Metal surface plasmons enhance single-cell fluorescence

The use of fluorophore-metal interactions has the potential to dramatically increase the detectability of single fluorophores for both single-molecule detection (SMD) and fluorescence-correlation-spectroscopy (FCS) experiments.

May 1st, 2008

The use of fluorophore-metal interactions has the potential to dramatically increase the detectability of single fluorophores for both single-molecule detection (SMD) and fluorescence-correlation-spectroscopy (FCS) experiments. For the past few years, researchers at the University of Maryland’s Center for Fluorescence Spectroscopy (CFS; Baltimore, MD) have been studying the interactions of fluorophores with metallic particles or surfaces and have observed a number of important spectral changes, including increases in intensity and photostability, decreased lifetimes due to increased rates of radiative decay, and increased distances for FRET. They have also shown that fluorophores can create surface plasmons in metals, which in turn create light.

In a paper published March 15 online by the American Chemical Society (ASAP Nano Lett., 10.1021/nl080093z), Joseph Lakowicz, director of the CFS, and colleagues from the School of Medicine demonstrated the role of plasmon-controlled fluorescence in single-molecule counting. Multiple Alexa Fluor 647-conjugated concanavalin A molecules were covalently bound to a single 20 nm silver particle to synthesize metal plasmon-coupled probes (PCPs). Fluorescence images were recorded using scanning-confocal microscopy in both intensity and lifetime. The brightness of the PCPs was 30 times brighter than those of free conA, and the lifetime of the PCPs was shortened dramatically. These results suggest that by using fluorophore-metal interactions it will be possible to control the migration of electromagnetic energy across and through metal surfaces, and to control when and where the energy is converted back into light. According to Lakowicz, this phenomenon represents a paradigm shift in fluorescence spectroscopy that will expand its capabilities in research, medical diagnostics, and imaging. Contact Joseph Lakowicz at lakowicz@cfs.umbi.umd.edu.

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