Trx-red (NBL-SS) displayed multiple favorable properties, such as red emission, fast response, and high fluorescence signal. Thioredoxin (Trx) is a ubiquitous redox-regulating protein essentially involved in cell growth, differentiation, and death[1]. When HeLa cells are incubated with Trx-red (NBL-SS; 5 μM; 0-30 min), a clear time-dependent increase of the fluorescence is observed[1].

Trx-red (NBL-SS; 10 μM; 30 min) is also suitable to image thioredoxin in 6 day-old zebrafish larvae[1].