Plasmon-Enhanced Fluorescence from Single Proteins in Living Bacteria

Abstract

The sensitivity and resolution of single-molecule fluorescence imaging in biology are mainly limited by two known weaknesses of fluorescent proteins: label brightness and photostability. In this work, we use patterned gold substrates to achieve plasmon-enhanced emission from intrinsically fluorescent proteins in living pathogenic bacteria cells. By coupling membrane-bound single fluorescent protein fusions to the virulence regulator TcpP in living Vibrio cholerae bacteria to extracellular gold nanotriangle arrays, we use plasmonics to improve our measurements of this important question in pathogenesis: how does V. cholerae produce its deadly toxin? Based on a simple experimental geometry, we observe a 1.3× enhancement in the rate of emission and a 1.4× enhancement in the number of photons detected prior to photobleaching. Furthermore, by enhancing both the rate of emission and the total number of photons detected from single-molecule fluorescent probes in live cells, we show that plasmon-enhanced fluoresc...