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Researchers print, tune graphene sensors to monitor food freshness, safety

Posted By Graphene Council, Friday, June 26, 2020
Researchers dipped their new, printed sensors into tuna broth and watched the readings. It turned out the sensors – printed with high-resolution aerosol jet printers on a flexible polymer film and tuned to test for histamine, an allergen and indicator of spoiled fish and meat – can detect histamine down to 3.41 parts per million.

The U.S. Food and Drug Administration has set histamine guidelines of 50 parts per million in fish, making the sensors more than sensitive enough to track food freshness and safety.

Making the sensor technology possible is graphene, a supermaterial that’s a carbon honeycomb just an atom thick and known for its strength, electrical conductivity, flexibility and biocompatibility. Making graphene practical on a disposable food-safety sensor is a low-cost, aerosol-jet-printing technology that’s precise enough to create the high-resolution electrodes necessary for electrochemical sensors to detect small molecules such as histamine.

“This fine resolution is important,” said Jonathan Claussen, an associate professor of mechanical engineering at Iowa State University and one of the leaders of the research project. “The closer we can print these electrode fingers, in general, the higher the sensitivity of these biosensors.”

Claussen and the other project leaders – Carmen Gomes, an associate professor of mechanical engineering at Iowa State; and Mark Hersam, the Walter P. Murphy Professor of Materials Science and Engineering at Northwestern University in Evanston, Illinois – have recently reported their sensor discovery in a paper published online by the journal 2D Materials. (See sidebar for a full listing of co-authors.)

The National Science Foundation, the U.S. Department of Agriculture, the Air Force Research Laboratory and the National Institute of Standards and Technology have supported the project.

The paper describes how graphene electrodes were aerosol jet printed on a flexible polymer and then converted to histamine sensors by chemically binding histamine antibodies to the graphene. The antibodies specifically bind histamine molecules.

The histamine blocks electron transfer and increases electrical resistance, Gomes said. That change in resistance can be measured and recorded by the sensor.

“This histamine sensor is not only for fish,” Gomes said. “Bacteria in food produce histamine. So it can be a good indicator of the shelf life of food.”

The researchers believe the concept will work to detect other kinds of molecules, too.

“Beyond the histamine case study presented here, the (aerosol jet printing) and functionalization process can likely be generalized to a diverse range of sensing applications including environmental toxin detection, foodborne pathogen detection, wearable health monitoring, and health diagnostics,” they wrote in their research paper.

For example, by switching the antibodies bonded to the printed sensors, they could detect salmonella bacteria, or cancers or animal diseases such as avian influenza, the researchers wrote.

Claussen, Hersam and other collaborators (see sidebar) have demonstrated broader application of the technology by modifying the aerosol-jet-printed sensors to detect cytokines, or markers of inflammation. The sensors, as reported in a recent paper published by ACS Applied Materials & Interfaces, can monitor immune system function in cattle and detect deadly and contagious paratuberculosis at early stages.

Claussen, who has been working with printed graphene for years, said the sensors have another characteristic that makes them very useful: They don’t cost a lot of money and can be scaled up for mass production.

“Any food sensor has to be really cheap,” Gomes said. “You have to test a lot of food samples and you can’t add a lot of cost.”

Claussen and Gomes know something about the food industry and how it tests for food safety. Claussen is chief scientific officer and Gomes is chief research officer for NanoSpy Inc., a startup company based in the Iowa State University Research Park that sells biosensors to food processing companies.

They said the company is in the process of licensing this new histamine and cytokine sensor technology.

It, after all, is what they’re looking for in a commercial sensor. “This,” Claussen said, “is a cheap, scalable, biosensor platform.”

Tags:  3D Printing  Biosensor  Carmen Gomes  Graphene  Iowa State University  Jonathan Claussen  Mark Hersam  Northwestern University  Sensors 

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Aerosol-printed graphene unveiled as low cost, faster food toxin sensor

Posted By Graphene Council, Wednesday, June 10, 2020
Researchers in the USA have developed a graphene-based electrochemical sensor capable of detecting histamines (allergens) and toxins in food much faster than standard laboratory tests.

The team used aerosol-jet printing to create the sensor. The ability to change the pattern geometry on demand through software control allowed rapid prototyping and efficient optimization of the sensor layout.

Commenting on the findings, which are published today in the IOP Publishing journal 2D Materials, senior author Professor Mark Hersam, from Northwestern University, said: "We developed an aerosol-jet printable graphene ink to enable efficient exploration of different device designs, which was critical to optimizing the sensor response."

As an additive manufacturing method that only deposits material where it is needed and therefore minimizes waste, aerosol-jet-printed sensors are low-cost, straightforward to make, and portable. This could potentially enable their use in places where continuous on-site monitoring of food samples is needed to determine and maintain the quality of products, as well as other applications.

Senior author Professor Carmen Gomes, from Iowa State University, said: "Aerosol-jet printing was fundamental to the development of this sensor. Carbon nanomaterials like graphene have unique material properties such as high electrical conductivity, surface area, and biocompatibility that can significantly improve the performance of electrochemical sensors.

"But, since in-field electrochemical sensors are typically disposable, they need materials that are amenable to low-cost, high-throughput, and scalable manufacturing. Aerosol-jet printing gave us this."

The team created high-resolution interdigitated electrodes (IDEs) on flexible substrates, which they converted into histamine sensors by covalently linking monoclonal antibodies to oxygen moieties created on the graphene surface by a CO2 thermal annealing process.

They then tested the sensors in both a buffering solution (PBS) and fish broth, to see how effective they were at detecting histamines.

Co-author Kshama Parate, from Iowa State University, said: "We found the graphene biosensor could detect histamine in PBS and fish broth over toxicologically-relevant ranges of 6.25 to 100 parts per million (ppm) and 6.25 to 200 ppm, respectively, with similar detection limits of 2.52 ppm and 3.41 ppm, respectively. These sensor results are significant, as histamine levels over 50 ppm in fish can cause adverse health effects including severe allergic reactions - for example, scombroid food poisoning.

"Notably, the sensors also showed a quick response time of 33 minutes, without the need for pre-labelling and pre-treatment of the fish sample. This is a good deal faster than the equivalent laboratory tests."

The researchers also found the biosensor's sensitivity was not significantly affected by the non-specific adsorption of large protein molecules commonly found in food samples and used as blocking agents.

Senior author Dr Jonathan Claussen, from Iowa State University, said: "This type of biosensor could be used in food processing facilities, import and export ports, and supermarkets where continuous on-site monitoring of food samples is needed. This on-site testing will eliminate the need to send food samples for laboratory testing, which requires additional handling steps, increases time and cost to histamine analysis, and consequently increases the risk of foodborne illnesses and food wastage.

"It could also likely be used in other biosensing applications where rapid monitoring of target molecules is needed, as the sample pre-treatment is eliminated using the developed immunosensing protocol. Apart from sensing small allergen molecules such as histamine, it could be used to detect various targets such as cells and protein biomarkers. By switching the antibody immobilized on the sensor platform to one that is specific towards the detection of suitable biological target species, the sensor can further cater to specific applications. Examples include food pathogens (Salmonella spp.), fatal human diseases (cancer, HIV) or animal or plant diseases (avian influenza, Citrus tristeza)."

Tags:  Biosensor  Carmen Gomes  Graphene  Iowa State University  Jonathan Claussen  Kshama Parate  Mark Hersam  Northwestern University  Sensors 

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New Nanosensor Detects Microscopic Contaminants in Water

Posted By Graphene Council, Tuesday, November 19, 2019
Good things come in small packages. Sadly, so do bad things. That’s where Iowa State University’s (ISU) Department of Mechanical Engineering comes in.

Led by Dr. Jonathan Claussen, ISU researchers have used nanotechnology to develop a sensor that can detect organophosphates at levels 40 times smaller than the U.S. Environmental Protection Agency (EPA) recommendations. Organophosphates are certain classes of insecticides used on crops throughout the world to kill insects.

“It is important that we quantify insecticide runoff and drift so that we can characterize its long-term effects and find ways to minimize those effects.”

USDA’s National Institute of Food and Agriculture is supporting this research through a pair of Agriculture and Food Research Initiative grants totaling $573,000.

Claussen used the grants to develop Salt Impregnated Inkjet Maskless Lithography (SIIML), which uses an inkjet printer to create inexpensive graphene circuits with high electrical conductivity. He adds salts to the ink, which is later washed away to leave microsized divots or craters in the surface. This textured printed graphene surface is able to bind with pesticide-sensing enzymes to increase sensitivity during pesticide biosensing.

These sensors can detect contaminants as small as 0.6 nanometers (nM) in length, well below the EPA standard of 24 nM and Canada’s standard of 170 nM.

Claussen compares the graphene sensors to glucose test strips that diabetics use to monitor their blood. Both the glucose test strip and the graphene pesticide test strip monitor selected compounds through electrochemical means.

This technology can be adapted for field use to detect a wide range of samples, including pathogens in food and fertilizer in soil and water. The technology is so inexpensive, Claussen said, that sensors could be used across an entire farm field to monitor pesticides and fertilizers so that farmers could limit their use and apply only what is truly needed.

In addition to improving the environmental ecosystem, Claussen said that SIIML could improve food safety, from farm to fork.

“The sensors could be designed to detect pathogens in food processing facilities to prevent food contamination,” he said. “The sensors could also be used to monitor cattle diseases, for example, before physical symptoms are present. This technique could really be a game changer for a variety of in-field sensing applications that require low-cost but highly sensitive biosensors.”
 

Tags:  biosensors  Graphene  Iowa State University  Jonathan Claussen  Sensors 

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