FRET-mediated quenching of BODIPY fluorescent nanoparticles by methylene blue and its application to bacterial imaging.

High resolution and a good signal to noise ratio are a requirement in cell imaging. However, after labelling with fluorescent entities, and after several washing steps, there is often an unwanted fluorescent background that reduces the images resolution. For this purpose, we developed an approach to remove the signal from extra-cellular fluorescent nanoparticles (FNPs) during bacteria imaging, without the need for any washing steps. Our idea is to use methylene blue to quench > 90% of the emission of BODIPY-based fluorescent polymer nanoparticle by a FRET process. This "Hide-and-Seek Game" approach offers a novel strategy to apply fluorescence quenching in bioimaging to improve image accuracy.