Rare-Earth Eu³⁺/Gold Nanocluster Ensemble-Based Fluorescent Photoinduced Electron Transfer Sensor for Biomarker Dipicolinic Acid Detection

Abstract

The use of metal ions to bridge the fluorescent materials to target analytes has been demonstrated to be a promising way to sensor design. Herein, the effect of rare-earth ions on the fluorescence of L-methioninestabilized gold nanoclusters (Met-AuNCs) was investigated. It was found that europium (Eu 3+ ) can significantly suppress the emission of Met-AuNCs, while other rare-earth ions showed a negligible impact. The mechanism on the observed fluorescence quenching of Met-AuNCs triggered by Eu 3+ was systematically explored, with results revealing the dominant role of photoinduced electron transfer (PET). Eu 3+ can bind to the surface of Met-AuNCs by the coordination effect and accepts the electron from the excited Met-AuNCs, which results in Met-AuNC fluorescence suppression. After introducing dipicolinic acid (DPA), an excellent biomarker for spore-forming pathogens, Eu 3+ was removed from the surface of Met-AuNCs owing to the higher binding affinity between Eu 3+ and DPA. Consequently, an immediate fluorescence recovery occurred when DPA was present in the system. Based on the Met-AuNC/Eu 3+ ensemble, we then established a simple and sensitive fluorescence strategy for turn-on determination of biomarker DPA, with a linear range of 0.2−4 μM and a low limit of detection of 110 nM. The feasibility of the proposed method was further validated by the quantitative detection of DPA in the soil samples. We believe that this study would significantly facilitate the construction of metal-ion-mediated PET sensors for the measurement of various interested analytes by applying fluorescent AuNCs as detection probes.

Europium(III)-Modified Silver Nanoparticles as Ratiometric Colorimetric and Fluorescent Dual-Mode Probes for Selective Detection of Dipicolinic Acid in Bacterial Spores and Lake Waters

“…Interestingly, compared with the Eu 3+ −DPA system, the fluorescence intensity of the AgNPs−Eu 3+ -DPA system is greatly enhanced. The possible explanation is that the coordination number of Eu 3+ in its complex is 6−8 in the Eu 3+ −DPA system (the association constant of Eu 3+ −DPA, log K = 7.4), 42 and after it coordinates with DPA and is yet not saturated, Eu 3+ ions will coordinate with water molecules. However, in the AgNPs−Eu 3+ −DPA system, except for the coordination with DPA, Eu 3+ ions can also coordinate with the carboxyl groups on the surface of the Cit-modified AgNPs (the association constant of Eu 3+ −Cit, log K = 5.5), 43 which can reduce the coordination number with water molecules 44 and decrease the nonradiative energy loss and cause the fluorescence enhancement of the system.…”

Lanthanide Metal–Organic Framework-Based Fluorescent Sensor Arrays to Discriminate and Quantify Ingredients of Natural Medicine

“…22 Fluorescence chemosensors have been widely used in analytical chemistry and life science due to their low cost, simplicity, and rapidity. 23,24 Fluorescent sensor arrays not only adopt the above advantages but also can be applied to multitarget identification. 22,25 For instance, a Zn(salicylaldimine)-based fluorescent sensor array was reported to accurately discriminate nitroaromatics, in which the fluorescence was quenched to varying degrees.…”

“…Compared with approaches to detect one individual compound at a time, sensor arrays are able to discriminate multiple ingredients simultaneously . Fluorescence chemosensors have been widely used in analytical chemistry and life science due to their low cost, simplicity, and rapidity. , Fluorescent sensor arrays not only adopt the above advantages but also can be applied to multitarget identification. , For instance, a Zn­(salicylaldimine)-based fluorescent sensor array was reported to accurately discriminate nitroaromatics, in which the fluorescence was quenched to varying degrees . Abbasi-Moayed and co-workers have established a nanopaper-based ratiometric fluorescent sensor array using nanohybrids for the discrimination of heavy metal ions by RGB analysis .…”

Facilitated endospore detection for Bacillus spp. through automated algorithm‐based image processing

“…As mentioned before, DPA acts as a suitable biomarker and is often used for the spore detection as well [ 9 ]. DPA can either be detected by a historic colorimetric assay from the 1950‐1960s, using ammonium iron(II) sulfate [ 16 , 17 ] or in more recent publications with lanthanides such as europium(III) or terbium(III) [ 18 , 19 , 20 , 21 , 22 ]. Those assays have no special technical requirements and lead to a significant time‐saving compared to CFU.…”