A novel ratiometric fluorescent probe for selective detection and imaging of H2S

https://doi.org/10.1016/j.saa.2020.118959Get rights and content

Highlights

  • A novel phenoxazine-based fluorescent probe BPO-N3 was developed to detect H2S.

  • Linear response (0.1 to 20 μM), high selectivity and sensitivity (LOD = 30 nM) were observed.

  • The probe BPO-N3 could successfully detect endogenous and exogenous H2S in living cells.

Abstract

In this work, a novel phenoxazine-based fluorescent probe BPO-N3 was developed to detect H2S. The results showed that the probe had high selectivity and sensitivity toward H2S, and its detection mechanism was based the ratio between green and red fluorescence signals; its detection limit was as low as 30 nM. The fluorescent imaging experiments further showed that the probe BPO-N3 could successfully detect endogenous and exogenous H2S in living cells. This probe can be used as a powerful tool for in-depth study of H2S function in various physiological processes.

Introduction

H2S is a colorless, highly toxic, acidic gas with a smell of rotten egg. Recent studies have found that H2S is the third gaseous signal molecule after NO and CO [1]. It is widely found in the human body and other organisms, and plays an important role in various physiological processes, such as regulating cell growth, protecting the cardiovascular system, taking part in anti-oxidation [[2], [3], [4], [5]]. Therefore, the development of a simple and sensitive method for H2S detection in living organisms is of great significance for further understanding of the physiological function of H2S.

In recent years, the development of fluorescent probes that have high selectivity and sensitivity and can be used in living organisms has become a hot research topic [[6], [7], [8]]. Fluorescent probes are known to have high spatial and temporal resolution, thus can be used in real-time imaging by a fluorescent confocal microscope [9,10]. Although some excellent H2S fluorescent probes with “off-on” or “turn-on” response have been reported [[11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22]], these probes have some limitations when they are employed in quantitative analysis as they are concentration-dependent and can be affected by test environments, excitation intensity and other factors. These factors can, however, be effectively eliminated by using the ratio fluorescent probe, by which the ratio of fluorescence intensity of two wavelengths is adopted in the quantitative analysis [23]. In addition, water solubility, light stability, emission wavelength, etc. can also restrict its application in vivo to a certain extent [[24], [25], [26]]. Therefore, it is still necessary to develop a ratio-type fluorescent probe that has good stability, high quantum yield, and long analytical wavelength. In this work, we designed a novel probe BPO-N3 using phenoxazine as the fluorescent matrix. We introduced an azide group, which is an electron-withdrawing group, into the phenoxazine matrix. Since the azide group can be effectively reduced to an amino group by H2S [[27], [28], [29], [30], [31]], this electron-withdrawing group can be converted into an electron donor group on the phenoxazine fluorescent framework, which can then lead to the change of fluorescence spectrum. This mechanism can provide us with a ratio-type tool that can be used for detecting H2S in vivo.

Section snippets

Instrumentation and reagents

UV–Vis and Fluorescence spectra were recorded on an F-2700 fluorescence spectrometer (Hitachi Co., Ltd. Japan) and Cary 50 UV–vis spectrometer (Varian Inc., USA) with a 1-cm quartz cuvette. 1H NMR spectra were recorded on Mercury 300 BB NMR spectrometer (Varian Inc., USA). Mass spectra (MS) were performed on a Bruker microTOF Q II (Bruker Daltonics Inc., Germany). pH was measured on an INESA Scientific PHS-3C pH meter (Sartorius AG, Germany). Cell imaging experiments were carried out on an LSM

Absorption spectral changes of probe in response to H2S

The color and absorption spectrum of the probe BPO-N3 before and after reacting with H2S were significantly different, as shown in Fig. 2(A). Before adding H2S, the color of the probe BPO-N3 was green, and the maximum absorption wavelength was 530 nm. Upon the addition of H2S, the solution color was changed from green to purple, and the maximum absorption peak was shifted to 600 nm, which is consistent with the characteristic peak of BPO-NH2.

Fluorescence spectral change of probe in response to H2S, and linear relationship

To investigate the fluorescence spectral properties

Conclusion

In this paper, we developed a novel probe BPO-N3, using phenoxazine as the fluorescence matrix, that has high sensitivity and selectivity. The detection limit of the probe in the detection of H2S was 30 nM. The spectral properties of the probe were examined, the effects of pH, temperature and time on its performance were investigated, and its theoretical luminescence mechanism was calculated. Finally, the probe was successfully employed to detect exogenous and endogenous H2S in HepG2 cells.

CRediT authorship contribution statement

Linlin Lv: Conceptualization, Methodology, Visualization, Writing - original draft. Weiwei Luo: Investigation, Formal analysis. Quanping Diao: Project administration, Funding acquisition.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by Natural Science Foundation of Liaoning Province of China (No. 2019-ZD-0358).

References (39)

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