Blood Test

W. Grant McGimpsey is developing an optical sensor that analyzes whole blood more efficiently and cost-effectively.

Michelle Lang -- Design News, November 22, 2004

Present Position: Professor of Chemistry, Worcester Polytechnic Institute

Degrees: B.Sc., M.Sc., Chemistry, Brock Univ.; Ph.D., Chemistry, Queen's Univ.

How are you developing optical sensors for whole blood analysis? We design a molecule that will bind to a particular analyte, or blood component, without attracting other components. We next carry out detailed computational analysis called molecular modeling and molecular dynamics, and then devise schemes for synthesizing the molecule. We test its response to analytes, and incorporate it into a sensor.

How is the blood then analyzed? Some of that molecule can emit fluorescence when it is probed with UV light. Under conditions when the analyte is not bound to the molecule, the fluorescence emission is switched off by a process called electron transfer. When the ion is bound to the molecule, its electrostatic field disrupts the electron transfer quenching and the fluorescence is switched on. Essentially, we create an 'off-on' fluorescence switch.

How is whole blood currently analyzed? An electrochemical approach uses ion selective electrodes (ISE) to provide a nearly instantaneous potentiometric response to the analyte ion.

Why switch to optical sensors then? The downside to electrochemical sensors is that there are a lot of calibration steps that need to be performed for each sample. Bulk optical sensors are potentially cheaper to manufacture and use, though the measurement is longer (at least 30 sec).

Any other applications? Military and homeland security; many chemicals are similar in structure to chemical warfare structures but are completely harmless, so we need sensors that will respond only where appropriate.

For more info on this research, visit http://rbi.ims.ca/3859-533 ; and for McGimpsey's further research into untethered healthcare, visit http://rbi.ims.ca/3859-534 . Contact McGimpsey at wgm@wpi.edu .

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