A novel pyrene based fluorescent probe for selective detection of cysteine in presence of other bio-thiols in living cells

• A pyrene based fluorescent sensor for selective and sensitive detection of cysteine was developed.
• Cysteine was determined based on the enhancement of emission intensity of the probe.
• Cysteine specially finds with the α,β-unsaturated carbonyl group via Michael addition process.
• Limit of detection of 10−12 M cysteine under biological pH condition was achieved.
• The sensor was successfully applied for the selective detection of Cys in living HeLa cells.

This manuscript reports the synthesis of pyrene-based fluorescent probe (PA-1) containing α,β-unsaturated carbonyl moiety and its application towards the selective and sensitive detection of cysteine (Cys) over other bio-thiols. The probe, 3-(2-hydroxyphenyl)-1-pyrenyl-2-propenone (PA-1) was synthesized through Claisen-Schmidt condensation between acetyl pyrene and salicylaldehyde. The formed product was characterized by 1H NMR, 13C NMR and GC–MS techniques. The probe exhibited absorption maximum at 374 nm and emission maximum at 467 nm (λex=342 nm). The emission intensity of PA-1 was greatly enhanced while adding 2.5 nM Cys. This can be attributed to the nucleophilic attack of Cys to the α,β-unsaturated ketone resulting in switching off, intramolecular charge transfer (ICT) from pyrene moiety to the phenolic nucleus. This was confirmed by DFT measurements. The PA-1 exhibited an excellent selectivity towards the determination of 40 nM cys in the presence of 250,000-fold higher concentration of common interferents. The emission intensity was linearly increased and the limit of detection was found to be 10 pM/L (S/N=3). Interestingly, the response of the PA-1 towards Cys is less than 1 min. The confocal laser scanning micrographs of HeLa cells confirmed the cell permeability of the PA-1 and its ability to selectively detect Cys in living cells. In addition, the proposed probe was successfully applied for the determination of Cys in blood serum samples.