an important subject, but its increasing applications may lead to resistance in microorganisms. For example, various mechanisms of silver resistance have been carefully studied at the molecular level, and it has been observed that Salmonella typhimurium has mechanisms to resist silver ions, which are controlled by specific genes on plasmids.
