A Golgi-localized fluorescence probe for measuring cysteine based on a naphthalimide derivative

• A Golgi-targetable fluorescent probe for cysteine has been reported. • The probe displays high sensitivity and high selectivity for cysteine. • The probe can be utilized for determination of cysteine within the Golgi apparatus of living cells. Cysteine is an essential thiol-containing amino acid in biological systems and is involved in several physiological processes in the human body. The Golgi apparatus is the main site of protein processing, and the normal concentration of cysteine is an important factor to maintain the homeostasis in Golgi apparatus. Once the Golgi apparatus homeostasis is disrupted, it will lead to the Golgi apparatus dysfunction, which will lead to a series of diseases. Herein a new Golgi-localized fluorescent probe was constructed for measuring cysteine. The developed probe was assembled by utilizing a 1,8-naphthalimide derivative as the fluorescent component, appending a phenylsulfonamide group to target the Golgi apparatus, and incorporating an acrylate recognition unit to interact with and detect cysteine. Within the concentration range of 2.0 × 10 −7 –1.0 × 10 −5 mol·L −1 , a favorable linear correlation was observed between the fluorescence intensity of the probe at 550 nm and the cysteine concentration. Furthermore, the detection limit was determined to be 1.56 × 10 −8 mol·L −1 . The proposed probe exhibited superior selectivity, swift response time, and wide pH operational scope. In addition, the proposed probe was almost non-cytotoxic and was able to localize to the Golgi apparatus and detect endogenous and exogenous cysteine in A549 cells.