November 05, 2005

Not nano but Aids blood test lab on a chip

A new HIV test the size of a credit card promises to diagnose the disease in minutes rather than weeks, and could be deployed in sub-Saharan Africa as early as next year. In tests, it has detected the amount of CD4 cells in the blood in as little as 10 minutes. The CD4 count indicates the stage of HIV in a patient, and helps doctors determine the best treatment and how much of it to administer. The new test works by dropping a patient's blood sample onto a plastic biochip, which detects elements in the blood, says John McDevitt, the University of Texas chemist who helped develop the technology. The card is then inserted into a toaster-size analyzer, which determines the CD4 cell count.

"We etch silicon chips in ways that are very similar to what are used to make Pentium and other computer chips," McDevitt says. "But instead of transistors, we create little test tubes -- these little test tubes are miniature reaction vessels that hold artificial taste buds."

Austin biotech startup LabNow has licensed the technology and is developing it into a system that could be used to diagnose HIV quickly and cheaply. And HIV is likely only the beginning for McDevitt's technology. It can be reprogrammed, he says, to serve numerous application areas by simply changing the system's molecular-level code. He is developing systems for heart disease, cancer and infectious diseases, as well as bioterrorism-screening tools and environmental-monitoring aids.

"It is a lot like putting new software into a computer each time you want to work a new application area," he says. "You need not purchase a new computer; you simply use the existing infrastructure."

McDevitt is working with the Department of Defense to develop detectors that can "sniff" the air for anthrax spores and other bioterrorism agents.

Nanotechnology based drugstore cancer tests

Recent advances in nanotech devices, point to new ways for developing inexpensive and effective cancer-screening devices.

One of the most promising of these new detectors is being built by Charles Lieber, a chemist at Harvard University. In an article this month in Nature Biotechnology, he announced a highly-sensitive detector that can simultaneously find multiple cancer markers.

According to Lieber, the device, which uses nanowires to detect telltale cancer proteins, could lead to inexpensive and highly-accurate tests -- people could even buy them in a local drugstore and perform the testing themselves. "We can take a very small amount of blood and with a very simple filtration step get an answer within five minutes," Lieber says, adding that the device has "a sensitivity a thousand times better" than in a lab.

Lieber’s prototype builds on what University of California, Berkeley chemistry professor Paul Alivisatos has called "a breakthrough series of experiments." To detect specific cancer markers, Lieber attached a monoclonal antibody specific for a certain type of protein to nanowires each about as narrow as a virus. Some earlier experiments showed that changes in the conductivity of nanowires occurs when proteins bind to an antibody. The more proteins that bind, the more the conductivity changes, revealing the concentration of the protein.

Another benefit of the nanowire system is its flexibility. As new cancer markers are found, Lieber says, they could easily be incorporated into the device: "We could immediately take this new species and add that to our existing sensor."

Lieber’s method of measuring multiple biomarkers simultaneously has the potential to "diagnose the vast majority of people very accurately."

In fact, according to Lieber, the "biggest advantage" of the nanowire detectors is that they could detect "10 or 100 things in parallel" without adding cost to the test.

In talks with Lieber, oncologists have also suggested another application. Because the device gives results in real time, it could be used to monitor the effectiveness of cancer treatments. Right now, Lieber explains, the amount of drug a patient depends on his or her weight. Yet each person responds differently to different treatments. With such a nano-device, though, one could "fine-tune the dosage to make treatment much more effective."

Lieber and his research group have already tested the ability of the device to detect cancer markers in human blood -- a challenging task, since the target protein has a concentration around 100 billion times lower than the background proteins in serum. And they have also addressed some engineering issues with maintaining reliability.

How soon a cancer-detecting nano-device will be available depends, to a large extent, on developing the technology for mass production, according to Lieber, rather than with overcoming basic science obstacles.

So with molecular manufacturing: such tests will definitely be real time and for every person all the time. Enabling constant and detailed health monitoring.

November 03, 2005

Faster fluid flow in carbon nanotubes

Membranes composed of manmade carbon nanotubes permit a fluid flow nearly 10,000 to 100,000 times faster than conventional fluid flow theory would predict because of the nanotubes' nearly friction-free surface, researchers at the University of Kentucky report in the Nov. 3 issue of Nature.

In their study, Mainak Majumder, Nitin Chopra and Bruce J. Hinds of UK's Chemical and Materials Engineering Department, and Rodney Andrews of UK's Center for Applied Energy Research found the flow dynamics of carbon nanotube (CNT) membranes with pores measuring 7 nanometers in diameter permit a fluid flow exceeded the flows predicted by conventional hydrodynamic predictions.

In their study "Enhanced Flow in Carbon Nanotubes," the researchers note an "aligned CNT membrane has fast transit approaching the extraordinary speed of biological channels. The membrane fabrication is scalable to large areas, allowing for industrially useful chemical separations.

"(E)ach side of the membrane can be independently functionalized. These advantages make the aligned CNT membrane a promising large-area platform to mimic protein channels for sophisticated chemical separations, trans-dermal drug delivery and selective chemical sensing," the researchers say.

November 01, 2005

Systematic analysis of temperature/pressure variation on cadmium selenium growth

What are called nanosaws, nanocombs and nanowires can be grown (self-assembled) from cadmium selenium. A study of the temperature and pressure conditions were systematically varied and the impact on the growth was determined.

The nanosaws and combs seem to be 2 microns wide.
I think the nanowires are a few nanometers thick.

While this is still at a larger scale than molecular manufacturing systems...achieving greater control of 3 dimensional structures is an improvement towards top down control.

they use a vapor-liquid-solid process.

the work was done at georgia tech.


October 31, 2005

Quantum computing: Avenue to room tempurature quantum info processing

Researchers at UC Santa Barbara have potentially opened up a new avenue toward room temperature quantum information processing. By demonstrating the ability to image and control single isolated electron spins in diamond, they unexpectedly discovered a new channel for transferring information to other surrounding spins -- an initial step towards spin-based information processing.

A team of researchers including graduate students Ryan Epstein and Felix Mendoza, and their advisor, David Awschalom, a professor of physics, were intrigued by the long-lived electronic spins of so-called nitrogen-vacancy impurities in the diamond crystal -- defects that only consist of two atomic sites. So, about two years ago, they embarked on developing a sensitive room temperature microscope that would allow them to study individual defects through their light emission.

This microscope, with its unique precision in the control of the magnetic field alignment, has allowed them to not only detect individual nitrogen-vacancy defects, but also small numbers of previously invisible 'dark' spins from nitrogen defects in their vicinity. These spins are called 'dark' because they cannot be directly detected by light emission and yet, it appears that they may prove extremely useful.

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