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

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 fluorescence chemoprobe 4-cyano-[1,1-biphenyl]-4-yl propiolate appended N-butyl-1,8-naphthalimide (BUNB) for the specific recognition of Cys for cellular recognition was synthesized. BUNB exhibited an excellent selectivity with a low detection limit (0.24 mu M) 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.