A Highly Sensitive and Selective Fluorescein-Based Cu2+ Probe and Its Bioimaging in Cell

Xin Leng; Mengyao She; Xilang Jin; Jiao Chen; Xuehao Ma; Fulin Chen; Jianli Li; Bingqin Yang

doi:10.3389/fnut.2022.932826

A Highly Sensitive and Selective Fluorescein-Based Cu²⁺ Probe and Its Bioimaging in Cell

Front Nutr. 2022 Jun 27:9:932826. doi: 10.3389/fnut.2022.932826. eCollection 2022.

Authors

Xin Leng^{1

2

3

4}, Mengyao She^{1

2

3}, Xilang Jin⁵, Jiao Chen^{1

2

3}, Xuehao Ma⁵, Fulin Chen^{1

2

3}, Jianli Li⁴, Bingqin Yang⁴

Affiliations

¹ Key Laboratory of Resource Biology and Biotechnology in Western China, Ministry of Education, Xi'an, China.
² Biomedicine Key Laboratory of Shaanxi Province, Xi'an, China.
³ Lab of Tissue Engineering, Faculty of Life Science & Medicine, The College of Life Sciences, Northwest University, Xi'an, China.
⁴ Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an, China.
⁵ School of Materials and Chemical Engineering, Xi'an Technological University, Xi'an, China.

Abstract

Copper is a vital trace metal in human body, which plays the significant roles in amounts of physiological and pathological processes. The application of copper-selective probe has attracted great interests from environmental tests to life process research, yet a few of sensitive Cu²⁺ tests based on on-site analysis have been reported. In this paper, a novel fluorescein-based fluorescent probe N4 was designed, synthesized, and characterized, which exhibited high selectivity and sensitivity to Cu²⁺ comparing with other metal ions in ethanol-water (1/1, v/v) solution. The probe N4 bonded with Cu²⁺ to facilitate the ring-opening, and an obvious new band at 525 nm in the fluorescence spectroscopy appeared, which could be used for naked-eye detection of Cu²⁺ within a broad pH range of 6-9. Meanwhile, a good linearity between the fluorescence intensity and the concentrations of Cu²⁺ ranged 0.1-1.5 eq. was observed, and the limit of detection of N4 to Cu²⁺ was calculated to be as low as 1.20 μm. In addition, the interaction mode between N4 and Cu²⁺ was found to be 1:1 by the Job's plot and mass experiment. Biological experiments showed that the probe N4 exhibited low biological toxicity and could be applied for Cu²⁺ imaging in living cells. The significant color shift associated with the production of the N4-Cu²⁺ complex at low micromolar concentrations under UV light endows N4 with a promising probe for field testing of trace Cu²⁺ ions.

Keywords: cells imaging; copper ion; fluorescent probe; test strips; trace metal.