Ultrasensitive mercury ion and biothiol detection based on Dansyl-His-Pro-Gly-Asp-NH₂ fluorescent sensor

Mercury is an environmental contaminant, which is highly toxic even at extremely low concentrations. Long-term accumulation of mercury in human body will damage the central nervous system or digestive tract system. Here, a new fluorescent chemical sensor Dansyl-His-Pro-Gly-Asp-NH₂ (D-P4) was synthesized for the determination of Hg²⁺. The D-P4 sensor exhibits excellent selectivity and sensitivity to Hg²⁺ in aqueous solution with a 'turn-off' fluorescence response. Furthermore, D-P4-Hg system displays a good 'turn-on' fluorescence response to biothiols. The calculated binding constant for the 1:1 complex of D-P4 with Hg^{2 +} is 1.07 × 10⁵ M^-1, which also confirms the high affinity of D-P4 for Hg²⁺. Results indicate that the detection limit of D-P4 for Hg²⁺ is 61.0 nM, and that of D-P4-Hg system for Cys is as low as 80.0 nM.