Europium Ions as a Dual Magnetic-Trapping and Fluorescence-Sensing Probe For Bacterial Detection

A new method using utilizing Europium ions (Eu³⁺) as a magnetic-trapping and fluorescence-sensing probe against pathogenic bacteria serves as an advancement in rapid bacterial detection, according to a recent study published in Analytical Chemistry (1).

Eu³⁺ serves as viable probe in biomedical and environmental applications, because it functions both as a magnetic trap and as a fluorescence sensor. Eu³⁺ has luminescent properties that enable sensitive detection through fluorescence, where it emits a well-characterized emission spectrum after excitation. Additionally, the magnetic moments of Eu³⁺ ions allow for their incorporation as magnetic traps, which act to capture and concentrate specific analyte molecules or even cells from complex samples. By combining fluorescence sensing and magnetic-trapping functions, Eu³⁺ probes provide a multifunctional capability for the selective detection and analyte manipulation of target substances. This set of features is providing tools for medical diagnostics, environmental monitoring, and drug discovery.

Pathogenic bacteria are a special type of bacteria that are disease causing and can sometimes overcome normal body defenses. They are often associated with diseases that humans are often afflicted with. In particular, pathogenic bacteria are often able to make changes to the human microbiome, and they exploit microbiota-derived sources of nitrogen and carbon to promote their own growth and virulence (2). Because the microbiome plays an important role in human health, it is important that the microbiome remains free of this type of bacteria (2).

Bacteria. Bacterium. Blue color. Prokaryotic microorganisms. 3d illustration. | Image Credit: © MP - stock.adobe.com.

As a result, it is important that rapid detection tools function properly to enable clinicians, scientists, and health practitioners to detect pathogenic bacteria in the human microbiome. A recent study, led by Yu-Chi Chen from the National Yang Ming Chiao University, explored this very issue. Their study proposed a novel method that uses Europium ions (Eu³⁺) as a magnetic-trapping and fluorescence-sensing probe against pathogenic bacteria (1).

The research team capitalized on the unique properties of Eu³⁺, leveraging its fluorescence enhancement when chelated with analytes like tetracycline (TC) (1). With six unpaired electrons in its f-orbital, Eu³⁺ exhibits paramagnetism, which gives it the ability to chelate with oxygen-containing functional groups found on the surfaces of pathogenic bacteria (1). As a result, this allowed Eu³⁺ to serve as a magnetic probe, efficiently trapping bacteria including Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Acinetobacter baumannii, Bacillus cereus, and Pseudomonas aeruginosa (1).

The addition of TC was valuable for the detection process. Through fluorescence spectroscopy, TC helped enable the easy identification of magnetic Eu³⁺–bacterium conjugates. Additionally, matrix-assisted laser desorption–ionization mass spectrometry was employed to differentiate bacteria tapped by the magnetic probes, enhancing the specificity of the method (1).

The method the researchers presented offered distinct advantages compared to other methods. One benefit of this method was that there was no need for overnight cultures, which meant that the detection process was more streamlined (1). By offering a dual functionality as both a trapping and sensing probe, Eu³⁺ presents a versatile solution for rapid bacterial screening, with the developed method boasting simplicity and speed (1).

The researchers’ new method using Eu³⁺ as a biosensing probe is versatile for several applications, including food safety and public health, where timely identification of bacterial contamination is essential (1). The rapid screening capability of the Eu³⁺-based method opens new avenues for efficiently tackling bacterial threats, underscoring its potential for point-of-care applications (1).

Furthermore, the versatility of this approach extends beyond bacteria, with potential applications in detecting fungi and viruses, promising broader implications for disease detection and prevention.

References

(1) Jannatin, M.; Yang, T.-L.; Su, Y.-Y.; Mai, R.-T.; Chen, Y.-C. Europium Ion-Based Magnetic-Trapping and Fluorescence-Sensing Method for Detection of Pathogenic Bacteria. Anal. Chem. 2024, 96 (14), 5669–5676. DOI: 10.1021/acs.analchem.4c00655

(2) Baumler, A. J.; Sperandio, V. Interactions Between the Microbiota and Pathogenic Bacteria in the Gut. Nature 2016, 535, 85–93. DOI: 10.1038/nature18849