Sensitive Terbium Probes for Luminescent Determination of both Alkaline Phosphatase and Codeine Phosphate

Abstract

New terbium complexes of 2-oxo-4-hydroxy-quinoline-3-carboxylic acid derivatives are reported for determination of alkaline phosphatase (aPase) and codeine phosphate (CP). Complexation with terbium occurs by way of the oxygen atoms of the 4-hydroxyl group and the carbonyl group of the 3-carboxy function, respectively. The complexes are highly luminescent and do not require luminescence enhancers. The excitation maxima of the terbium chelates are at 320 nm. The assay is based on the quenching of the hypersensitive 545-nm luminescence of the terbium complexes with the ligands 4-hydroxy-1-methyl-2-oxo-1,2-dihydro-quinoline-3-carboxylic acid (5-ethyl-[1,3,4]thiadiazol-2-yl)-amide (L(1)) and 1-ethyl-4-hydroxy-2-oxo-1,2-dihydro-quinoline-3-carboxylic acid (4-trifluoromethyl-phenyl)-amide (L(2)) by phosphate ions. The assays require equimolar (1.0 microM) concentrations of Tb(3+) and of the ligand at pH 8.0 (Tris-HCl buffer). The luminescence quenching is proportional to the concentration of aPase and CP within the range of 0.1-70 mU mL(-1) and 0.3-20 microg mL(-1), respectively. The detection limits were 0.05 mU mL(-1)=40.0 pmol L(-1) of aPase and 0.120 microg mL(-1) of CP.

Lanthanide luminescence for functional materials and bio-sciences

“…409 Alkaline phosphatase enhances the luminescence of [Eu 3 (45a)] and the corresponding time-resolved luminescence assay has a detection limit of 4 mmol L À1 . 410 Applications of europium tetracycline complexes in assays for phosphate, malate, lecithin, heparin, HSA, citrate, low density lipoproteins (LDL), and so on are detailed in the review by Courrol and Samad, 400 while more Eu III probes are described and compared in Spangler et al 56 Nucleotides and phosphate probes often rely on Tb III luminescence, 411 for instance the 4.5 : 1 complex of Tb III with norfloxacin ( 46) exhibits a five-fold increase in luminescence upon interaction with ATP. Many probes for DNA analysis have been proposed, 55,412,413 some of them exploiting the time-resolved capability of the Ln III ions leading to detection limits up to 50-fold larger than those reached with the organic dye FITC, [414][415][416] their propensity to be easily entrapped into nanoparticles, 402 their up-conversion ability, 417 or their NIR luminescence.…”

Lanthanide Luminescence for Biomedical Analyses and Imaging

“…The assay is conducted with equimolar concentrations of the ligand and Tb III ions at pH 8 and leads to a much lower limit of detection: 40 pM, or 0.05 mU mL −1 (linear range 0.1−70 mU mL −1 ). Ligand H 2 L23a is used for the ALP assay, while H 2 L23b performs well for the determination of codeine phosphate in the same samples, with LOD = 120 μg mL −1 (linear range 0.3−20 μg mL −1 ) . More recently, the series of ligands H 2 L24a − c was tested and the complex [Eu( L24b )(H 2 O) 2 ] + was found to significantly interact with ATP at pH 7, positioning this system as a potential ATP probe …”

“…Ligand H 2 L23a is used for the ALP assay, while H 2 L23b performs well for the determination of codeine phosphate in the same samples, with LOD ) 120 µg mL -1 (linear range 0.3-20 µg mL -1 ). 178 More recently, the series of ligands H 2 L24a-c was tested and the complex [Eu(L24b)(H 2 O) 2 ] + was found to significantly interact with ATP at pH 7, positioning this system as a potential ATP probe. 179…”

New terbium complex as a luminescent probe for determination of chlorogenic acid in green coffee and roasted coffee infusions

“…Such complexes are ideal probes for luminescence assays based on changes of luminescence intensity or lifetime. In the last years, the analytical use of sensitized lanthanide luminescence as well as its response with decrease or enhancement of luminescence intensity or lifetime towards the presence of relevant biomolecules demonstrated their potential as useful probes [ 16 – 18 ].…”