Single Fluorescent Peptide Nanodots

Fluorescent peptide nanodots (PNDs) are bioorganic nanoparticles self-assembled from peptide bio-molecules of different origin and complexity. These recently discovered nanodots of biological origin are highly promising for biomedical imaging applications due to their biocompatibility, bright and tunable fluorescence over the entire visible range and photostability. Here we apply single-particle microscopy methods to study the photophysical properties of individual PNDs. We show that the fluorescence spectrum tunability, studied previously only for PND ensembles in solutions, origins at the single-particle level. Temporal dynamics measurements of the single particles reveal fluorescence lifetime in the range of nanoseconds and pronounced fluorescence blinking with continuous bright states of seconds. The latter provides a first evidence of quantum emitter transitions between two states (ON and OFF) in fluorescent PNDs. All these findings advance the understanding of the fluorescence mechanism of PNDs and provide strong motivation for using PNDs as fluorescent agents for various bioimaging and super-resolution techniques.