A sequential and reversibility fluorescent pentapeptide probe for Cu(II) ions and hydrogen sulfide detections and its application in two different living cells imaging.

In this study, we report a sequential and reversibility fluorescent probe (DP5) based on pentapeptide conjugated with dansyl groups using the solid phase peptide synthesis (SPPS) technology. DP5 showed immediate "turn off" response toward Cu2+ ions at an excitation wavelength of 330 nm with detection limits of 23.5 nM. The 2:1 binding ratio between DP5 and Cu2+ were confirmed using Job's plot method and fluorescence titration study, and DP5-Cu complex was observed with an association constant of 6.76 × 108 M-2. As designed, DP5-Cu complex as a promising analytical probe exhibited highly selective for H2S detection in aqueous solutions. The detection limit for H2S was obtained to be 17.2 nM, and lower than EPA and WHO guidelines. In addition, the reversibility and cyclicity were imparted to the DP5 during the detection of Cu2+ and H2S, and cycle effect is very good. Furthermore, DP5 displayed better biocompatibility and low biotoxicity, and sequential fluorescence "on-off-on" responses of DP5 to Cu2+ and H2S were successfully applied in two different living cells.