Abstract
The speaker and his research group have explored all-electronic chemical detectors based on bio-nano hybrids, where the biomolecule (DNA or protein) provides chemical recognition and a carbon nanotube (NT) or graphene transistor enables electronic readout. This sensor class represents a promising approach towards sensitive detection of liquid- and vapor-phase anayltes. NT or graphene transistors are functionalized with proteins through an amide bond using a robust process based on carboxylated diazonium salts. Control of protein orientation is achieved through the use of a Ni-nitrilotriacetic acid (Ni-NTA) chemistry with affinity for the histidine tag on an engineered protein. They used this approach to create a nanoelectronic interface to olfactory receptor proteins (ORs) that were embedded in synthetic nanoscale cell membrane analogues. Olfactory receptor proteins (ORs) are the most numerous class of G-protein coupled receptors (GPCRs), a large family of membrane proteins that are important pharmaceutical targets. They have also very recently used similar methods based on an engineered antibody to demonstrate detection of a cancer biomarker at levels of 1 pg/mL, far more sensitive than methods used in the clinic today. Non-covalent functionalization of carbon nanotube transistors is achieved through self-assembly of monolayers of single-stranded DNA on the NT sidewall. The DNA is used not for its self-recogntion properties but rather for its chemical recognition for small molecule analytes. The DNA/NT sensor system shows excellent characteristics and might provide a pathway to an electronic olfaction system.
About the speaker
Prof Charlie Johnson received his PhD in Physics from Harvard University in 1990. He did his postdoctoral work at Delft University of Technology and the US National Institute of Standards and Technology. Since 1994, he has joined the faculty of the University of Pennsylvania, where he is currently Professor of Physics. He is also the Scientific Founder and Chair of the Scientific Advisory Board for two startup companies (Graphene Frontiers and Adamant Technologies).
Prof Johnson is a condensed matter physics experimentalist and world-known expert in the area of nanostructure physics, most recently carbon nanotube and graphene electronics. His research group made critical contributions to understanding electron and thermal transport in carbon nanotubes and related structures. Recently they turned to the physics and chemistry of biomolecule-nanocarbon hybrids using a combination of experiment and molecular dynamics simulation. The group is pioneer in the application of these nanostructures in chemical and biomolecular sensing, including electronic nose applications. Prof Johnson’s current research activities are focused on the development of manufacturable wafer-scale films of carbon nanotubes and graphene for electronic and sensing applications as well as quantitative models for the sensing responses of biomolecule-nanocarbon hybrids.
Prof Johnson has received awards including the Christian R. and Mary F. Lindback Foundation Award for distinguished teaching at the University of Pennsylvania, and the Jack Raper Outstanding Technology Directions Paper Award at the International Solid State Circuit Conference in 1999. He is a Fellow of the American Physical Society.
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