Tag Archives: Astrid Avellan

Nano-enabled precision delivery methods for agriculture

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A July 23, 2024 news item on Nanowerk provides an introduction to nanoparticles and their potential use in agriculture, Note: Links have been removed,

Nanoparticles could potentially help address agricultural and environmental sustainability issues on a global scale.

Those issues include rising food demand, increasing greenhouse gas emissions generated by agricultural activities, climbing costs of agrochemicals, reducing crop yields induced by climate change, and degrading soil quality. A class of nanoscale particles called “nanocarriers” could make crop agriculture more sustainable and resilient to climate change, according to a group of specialists that includes Kurt Ristroph, assistant professor of agricultural and biological engineering at Purdue University.

“Saying ‘nanoparticle’ means different things to different people,” Ristroph said. In nanodrug delivery, a nanoparticle usually ranges in size from 60 to 100 nanometers and is made of lipids or polymers. “In the environmental world, a nanoparticle usually means a 3- to 5-nanometer metal oxide colloid. Those are not the same thing, but people use ‘nanoparticle’ for both.”

Ristroph helped organize a 2022 interdisciplinary workshop on nanomethods for drug delivery in plants. Funded by the National Science Foundation and the U.S. Department of Agriculture, the workshop was attended by 30 participants from academia, industry and government laboratories.

Many of the workshop participants, including Ristroph, have now published their conclusions in Nature Nanotechnology (“Towards realizing nano-enabled precision delivery in plants”). Their article reviews the possibility nanocarriers could make crop agriculture more sustainable and resilient to climate change.

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A July 23, 2024 Purdue University news release (also on EurekAlert but published July 19, 2024) by Steve Koppes, which originated the news item, delves further into the topic of how agriculture could be made more sustainable with nanotechnology-enabled delivery methods, Note: Links have been removed,

“Nano-enabled precision delivery of active agents in plants will transform agriculture, but there are critical technical challenges that we must first overcome to realize the full range of its benefits,” said the article’s co-lead author Greg Lowry, the Walter J. Blenko, Sr. Professor of Civil and Environmental Engineering at Carnegie Mellon University. “I’m optimistic about the future of plant nanobiotechnology approaches and the beneficial impacts it will have on our ability to sustainably produce food.”

Plant cells and human cells have major physiological differences. Plant cells have a cell wall while human cells don’t, for example. But certain tools can be transferred from nanomedicine to plant applications.

“People have developed tools for studying the bio-corona formation around nanoparticles in an animal. We could think about bringing some of those tools to bear on nanoparticles in plants,” Ristroph said. 

When nanoparticles are injected into the bloodstream, many components of the blood stick onto the surface of the nanoparticles. The various proteins sticking to a nanoparticle’s surface make it look different.

The task then becomes figuring out what proteins or other molecules will stick to the surface and where the particle will go as a result. A nanoparticle designed to move toward a certain organ may have its destination altered by white blood cells that detect the particle’s surface proteins and send it to a different organ.

“Broadly speaking, that’s the idea of bio-corona formation and trafficking,” Ristroph said. “People in drug delivery nanomedicine have been thinking about and developing tools for studying that kind of thing. Some of those thoughts and some of those tools could be applied to plants.” 

Researchers already have developed many different architectures and chemistries for making nanoscale delivery vehicles for nanomedicine. “Some of the particle types are transferable,” he said. “You can take a nanoparticle that was optimized for movement in humans and put it in a plant, and you’ll probably find that it needs to be redesigned at least somewhat.”

Ristroph focuses on organic (carbon-based) nanocarriers that have a core-shell structure. The core contains a payload, while the shell forms a protective outer layer. Researchers have used many different types of nanomaterial in plants. The most popular materials are metallic nanoparticles because they are somewhat easier to make, handle and track where they go in a plant than organic nanoparticles.

“One of the first questions that you want to figure out is where these nanoparticles go in a plant,” Ristroph said. “It’s a lot easier to detect a metal inside of a plant that’s made of carbon than it is to detect a carbon-based nanoparticle in a plant that’s made of carbon.”

Last March, Ristroph and Purdue PhD student Luiza Stolte Bezerra Lisboa Oliveira published a critical review of the research literature on the Uptake and Translocation of Organic Nanodelivery Vehicles in Plants in Environmental Science and Technology.

“Not a lot is understood about transformations after these things go into a plant, how they’re getting metabolized,” Ristroph said. His team is interested in studying that, along with ways to help ensure that the nanoparticles are delivered to their proper destinations, and in corona formation. Coronas are biomolecular coatings that affect nanoparticle functions. 

The manufacturability of nanocarriers is another interest area that could be transferred to agriculture from nanomedicine.

“I care a lot about manufacturability and making sure that whatever techniques we’re using to make the nanoparticles are scalable and economically feasible,” Ristroph said.

The manufacturability of nanocarriers is another interest area that could be transferred to agriculture from nanomedicine.

“I care a lot about manufacturability and making sure that whatever techniques we’re using to make the nanoparticles are scalable and economically feasible,” Ristroph said.

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

Towards realizing nano-enabled precision delivery in plants by Gregory V. Lowry, Juan Pablo Giraldo, Nicole F. Steinmetz, Astrid Avellan, Gozde S. Demirer, Kurt D. Ristroph, Gerald J. Wang, Christine O. Hendren, Christopher A. Alabi, Adam Caparco, Washington da Silva, Ivonne González-Gamboa, Khara D. Grieger, Su-Ji Jeon, Mariya V. Khodakovskaya, Hagay Kohay, Vivek Kumar, Raja Muthuramalingam, Hanna Poffenbarger, Swadeshmukul Santra, Robert D. Tilton & Jason C. White. Nature Nanotechnology (2024) DOI: https://doi.org/10.1038/s41565-024-01667-5 Published: 06 June 2024

This paper is behind a paywall.

Gold nanoparticles not always always biologically stable

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It’s usually silver nanoparticles (with a nod to titanium dioxide as another problem nanoparticle) which star in scenarios regarding environmental concerns, especially with water. According to an Aug. 28, 2018 news item on Nanowerk, gold nanoparticles under certain conditions could also pose problems,

It turns out gold isn’t always the shining example of a biologically stable material that it’s assumed to be, according to environmental engineers at Duke’s Center for the Environmental Implications of NanoTechnology (CEINT).

In a nanoparticle form, the normally very stable, inert, noble metal actually gets dismantled by a microbe found on a Brazilian aquatic weed.

While the findings don’t provide dire warnings about any unknown toxic effects of gold, they do provide a warning to researchers on how it is used in certain experiments.

Here’s an image of one of the researchers standing in the test bed where they made their discovery (the caption will help to make sense of the reference to mesocosms in the news release, which follows,,

Mark Wiesner stands with rows of mesocosms—small, manmade structures containing different plants and microorganisms meant to represent a natural environment with experimental controls. Courtesy: Duke University

An August 28, 2018 Duke University news release (also on EurekAlert) by Ken Kingery, which originated the news item, provides more detail about gold nanoparticle instability,

CEINT researchers from Duke, Carnegie Mellon and the University of Kentucky were running an experiment to investigate how nanoparticles used as a commercial pesticide affect wetland environments in the presence of added nutrients. Although real-world habitats often receive doses of both pesticides and fertilizers, most studies on the environmental effects of such compounds only look at a single contaminant at a time.

For nine months, the researchers released low doses of nitrogen, phosphorus and copper hydroxide nanoparticles into wetland mesocosms [emphasis mine]– small, manmade structures containing different plants and microorganisms meant to represent a natural environment with experimental controls. The goal was to see where the nanoparticle pesticides ended up and how they affected the plant and animal life within the mesocosm.

The researchers also released low doses of gold nanoparticles as tracers, assuming the biologically inert nanoparticles would remain stable while migrating through the ecosystem. This would help the researchers interpret data on the pesticide particles that partly dissolve by showing them how a solid metal particle acts within the system.

But when the researchers went to analyze their results, they found that many of the gold nanoparticles had been oxidized and dissolved.

“We were taken completely by surprise,” said Mark Wiesner, the James B. Duke Professor and chair of civil and environmental engineering at Duke. “The nanoparticles that were supposed to be the most stable turned out to be the least stable of all.”

After further inspection, the researchers found the culprit — the microbiome growing on a common Brazilian waterweed called Egeria densa. Many bacteria secrete chemicals to essentially mine metallic nutrients from their surroundings. With their metabolism spiked by the experiment’s added nutrients, the bacteria living on the E. densa were catalyzing the reaction to dissolve the gold nanoparticles.

This process wouldn’t pose any threat [emphasis mine] to humans or other animal species in the wild. But when researchers design experiments with the assumption that their gold nanoparticles will remain intact, the process can confound the interpretation of their results.

“The assumption that gold is inert did not hold in these experiments,” said Wiesner. “This is a good lesson that underscores how real, complex environments, that include for example the bacteria growing on leaves, can give very different results from experiments run in a laboratory setting that do not include these complexities.”

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

Gold nanoparticle biodissolution by a freshwater macrophyte and its associated microbiome by Astrid Avellan, Marie Simonin, Eric McGivney, Nathan Bossa, Eleanor Spielman-Sun, Jennifer D. Rocca, Emily S. Bernhardt, Nicholas K. Geitner, Jason M. Unrine, Mark R. Wiesner, & Gregory V. Lowry. Nature Nanotechnology (2018) DOI: https://doi.org/10.1038/s41565-018-0231-y Published

This paper is behind a paywall.

Algae outbreaks (dead zones) in wetlands and waterways

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It’s been over seven years since I first started writing about Duke University’s  Center for the Environmental Implications of Nanotechnology and mesocosms (miniature ecosystems) and the impact that nanoparticles may have on plants and water (see August 11, 2011 posting). Since then, their focus has shifted from silver nanoparticles and their impact on plants, fish, bacteria, etc. to a more general examination of metallic nanoparticles and water. A June 25, 2018 news item on ScienceDaily announces some of their latest work,

The last 10 years have seen a surge in the use of tiny substances called nanomaterials in agrochemicals like pesticides and fungicides. The idea is to provide more disease protection and better yields for crops, while decreasing the amount of toxins sprayed on agricultural fields.

But when combined with nutrient runoff from fertilized cropland and manure-filled pastures, these “nanopesticides” could also mean more toxic algae outbreaks for nearby streams, lakes and wetlands, a new study finds.

A June 25, 2018 Duke University news release (also on EurekAlert) by Robin A. Smith, which originated the news item, provides more detail,

Too small to see with all but the most powerful microscopes, engineered nanomaterials are substances manufactured to be less than 100 nanometers in diameter, many times smaller than a hair’s breadth.

Their nano-scale gives them different chemical and physical properties from their bulk counterparts, including more surface area for reactions and interactions.

Those interactions could intensify harmful algal blooms in wetlands, according to experiments led by Marie Simonin, a postdoctoral associate with biology professor Emily Bernhardt at Duke University.

Carbon nanotubes and teeny tiny particles of silver, titanium dioxide and other metals are already added to hundreds of commercial products to make everything from faster, lighter electronics, self-cleaning fabrics, and smarter food packaging that can monitor food for spoilage. They are also used on farms for slow- or controlled-release plant fertilizers and pesticides and more targeted delivery, and because they are effective at lower doses than conventional products.

These and other applications have generated tremendous interest and investment in nanomaterials. However the potential risks to human health or the environment aren’t fully understood, Simonin said.

Most of the 260,000 to 309,000 metric tons of nanomaterials produced worldwide each year are eventually disposed in landfills, according to a previous study. But of the remainder, up to 80,400 metric tons per year are released into soils, and up to 29,200 metric tons end up in natural bodies of water.

“And these emerging contaminants don’t end up in water bodies alone,” Simonin said. “They probably co-occur with nutrient runoff. There are likely multiple stressors interacting.”

Algae outbreaks already plague polluted waters worldwide, said Steven Anderson, a research analyst in the Bernhardt Lab at Duke and one of the authors of the research.

Nitrogen and phosphorous pollution makes its way into wetlands and waterways in the form of agricultural runoff and untreated wastewater. The excessive nutrients cause algae to grow out of control, creating a thick mat of green scum or slime on the surface of the water that blocks sunlight from reaching other plants.

These nutrient-fueled “blooms” eventually reduce oxygen levels to the point where fish and other organisms can’t survive, creating dead zones in the water. Some algal blooms also release toxins that can make pets and people who swallow them sick.

To find out how the combined effects of nutrient runoff and nanoparticle contamination would affect this process, called eutrophication, the researchers set up 18 separate 250-liter tanks with sandy sloped bottoms to mimic small wetlands.

Each open-air tank was filled with water, soil and a variety of wetland plants and animals such as waterweed and mosquitofish.

Over the course of the nine-month experiment, some tanks got a weekly dose of algae-promoting nitrates and phosphates like those found in fertilizers, some tanks got nanoparticles — either copper or gold — and some tanks got both.

Along the way the researchers monitored water chemistry, plant and algae growth and metabolism, and nanoparticle accumulation in plant tissues.

“The results were surprising,” Simonin said. The nanoparticles had tiny effects individually, but when added together with nutrients, even low concentrations of gold and copper nanoparticles used in fungicides and other products turned the once-clear water a murky pea soup color, its surface covered with bright green smelly mats of floating algae.

Over the course of the experiment, big algal blooms were more than three times more frequent and more persistent in tanks where nanoparticles and nutrients were added together than where nutrients were added alone. The algae overgrowths also reduced dissolved oxygen in the water.

It’s not clear yet how nanoparticle exposure shifts the delicate balance between plants and algae as they compete for nutrients and other resources. But the results suggest that nanoparticles and other “metal-based synthetic chemicals may be playing an under-appreciated role in the global trends of increasing eutrophication,” the researchers said.

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

Engineered nanoparticles interact with nutrients to intensify eutrophication in a wetland ecosystem experiment by Marie Simonin, Benjamin P. Colman, Steven M. Anderson, Ryan S. King, Matthew T. Ruis, Astrid Avellan, Christina M. Bergemann, Brittany G. Perrotta, Nicholas K. Geitner, Mengchi Ho, Belen de la Barrera, Jason M. Unrine, Gregory V. Lowry, Curtis J. Richardson, Mark R. Wiesner, Emily S. Bernhardt. Ecological Applications, 2018; DOI: 10.1002/eap.1742 First published: 25 June 2018

This paper is behind a paywall.