A fluorescent chemoprobe based on 1,8–naphthalimide derivative specific for cellular recognition of cysteine over homocysteine and glutathione

• A new 1,8–naphthalimide based fluorescence chemoprobe BUNB for the recognition of Cys was developed and validated. • The BUNB showed an excellent selectivity with a low detection limit (0.24 μM) for Cys over GSH and Hcy. • The binding between BUNB and Cys was verified using MALDI TOF–MS, emission spectra and DFT. • The BUNB could be successfully used for Cys in both healthy and cancerous cells. Development of highly selective, sensitive and low–cost fluorescence probes for the specific recognition of cysteine (Cys) over homocysteine (Hcy) and glutathione (GSH) is of considerable importance. Herein, a new 1,8–naphthalimide based fluorescence chemoprobe ( BUNB ) for the specific recognition of Cys for cellular recognition was synthesized. BUNB exhibited an excellent selectivity with a low detection limit (0.24 μM) for Cys over GSH and Hcy. The validation study was also performed using the appropriate analytical parameters and statistical tests. The thiol–propiolate cyclization/addition sequence phenomenon of the binding between BUNB and Cys was verified using MALDI TOF–MS, emission spectra and DFT computation. Moreover, the fluorescence imaging study in living–cells was carried out and the results indicated that BUNB could be successfully used for monitoring Cys in both healthy ( normal human hepatocytes, THLE2 ) and cancerous ( hepatocellular carcinoma, HepG2 ) cells.