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

Abstract

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 S2−, NO3–, SO42− CO32–, 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 theΔHθ andΔSθ 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.