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. 2024 Jun 5;15(1):4787.
doi: 10.1038/s41467-024-49238-5.

Supramolecular assembly activated single-molecule phosphorescence resonance energy transfer for near-infrared targeted cell imaging

Xiaolu Zhou #  1 , Xue Bai #  1 , Fangjian Shang  1 , Heng-Yi Zhang  1 , Li-Hua Wang  1 , Xiufang Xu  1 , Yu Liu  2   3
Affiliations

Supramolecular assembly activated single-molecule phosphorescence resonance energy transfer for near-infrared targeted cell imaging

Xiaolu Zhou et al. Nat Commun. .

Abstract

Pure organic phosphorescence resonance energy transfer is a research hotspot. Herein, a single-molecule phosphorescence resonance energy transfer system with a large Stokes shift of 367 nm and near-infrared emission is constructed by guest molecule alkyl-bridged methoxy-tetraphenylethylene-phenylpyridines derivative, cucurbit[n]uril (n = 7, 8) and β-cyclodextrin modified hyaluronic acid. The high binding affinity of cucurbituril to guest molecules in various stoichiometric ratios not only regulates the topological morphology of supramolecular assembly but also induces different phosphorescence emissions. Varying from the spherical nanoparticles and nanorods for binary assemblies, three-dimensional nanoplate is obtained by the ternary co-assembly of guest with cucurbit[7]uril/cucurbit[8]uril, accompanying enhanced phosphorescence at 540 nm. Uncommonly, the secondary assembly of β-cyclodextrin modified hyaluronic acid and ternary assembly activates a single intramolecular phosphorescence resonance energy transfer process derived from phenyl pyridines unit to methoxy-tetraphenylethylene function group, enabling a near-infrared delayed fluorescence at 700 nm, which ultimately applied to mitochondrial targeted imaging for cancer cells.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Schematic illustration of the tunable self-assembly mechanism between TPE-DPY, CB[7], and CB[8], as well as the single-molecule PRET process in assembly.
Fig. 2
Fig. 2. Topological morphology characterization of TPE-DPY and the assemblies.
a–d Three-dimensional models of assembly structures. e–h TEM images of TPE-DPY ([TPE-DPY] = 1 × 10−5 M), TPE-DPY/CB[8] ([TPE-DPY] = 1 × 10−5 M, [CB[8]] = 1 × 10−5 M), TPE-DPY/4CB[7] ([TPE-DPY] = 5 × 10−6 M, [CB[7]] = 2 × 10−5 M), TPE-DPY/CB[7]/CB[8]. ([TPE-DPY] = 1 × 10−5 M, [CB[7]] = 2 × 10−5 M, [CB[8]] = 1 × 10−5 M) (from left to right). i–l SEM images of TPE-DPY, TPE-DPY/CB[8], TPE-DPY/4CB[7] and TPE-DPY/CB[7]/CB[8]. Each experiment was repeated three times independently with similar results.
Fig. 3
Fig. 3. Characterization of binding behavior between TPE-PY and CB[7]/CB[8].
a 1H NMR spectra (400 MHz, D2O with 10% DMSO-d6, 298 K) of TPE-PY (red), TPE-PY:CB[7] = 1:1 (black), TPE-PY:CB[7] = 1:2 (green), TPE-PY:CB[7]:CB[8] = 2:2:1 (blue); b From left to right, the binding constants of PY-1 and TPE-2 with the addition of CB[7], and TPE-PY with the addition of CB[8]. c UV-vis absorption of TPE-DPY ([TPE-DPY] = 1 × 10−5 M), TPE-DPY/2CB[7] ([TPE-DPY] = 1 × 10−5 M, [CB[7]] = 2 × 10−5 M), TPE-DPY/4CB[7] ([TPE-DPY] = 1 × 10−5 M, [CB[7]] = 4 × 10−5 M), TPE-DPY/CB[8] ([TPE-DPY] = 1 × 10−5 M, [CB[8]] = 1 × 10−5 M), TPE-DPY/CB[7]/CB[8]. ([TPE-DPY] = 1 × 10−5 M, [CB[7]] = 2 × 10−5 M, [CB[8]] = 1 × 10−5 M).
Fig. 4
Fig. 4. Photophysical properties of TPE-DPY and the assemblies.
a, b The steady-state PL spectra and phosphorescence spectra of TPE-DPY ([TPE-DPY] = 1 × 10−5 M, λex = 315 nm), TPE-DPY/2CB[7] ([TPE-DPY] = 1 × 10−5 M, [CB[7]] = 2 × 10−5 M, λex = 318 nm), TPE-DPY/4CB[7] ([TPE-DPY] = 1 × 10−5 M, [CB[7]] = 4 × 10−5 M, λex = 320 nm), TPE-DPY/CB[8] ([TPE-DPY] = 1 × 10−5 M, [CB[8]] = 1 × 10−5 M, λex = 330 nm), TPE-DPY/CB[7]/CB[8] ([TPE-DPY] = 1 × 10−5 M, [CB[7]] = 2 × 10−5 M, [CB[8]] = 1 × 10−5 M, λex = 333 nm). c Time-resolved decay curves of TPE-DPY/2CB[7], TPE-DPY/4CB[7], TPE-DPY/CB[8] and TPE-DPY/CB[7]/CB[8] in aqueous solution.
Fig. 5
Fig. 5. HACD-mediated PRET process for the secondary assembly.
a TEM image of TPE-DPY/CB[7]/CB[8]@HACD (The experiment was repeated three times independently with similar results). b Size distribution of TPE-DPY/CB[7]/CB[8]@HACD determined by dynamic light scattering. c Schematic illustration of supramolecular assembly activated single-molecule PRET process. d Normalized phosphorescence emission spectrum of PY-1/CB[8] ([PY-1] = 2.5 × 10−5 M, [CB[8]] = 1.25 × 10−5 M), and the excitation and emission spectra of TPE-1/CB[7] ([TPE-1] = 2.5 × 10−5 M, [CB[7]] = 5 × 10−5 M). e Phosphorescence spectra of TPE-DPY/CB[7]/CB[8] upon the addition of 0-0.045 mg/ml HACD ([TPE-DPY] = 2.5 × 10−5 M, [CB[7]] = 5 × 10−5 M, [CB[8]] = 2.5 × 10−5 M). f The time-resolved decay curves of TPE-DPY/CB[7]/CB[8]@HACD aqueous solution record at 530 nm and 700 nm.
Fig. 6
Fig. 6. Application of TPE-DPY/CB[7]/CB[8]@HACD in targeted imaging for cancer cells.
a, b Confocal microscopy images and merged images of Hela cells in the presence of TPE-DPY/CB[7]/CB[8]@HACD, Hoechst and Mito-Tracker Green. c Confocal microscopy images and merged images of 293T cells in the presence of TPE-DPY/CB[7]/CB[8]@HACD and Hoechst. ([TPE-DPY] = 1 × 10−5 M, [CB[7]] = 2 × 10−5 M, [CB[8]] = 1 × 10−5 M, [HACD] = 0.018 mg/ml, Green channel: 450−550 nm, red channel: 650−800 nm, each experiment was repeated two times independently with similar results).
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