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Preparation of near-infrared AIEgen-active fluorescent probes for mapping amyloid-β plaques in brain tissues and living mice

Nature Protocols (2023)Cite this article

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Abstract

Fibrillar aggregates of the amyloid-β protein (Aβ) are the main component of the senile plaques found in brains of patients with Alzheimer’s disease (AD). Development of probes allowing the noninvasive and high-fidelity mapping of Aβ plaques in vivo is critical for AD early detection, drug screening and biomedical research. QM-FN-SO3 (quinoline-malononitrile-thiophene-(dimethylamino)phenylsulfonate) is a near-infrared aggregation-induced-emission-active fluorescent probe capable of crossing the blood–brain barrier (BBB) and ultrasensitively lighting up Aβ plaques in living mice. Herein, we describe detailed procedures for the two-stage synthesis of QM-FN-SO3 and its applications for mapping Aβ plaques in brain tissues and living mice. Compared with commercial thioflavin (Th) derivatives ThT and ThS (the gold standard for detection of Aβ aggregates) and other reported Aβ plaque fluorescent probes, QM-FN-SO3 confers several advantages, such as long emission wavelength, large Stokes shift, ultrahigh sensitivity, good BBB penetrability and miscibility in aqueous biological media. The preparation of QM-FN-SO3 takes ~2 d, and the confocal imaging experiments for Aβ plaque visualization, including the preparation for mouse brain sections, take ~7 d. Notably, acquisition and analyses for in vivo visualization of Aβ plaques in mice can be completed within 1 h and require only a basic knowledge of spectroscopy and chemistry.

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Fig. 1: Comparison of QM-FN-SO3 with extensively used ThT for sensing Aβ aggregates.
Fig. 2: Step-by-step strategy for building up probes enabling ultrasensitive in vivo mapping of Aβ plaques.
Fig. 3: Overview of applying QM-FN-SO3 for brain section and animal experiments.
Fig. 4: Spectroscopic characterization of QM-FN-SO3 toward Aβ aggregates.
Fig. 5: High-fidelity mapping of Aβ plaques in brain tissues and validation of the BBB penetrability of QM-FN-SO3.
Fig. 6: In vivo mapping of Aβ plaques in AD model mice.

Data availability

Source data are provided with this paper. All other data are available from the corresponding author.

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Acknowledgements

This work was supported by NSFC/China (22225805, 21878087 and 21908060), National Key Research and Development Program (2021YFA0910000), Innovation Program of Shanghai Municipal Education Commission, Shanghai Frontier Science Research Base of Optogenetic Techniques for Cell Metabolism (Shanghai Municipal Education Commission, grant 2021 Sci & Tech 03-28), Shanghai Municipal Science and Technology Major Project (Grant 2018SHZDZX03), Shanghai Science and Technology Committee Rising-Star Program (22QC1400400) and Programme of Introducing Talents of Discipline to Universities (B16017).

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Authors and Affiliations

  1. Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, Institute of Fine Chemicals, Frontiers Science Center for Materiobiology and Dynamic Chemistry, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai, China

    Chenxu Yan, Jianfeng Dai, Yongkang Yao, Wei Fu, He Tian, Wei-Hong Zhu & Zhiqian Guo

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Contributions

All the experiments were conducted by C.Y., J.D., Y.Y. and W.F. with the supervision of H.T., W.-H.Z. and Z.G. All the authors analyzed the data and contributed to the manuscript writing.

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Correspondence to Zhiqian Guo.

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Competing interests

Z.G. has filed a patent application for the QM-FN-SO3 probe. The patent application number is CN201811069366 (patent number: ZL 201811069366.9).

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Nature Protocols thanks Juyoung Yoon and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Key reference using this protocol

Fu, W. et al. J. Am. Chem. Soc. 141, 3171–3177 (2019): https://doi.org/10.1021/jacs.8b12820

Supplementary information

Supplementary Information

Supplementary Figs. 1–9 and Methods 1 and 2

Supplementary Data 1

Statistical data for Supplementary Figs. 2, 3, 7b and 9a,b

Source data

Source Data Fig. 2

Value of S/N ratio of the probes (ThT, DCM-N, QM-FN and QM-FN-SO3)

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Yan, C., Dai, J., Yao, Y. et al. Preparation of near-infrared AIEgen-active fluorescent probes for mapping amyloid-β plaques in brain tissues and living mice. Nat Protoc (2023). https://doi.org/10.1038/s41596-022-00789-1

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