Development of fluorosensor for selective and sensitive determination of Ln(III) IONS

                     Romana Ševčíková^1, Jakub Vaněk^1,2 and Přemysl Lubal^1,2

^1  Masaryk University, Department of Chemistry, Kotlářská 2, 611 37 Brno, Czech Republic

^2  Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5,

  625 00 Brno, Czech Republic

Ln(III) complexes of macrocyclic ligands are utilized in medicine and preclinical research as MRI
(Gd), optical (Eu/Tb or Yb/Nd luminescence in VIS or NIR region) or nuclear probes for diagnostics
and/or for cancer treatment (e.g. metal radioisotopes ^90Y, ^153Sm, ^166Ho, ^177Lu in nuclear
medicine). For biomedical applications, such complexes should exhibit a high thermodynamic
stability as well as kinetic inertness under physiological conditions and their knowledge of
thermodynamic/kinetic properties is important to evaluate their possible in vivo applications. We
studied the kinetic, thermodynamic and analytical properties of Ln(III) complexes of the
mono(pyridine-N-oxide) analogue of the H[4]dota macrocylic ligand (H[3]do3a-pyNO, Scheme 1). It was
found that this ligand forms thermodynamically stable and kinetically inert Ln(III) complexes. Its
Eu(III) and Tb(III) complexes exhibit a strong long-lived fluorescence as a result of the antenna
effect of the pyridine-N-oxide fluorophore pendant arm. Using an excitation wavelength of 286 nm,
this ligand can be employed as a fluorogenic reagent for the determination of Eu(III) and Tb(III)
at pH 6.5 and c[L] = 1 mM detected luminescence at 615 nm for Eu(III) complex and at 547 nm for
Tb(III)complex. Detection limits are at concentrations around 1.0 µM and linearity of the method
spans over 2 orders of magnitude. The method was applied to artificial and real samples (spiked
mineral waters, extracts from luminophore CRT dust) with satisfactory results. The method is simple
and rapid without interference of other metal ions.

R

                                                                                                    Ligand

                                                 H

                                                                                                   H[3]do3a

                                             CH[2]COOH

                                                                                                   H[4]dota

                                                      H[3]do3a-py^NO = H[3]L

Scheme 1 The formulas of macrocyclic ligands discussed in the text