Nanosilver might not be gold for water

Julia Cummins represented Australia at World Water Week and will participate in the Stockholm Junior Water Prize, following her research into nanosilver. Inside Water spoke to her about her achievements, what it means, and her plans for the future.

Julia Cummins represented Australia at World Water Week and will participate in the Stockholm Junior Water Prize, following her research into nanosilver. Inside Water spoke to her about her achievements, what they meant, and her plans for the future.

Science has always been a part of Julia Cummins’ life. She was always involved in extracurricular science activities from her primary school years, including building model volcanoes. These preliminary science experiments inspired her to get involved in more aspects of the scientific community.

As a Presbyterian Ladies College (PLC) Sydney student, Cummins was welcomed into its biannual Science Summit. Interacting with guest speakers encouraged her to consider utilising science and communication as tools for innovation.

“I just love learning about how things work and how it fits together in the world,” said Cummins.

How nanosilver fits into Cummins’ interests

Nanosilver is a unique selection for a young woman, but Cummins explained why she investigated it.

“I live near the water, so every couple of days, I would see kilograms of rubbish dumped on the shore. Plastic, needles, and all sorts of things are in these loads of awful rubbish. It got me thinking about the things we cannot see,” said Cummins.

Cummins referenced microplastics as being a key focus. She had asked herself about the other problematic things we cannot see in the water. This is where she began her research and started with nanoparticles.

“Nanoparticles are an area of science that we do not know much about. From there, I found out about nanosilver,” said Cummins.

In her presentation, Cummins explained that nanosilver is nanoparticles of silver 1-100 nm in size. It is the most used nanoparticle in consumer goods such as cosmetics, textiles, and disinfectants. Nanosilver is used in these products for its antimicrobial properties, which kill bacteria, such as those in clothes, to prevent odour. Due to its nanosized particles, nanosilver poses potential ecotoxicity to ecosystems. To mitigate this damage, Cummins believes a threshold should be developed that cannot be exceeded regarding nanosilver being used in products.

The risks of nanosilver

Cummins explained that nanosilver is everywhere in our modern lives. She cited its use in toothpaste, bandages, photographic films, children’s socks and internal catheters. Its antimicrobial properties are of particular interest to manufacturers.

“All these products release nanosilver into the environment when thrown away or washed. The nanosilver is not effectively removed in wastewater treatment plants, so it enters the environment. In that regard, it enters our bodies. The really concerning thing is that we don’t know much about how nanoparticles or nanosilver specifically affect the human body,” Cummins said.

Compared to bulk forms of silver, nanosilver particles have a larger surface area to volume ratio, accelerating the release of silver ions, the primary mode of nanosilver toxicity. This makes nanosilver more toxic. Silver ions penetrate cell membranes, leading to cellular compartment leakage and cellular death.

Cummins spoke about the opportunity to meet Professor Wojtek Chrzanowski at the University of Sydney Nano Institute. Professor Chrzanowski described to Cummins how when nanoparticles enter a cell, they damage DNA, lipids, and proteins, interfering with intracellular biological functions. This makes nanosilver a powerful microbial agent, a key reason its use is so widespread.

“While nanosilver is a powerful antimicrobial agent, its overuse outside medical applications makes it less and less effective where it is needed most,” said Professor Chrzanowski. “Declining antimicrobial activity is because bacteria develop a resistance to silver, similarly to antibiotic resistance. In addition, nanosilver incorporated into clothing impacts the skin microbiome. While there is no evidence that this impacts human health negatively, any disturbance to the microbiome can lead to negative immunological responses.”

“Importantly, when silver enters the environment, it has detrimental effects on the function of microorganisms. As evidenced by Miss Cummins and others, it alters the microbiological balance. Consequently, it influences the overall ‘health’ of holobiont – a biomolecular network composed of the host plus its associated microbes. Therefore, it is essential to understand nanosilver’s effect on environmental, micro- and organisms and human health. We must develop strategies to mitigate the negative impacts of nanosilver, which is at the centre of Miss Cummins’ research project. Miss Cummins’ project aligns with the United Nations Sustainable Development Goals by focusing on good health, clean water, and life on land and below water. Her work also contributes to broader research programs that promote a healthier and sustainable future for us all,” said Professor Chrzanowski.

As the commercial applications of nanosilver increase, the level of nanosilver released into the environment also increases. When laundered, fabrics release on average 425 μg of nanosilver per kilogram of fabric into wastewater which, once treated, is released into the environment.

Nanosilver cannot be cleared from the wastewater plants easily

Cummins said there is no specific process targeted at removing nanoparticles from water.

“While screening procedures exist in wastewater treatment plants, they tend to focus on factors like pH level. At the moment, there are no specific methods or mechanisms for dealing with nanoparticles,” said Cummins.

Some research in Europe and the United States has indicated some potential positive outcomes by using a super sulphide to remove nanoparticles in wastewater treatment plants. This is preliminary research, and more work needs to be done.

“These studies also showed that the nanoparticles were still entering the environment. The reality is that we still do not know enough about nanosilver. There is not enough urgency behind their study of wastewater treatment plants. We need to be figuring out targeted ways of removing nanosilver from the water before it enters the environment and waterways,” said Cummins.

Studying nanosilver with tiny aquatic creatures

In her experiment, Cummins used Daphnia Magna, a small planktonic crustacean that could be considered a tiny water flea. In her presentation, Cummins argued that Daphnia Magna is an established bioindicator of ecotoxicology, central to the food webs of freshwater lentic habitats. They are excellent model organisms with transparent bodies and hearts that are easy to see under the microscope. As nanosilver is toxic to aquatic organisms, it follows that nanosilver is also toxic to humans. The potential for nanoparticles to cross the blood-brain barrier poses a threat to human health.

Cummins found a clear difference between the effect of different concentrations of nanosilver on the population numbers (survival) and heart rates (metabolic integrity) of Daphnia Magna. As the concentration of nanosilver increased, the population and their heart rates of Daphnia Magna decreased. She determined that the minimum concentration of toxic nanosilver for Daphnia Magna is between 0.26-0.50 mg/L of nanosilver.

“While I could establish a range of toxicity for Daphnia Magna, there is a difference between animal and human studies,” she said. “I also focused on water organisms because they are the ones who are currently most affected by nanosilver. However, comparing the value in Daphnia Magna and nano silver, we could look at other contaminants to get a rough idea of relative toxicity. The current problem is that we know so little about nanosilver and nanoparticles that we do not understand how these nanoparticles cross the blood-brain barrier. That’s completely different from how they interact with aquatic organisms.”

Silver has been used for decades for its antimicrobial properties in macro and nano forms. There is nothing that society can substitute for nanosilver. Cummins identifies this as a problem as nanosilver is used to offset antibiotic resistance.

“Nanoparticles represent a broad area of research. In the future, we may use them safely or develop something that could have similar effects to nanosilver. However, the problem we are facing now is that pathogens adapt to the materials we use to kill them. To coin a phrase, there is no silver bullet right now,” said Cummins.

The future for Cummins

Cummins has started her first year of a medical degree at Western Sydney University. She acknowledged that while her research did not have a direct link to her academic pursuits, she does want to study the impact of nanoparticles on the body.

“People consume water all the time, so there will almost certainly be many crossovers between water, nanoparticles and medicine,” she said. “I will remain interested in nanosilver. There is a condition where your skin colour can change if you consume too much silver. We know that silver does impact the body, so the opportunity to examine bioaccumulation of nanosilver, micro plastics or other nanoparticles would be fascinating.”

She was excited about being in Stockholm to learn about all the different problems identified by the competitors. Cummins has already connected with several competitors. She realised that the Stockholm Junior Water Prize is an opportunity to interact and collaborate with young scientists from around the world in a field that she is genuinely passionate about.

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