Reversible pH-Responsive Red Fluorescent Switch Based on a Water-soluble Pillar[5]arene-Triphenylamine Assembly for Cellular Imaging

doi:10.1007/s40242-026-6151-8

Chemical Research in Chinese Universities ›› 2026, Vol. 42 ›› Issue (5): 1484-1488.doi: 10.1007/s40242-026-6151-8

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Reversible pH-Responsive Red Fluorescent Switch Based on a Water-soluble Pillar[5]arene-Triphenylamine Assembly for Cellular Imaging

NIU Mei, QIAN Zhenkai, ZHAO Wantong, YUAN Fengli, LIU Zhengyue, SUN Yonghui, XIN Pengyang

Pingyuan Laboratory, State Key Laboratory of Antiviral Drugs, School of Pharmaceutical Sciences, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, P. R. China

Received:2026-06-26 Accepted:2026-08-05 Online:2026-10-01 Published:2026-09-24
Supported by:
This work was supported by the National Natural Science Foundation of China (Nos. 22501074, 22571073, 22271079 and 82130103), the Natural Science Foundation of Henan Province, China (Nos. 252300420786, 262300421043) and the Henan Normal University Research Foundation for the Doctoral Program, China (No. QD2023058). The authors also thank the Research Project from Pingyuan Laboratory (No. 2023PY-ZZ-0201) and the Central Plains Scholars and Scientists Studio Fund (No. 2018002).

Abstract

Abstract: Herein, we report a water-compatible, reversibly switchable fluorescent assembly engineered from a pyridinium-functionalized triphenylamine (TPA) and a water-soluble pillar[5]arene (WP5). UV-Vis titration confirmed a strong 1:1 host-guest stoichiometry with a high association constant (2.95×10⁶ L/mol). Supramolecular confinement induces significant bathochromic shifts in both absorption (453→472 nm) and emission (607→635 nm), alongside a nearly tenfold fluorescence enhancement. Mechanistically, protonation of the carboxylate rim at low pH reconfigures interfacial electrostatic and hydrophobic interactions, triggering a further redshift to 639 nm and elevating the absolute quantum yield from 1.04% (free TPA) to 5.20% (acidified complex). Crucially, TPA@WP5 exhibits negligible cytotoxicity (94%—100% viability) in A549 cells at concentrations up to 80 μmol/L and enables real-time intracellular imaging of acidic microenvironments. This work establishes a robust platform for pH-gated fluorescence amplification, offering a paradigm for designing responsive supramolecular probes.

Key words: Pillar[5]arene, Host-guest assembly, pH-responsive, Triphenylamine, Cellular imaging

NIU Mei, QIAN Zhenkai, ZHAO Wantong, YUAN Fengli, LIU Zhengyue, SUN Yonghui, XIN Pengyang. Reversible pH-Responsive Red Fluorescent Switch Based on a Water-soluble Pillar[5]arene-Triphenylamine Assembly for Cellular Imaging[J]. Chemical Research in Chinese Universities, 2026, 42(5): 1484-1488.

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Reversible pH-Responsive Red Fluorescent Switch Based on a Water-soluble Pillar[5]arene-Triphenylamine Assembly for Cellular Imaging

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