Tag Archives: biosensor

Nanocanaries don’t die

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It’s upsetting to think about the canaries in the mines singing to their heart’s content only to topple over and die when toxic gases make their presence felt during the mining process. The alternative, of course, is to sacrifice miners. Thankfully, choosing the lesser of two evils will no longer be necessary (actually, I don’t they’ve used canaries in quite a while) as scientists work on sensors that can detect any number of things not just toxic gases in the mines. The University of Massachusetts at Lowell is the latest to announce work on sensors (from the Nov. 15, 2012 news item on Nanowerk),

To detect the toxicity of engineered nanomaterials, such as carbon nanotubes, on living cells, electrical engineering Assoc. Prof. Joel Therrien — along with biology Prof. Susan Braunhut, chemistry Prof. Kenneth Marx and work environment Asst. Prof. Dhimiter Bello — has developed a “nanocanary,” the modern-day, high-tech equivalent of the canary in a coal mine that warned miners of dangerous buildups of toxic gases in the mine shaft.
The nanocanary is an ultrasensitive biosensor designed to continuously monitor tiny physiological changes in the live cells contained within it.

The Nov. 14, 2012 news release by Edwin L. Aguirre, which originated the news item, mentions a recent podcast by one of the researchers (Joel Therrien),

In a recent podcast produced by the Museum of Science in Boston, Therrien talked about the importance of studying how nano-sized particles affect human health and the environment as well as in the safe development of commercial nano products.

“Our biosensor has a wide range of applications, from testing for toxicity in nanomanufacturing to drug development and customized cancer therapeutics,” notes Therrien.

“In testing the toxicity of carbon nanotubes, for example, since the sensor can directly detect adverse effects on living cells, we are able to identify the threshold concentration at which carbon nanotubes lead to the cells’ death,” he explains. “The sensor can also be used to test the response of normal and cancerous cells to drug therapies. In the future, this technology may help guide oncologists in selecting the most appropriate drug for a cancer patient. We also see the potential for this to partially replace animals in testing drugs and other products.”

Therrien’s 16 min. podcast can be heard here.

I’ll cry if I want to—measuring glucose levels in your tears

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If you look closely, you’ll see a tiny sensor beneath the eye. Inside there are nano-size biosensors which can detect your glucose levels in your tears (or sweat, if prefer). For a diabetic, checking glucose levels has to be done daily by pricking the skin to draw blood.

With this nano-sized biosensor, diabetes patients can measure their glucose levels with the fluid from the tears of their eyes. (copyright Fraunhofer IMS)

A Sept. 4, 2012 news item on Nanowerk provides more details,

Pricking a finger everyday is just part of everyday life for many diabetes patients. A non-invasive measurement approach could release them from the constant pain of pin pricks. The linchpin is a biosensor engineered by Fraunhofer researchers: A tiny chip combines measurement and digital analysis – and can be radioed to a mobile device.

The Sept. 3, 2012 news release from Fraunhofer, an application-oriented research organization, provides more detail about the technology and its advantages,

The principle of measurement involves an electrochemical reaction that is activated with the aid of an enzyme. Glucose oxidase converts glucose into hydrogen peroxide (H2O2) and other chemicals whose concentration can be measured with a potentiostat. This measurement is used for calculating the glucose level. The special feature of this biosensor: the chip, measuring just 0.5 x 2.0 millimeters, can fit more than just the nanopotentiostat itself. Indeed, Fraunhofer researchers have attached the entire diagnostic system to it. “It even has an integrated analog digital converter that converts the electrochemical signals into digital data,” explains Tom Zimmermann, business unit manager at IMS. The biosensor transmits the data via a wireless interface, for example to a mobile receiver. Thus, the patient can keep a steady eye on his or her glucose level. “In the past, you used to need a circuit board the size of a half-sheet of paper,” says Zimmermann. “And you also had to have a driver. But even these things are no longer necessary with our new sensor.”
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The minimal size is not the only thing that provides a substantial advantage over previous biosensors of this type. In addition, the sensor consumes substantially less power. Earlier systems required about 500 microamperes at five volts; now, it is less than 100 microamperes. That increases the durability of the system – allowing the patient to wear the sensor for weeks, or even months. The use of a passive system makes this durability possible. The sensor is able to send and receive data packages, but it can also be supplied with power through radio frequency.

The glucose sensor was engineered by the researchers at Noviosens, a Dutch medical technology firm. Since it can be manufactured so cost-effectively, it is best suited for mass production.

This looks pretty exciting. Of course, I’d still like to see find out the level of accuracy for this new way to measure glucose as compared to the current technique (no mention of clinical trials). Also, how do you affix the sensor to your skin? Is there a glue? Can you accidentally wash, wipe,  or knock your sensor off? Or, is it difficult to remove? For people who do choose to wear it beneath an eye, how does makeup affect the sensor?

Assuming that the accuracy is the same or better and that any pitfalls due to wearing a sensor have been addressed, I imagine the next hurdle will be scaling up production.

As for the ‘I’ll cry if I want to’ part of the headline for this piece, I have shamelessly borrowed [corrected 2:27 pm PDT, Sept. 5, 2012] from Lesley Gore’s 1963 hit, ‘I’s my party and I’ll cry if want to’. I’ve never loved the lyrics (for the most part) but the chorus has a haunting quality (as far as I’m concerned). Here is Lesley Gore,

Blood, tears, and urine for use in diagnostic tools

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Frankly, I’d rather just spit into a cup or onto a slide for diagnostic tests than having to supply urine or have my blood drawn. I don’t think that day has arrived yet but scientists at Purdue University (Indiana, US) have made a breakthrough. From the Aug. 23, 2012 news item on ScienceDaily,

Researchers have created a new type of biosensor that can detect minute concentrations of glucose in saliva, tears and urine and might be manufactured at low cost because it does not require many processing steps to produce.

“It’s an inherently non-invasive way to estimate glucose content in the body,” said Jonathan Claussen, a former Purdue University doctoral student and now a research scientist at the U.S. Naval Research Laboratory. “Because it can detect glucose in the saliva and tears, it’s a platform that might eventually help to eliminate or reduce the frequency of using pinpricks for diabetes testing. We are proving its functionality.”

Claussen and Purdue doctoral student Anurag Kumar led the project, working with Timothy Fisher, a Purdue professor of mechanical engineering; D. Marshall Porterfield, a professor of agricultural and biological engineering; and other researchers at the university’s Birck Nanotechnology Center.

The originating Aug. 20, 2012 Purdue University news release by Emil Venere provides details as to how this biosensor works,

The sensor has three main parts: layers of nanosheets resembling tiny rose petals made of a material called graphene, which is a single-atom-thick film of carbon; platinum nanoparticles; and the enzyme glucose oxidase.

Each petal contains a few layers of stacked graphene. The edges of the petals have dangling, incomplete chemical bonds, defects where platinum nanoparticles can attach. Electrodes are formed by combining the nanosheet petals and platinum nanoparticles. Then the glucose oxidase attaches to the platinum nanoparticles. The enzyme converts glucose to peroxide, which generates a signal on the electrode.

“Typically, when you want to make a nanostructured biosensor you have to use a lot of processing steps before you reach the final biosensor product,” Kumar said. “That involves lithography, chemical processing, etching and other steps. The good thing about these petals is that they can be grown on just about any surface, and we don’t need to use any of these steps, so it could be ideal for commercialization.”

In addition to diabetes testing, the technology might be used for sensing a variety of chemical compounds to test for other medical conditions.

Here’s a representation of the ‘rose petal’ nanosheets,

These color-enhanced scanning electron microscope images show nanosheets resembling tiny rose petals. The nanosheets are key components of a new type of biosensor that can detect minute concentrations of glucose in saliva, tears and urine. The technology might eventually help to eliminate or reduce the frequency of using pinpricks for diabetes testing. (Purdue University photo/Jeff Goecker)
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My most recent piece, prior to this, about less invasive diagnostic tests was this May 8, 2012 posting on a handheld diagnostic device that tests your breath for disease.