Tag Archives: sarin

Spinach and plant nanobionics

Who knew that spinach leaves could be turned into electronic devices? The answer is: engineers at the Massachusetts Institute of Technology, according to an Oct. 31, 2016 news item on phys.org,

Spinach is no longer just a superfood: By embedding leaves with carbon nanotubes, MIT engineers have transformed spinach plants into sensors that can detect explosives and wirelessly relay that information to a handheld device similar to a smartphone.

This is one of the first demonstrations of engineering electronic systems into plants, an approach that the researchers call “plant nanobionics.”

An Oct. 31, 2016 MIT news release (also on EurekAlert), which originated the news item, describes the research further (Note: Links have been removed),

“The goal of plant nanobionics is to introduce nanoparticles into the plant to give it non-native functions,” says Michael Strano, the Carbon P. Dubbs Professor of Chemical Engineering at MIT and the leader of the research team.

In this case, the plants were designed to detect chemical compounds known as nitroaromatics, which are often used in landmines and other explosives. When one of these chemicals is present in the groundwater sampled naturally by the plant, carbon nanotubes embedded in the plant leaves emit a fluorescent signal that can be read with an infrared camera. The camera can be attached to a small computer similar to a smartphone, which then sends an email to the user.

“This is a novel demonstration of how we have overcome the plant/human communication barrier,” says Strano, who believes plant power could also be harnessed to warn of pollutants and environmental conditions such as drought.

Strano is the senior author of a paper describing the nanobionic plants in the Oct. 31 [2016] issue of Nature Materials. The paper’s lead authors are Min Hao Wong, an MIT graduate student who has started a company called Plantea to further develop this technology, and Juan Pablo Giraldo, a former MIT postdoc who is now an assistant professor at the University of California at Riverside.

Environmental monitoring

Two years ago, in the first demonstration of plant nanobionics, Strano and former MIT postdoc Juan Pablo Giraldo used nanoparticles to enhance plants’ photosynthesis ability and to turn them into sensors for nitric oxide, a pollutant produced by combustion.

Plants are ideally suited for monitoring the environment because they already take in a lot of information from their surroundings, Strano says.

“Plants are very good analytical chemists,” he says. “They have an extensive root network in the soil, are constantly sampling groundwater, and have a way to self-power the transport of that water up into the leaves.”

Strano’s lab has previously developed carbon nanotubes that can be used as sensors to detect a wide range of molecules, including hydrogen peroxide, the explosive TNT, and the nerve gas sarin. When the target molecule binds to a polymer wrapped around the nanotube, it alters the tube’s fluorescence.

In the new study, the researchers embedded sensors for nitroaromatic compounds into the leaves of spinach plants. Using a technique called vascular infusion, which involves applying a solution of nanoparticles to the underside of the leaf, they placed the sensors into a leaf layer known as the mesophyll, which is where most photosynthesis takes place.

They also embedded carbon nanotubes that emit a constant fluorescent signal that serves as a reference. This allows the researchers to compare the two fluorescent signals, making it easier to determine if the explosive sensor has detected anything. If there are any explosive molecules in the groundwater, it takes about 10 minutes for the plant to draw them up into the leaves, where they encounter the detector.

To read the signal, the researchers shine a laser onto the leaf, prompting the nanotubes in the leaf to emit near-infrared fluorescent light. This can be detected with a small infrared camera connected to a Raspberry Pi, a $35 credit-card-sized computer similar to the computer inside a smartphone. The signal could also be detected with a smartphone by removing the infrared filter that most camera phones have, the researchers say.

“This setup could be replaced by a cell phone and the right kind of camera,” Strano says. “It’s just the infrared filter that would stop you from using your cell phone.”

Using this setup, the researchers can pick up a signal from about 1 meter away from the plant, and they are now working on increasing that distance.

Michael McAlpine, an associate professor of mechanical engineering at the University of Minnesota, says this approach holds great potential for engineering not only sensors but many other kinds of bionic plants that might receive radio signals or change color.

“When you have manmade materials infiltrated into a living organism, you can have plants do things that plants don’t ordinarily do,” says McAlpine, who was not involved in the research. “Once you start to think of living organisms like plants as biomaterials that can be combined with electronic materials, this is all possible.”

“A wealth of information”

In the 2014 plant nanobionics study, Strano’s lab worked with a common laboratory plant known as Arabidopsis thaliana. However, the researchers wanted to use common spinach plants for the latest study, to demonstrate the versatility of this technique. “You can apply these techniques with any living plant,” Strano says.

So far, the researchers have also engineered spinach plants that can detect dopamine, which influences plant root growth, and they are now working on additional sensors, including some that track the chemicals plants use to convey information within their own tissues.

“Plants are very environmentally responsive,” Strano says. “They know that there is going to be a drought long before we do. They can detect small changes in the properties of soil and water potential. If we tap into those chemical signaling pathways, there is a wealth of information to access.”

These sensors could also help botanists learn more about the inner workings of plants, monitor plant health, and maximize the yield of rare compounds synthesized by plants such as the Madagascar periwinkle, which produces drugs used to treat cancer.

“These sensors give real-time information from the plant. It is almost like having the plant talk to us about the environment they are in,” Wong says. “In the case of precision agriculture, having such information can directly affect yield and margins.”

Once getting over the excitement, questions spring to mind. How could this be implemented? Is somebody  going to plant a field of spinach and then embed the leaves so they can detect landmines? How will anyone know where to plant the spinach? And on a different track, is this spinach edible? I suspect that if spinach can be successfully used as a sensor, it might not be for explosives but for pollution as the researchers suggest.

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

Nitroaromatic detection and infrared communication from wild-type plants using plant nanobionics by Min Hao Wong, Juan P. Giraldo, Seon-Yeong Kwak, Volodymyr B. Koman, Rosalie Sinclair, Tedrick Thomas Salim Lew, Gili Bisker, Pingwei Liu, & Michael S. Strano. Nature Materials (2016) doi:10.1038/nmat4771 Published online 31 October 2016

This paper is behind a paywall.

The last posting here which featured Strano’s research is in an Aug. 25, 2015 piece about carbon nanotubes and medical sensors.

Good chemicals, bad chemicals, everything is chemical: the cry of the lonely chemist

The UK’s Sense about Science folks (first mentioned here in an Aug. 9, 2012 posting) have launched (today, May 19, 2014) a campaign/book, Making Sense of Chemical Stories with an eye catching and thought provoking poster,

]downloaded from http://www.theguardian.com/science/blog/2014/may/19/manmade-natural-tasty-toxic-chemicals]

]downloaded from http://www.theguardian.com/science/blog/2014/may/19/manmade-natural-tasty-toxic-chemicals]

That’s right, pears contain formaldehyde. (BTW, A courgette in Canada and the US is commonly known as a zucchini.) The poster accompanies a book, Making Sense of Chemical Stories, and is referenced in a passionate Guardian science blogs May 19, 2014 posting by chemist, Mark Lorch (Note: Links have been removed),

Chemicals are bad, right? Otherwise why would so many purveyors of all things healthy proudly proclaim their products to be “chemical-free” and why would phrases such as “it’s chock full of chemicals” be so commonly used to imply something is unnatural and therefore inherently dangerous?

On one level these phrases are meaningless – after all, chemicals are everywhere, in everything. From the air that we breathe to the pills we pop, it’s all chemicals. Conversely, many would argue (the Advertising Standards Agency included) that we all know perfectly well what “chemical-free” means and those who rail against the absurdity of the phrase are just being pedantic.

… The point is that every time anti-chemical slogans are used people are being misinformed. The implication is always that the terms “chemical” and “poison” are interchangeable. This is a perception that permeates our subconscious to the extent that chemists themselves have been guilty of exactly the same lazy language.

As a result of this common usage of “chemicals” the whole subject has been tainted with unpleasant connotations. And while physics and biology have their celebrity scientists extolling the wonders of bosons, bugs and big bangs, chemists are left floundering in their wake or are left completely unrepresented in the mainstream media (where’s the Guardian’s chemistry blog?).

Lorch makes a good point when he notes that biologists and physicists get more attention. Frankly, I’d add mathematicians and, possibly, engineers to the list of those with better outreach programmes.

Here’s more about the book, Making Sense of Chemical Stories, from its webpage on the Sense about Science website (Note: Links have been removed),

The new edition of our public guide, Making Sense of Chemical Stories, was published by Sense About Science today with support from Royal Society of Chemistry.

People are still being misled by chemical myths. This needs to stop. We urge everyone to stop repeating misconceptions about chemicals. The presence of a chemical isn’t a reason for alarm. The effect of a chemical depends on the dose.

In lifestyle commentary, chemicals are presented as something that can be avoided, or eliminated using special socks, soaps or diets, and that cause only harm to health and damage to the environment.

The public guide flags up the more serious misconceptions that exist around chemicals and suggests straightforward ways for people to evaluate them.

People needn’t be scared by chemical stories. The reality boils down to six points:

You can’t lead a chemical-free life
Natural isn’t always good for you and man-made chemicals are not inherently dangerous
Synthetic chemicals are not causing many cancers and other diseases
‘Detox’ is a marketing myth
We need man-made chemicals
We are not just subjects in an unregulated, uncontrolled environment, there are checks in place

The poster was designed by Compound Interest (from the About page),

‘Compound Interest’ is a blog by a graduate chemist & teacher in the UK, creating graphics looking at the chemistry and chemical reactions we come across on a day-to-day basis.

I found a few tidbits in their May 19, 2014 post which describes a (new to me) condition and which highlights one of the other graphics Compound Interest has created for the Making Sense of Chemical Stories book/campaign,

The term ‘chemophobia’ has been used on social media amongst chemists with increasing regularity over the past year. Defined as ‘a fear of chemicals’, more specifically it refers to the growing tendency for the public to be suspicious and critical of the presence of any man-made (synthetic) chemicals in foods or products that they make use of.

I think this campaign/book is a good reminder to check our assumptions even for those of us (moi) who fancy ourselves as being thoughtful, critical readers. I got my first reminder (comeuppance) earlier this year in a Jan. 26, 2014 article by Melinda Wenner Mayer for Slate.com (Note: Links have been removed),

I want to start off by saying that this column is not about whether organic agriculture is worth supporting for its environmental benefits (I think it is) or whether we as a society should care about the chemicals found in our foods and household products (I think we should).

So let’s focus on that other major claim about organic food—that is it’s healthier, particularly for kids, because it contains fewer pesticides. First, let’s start with the fact that organic does not mean pesticide-free. As scientist and writer Christie Wilcox explains in several eye-opening blog posts over at Scientific American, organic farmers can and often do use pesticides. The difference is that conventional farmers are allowed to use synthetic pesticides, whereas organic farmers are (mostly) limited to “natural” ones, chosen primarily because they break down easily in the environment and are less likely to pollute land and water. (I say “mostly” because several synthetic chemicals are approved for use in organic farming, too.)

The assumption, of course, is that these natural pesticides are safer than the synthetic ones. Many of them are, but there are some notable exceptions. Rotenone, a pesticide allowed in organic farming, is far more toxic by weight than many synthetic pesticides. The U.S Environmental Protection Agency sets exposure limits for the amount of a chemical that individuals (including kids) can be exposed to per day without any adverse effects. For Rotenone, the EPA has determined that people should be exposed to no more than 0.004 milligrams per kilogram of body weight per day. Let’s compare this toxicity to that of some commonly used synthetic pesticides, like the organophosphate pesticide Malathion. The nonprofit Pesticide Action Network calls organophosphates “some of the most common and most toxic insecticides used today.” (Sarin, the nerve gas used in two Japanese terrorist attacks in the 1990s, is a potent organophosphate.) Yet the EPA has deemed it safe, based on animal tests, for humans to be exposed to 0.02 milligrams of Malathion per kilogram of body weight per day. This is five times more than the amount deemed safe for Rotenone. In other words, by weight, the natural pesticide Rotenone is considered five times more harmful than synthetic pesticide Malathion. [emphasis mine]


Following through logically, one wants to know what dosages of Rotenone are used in farming and how much of that is later found in one’s fruits and vegetables. Getting back to where this post began, ‘The Dose Makes the Poison’.

Textiles laced with carbon nanotubes for clothing that protects against poison gas

The last time I featured carbon nanotube-infused clothing was in a Nov. 4, 2013 post featuring a $20,000+ bulletproof business suit. It now seems that carbon nanotubes in clothing might also be used to protect the wearer against poison gases (from a May 7, 2014 news item on Nanowerk; Note:  A link has been removed),

Nerve agents are among the world’s most feared chemical weapons, but scientists at the National Institute of Standards and Technology (NIST) have demonstrated a way to engineer carbon nanotubes to dismantle the molecules of a major class of these chemicals (“Functionalized, carbon nanotube material for the catalytic degradation of organophosphate nerve agents”). In principle, they say, the nanotubes could be woven into clothing that destroys the nerve agents on contact before they reach the skin.

A May 6, 2014 US NIST news release, which originated the news item, describes the research in more detail,

The team’s experiments show that [carbon] nanotubes—special molecules that resemble cylinders formed of chicken wire—can be combined with a copper-based catalyst able to break apart a key chemical bond in the class of nerve agents that includes Sarin. A small amount of catalyst can break this bond in a large number of molecules, potentially rendering a nerve agent far less harmful. Because nanotubes further enhance the breakdown capability of the catalyst and can be woven into fabric easily, the NIST team members say the findings could help protect military personnel involved in cleanup operations.

Sarin—used in a 1995 Tokyo subway attack—is one of several deadly nerve agents of a group called organophosphates. Many are classified as weapons of mass destruction. While organophosphates are harmful if inhaled, they also are dangerous if absorbed through the skin, and can be even be re-released from clothing if not thoroughly decontaminated.

To protect themselves during research, the team did not work with actual nerve agents, but instead used a “mimic molecule” that contains a chemical bond identical to the one found in organophosphates. Breaking this bond splits the molecule into pieces that are far less dangerous.

The team developed a way to attach the catalyst molecule to the nanotubes and then tested the effectiveness of the tube-catalyst complex to break the bonds. To perform the test, the complex was deposited onto a small sheet of paper and put into a solution containing the mimic molecule. For comparison, the catalyst without nanotubes was tested simultaneously in a different solution. Then it was a simple matter of stirring and watching chemistry in action.

“The solution was initially transparent, almost like water,” says the team’s John Heddleston, “but as soon as we added the paper, the solution started to turn yellow as the breakdown product accumulated. Measuring this color change over time told us the amount and rate of catalysis. We began to see a noticeable difference within an hour, and the longer we left it, the more yellow it became.” The catalyst-nanotube complex far outperformed the catalyst alone.

Principal investigator Angela Hight Walker says that several questions will need to be addressed before catalytic nanotubes start showing up in clothing, such as whether it is better to add the catalyst to the nanotubes before or after they are woven into the fabric.

“We’d also like to find ways to make the catalytic reaction go faster, which is always better,” Hight Walker says. “But our research group has been focusing on the fundamental science of nanoparticles for years, so we are in a good position to answer these questions.”

It’s not clear to me if this technique of combining carbon nanotubes with copper for protection against poison gas will affect, adversely or otherwise, the bulletproofing properties associated with carbon nanotubes. In any event, here’s a link to and a citation for the paper from the NIST researchers,

Functionalized, carbon nanotube material for the catalytic degradation of organophosphate nerve agents by Mark M. Bailey, John M. Heddleston, Jeffrey Davis, Jessica L. Staymates, & Angela R. Hight Walker.  Nano Research March 2014, Volume 7, Issue 3, pp 390-398

This paper is behind a paywall.

“It is more important to have beauty in one’s equations than to have them fit experiment” and nano protection against nerve agents

Michael Berger’s Nov. 7, 2012 Nanowerk Spotlight article about nanoporous adsorbents and protection against toxic nerve agents features Dr. Piotr Kowalczyk, a Senior Research Fellow at the Nanochemistry Research Institute at Curtin University of Technology in Australia, quoting English theoretical physicist, Paul Dirac,

“Some of my colleagues asked me if I believe in our theoretical results” says Kowalczyk. “The great physicist Paul Dirac used to say: ‘This result is too beautiful to be false; it is more important to have beauty in one’s equations than to have them fit experiment’.”

“And I truly believe that our theoretical results have to be correct – within the assumed model of nanopores – because they are so simple and beautiful” he concludes.

Kowalczyk is discussing some of  his latest work on protection against toxic nerve agents (Note: I have removed a link),

In a paper published in the October 31, 2012 online edition of Physical Chemistry Chemical Physics (“Screening of Carbonaceous Nanoporous Materials for Capture of Nerve Agents”), an international team led by Kowalczyk and Alexander V Neimark, a professor at Rutgers University, together with scientists from the Physicochemistry of Carbon Materials Research Group at Nicolaus Copernicus University in Poland, is shedding new light on the selection of an optimal nanomaterial for capturing highly volatile nerve agents.

Berger’s article gives some context for this research,

Protection against nerve agents – such as tabun, sarin, soman, VX, and others – is a major terrorism concern of security experts. Nerve agents, which attack the nervous system of the human body, are clear and colorless or slightly colored liquids and may have no odor or a faint, sweetish smell. They evaporate at various rates and are denser than air. Current methods to detect nerve agents include surface acoustic wave sensors; conducting polymer arrays; vector machines; and the most simple: color change paper sensors. Most of these systems have have certain limitations including low sensitivity and slow response times.

You can find more detail about nanopores and toxic nerve agents in Berger’s article.