Illinois Institute of Technology:   Colloquium


Building a Biosensor to Detect Single Bacterial Cells


William R. Penrose

BCPS Department, IIT, Chicago, IL 60616


8 Oct. 2003; 3:35-4:30 p.m.; Life Science Bldg. (corner 31st and State St., Chicago)


The definition of ‘biosensor’ has become refined in the past few years to mean a chemical sensor with a receptor of biological origin, coupled to a transducer element that produces a signal that an engineer can understand (electrical, optical, etc.). The main reason for using selective elements drawn from biology is their exquisite selectivity. For example, a single monoclonal antibody can seek out and bind with a single antigenic site (epitope) on a target molecule, even in such a bewilderingly complex mixture as human blood. In many cases, bioreceptors are also the key to high sensitivity. Biosensors are needed in many medical areas, but they have potential in industrial processes and national security.


Our goal has been the detection of single microorganisms of a particular type. We have been exploring the potential of a unique transducer platform, which we call the ChemArray. It is a matrix of 256 x 364 microfabricated capacitive sensors. Each of these is two gold plates spaced 3.5 microns apart and covered by a very thin layer of glass. The electrical lines of force between the plates reach through the glass into the medium, and can measure electrical resistance and dielectric constant. We have been trying to teach this transducer to detect very small numbers of bacteria, by activating the surface with specific antibodies, and allowing the bacteria to bind to the activated surface. With the bacteria held within the electric field of the tiny capacitors, we expect to see a change in electrical impedance that could be used to detect the presence of single organisms.



William Penrose took his PhD from the University of Michigan in 1969 and has worked in molecular biology and environmental, analytical, and radiochemistry. He has worked in the field of chemical sensors for over 20 years. At Argonne National Laboratory, he joined Dr. Stetter’s research group and participated in the development of the first electronic nose. In 1989, he moved to Transducer Research, Inc., in Naperville, and developed gas analysis instruments of a variety of types, including a carbon dioxide sensor that is on the market today. In 1997, Dr. Penrose joined Dr. Stetter’s laboratory at IIT and continued his research into the practical applications of biosensors and chemical sensors.




Information; 312 567 3480 or 5875; visit; contact;