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Proc Natl Acad Sci U S A. 2008 Dec 30;105(52):20701-4. doi: 10.1073/pnas.0808988106. Epub 2008 Dec 15.

Single virus detection from the reactive shift of a whispering-gallery mode.

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  • 1The Rowland Institute, Harvard University, Cambridge, MA 02142, USA.


We report the label-free, real-time optical detection of Influenza A virus particles. Binding of single virions is observed from discrete changes in the resonance frequency/wavelength of a whispering-gallery mode excited in a microspherical cavity. We find that the magnitude of the discrete wavelength-shift signal can be sufficiently enhanced by reducing the microsphere size. A reactive sensing mechanism with inverse dependence on mode volume is confirmed in experiments with virus-sized polystyrene nanoparticles. By comparing the electromagnetic theory for this reactive effect with experiments, the size and mass ( approximately 5.2 x 10(-16) g) of a bound virion are determined directly from the optimal resonance shift.

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