Optical imaging (OI) can be used as a non-invasive tool for assessment of drug delivery. Most modalities are intensity-based, so cannot discriminate between extracellular accumulation and intracellular delivery. Förster Resonance Energy Transfer (FRET), oftentimes referred to as the "molecular ruler", is a physical phenomenon involving two fluorophores – donor and acceptor. Measuring FRET enables one to assess molecular interactions on the nanoscale, such as quantifying intracellular delivery, across large fields of view with short acquisition times.

There are two approaches in FRET quantification – intensity-based and lifetime-based. Lifetime FRET sensing is non-invasive and non-radiative approach. Förster Resonance Energy Transfer (FRET) is the radiationless transfer of energy from an excited donor fluorophore to an appropriate acceptor in close proximity. The energy transfer only occurs between fluorophores separated by less than ~10 nm, allowing to sense protein interactions. However, to date, FRET applications are confined to microscopy or spectroscopy of cells culture or cell lysates. It is critical to translate FRET assays to small animal imaging where the in vivo physiological context is essential for drug development, the study of diseases, and fundamental cellular and molecular biology. We develop new methods to perform quantitative FRET tomography in live animals. Learn more>>