Novel Biosensor

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Carbon nanotube coated with platinum.

FAYETTEVILLE, Ark. — Researchers at the University of Arkansas have fabricated and tested a novel biosensor that detects glucose close to real time and with much greater sensitivity than other comparable, biocompatible sensors.

“To manage and control diabetes, patients must continuously monitor blood-glucose levels,” said Jining Xie, research assistant professor of electrical engineering. “So they understand the importance of a device that provides rapid response.”

The UA sensor, designed and developed by Xie and researchers in the department of electrical engineering, is made of multi-walled carbon nanotubes, which are coated with platinum nanoparticles between 1 and 5 nanometers in diameter. The researchers tested sensors with and without the platinum nanoparticles, and discovered that the carbon nanotubes with platinum exhibited a substantially higher sensitivity than those without platinum.

“At this stage of the research, we believe that the improved electro-chemical performance is due to the platinum nanoparticles,” Xie said. “We are currently investigating mechanisms to optimize this performance.”

Conducted in the university’s Nanomaterials Research Laboratory, the research was performed by Xie and Vijay Varadan, Distinguished Professor of electrical engineering. Shouyan Wang, post-doctoral fellow, and Lavanya Aryasomayajula, graduate assistant, also contributed to the project.

Tests revealed that for every square centimeter tested, a typical platinum-coated nanotube-based glucose sensor had a sensitivity of around 50 micro Amps per mili mole. Micro Amps refer to levels of electrical current. In this case, mili moles are units that describe molecular concentrations of glucose. The sensitivity value of the researchers’ device is among the best results reported for glucose biosensors.

Xie said their goal is to further increase the sensitivity value of 52.7 micro Amps per mili mole. Equally important, the UA biosensor has a response time of 15 to 30 seconds, which renders it capable of providing glucose screenings close to real time.

The researchers attributed the improved sensibility to various factors related to the application of platinum to the multi-walled nanotubes. Most importantly, the platinum nanoparticles created a larger electro-active surface area on the carbon nanotubes. Xie said the larger surface area allowed the carbon nanotubes to act as a glucose-oxidase reservoir, which helped create uniform immobilization and high loading of glucose oxides for sensing. In addition, the platinum nanoparticles enhanced electron transfer and facilitated better physical and chemical bonding between glucose oxides and carbon nanotubes.

The researchers’ findings were published in the February issue of Nanotechnology, an Institute of Physics Publishing journal. An online version of the article is available at http://www.iop.org/EJ/abstract/-ffissn=0957-4484/-ff30=all/0957-4484/18/6/065503 .

Varadan said there has been no previous research on the use of platinum nanoparticles coated on carbon nanotubes to develop a biosensor capable of detecting blood-glucose concentrations. The research is sponsored by NeoPharma Industries, which hopes to develop a commercial product by the end of 2007.

In addition to his position as distinguished professor, Varadan holds the College of Engineering’s Twenty First Century Endowed Chair in Nano- and Bio-Technologies and Medicine and the college’s Chair in Microelectronics and High Density Electronics. He is also director of the university’s High Density Electronics Center and is a professor of neurosurgery in the College of Medicine at the University of Arkansas for Medical Sciences.