A novel fluorescence sensor for uranyl ion detection based on a dansyl-modified peptide

It is of great significance to sensitively and selectively detect uranyl ion (UO₂²⁺) in environmental and biological samples due to the high risks of UO₂²⁺ to human health. However, such suitable sensors are still scarce. A novel fluorescence sensor based on a dansyl-modified peptide, Dansyl-Glu-Glu-Pro-Glu-Trp-COOH (D-P5), was efficiently synthesized by Fmoc solid phase peptide synthesis. As the first linear peptide-based fluorescence sensor for UO₂²⁺, D-P5 exhibited high selectivity and sensitivity to UO₂²⁺ over 27 metal ions (UO₂²⁺, Cr³⁺, Cu²⁺, Ba²⁺, Hg²⁺, Pb²⁺, Co²⁺, Ag⁺, Fe³⁺, Ca²⁺, K⁺, Mg²⁺, Mn²⁺, Na⁺, Ni²⁺, Cd²⁺, Zn²⁺, Al³⁺, Dy³⁺, Er³⁺, Gd²⁺, Ho³⁺, La³⁺, Lu³⁺, Pr³⁺, Sm³⁺, Tm³⁺) by a turn-off fluorescence response in 10 mM HEPES buffer (pH 6.3). The effects of anions such as S^2-, NO₃^-, SO₄^2- CO₃^2-, HCOO^-, antioxidant ascorbic acid and 4-nitrophenyl acetate on the selectivity for UO₂²⁺ detection were also studies. D-P5 sensor could be used for detecting UO₂²⁺ in a good linear relationship with concentration in the range of 0-8.0 μM with a low limit of detection of 83.2 nM. Furthermore, the interaction of the sensor with UO₂²⁺ was characterized by ESI-MS, IR, XPS and ITC measurements. The 1:1 binding stoichiometry between the sensor and UO₂²⁺ was measured by the job's plot and further verified by ESI-MS. The binding constant of the sensor with UO₂²⁺ was calculated to be 9.8 × 10⁴ M^-1 by modified Benesi-Hildebrand equation. ITC results showed that theΔH^θ andΔS^θ for the interaction of D-P5 with UO₂²⁺ were -(7.167 ± 1.25) kJ·mol^-1 and 66.5 J·mol^-1·K^-1, respectively. Time-resolved fluorescence spectroscopy indicated that the mechanism of fluorescence quenching of D-P5 by UO₂²⁺ ion was static quenching process. In addition, this sensor displayed a good practicality for UO₂²⁺ detection in lake water sample without tedious sample pretreatment.