Transient State Imaging microscopy (TRAST) for cancer diagnosis

Application note: Transient State Imaging or TRAST microscopy for measuring oxygen concentration in cancerous cells.

In the field of biology it is a general consensus that cancerous cells often use other metabolic pathways, than corresponding healthy cells, and thereby consume less oxygen. If it is possible to measure the oxygen levels of cells by fluorescence microscopy this could be exploited as a future tool in clinical cancer diagnosis. However, measuring oxygen concentration of live cells is not totally straight forward. Traditional fluorophores have too short excited state lifetimes (nanoseconds) to be significantly influenced by molecular oxygen collisions, typically taking place in the microsecond time range.

A new technique called Transient State Imaging (TRAST) is set to change the way oxygen concentration of cells is measured, by taking advantage of transitions to and from the dark lowest triplet state (T1) of fluorophores (1). T1 is a photo-induced, long-lived non-fluorescent state, found in essentially all fluorophore molecules. Combining fluorescence microsocpy with a modulated laser source, and systematically varying the modulation characteristcs, it is possible to extract kinetic information about the T1 state.