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Remove 80 percent of dye pollutants from wastewater with wood nanocrystals

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They’re usually known as cellulose nanocrystals (CNCs) but the term wood nanocrystals works too. From a March 23, 2023 news item on Nanowerk,

Researchers at Chalmers University of Technology, Sweden, have developed a new method that can easily purify contaminated water using a cellulose-based material. This discovery could have implications for countries with poor water treatment technologies and combat the widespread problem of toxic dye discharge from the textile industry.

Clean water is a prerequisite for our health and living environment, but far from a given for everyone. According to the World Health Organization, WHO, there are currently over two billion people living with limited or no access to clean water.

This global challenge is at the centre of a research group at Chalmers University of Technology, which has developed a method to easily remove pollutants from water. The group, led by Gunnar Westman, Associate Professor of Organic Chemistry focuses on new uses for cellulose and wood-based products and is part of the Wallenberg Wood Science Center.

The researchers have built up solid knowledge about cellulose nanocrystals* – and this is where the key to water purification lies. These tiny nanoparticles have an outstanding adsorption capacity, which the researchers have now found a way to utilise.

“We have taken a unique holistic approach to these cellulose nanocrystals, examining their properties and potential applications. We have now created a biobased material, a form of cellulose powder with excellent purification properties that we can adapt and modify depending on the types of pollutants to be removed,” says Gunnar Westman.

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Caption: Researchers at Chalmers University of Technology, Sweden, have developed a new biobased material, a form of powder based on cellulose nanocrystals to purify water from pollutants, including textile dyes. When the polluted water passes through the filter with cellulose powder, the pollutants are absorbed, and the sunlight entering the treatment system causes them to break down quickly and efficiently. Laboratory tests have shown that at least 80 percent of the dye pollutants are removed with the new method and material, and the researchers see good opportunities to further increase the degree of purification. Credit: Chalmers University of Technology, Sweden | David Ljungberg

A March 23, 2023 Chalmers University of Technology press release (also on EurekAlert), which originated the news item, describes the water treatment in more detail including how it will be tested in field conditions,

Absorbs and breaks down toxins
In a study recently published in the scientific journal Industrial & Engineering Chemistry Research, the researchers show how toxic dyes can be filtered out of wastewater using the method and material developed by the group. The research was conducted in collaboration with the Malaviya National Institute of Technology Jaipur in India, where dye pollutants in textile industry wastewater are a widespread problem.

The treatment requires neither pressure nor heat and uses sunlight to catalyse the process. Gunnar Westman likens the method to pouring raspberry juice into a glass with grains of rice, which soak up the juice to make the water transparent again. 

“Imagine a simple purification system, like a portable box connected to the sewage pipe. As the contaminated water passes through the cellulose powder filter, the pollutants are absorbed and the sunlight entering the treatment system causes them to break down quickly and efficiently. It is a cost-effective and simple system to set up and use, and we see that it could be of great benefit in countries that currently have poor or non-existent water treatment,” he says. 

The method will be tested in India
India is one of the developing countries in Asia with extensive textile production, where large amounts of dyes are released into lakes, rivers and streams every year. The consequences for humans and the environment are serious. Water contaminant contains dyes and heavy metals and can cause skin damage with direct contact and increase the risk of cancer and organ damage when they enter into the food chain. Additionally, nature is affected in several ways, including the impairment of photosynthesis and plant growth.

Conducting field studies in India is an important next step, and the Chalmers researchers are now supporting their Indian colleagues in their efforts to get some of the country’s small-scale industries to test the method in reality. So far, laboratory tests with industrial water have shown that more than 80 percent of the dye pollutants are removed with the new method, and Gunnar Westman sees good opportunities to further increase the degree of purification.

“Going from discharging completely untreated water to removing 80 percent of the pollutants is a huge improvement, and means significantly less destruction of nature and harm to humans. In addition, by optimising the pH and treatment time, we see an opportunity to further improve the process so that we can produce both irrigation and drinking water. It would be fantastic if we can help these industries to get a water treatment system that works, so that people in the surrounding area can use the water without risking their health,” he says.

Can be used against other types of pollutants
Gunnar Westman also sees great opportunities to use cellulose nanocrystals for the treatment of other water pollutants than dyes. In a previous study, the research group has shown that pollutants of toxic hexavalent chromium, which is common in wastewater from mining, leather and metal industries, could be successfully removed with a similar type of cellulose-based material. The group is also exploring how the research area can contribute to the purification of antibiotic residues.

“There is great potential to find good water purification opportunities with this material, and in addition to the basic knowledge we have built up at Chalmers, an important key to success is the collective expertise available at the Wallenberg Wood Science Center,” he says.

More about the scientific article
Read the full article in Industrial & Engineering Chemistry Research: Cellulose nanocrystals derived from microcrystalline cellulose for selective removal of Janus Green Azo Dye. The authors of the article are Gunnar Westman and Amit Kumar Sonker of Chalmers University of Technology, and Ruchi Aggarwal, Anjali Kumari Garg, Deepika Saini, and Sumit Kumar Sonkar of Malaviya National Institute of Technology Jaipur in India. The research is funded by the Wallenberg Wood Science Center, WWSC and the Indian group research is funded by Science and Engineering Research Board under Department of Science and Technology (DST-SERB) Government of India. 

*Nanocrystals 
Nanocrystals are nanoparticles in crystal form that are extremely small: a nanoparticle is between 1 and 100 nanometres in at least one dimension, i.e. along one axis. (one nanometre = one billionth of a metre).

Wallenberg Wood Science Center
•    The Wallenberg Wood Science Center, WWSC, is a research centre that aims to develop new sustainable biobased materials using raw materials from the forest. The WWSC is a multidisciplinary collaboration between Chalmers University of Technology, KTH Royal Institute of Technology and Linköping University, and is based on a donation from the Knut and Alice Wallenberg Foundation.
•    The centre involves about 95 researchers and faculty members and 50 doctoral students. Eight research groups from Chalmers are part of the centre.

About dye pollutants and access to clean water
•    Over two billion people in the world live with limited or no access to clean water. It is estimated that over 3.5 million people die each year from lack of access to clean water and proper sanitation.
•    The global textile industry, which is concentrated in Asia, contributes to widespread water pollution. Production often takes place in low-wage countries, where much of the technology is antiquated and environmental legislation and oversight may be lacking.
•    Emissions contribute to eutrophication and toxic effects in water and soil. There are examples in China and India where groundwater has been contaminated by dye and processing chemicals.
•    Producing one kilogram of new textiles requires between 7,000 and 29,000 litres of water, and between 1.5 and 6.9 kg of chemicals.
•    In 2021, around 327 thousand tonnes of dyes and pigments were produced in India. A large proportion of the country’s dye pollutants is discharged untreated.

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Sources 

Swedish Environmental Protection Agency: https://www.naturvardsverket.se/amnesomraden/textil/dagens-textila-floden-ar-en-global-miljoutmaning/ 

WHO: https://www.who.int/news-room/fact-sheets/detail/drinking-water

A critical review on the treatment of dye-containing wastewater: Ecotoxicological and health concerns of textile dyes and possible remediation approaches for environmental safety. Ecotoxicology and Environmental Safety, February 2022

https://www.sciencedirect.com/science/article/pii/S0147651321012720

Effects of textile dyes on health and the environment and bioremediation potential of living organisms. Biotechnology Research and Innovation, July–December 2019

https://www.sciencedirect.com/science/article/pii/S2452072119300413

Swedish Chemicals Agency: https://www.kemi.se/kemiska-amnen-och-material/nanomaterial

Statista: https://www.statista.com/statistics/726947/india-dyes-and-pigments-production-volume/#:~:text=In%20fiscal%20year%202021%2C%20the,around%20327%20thousand%20metric%20tons

Even though there’s a link to the research in the press release, here’s my link to and citation for the paper, which specifies a particular dye suggesting this is not a universal treatment,

Cellulose Nanocrystals Derived from Microcrystalline Cellulose for Selective Removal of Janus Green Azo Dye by Ruchi Aggarwal, Anjali Kumari Garg, Deepika Saini, Sumit Kumar Sonkar, Amit Kumar Sonker, and Gunnar Westman. Ind. Eng. Chem. Res. 2023, 62, 1, 649–659 DOI: https://doi.org/10.1021/acs.iecr.2c03365 Publication Date: December 26, 2022 Copyright © 2022 American Chemical Society

This paper is behind a paywall.

Nanocellulose wound dressing reveals early signs of infection?

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The wound dressing changes colour from yellow to blue when the wound is infected. Credit: Olov Planthaber Courtesy: Linköping University

An April 18, 2023 news item on Nanowerk announces a new nanocellulose-based wound dressing that can monitor infections, Note: A link has been removed,

A nanocellulose wound dressing that can reveal early signs of infection without interfering with the healing process has been developed by researchers at Linköping University, Sweden. Their study, published in Materials Today Bio (“Nanocellulose composite wound dressings for real-time pH wound monitoring”), is one further step on the road to a new type of wound care.

The wound dressing is made of tight mesh nanocellulose, preventing bacteria and other microbes from getting in. At the same time, the material lets gases and liquid through. Credit: Olov Planthaber Courtesy: Linköping University

An April 19, 2023 Linköping University press release (also on EurekAlert but published April 18, 2023), which originated the news item, provides context for the research and more technical details about it,

The skin is the largest organ of the human body. A wound disrupts the normal function of the skin and can take a long time to heal, be very painful for the patient and may, in a worst case scenario, lead to death if not treated correctly. Also, hard-to-heal wounds pose a great burden on society, representing about half of all costs in out-patient care.

In traditional wound care, dressings are changed regularly, about every two days. To check whether the wound is infected, care staff have to lift the dressing and make an assessment based on appearance and tests. This is a painful procedure that disturbs wound healing as the scab breaks repeatedly. The risk of infection also increases every time the wound is exposed.

Researchers at Linköping University, in collaboration with colleagues from Örebro and Luleå Universities [Örebro University and Luleå University of Technology in Sweden], have now developed a wound dressing made of nanocellulose that can reveal early signs of infection without interfering with the healing process.

“Being able to see instantly whether a wound has become infected, without having to lift the dressing, opens up for a new type of wound care that can lead to more efficient care and improve life for patients with hard-to-heal wounds. It can also reduce unnecessary use of antibiotics,” says Daniel Aili, professor in the Division of Biophysics and Bioengineering at Linköping University.

The dressing is made of tight mesh nanocellulose, preventing bacteria and other microbes from getting in. At the same time, the material lets gases and liquid through, something that is important to wound healing. The idea is that once applied, the dressing will stay on during the entire healing process. Should the wound become infected, the dressing will show a colour shift.

Non-infected wounds have a pH value of about 5.5. When an infection occurs, the wound becomes increasingly basic and may have a pH value of 8, or even higher. This is because bacteria in the wound change their surroundings to fit their optimal growth environment. An elevated pH value in the wound can be detected long before any pus, soreness or redness, which are the most common signs of infection.

To make the wound dressing show the elevated pH value, the researchers used bromthymol blue, BTB, a dye that changes colour from yellow to blue when the pH value exceeds 7. For BTB to be used in the dressing without being compromised, it was loaded onto a silica material with pores only a few nanometres in size. The silica material could then be combined with the dressing material without compromising the nanocellulose. The result is a wound dressing that turns blue when there is an infection.

Wound infections are often treated with antibiotics that spread throughout the body. But if the infection is detected at an early stage, local treatment of the wound may suffice. This is why Daniel Aili and his colleagues at Örebro University are also developing anti-microbial substances based on so-called lipopeptides [emphasis mine] that kill off all types of bacteria.

“The use of antibiotics makes infections increasingly problematic, as multi-resistant bacteria are becoming more common. If we can combine the anti-microbial substance with the dressing, we minimise the risk of infection and reduce the overuse of antibiotics,” says Daniel Aili.

Daniel Aili says that the new wound dressing and the anti-microbial substance are part of developing a new type of wound treatment in out-patient care. But as all products to be used in medical care settings have to pass rigorous and expensive testing, he thinks that it will be five to ten years before it will be available there.

Both studies are part of the HEALiX research project financed by the Swedish Foundation for Strategic Research with the objective of developing a new type of wound treatment. Funding was also received from, among others, the Swedish Government Strategic Research Area in Materials Science on Functional Materials (AFM) at Linköping University, Vinnova, the Knut and Alice Wallenberg Foundation and the Swedish Research Council.

For the curious, the HEALiX research project is here.

As noted in the press release, there are two studies. First, here’s a link and citation for the work on antimicrobial lipopeptides,

Development of novel broad-spectrum antimicrobial lipopeptides derived from plantaricin NC8 β by Emanuel Wiman, Elisa Zattarin, Daniel Aili, Torbjörn Bengtsson, Robert Selegård & Hazem Khalaf. Scientific Reports volume 13, Article number: 4104 (2023) DOI: https://doi.org/10.1038/s41598-023-31185-8
Published: 13 March 2023

This paper is open access.

Now, here’s a link to and a citation for the paper about nanocellulose-based wound dressings,

Nanocellulose composite wound dressings for real-time pH wound monitoring by Olof Eskilson, Elisa Zattarin, Linn Berglund, Kristiina Oksman, Kristina Hanna, Jonathan Rakar, Petter Sivlér, Mårten Skog, Ivana Rinklake, Rozalin Shamasha, Zeljana Sotra, Annika Starkenberg, Magnus Odén, Emanuel Wiman, Hazem Khalaf, Torbjörn Bengtsson, Johan P.E. Junker, Robert Selegård, Emma M. Björk, Daniel Aili. Materials Today Bio, Volume 19, April 2023, 100574 DOI: 10.1016/j.mtbio.2023.100574 Published online on 6 February 2023

This paper too is open access.

Artificial organic neuron mimics characteristics of biological nerve cells

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There’s a possibility that in the future, artificial neurons could be used for medical treatment according to a January 12, 2023 news item on phys.org,

Researchers at Linköping University (LiU), Sweden, have created an artificial organic neuron that closely mimics the characteristics of biological nerve cells. This artificial neuron can stimulate natural nerves, making it a promising technology for various medical treatments in the future.

Work to develop increasingly functional artificial nerve cells continues at the Laboratory for Organic Electronics, LOE. In 2022, a team of scientists led by associate professor Simone Fabiano demonstrated how an artificial organic neuron could be integrated into a living carnivorous plant [emphasis mine] to control the opening and closing of its maw. This synthetic nerve cell met two of the 20 characteristics that differentiate it from a biological nerve cell.

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I wasn’t expecting a carnivorous plant, living or otherwise. Sadly, they don’t seem to have been able to include it in this image although the ‘green mitts’ are evocative,

Caption: Artificial neurons created by the researchers at Linköping University. Credit: Thor Balkhed

A January 13, 2023 Linköping University (LiU) press release by Mikael Sönne (also on EurkeAlert but published January 12, 2023), which originated the news item, delves further into the work,

In their latest study, published in the journal Nature Materials, the same researchers at LiU have developed a new artificial nerve cell called “conductance-based organic electrochemical neuron” or c-OECN, which closely mimics 15 out of the 20 neural features that characterise biological nerve cells, making its functioning much more similar to natural nerve cells.

“One of the key challenges in creating artificial neurons that effectively mimic real biological neurons is the ability to incorporate ion modulation. Traditional artificial neurons made of silicon can emulate many neural features but cannot communicate through ions. In contrast, c-OECNs use ions to demonstrate several key features of real biological neurons”, says Simone Fabiano, principal investigator of the Organic Nanoelectronics group at LOE.

In 2018, this research group at Linköping University was one of the first to develop organic electrochemical transistors based on n-type conducting polymers, which are materials that can conduct negative charges. This made it possible to build printable complementary organic electrochemical circuits. Since then, the group has been working to optimise these transistors so that they can be printed in a printing press on a thin plastic foil. As a result, it is now possible to print thousands of transistors on a flexible substrate and use them to develop artificial nerve cells.

In the newly developed artificial neuron, ions are used to control the flow of electronic current through an n-type conducting polymer, leading to spikes in the device’s voltage. This process is similar to that which occurs in biological nerve cells. The unique material in the artificial nerve cell also allows the current to be increased and decreased in an almost perfect bell-shaped curve that resembles the activation and inactivation of sodium ion channels found in biology.

“Several other polymers show this behaviour, but only rigid polymers are resilient to disorder, enabling stable device operation”, says Simone Fabiano

In experiments carried out in collaboration with Karolinska Institute (KI), the new c-OECN neurons were connected to the vagus nerve of mice. The results show that the artificial neuron could stimulate the mice’s nerves, causing a 4.5% change in their heart rate.

The fact that the artificial neuron can stimulate the vagus nerve itself could, in the long run, pave the way for essential applications in various forms of medical treatment. In general, organic semiconductors have the advantage of being biocompatible, soft, and malleable, while the vagus nerve plays a key role, for example, in the body’s immune system and metabolism.

The next step for the researchers will be to reduce the energy consumption of the artificial neurons, which is still much higher than that of human nerve cells. Much work remains to be done to replicate nature artificially.

“There is much we still don’t fully understand about the human brain and nerve cells. In fact, we don’t know how the nerve cell makes use of many of these 15 demonstrated features. Mimicking the nerve cells can enable us to understand the brain better and build circuits capable of performing intelligent tasks. We’ve got a long road ahead, but this study is a good start,” says Padinhare Cholakkal Harikesh, postdoc and main author of the scientific paper.

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

Ion-tunable antiambipolarity in mixed ion–electron conducting polymers enables biorealistic organic electrochemical neurons by Padinhare Cholakkal Harikesh, Chi-Yuan Yang, Han-Yan Wu, Silan Zhang, Mary J. Donahue, April S. Caravaca, Jun-Da Huang, Peder S. Olofsson, Magnus Berggren, Deyu Tu & Simone Fabiano. Nature Materials volume 22, pages 242–248 (2023) DOI: https://doi.org/10.1038/s41563-022-01450-8 Published online: 12 January 2023 Issue Date: February 2023

This paper is open access.