Dr Michael Cooney

I believe our work demonstrates the great potential of fluorescence to study the spatial distribution of enzymes within immobilization polymers, as well as the microchemical environment immediately surrounding the enzyme. Much of this knowledge has been previously assumed but not directly verified, whether qualitatively or quantitatively. Much can also be learned about the enzyme-polymer interaction as the polymer "sets", which is also quite interesting given the obvious charge-charge or hydrophobic interactions which will affect the immobilization process. 

2. What has motivated you to conduct this work? 

My colleague, Dr. Bor Yann Liaw, and I have been developing in situ characterization techniques that linked classic electrochemical characterization techniques with biochemical. Initially we looked at coupling electrochemical measurements such as cyclic voltammetry and current-voltage polarization with spectrophotometric detection of reaction end products or unused substrates (in continuous systems). As we began to immobilize enzymes and to link kinetic measurements of activity with electrochemical measurement of electrons passed to the electrode, it became quite obvious that no real technique existed to verify the spatial distribution of the enzyme or even to probe the interaction of the enzyme with its immobilization matrix. It can be important, for example, to verify that a particular protocol for immobilizing a particular enzyme in a particular polymer supported the uniform distribution of that enzyme, or to verify that the pH or polarity of the medium immediately surrounding the enzyme was both appropriate or evenly distributed throughout the immobilization matrix. It was pretty much through this thinking that I came across the idea of using fluorescence, which as been used to probe cellular structure and activity, to probe polymer matrices that are used to immobilize enzymes in enzyme fuel cells.   

3. Where do you see this work developing in the future? 

I would like to apply this technique to visualizing the spatial distribution of multiple enzyme systems as well as pH gradients (or fluxes) at membrane/electrode interfaces. 

4. Are there any particular challenges facing future research in this area? 

In the context of studying enzyme fuel cells, which really want high density loading, the great advantage to fluorescence (its sensitivity at low levels) is also its great disadvantage. The system is so sensitive that it can be hard to truly quantitate the emission spectra coming from (tagged) enzymes. The real challenge, therefore, will lie in the use of sophisticated photon counting detectors and algorithms coupled with highly focused microscopes such as confocal laser scanning microscopy which promise, when coupled with appropriate detectors, the ability to detect individual enzymes.