Tag Archives: colloidal silver

Antimicrobial ‘safe-tea’ with silver nanoparticles and green tea

This work is not about drinking tea with silver nanoparticles in it or ingesting colloidal silver by any means, a dangerous practice as Nicole Karlis’s January 7, 2024 article for Salon highlights, Note: Links have been removed,

The HBO docuseries “Love Has Won: The Cult of Mother God” begins with a jarring image. The corpse of the cult leader, Amy Carlson, laying in a bed, wrapped in blankets and string lights. She is noticeably gaunt and her face is a very blue color. When Carlson died in 2021 at the age of 45, a coroner’s report deemed her cause of death to be “alcohol abuse, anorexia and chronic colloidal silver ingestion.”

Most medical experts advise against ingesting silver — especially in large amounts. That’s because too much of it can build up in a person’s body and lead to argyria, which is the condition that Carlson and Stan Jones both had that turned them a blue. While argyria alone isn’t a serious health condition, it doesn’t go away when a person stops ingesting silver. Plus, too much silver can be fatal. [emphasis mine]

A November 17, 2023 news item on phys.org announced research from the Polish Academy of Sciences into improving antimicrobial activity, Note: A link has been removed,

Researchers at the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) have demonstrated that green tea–silver nanoparticles as a powerful tool against pathogens such as bacteria and yeast. Their work is published in Nanoscale Advances.

An undated Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) press release (also published on EurekAlert and dated November 17, 2023), which originated the news item, describes this work, which is intended for medical applications, in more detail,

Once upon a time, people believed to be invincible against bacterial diseases, thanks to the antibiotics. Does this sound like a fairy tale? By all means! Nothing could be further from the truth. Despite widespread access to antibiotic therapy, many lives are lost due to pathogens invisible to the eye. The ability to develop drugs that can combat resistant strains of bacteria has not kept pace with the spread of resistance. So far, innovations to defeat antimicrobial-resistant strains of bacteria are in high demand. Recently, researchers at the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) demonstrated green tea-silver nanoparticles as a powerful tool against pathogens such as bacteria and yeast. Their goal was to develop an efficient method to combat bacteria that are otherwise unaffected by antimicrobial agents, such as antibiotics.

Following the discovery of antibiotics, there came a change in the curse of mankind by accelerating the development of medicine and extending human life expectancy. Their successful implementation led to the rapid development of pharmacy, providing more and more drugs against many pathogens. Nevertheless, the overuse of antibiotics has led to the emergence of resistance to these compounds, becoming one of the biggest health threats worldwide. As a result, antibiotic resistance has emerged faster than the advancement of antibiotics . The appearance of new drugs on the horizon to combat these pathogens is a short-lasting spark. Even if we seem to be on the losing end, there is still a chance to defeat an invisible enemy.

This hitch was researched by the team of scientists from the IPC PAS under the supervision of Prof. Jan Paczesny, who proposed new nanoformulations for use against widespread and challenging pathogens such as ESKAPE bacteria (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.) and other problematic yeast pathogens such as Candida auris or Cryptococcus neoformans. These microorganisms, treated with commercially available antibiotics, rapidly develop antibiotic resistance. Researchers chose ESKAPE as the target group since these pathogens lead to serious diseases, from sepsis to even cancer. How? This is where the story begins.

A few months ago, Paczesny’s team decided to try combining silver nanoparticles, which are known for their antimicrobial and antifungal properties, and tea extracts rich in polyphenols additionally possessing antioxidant properties. The concept was built to enhance broad-spectrum efficacy against pathogens using green hybrid silver nanoparticles (AgNPs), which are significantly more effective than all ingredients and even more effective than certain antibiotics. Why are these hybrid particles so special? In their work, three well-known tea varieties: black tea (B-Tea), green tea (G-Tea) and Pu-erh tea (R-Tea) were used as a capping agent, which acts as a stabilizer to protect the synthesized  particles from aggregation. In this way, the particles offer a high active surface area compared to other formulations. Additionally, such synthesis is eco-friendly for the use of natural ingredients during precipitation. The structures produced vary in shape and size from 34 to 65 nm, depending on the type of tea used during synthesis, and show different reactivity towards microorganisms.

Initially, silver nanoparticles produced in the presence of tea extracts (B-TeaNPs, G-TeaNPs and R-TeaNPs) were used to treat Gram-negative (E. coli) and Gram-positive (E. faecium) bacterial strains to test the effect on strains with different cell envelope morphologies. They looked at the interactions between the manufactured nanoparticles and the pathogens to determine efficacy, comparing the results with commercially available antibiotics. The ESKAPE pathogens were then tested according to a protocol for the most effective concentration and composition of the particles, revealing up to a 25% decrease in the number of bacterial cells in E. faecium and a 90% decrease in the case of E. cloacae. Interestingly, the green silver nanoparticles also showed antifungal activity, leading to an 80% decrease in the number of viable cells of C. auris and about a 90% decrease for C. neoformans.

The first author, Sada Raza claims “What is more, the size of nanoparticles is usually related to the cytotoxic effect of nanomaterials, with smaller particles being more cytotoxic. This should favor control AgNPs and R-TeaNPs over G-TeaNPs and B-TeaNPs in our experiments. This was not the case. In most experiments, C-AgNPs and R-TeaNPs showed the lowest antimicrobial efficacy. This is in line with other studies, which demonstrated that size is not a primary factor affecting the antimicrobial activity of AgNPs.

The antibacterial and antifungal properties of silver nanoparticles made with tea extracts are greater than those of silver nanoparticles alone due to their high content of phenolic compounds, isoflavonoids (especially catechins such as epigallocatechin (EGC) and epigallocatechin gallate (EGCG)). These combinations, using biologically active tea extracts and smaller amounts of silver nanoparticles, appear to be a potential way to combat a range of infections and even replace antibiotics in some applications.

“We established that silver nanoparticles synthesized with tea extracts have higher antibacterial properties than silver nanoparticles alone. Therefore, lower dosages of TeaNPs could be used (0.1 mg mL−1). We confirmed that in some cases, the synergistic effect of tea extracts and silver nanoparticles allowed for efficacy higher than that of antibiotics (ampicillin) when tested at the same concentrations (0.1 mg mL−1) and after a relatively short exposure time of three hours.” – remarks Mateusz Wdowiak, co-author of this work.

The researchers found that the antimicrobial hybrid nanoparticles resulted in a significant reduction in bacteria compared to antibiotics or compounds separately. Although not all bacteria were killed, this is a significant improvement that could aid the treatment of superbugs using much lower doses than other commercially available compounds. The amount of hybrid silver nanoparticles needed to overcome bacteria or fungal infections is extremely low, making them cost-effective, so the key to using them well is not only functionality, but also the low cost of application.

It is an approach that can also be adapted to combat other difficult-to-treat bacterial infections. The new nanoparticles developed by researchers at the IPC PAS could bring us one step closer to effectively killing deadly drug-resistant superbugs, providing an alternative to antibiotics against Gram-negative and Gram-positive bacteria. This study also shows how much more work there is to be done in this field. Compounds used separately were much less effective than the green hybrid.

In the future, the researchers’ main goal is to use nanoparticles in everyday life, starting with agricultural applications, replacing harmful compounds used in fields to overcome infestations in plants and bring us closer to organic farming. On a larger scale, the proposed material could also be used in biomedical applications, such as an additive for wound dressings to protect against Gram-negative and Gram-positive bacteria. They hope to use nanotechnology to develop more targeted treatments for drug-resistant superbugs.

Their work was published in Nanoscale Advances journal and was financed by the National Science Centre, Poland, within the SONATA BIS grant number 2017/26/E/ST4/00041 and Foundation for Polish Science from the European Regional Development Fund within the project POIR.04.04.00-00-14D6/18-00 ‘Hybrid sensor platforms for integrated photonic systems based on ceramic and polymer materials (HYPHa)’ (TEAM-NET program).

Here’s a link to and a citation for the paper,

Enhancing the antimicrobial activity of silver nanoparticles against ESKAPE bacteria and emerging fungal pathogens by using tea extracts by Sada Raza, Mateusz Wdowiak, Mateusz Grotek, Witold Adamkiewicz, Kostiantyn Nikiforow, Pumza Mente, and Jan Paczesny. Nanoscale Adv., 2023,5, 5786-5798 DOI: https://doi.org/10.1039/D3NA00220A

This paper is licensed under a Creative Commons Attribution 3.0 Unported Licence. “You can use material from this article in other publications without requesting further permissions from the RSC [Royal Society of Chemistry], provided that the correct acknowledgement is given.” Or, consider it an open access paper.

Finally, this is not a recommendation not is it an endorsement for the ingestion of colloidal silver.

Is there a risk of resistance to nanosilver?

Anyone who’s noticed how popular silver has become as an antibacterial, antifungal, or antiviral agent may have wondered if resistance might occur as its use becomes more common. I have two bits on the topic, one from Australia and the other from Canada.

Australia

Researchers in Australia don’t have a definitive statement on the issue but are suggesting more caution (from a March 31, 2017 news item on Nanowerk),

Researchers at the University of Technology Sydney [UTS] warn that the broad-spectrum antimicrobial effectiveness of silver is being put at risk by the widespread and inappropriate expansion of nanosilver use in medical and consumer goods.

As well as their use in medical items such as wound dressings and catheters, silver nanoparticles are becoming ubiquitous in everyday items, including toothbrushes and toothpaste, baby bottles and teats, bedding, clothing and household appliances, because of their antibacterial potency and the incorrect assumption that ordinary items should be kept “clean” of microbes.

Nanobiologist Dr Cindy Gunawan, from the ithree institute at UTS and lead researcher on the investigation, said alarm bells should be ringing at the commercialisation of nanosilver use because of a “real threat” that resistance to nanosilver will develop and spread through microorganisms in the human body and the environment.

A March 31 (?), 2017 University of Technology Sydney press release by Fiona McGill, which originated the news item, expands on the theme,

Dr Gunawan and ithree institute director Professor Liz Harry, in collaboration with researchers at UNSW [University of New South Wales] and abroad, investigated more than 140 commercially available medical devices, including wound dressings and tracheal and urinary catheters, and dietary supplements, which are promoted as immunity boosters and consumed by throat or nasal spray.

Their perspective article in the journal ACS Nano concluded that the use of nanosilver in these items could lead to prolonged exposure to bioactive silver in the human body. Such exposure creates the conditions for microbial resistance to develop.

E. coli bacteria. Photo: Flickr/NIAID

 

The use of silver as an antimicrobial agent dates back centuries. Its ability to destroy pathogens while seemingly having low toxicity on human cells has seen it widely employed, in treating burns or purifying water, for example. More recently, ultra-small (less than 10,000th of a millimetre) silver nanoparticles have been engineered for antimicrobial purposes.  Their commercial appeal lies in superior potency at lower concentrations than “bulk” silver.

“Nanosilver is a proven antimicrobial agent whose reliability is being jeopardised by the commercialisation of people’s fear of bacteria,” Dr Gunawan said.

“Our use of it needs to be far more judicious, in the same way we need to approach antibiotic usage. Nanosilver is a useful tool but we need to be careful, use it wisely and only when the benefit outweighs the risk.

“People need to be made aware of just how widely it is used, but more importantly they need to be made aware that the presence of nanosilver has been shown to cause antimicrobial resistance.”

What is also needed, Dr Gunawan said, is a targeted surveillance strategy to monitor for any occurrence of resistance.

Professor Harry said the findings were a significant contribution to addressing the global antimicrobial resistance crisis.

“This research emphasises the threat posed to our health and that of the environment by the inappropriate use of nanosilver as an antibacterial, particularly in ordinary household and consumer items,” she said.

Here’s a link to and a citation for the paper,

Widespread and Indiscriminate Nanosilver Use: Genuine Potential for Microbial Resistance by Cindy Gunawan, Christopher P. Marquis, Rose Amal, Georgios A. Sotiriou, Scott A. Rice⊥, and Elizabeth J. Harry. ACS Nano, Article ASAP DOI: 10.1021/acsnano.7b01166 Publication Date (Web): March 24, 2017

Copyright © 2017 American Chemical Society

This paper is behind a paywall.

Meanwhile, researchers at the University Calgary (Alberta, Canada) may have discovered what could cause resistance to silver.

Canada

This April 25, 2017 news release on EurekAlert is from the Experimental Biology Annual Meeting 2017,

Silver and other metals have been used to fight infections since ancient times. Today, researchers are using sophisticated techniques such as the gene-editing platform Crispr-Cas9 to take a closer look at precisely how silver poisons pathogenic microbes–and when it fails. The work is yielding new insights on how to create effective antimicrobials and avoid the pitfalls of antimicrobial resistance.

Joe Lemire, a postdoctoral fellow at the University of Calgary, will present his work in this area at the American Society for Biochemistry and Molecular Biology annual meeting during the Experimental Biology 2017 meeting, to be held April 22-26 in Chicago.

“Our overarching goal is to deliver the relevant scientific evidence that would aid policymakers in developing guidelines for when and how silver could be used in the clinic to combat and control infectious pathogens,” said Lemire. “With our enhanced mechanistic understanding of silver toxicity, we also aim to develop novel silver-based antimicrobial therapies, and potentially rejuvenate other antibiotic therapies that bacteria have come to resist, via silver-based co-treatment strategies.”

Lemire and his colleagues are using Crispr-Cas9 genome editing to screen for and delete genes that allow certain bacterial species to resist silver’s antimicrobial properties. [emphasis mine] Although previous methods allowed researchers to identify genes that confer antibiotic resistance or tolerance, Crispr-Cas9 is the first technology to allow researchers to cleanly delete these genes from the genome without leaving behind any biochemical markers or “scars.”

The team has discovered many biological pathways involved in silver toxicity and some surprising ways that bacteria avoid succumbing to silver poisoning, Lemire said. While silver is used to control bacteria in many clinical settings and has been incorporated into hundreds of commercial products, gaining a more complete understanding of silver’s antimicrobial properties is necessary if we are to make the most of this ancient remedy for years to come.

###

Joe Lemire will present this research at 12-2:30 p.m. Tuesday, April 25, [2017] in Hall F, McCormick Place Convention Center (poster B379 939.2) (abstract). Contact the media team for more information or to obtain a free press pass to attend the meeting.

About Experimental Biology 2017

Experimental Biology is an annual meeting comprised of more than 14,000 scientists and exhibitors from six host societies and multiple guest societies. With a mission to share the newest scientific concepts and research findings shaping clinical advances, the meeting offers an unparalleled opportunity for exchange among scientists from across the U.S. and the world who represent dozens of scientific areas, from laboratory to translational to clinical research. http://www.experimentalbiology.org #expbio

About the American Society for Biochemistry and Molecular Biology (ASBMB)

ASBMB is a nonprofit scientific and educational organization with more than 12,000 members worldwide. Founded in 1906 to advance the science of biochemistry and molecular biology, the society publishes three peer-reviewed journals, advocates for funding of basic research and education, supports science education at all levels, and promotes the diversity of individuals entering the scientific workforce. http://www.asbmb.org

Lemire’s co-authors for the work presented at the 2017 annual meeting are: Kate Chatfield-Reed (The University of Calgary), Lindsay Kalan (Perelman School of Medicine), Natalie Gugala (The University of Calgary), Connor Westersund (The University of Calgary), Henrik Almblad (The University of Calgary), Gordon Chua (The University of Calgary), Raymond Turner (The University of Calgary).

For anyone who wants to pursue this research a little further, the most recent paper I can find is this one from 2015,

Silver oxynitrate: An Unexplored Silver Compound with Antimicrobial and Antibiofilm Activity by Joe A. Lemire, Lindsay Kalan, Alexandru Bradu, and Raymond J. Turner. Antimicrobial Agents and Chemotherapy 05177-14, doi: 10.1128/AAC.05177-14 Accepted manuscript posted online 27 April 2015

This paper appears to be open access.

Carbohydrates could regulate the toxicity of silver nanoparticles

According to a Jan. 22, 2015 news item on Azonano, you can vary the toxic impact of silver nanoparticles on cells by coating them with carbohydrates,

The use of colloidal silver to treat illnesses has become more popular in recent years, but its ingestion, prohibited in countries like the US, can be harmful to health. Scientists from the Max Planck Institute in Germany have now confirmed that silver nanoparticles are significantly toxic when they penetrate cells, although the number of toxic radicals they generate can vary by coating them with carbohydrates.

A Jan. 21, 2015 Spanish Foundation for the Science and Technology (FECYT) news release on EurekAlert, which originated the news item, describes colloidal silver and its controversies and the research on limiting silver nanoparticle toxicity to cells,

Silver salts have been used externally for centuries for their antiseptic properties in the treatment of pains and as a surface disinfectant for materials. There are currently people who use silver nanoparticles to make homemade potions to combat infections and illnesses such as cancer and AIDS, although in some cases the only thing they achieve is argyria or blue-tinged skin.

Health authorities warn that there is no scientific evidence that supports the therapeutic efficiency of colloidal silver and in fact, in some countries like the US, its ingestion is prohibited. On the contrary, there are numerous studies which demonstrate the toxicity of silver nanoparticles on cells.

One of these studies has just been published in the ‘Journal of Nanobiotechnology‘ by an international team of researchers coordinated from the Max Planck Institute of Colloids and Interfaces (Germany). “We have observed that it is only when silver nanoparticles enter inside the cells that they produce serious harm, and that their toxicity is basically due to the oxidative stress they create,” explains the Spanish chemist Guillermo Orts-Gil, project co-ordinator, to SINC.

To carry out the study, the team has analysed how different carbohydrates act on the surface of silver nanoparticles (Ag-NP) of around 50 nanometres, which have been introduced into cultures of liver cells and tumour cells from the nervous system of mice. The results reveal that, for example, the toxic effects of the Ag-NP are much greater if they are covered with glucose instead of galactose or mannose.

‘Trojan horse’ mechanism

Although not all the details on the complex toxicological mechanisms are known, it is known that the nanoparticles use a ‘Trojan horse’ mechanism to trick the membrane’s defences and get inside the cell. “The new data shows how the different carbohydrate coatings regulate the way in which they do this, and this is hugely interesting for controlling their toxicity and designing future trials,” points out Orts-Gil.

The researcher highlights that there is a “clear correlation between the coating of the nanoparticles, the oxidative stress and toxicity, and thus, these results open up new perspectives on regulating the bioactivity of the Ag-NP through the use of carbohydrates”.

Silver nanoparticles are not only used to make homemade remedies; they are also increasingly used in drugs such as vaccines, as well as products such as clothes and cleaning cloths.

Here’s a link to and a citation for the paper,

Carbohydrate functionalization of silver nanoparticles modulates cytotoxicity and cellular uptake by David C Kennedy, Guillermo Orts-Gil, Chian-Hui Lai, Larissa Müller, Andrea Haase, Andreas Luch, and Peter H Seeberger. Journal of Nanobiotechnology 2014, 12:59 doi:10.1186/s12951-014-0059-z published 19 December 2014

This is an open access paper. One final observation, David Kennedy, the lead author, is associated with both the Max Planck Institute and the Canada National Research Council and, depending on which news release (SINC news site Jan. 20, 2015) you read, Guillermo Orts-Gil is identified as a Spanish chemist and coordinator for SINC (Science News and Information Service).

Surprising facts about silver nanoparticles from the University of Michigan

Dr. Andrew Maynard, Director of the University of Michigan’s Risk Science Center, has featured seven surprising facts about silver nanoparticles in his latest video in the Risk Bites series. Before getting to the video,here’s an introduction to the topic of silver nanoparticles from a Feb. 18, 2014 posting by Ishani Hewage on the University of Michigan’s Risk Sense blog (Note: A link has been removed),

Silver – known for its germ-killing capabilities – has been used for thousands of years. In recent times though, concerns have been raised over the potential health and environmental risks associated with one particular form of silver that has been used increasingly in a range of products: engineered silver nanoparticle. In this week’s Risk Bites, Andrew Maynard, director of the Risk Science Center, rounds-up seven aspects of silver nanoparticles that might help you weigh up their risks and benefits.

“Silver has long been used for its medicinal properties,” says Andrew. “People used to intentionally dose themselves with silver nanoparticles in the form a silver laced tonic as a cure-all.”

Nowadays, the use of silver nanoparticles is not just limited to the medical field. The military, athletes and manufactures are increasingly using them to develop smart new technologies that inhibit bacterial growth and enhance overall performance.  These microscopically small particles make it easier to get silver into products without compromising them …

Without more ado, here’s the video, ‘7 surprising facts about silver nanoparticles and health’:

Both the blog posting and this link will lead you to more information about silver nanoparticles.

Nanosilver history

According to Empa researchers, Bernd Nowack and Harald Krug, together with Murray Heights of the company HeiQ, silver at the nanoscale has a long history. From the Jan. 31,2011 news item on physorg.com,

Nanosilver is not a new discovery by nanotechnologists — it has been used in various products for over a hundred years, as is shown by a new Empa study. The antimicrobial effects of minute silver particles, which were then known as “colloidal silver,” were known from the earliest days of its use.

Their paper showing that nanosilver is not a 21st century discovery is being published in Environmental Science & Technology. From the news item,

Silver particles with diameters of seven to nine nm were mentioned as early as 1889. They were used in medications or as biocides to prevent the growth of bacteria on surfaces, for example in antibacterial water filters or in algaecides for swimming pools.

The nanoparticles were known as “colloidal silver” in those days, but what was meant was the same then as now – extremely small particles of silver. The only new aspect is the use today of the prefix “nano”. “However,” according to Bernd Nowack, “nano does not mean something new, and nor does it mean something that is harmful.” When “colloidal silver” became available on the market in large quantities in the 1920s it was the topic of numerous studies and subject to appropriate regulation by the authorities. [emphasis mine]

This suggests that there has been sufficient research on what we now call nano silver and its impact on the environment and on health. By contrast, the California Department of Toxic Substances Control (DTSC) had this to say in its recent call for information about analytical test methods for nanomaterials (from the Dec. 27, 2010 news item on Nanowerk),

Nano Silver

Nano silver is used increasingly in many consumer products. These include food contact materials (storage containers, cups, bowls and cutting boards), children’s toys and infant products, disinfectants, cosmetics, cleaning agents and machines, textiles, athletic apparel, dyes/paints, varnishes, polymers, and in medical products and applications. Given these diverse applications, nano silver is likely entering the environment. Several scientific studies describe potential adverse effects of nano silver on publicly owned treatment works (wastewater collection, treatment, and disposal systems).

Silver has been known historically as a potent antibacterial, antifungal, and antiviral agent. In recent years, silver is used as a biocide in solution, suspension, and in nano-particulate form. The strong antimicrobial activity is a major reason for the development of products that contain nano silver. Nano silver may also have applications in agricultural, vector, and urban pest control. However, little or no information about detecting and measuring the effect of nano silver in the environment exists. Recent published papers point out difficulties in quantifying the existence of nano particles in environmental and biological contexts, which presents challenges in estimating and assessing the hazards and risks of nano silver. [emphasis mine]

Nowack, one of the Empa researchers, provides evidence for his position in a commentary that was previously published in the journal Science (from the news item),

A commentary by Bernd Nowack in the scientific journal Science discusses the implications of the newest studies on nanosilver in sewage treatment plants. More than 90% remains bound in the sewage sludge in the form of silver sulfide, a substance which is extremely insoluble and orders of magnitude less poisonous than free silver ions. [emphasis mine] It apparently does not matter what the original form of the silver in the wastewater was, whether as metallic nanoparticles, as silver ions in solution or as precipitated insoluble silver salts.

“As far as the environmental effects are concerned, it seems that nanosilver in consumer goods is no different than other forms of silver and represents only a minor problem for eco-systems,” says Nowack. What is still to be clarified, however, is in what form the unbound silver is present in the treated water released from sewage works, and what happens to the silver sulfide in natural waters. Is this stable and unreactive or is it transformed into other forms of silver? [emphasis mine]

The two approaches are not directly contradictory but I do find the totality confusing. Which challenges about the hazards and risks of nano silver are the folks in California referring to? It seems they’re not familiar with the older research cited by Nowack or perhaps they know something Nowack and his colleagues do not. Meanwhile, Nowack’s Science commentary is reassuring but whoever wrote the news item was careful to point out that there is still some important work to be done before declaring nano silver to be a ‘safe’ substance.

I posted about the DTSC call for information, Feb. 7, 2011.