The Binding Finding of a Fluorescence Lifetime

By Ken Tichauer | Posted: 27 April 2014

In this afternoon’s session on Luminescence and Absorption on Cellular and Tissue Levels, Prof. Victor Chernomordik gave an overview of the extensive work he and his colleagues have been undertaking to make fluorescence molecular imaging more quantitative. Much of their work has focused specifically on how to quantify human epidermal growth factor receptor 2 (HER2) concentrations (a key receptor of interest in breast cancer) using kinetic models, and they have a number of publications in this area that I urge you to check out;1-5 however, what I was most intrigued by was there recent results demonstrating a dependence of fluorescence lifetime on the binding state of a targeted fluorescent tracer. In simpler terms, what they found was that the timing characteristics of fluorescence emission was significantly different depending on whether their fluorescent tracer was bound to the target of interest or not.6,7

This offers their group a window into separating non-specific uptake of a tracer, a major problem in conventional molecular imaging of tumors, from the more interesting bound fraction of the targeted tracer. Moreover, for reversible binding tracers (tracers that can dissociate from there targeted molecule), the ratio of the bound fraction of a tracer to the unbound fraction of tracer is directly proportional to the concentration of the targeted biomolecule.8 Therefore, as Prof. Chernomordik and his colleagues unearth the exact relationship between bound fraction and fluorescence lifetime, there is a clear pathway forward to using this approach to directly quantify HER2 concentration, something that is impossible to do with other conventional single tracer approaches in tumors.9

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