Developing a Novel Fluorescence Probe to Improve Copper Detection

The development of new fluorescence probe, coined W-3, is capable of improving the detection of copper (Cu²⁺) ions, according to a recent study published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (1).

The detection of Cu²⁺ ions in cellular processes has been explored extensively over the past decade (2–4). The redox activity of copper is important because it is normally required for sustaining and regulating metabolic processes (2). As a result, the development of fluorescent copper probes is valuable, and these probes can be effective biological screening tools (2). There are two types of fluorescent probes: recognition-based and reaction-based. Recognition-based probes interact with the copper metal present in an organism, but they are often hindered by intercellular chelators that interfere with this interaction (3). Meanwhile, reaction-based probes avoid the limitations of recognition-based probes by releasing fluorophores to avoid interference from chelators, allowing the probe to directly detect low concentrations of metal ions, such as copper (3).

Recently, a research team from Hebei North University looked at improving upon recognition-based fluorescent probes by developing W-3. The research was driven by Ting-Liang and Yan-Fei Kang, and they demonstrated in their study that W-3 improves chemical sensing and detects copper ions in both in vitro and in vivo settings (1). Unlike conventional methods, which often lack selectivity and sensitivity, W-3 demonstrates remarkable specificity for Cu²⁺ detection, accompanied by notable color and fluorescence changes upon interaction (1).

Ingots of pure copper or pink gold on a black background. | Image Credit: © Phawat - stock.adobe.com

The design of W-3 is unique. It incorporates picolinic acid as a recognition group, which plays a pivotal role in the selective detection of copper ions (1). Through a sophisticated mechanism involving intramolecular charge transfer (ICT), the probe exhibits minimal self-fluorescence until it encounters Cu²⁺, triggering a reversal of ICT and resulting in a distinctive fluorescence emission (1). This property not only enables precise detection of copper ions, but it also offers excellent quantitative analysis capabilities in sample detection.

W-3 also displayed versatility when applied to detecting copper ions in water and beverage samples through absorption detection methods (1). The integration of portable test paper and smartphone platforms further enhances its utility, enabling on-site and visual detection of Cu²⁺ with improved reliability.

One of the most significant implications of this research lies in its potential for biomedical imaging. W-3 has demonstrated the ability to image both exogenous and endogenous copper ions in cells, offering a promising avenue for distinguishing normal cells from cancerous ones (1). Furthermore, the probe's capability for in vivo imaging opens up new possibilities for understanding physiological and pathological changes associated with diseases. Its ability to facilitate both in vitro and in vivo detection marks a significant advancement in understanding the role of copper ions in health and disease.

References

(1) Wang, Y.-R.; Tan, Y.-W.; Zhang, A.-H. The Highly Selective and Sensitive Fluorescence Probe for Detection of Copper (II) Ions and its Bioimaging In Vitro and Vivo. Spectrochimica Acta Part A: Mol. Biomol. Spectrosc. 2024, 316, 124368. DOI: 10.1016/j.saa.2024.124328

(2) Cotruvo, Jr., J. A.; Aron, A. T.; Ramos-Torres, K. M.; et al. Synthetic Fluorescent Probes for Studying Copper in Biological Systems. Chem. Soc. Rev. 2015, 44 (13), 4400–4414. DOI: 10.1039/c4cs00346b

(3) Okuda, K.; Takashima, I.; Takagi, A. Advances in Reaction-Based Synthetic Fluorescent Probes for Studying the Role of Zinc and Copper Ions in Living Systems. J. Clin. Biochem. Nutr. 2023, 72 (1), 1–12. DOI: 10.3164/jcbn.22-92

(4) Leng, X.; She, M.; Jin, X.; et al. A Highly Sensitive and Selective Fluorescein-Based Cu²⁺ Probe and Its Bioimaging in Cell. Front. Nutr. 2022, 9, 932826. DOI: 10.3389/fnut.2022.932826