Understanding the mechanisms of antimicrobial actions by silver ions

Published: 23-Feb-2024

The antimicrobial mechanism of silver ions relies on the oligodynamic effect. But what is this and how does it work? Hannah Mullane from BioCote explains

Antimicrobial technologies have become increasingly important in a world where bacterial threats persist.

It is important to note that antimicrobial technologies extend beyond targeting bacteria, they disrupt the reproduction of all microorganisms.

Among these technologies is silver ions, known for their exceptional antimicrobial efficacy even at minimal concentrations.

This phenomenon is known as the oligodynamic effect

This phenomenon is known as the oligodynamic effect.

The intricate world of silver ions and their modes of action against a wide range of bacteria is widely unknown, at BioCote (trademarked) we have in-house experts who understand and consider the mechanisms of silver ion toxicity, and we aim to shed light on how they effectively combat microbial growth. 

The oligodynamic effect

The oligodynamic effect is a testament to the extraordinary power of silver ions in antimicrobial action.

Even at low concentrations, silver ions can effectively reduce bacteria within a mere 30 minutes of exposure.

Silver ions infiltrate bacterial cell membranes and interact with cytoplasmic components, proteins, and nucleic acids (Yamanaka 2005). The oligodynamic effect unfolds in a series of steps that lead to the destruction of microbes.

Step 1: Interaction with bacterial inner membrane

Silver ion technology is the interaction with the inner membrane of bacteria, disrupting its cell membrane causing it to lose potassium ions and reducing ATP levels attached to phospholipids (Percival 2005).

Studies by Jung et al (2008) showed that this interaction leads to the separation of the cytoplasmic membrane from the cell wall in both Gram-positive and Gram-negative bacteria.

This is significant because this membrane is essential for a cell’s proper function as it’s connected to vital enzymes. 

Step 2: Interaction with nucleic acids and enzymes

Silver ions do not stop at the membrane but disrupt further into the bacterial cell.

They naturally interact with the bases in DNA rather than the phosphate group (Therman and Gerba 1989). Moreover, it has been proven that silver ions interact with nucleic acids forming bonds with pyrimidine bases. As a consequence, DNA is condensed, inhibiting its replication (Dakal 2016).

Step 3: Reactive Oxygen Species production

Silver ions trigger the production of reactive oxygen species (ROS) within bacterial cells.

This surge of intracellular ROS leads to oxidative stress, protein damage, DNA strand breakage, leading to cell death (Yamanaka 2005).

Yamanaka’s (2005) study proved that silver ions interfere with both structural and functional proteins, especially those vital for respiration.

Confirming that when silver ions attach to ribosomal proteins, they distort the ribosome’s natural structure. This process inhibits protein biosynthesis. 

Step 4: Bacteriostatic and bactericidal effects

Research has made it clear that silver ions exert a formidable antimicrobial effect, preventing the growth of bacteria and preventing their replication.

This is also known as a bacteriostatic effect.

When silver ions successfully eliminate bacteria, it is referred to as a bactericidal effect

Moreover, silver ions increase intracellular ROS levels, leading to various destructive mechanisms within the cell to impair essential cell proteins, inhibiting their functions and contributing to the cell’s ultimate demise.

Furthermore, silver ions can inflict damage on the cell membrane, compromising its function and regulating what enters and exits.

When silver ions successfully eliminate bacteria, it is referred to as a bactericidal effect. 

Silver ion mode of action

Referencing Figure 1, we observe the comprehensive modes of silver ion action on both Gram-negative and Gram-positive bacteria, emphasising the differences in silver ion uptake methods.

Silver ions enter Gram-negative cells via major outer membrane proteins, showcasing the diversity of their antimicrobial strategies.

  1. Pore formation, metabolites, and ions leakage 
  2. Denaturation of structural and cytoplasmic proteins; enzymes inactivation
  3. Inactivation of respiratory chain enzymes
  4. Increase of intracellular reactive oxygen species 
  5. Interaction with ribosomes
  6. Interaction with nucleic acids
  7. Inhibition of signal transduction

Antimicrobial technology is becoming increasingly utilised as a weapon against a wide array of unwanted bacteria and their damaging effects.

Their multi-faceted modes of action, from membrane disruption to DNA damage and ROS reproduction, make them indispensable when wanting to reduce bacteria.

As research continues, the intricate mechanisms through which silver ions combat bacteria offer hope for more effective antimicrobial strategies.

BioCote antimicrobial technology

Explore the world of antimicrobial innovation with BioCote– a trusted partner in delivering advanced antimicrobial technology solutions.

With over 25 years of expertise, we are the leading supplier of antimicrobial additives, dedicated to helping businesses worldwide create products that are not only hygienic but also shielded against the damaging effects of microorganisms like bacteria and mould.

Our mission is to simplify complex regulations and provide comprehensive support.

We empower our partners and customers, enabling them to confidently navigate any challenges of antimicrobial solutions. We specialise in simplifying the complications of post-Brexit regulations, ensuring businesses success in the ever-evolving chemical regulatory landscape. 

We go beyond the norm, breaking down regulatory requirements and aiding businesses to meet industry standards.

Silver ions enter Gram-negative cells via major outer membrane proteins

We assist companies in creating more effective products safely by carefully selecting additives tailored to the product's manufacturing process and intended use, ensuring the perfect compatibility and antimicrobial dosage.

Our rigorous testing ensures that our additives consistently perform as expected. However, our contribution extends beyond the scientific realm, it's rooted in our deep understanding and extensive experience.

Our consultative approach offers a multitude of benefits, ensuring a seamless journey towards incorporating antimicrobial features and achieving business objectives.

Whether companies need guidance through complex regulations, the development of antimicrobial solutions, or improved product performance, we offer support at every step.

Our partnership programme is enhanced with technical support, as our experienced team guides the integration of BioCote additives into products and provide practical insights into the science of antimicrobial technology.

Silver ions can inflict damage on the cell membrane

We offer unrivalled expertise and a profound understanding of our additives, making the chemistry behind antimicrobial technology accessible.

Our services extend to microbiological support, providing answers to common customers' technical inquiries.

Furthermore, our services encompass quality control testing conducted by an independent laboratory.

This includes a range of rigorous methods such as ISO 20743:2021, ISO 22196, ASTM G21-15, ASTM E2149-13A, and KIRBY-BAUER testing, ensuring the highest standards.

We also conduct product-specific investigations, such as swabbing comparisons between untreated and BioCote-treated products, bolstering the effectiveness of the company's marketing messages.

Not only that, but we also provide support for new product development, particularly in the expansion of antimicrobial product lines.

Trusted and accredited solutions

Antimicrobial additives are subject to a set of specific regulations, with the EU governed by the Biocidal Products Regulation 528/2012 (EU BPR) and the USA the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) - regulated by the Environmental Protection Agency (EPA).

These regulations are region-specific and define the scope, locations, and methods for using antimicrobial additives.

This legislation covers the registration of BioCote additives and their application in customer products. 

Silver ions increase intracellular ROS levels

BioCote antimicrobial technology stands out as a trusted choice, certified as food contact safe, making it suitable for integration into food contact products and surfaces.

We meet the requirements of a Hazard Analysis Critical Control Point (HACCP) based Food Safety Programme, ensuring that products featuring BioCote technology meet the highest standards of safety and exceed performance. 

BioCote technology is designed to have antimicrobial performance at low dosage rates, without altering the structural integrity of polymeric materials. If a polymer is recyclable, the addition of BioCote will not affect its recyclability.











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