Peptides, Carbon Nanotubes Team Up


TEMPE, AZ - Motorola Labs and Arizona State University (ASU) have co-developed a coating process that allows chemical-detecting peptides to alert single-walled carbon nanotubes (SWNTs) to the presence of heavy-metal ions at the parts-per-trillion level.

These treated SWNTs in low-power field effect transistors (FETs) will be integrated into future devices to produce a network that communicates minute environmental changes. Peptides are the biological building blocks of proteins. According to Vida Ilderem, vice president of Tempe’s Embedded Systems Research Labs, attaching them to carbon nanotubes without affecting the electrical properties of the SWNT summarizes the primary challenge facing this form of research. “We determined a mode of attach that had a negligible effect on the SWNT’s resistance,” she added. Without disrupting a SWNT’s electrical signal transmissions, scientists apply peptides to a polymer, and then apply that peptide-functionalized polymer coating to SWNT-FETs, using an electro-chemical process. “Anything will change the nanotubes’ electronic properties. If you want to detect heavy metals, proteins, etc., you need molecular recognition,” explained Nongjian Tao, professor, department of electrical engineering, at ASU. The combination created by Motorola and ASU scientists quickly converts recognition events in the peptides into an electronic signal, he explained.

Xiulan Li and Erica Forzani, research students at ASU, test carbon nanotube chips to sense the heavy metal ions.
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“Carbon nanotubes are very wonderful materials for electronics, and they are also good for attachment to molecules,” said Tao. Since all of the nanotube’s atoms touch air, they will always attach to molecules, like peptides, to form chains. ASU conducted experiments to modify SWNTs so they could tune to recognize different things. Biological principles are applied to the electronic device - different amino acids identify different heavy metals; therefore, different combinations of peptides on SWNTs will alert the user to a specific element’s ion concentration in the air, water, or possibly inside the body.

The benefits for security and environmental monitoring are diverse. The environmental protection agency (EPA) partially funds the project; they hope to use a SWNT device to detect poisons in drinking water. “By attaching multiple peptide-coated sensors on one die, scientist can detect various gasses or combination gasses,” said Ilderem. Since they are now capable of attaching one type of sensing peptide to one SWNT, researchers will next investigate sensing abilities of other analytes and multi-analyte detection possibilities using selective sensing libraries, grouping several peptide types onto one SWNT and differentiating the signals produced by each.