Basis for Sensitive and Selective Time-Delayed Luminescence Detection of Hydroxyl Radical by Lanthanide Complexes

Abstract

Molecular probes for the detection of hydroxyl radical (HO•) by time-delayed luminescence spectroscopy directly in water at neutral pH with high sensitivity and selectivity are presented. The bimolecular probes consist of a lanthanide complex with open coordination sites and a reactive pre-antenna composed of an aromatic acid or amide; the latter binds to and sensitizes terbium emission upon hydroxylation by HO•. These probes exhibit long luminescence lifetimes compatible with time-delayed measurements that remove interfering background fluorescence from the sample. Six different reactive pre-antenna (benzoate, benzamide, isophthalate, isophthalamide, trimesate, and trimesamide) and two different terbium complexes (Tb-DO3A and Tb-DO2A) were evaluated. Of these the trimesamide/Tb-DO3A system enables the most sensitive detection of HO• with a ca. 1000-fold increase in metal-centered time-delayed emission upon hydroxylation of the pre-antenna to 2-hydroxytrimesamide. Excellent selectivity for both the trimesamide/Tb-DO3A and trimesate/Tb-DO3A systems over other reactive oxygen and nitrogen species are observed. Notably, the increase in metal-centered luminescence intensity is not associated with a decrease in the hydration number (q) of Tb-DO3A, suggesting that the antenna is interacting with the lanthanide via a second sphere coordination environment or that coordination by the antenna occurs by displacement of one or more of the carboxylate arms of DO3A. Formation of a weak ternary complex Tb-DO3A•hydroxytrimesamide was confirmed by temperature-dependent titration and a decrease in Kapp with increasing temperature.

Multiplex Detection of Enzymatic Activity with Responsive Lanthanide‐Based Luminescent Probes

“…These responses were 81-and 90-fold higher for EuCou/ EuBn and TbCou/TbBn, respectively, which are among the highest observed for Ln-based turn-on probes. [21] An over 50fold increase in the Ln emission was recorded for the b-Gal probe EuGal, and a 20-36-fold increase for EuPhos, EuMan, and EuGlu with alkaline phosphatase, a-Man, and b-Glu, respectively. Progress curves of different enzyme concentrations plotted versus time [enzyme] were non-superimposable, [22] thus suggesting eventual deactivation of the enzyme, presumably caused by the quinone methide by-product.…”

Detection of Ciprofloxacin in Urine through Sensitized Lanthanide Luminescence

“…Eu-(1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) (Eu-DOTA) [34], Eu-(1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid) (Eu-DO3A) [35] and Tb-(1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid) (Tb-DO3A) [36] were prepared by following the literature procedures. All the solvents used were of analytical grade.…”

Ultrabright Lanthanide Nanoparticles

“…All ligandsa re derived from two of the basic coordinating units of lanthanide coordination chemistry-dipicolinic acid (L 1 ), and 2-hydroxyisophthalic acid (L 5 ). Both units have been shown to be excellent photosensitizing units for Tb, [24,25] but they display distinct coordination behaviors. Dipicolinic acid acts as at ridentate chelator,w hich in complex forms two five-membered chelate rings, [26] whereas 2-hydroxyisophthalic acid essentially acts in ab identate mode, forming as ix-memberedr ing, [27] although one can easily imagine a m-bridging bis-bidentate mode, forming two six-memberedr ings with two lanthanide atoms, as observed for different Schiff-base complexes obtained from the parent2-hydroxy-1,3-diformylbenzene.…”