A Red‐Emissive Fluorescent Probe with a Compact Single‐Benzene‐Based Skeleton for Cell Imaging of Lipid Droplets

Abstract

Lipid droplets (LDs) are important organelles associated with many physiological processes as well as diseases. To visualize LDs and study their versatile functions, the fluorescence imaging technique is one of the most powerful tools. Thus, the development of fluorescent probes for LDs imaging has attracted increased attention in recent years. Herein, a new LDs fluorescent probe Ph‐Red is developed and its application in fluorescence imaging is carefully demonstrated. The probe Ph‐Red has a compact single‐benzene‐based molecular structure and can be easily synthesized via a one‐step reaction. Impressively, the probe displays strong red emission based on a very small π‐system consisting of only one benzene ring. Moreover, the probe shows high LDs staining selectivity and good cellular viability, and is tolerant for repeatedly fluorescence imaging. Given these advantages, the 3D confocal imaging in fixed cells as well as multicolor confocal imaging in live cells are successfully realized, highlighting the utility of the single‐benzene‐based fluorescent probe Ph‐Red for LDs imaging. In addition, the hydrophobicity of the probe and the molecular size are revealed to play critical roles for efficiently staining LDs, which are important insights for the development of new LDs fluorescent probes.

Red-Emitting SBBF (Single-Benzene-Based Fluorophore)-Silica Hybrid Material: One-Pot Synthesis, Characterization, and Biomedical Applications

“…For the hybridization of the SBBF and silica, we introduced a one-pot synthesis approach, based on an in situ two-step reaction: (i) condensation (SBBF formation) between DCD (dimethyl 1,4-cyclohexanedione-2,5-dicarboxylate) and the APTES (3-aminopropyl triethoxysilane) under an air atmosphere [ 24 ], and (ii) hydrolytic condensation and propagation of triethoxysilane moiety under a given reaction condition (solvent: ethanol, temperature: 80 °C). At the design stage of the SSH material, we outlined three points: (i) red-emission: the secondary amine moiety at the electron-donating site of the SBBF could generate a red-emission [ 25 ], which holds advantages in biological studies [ 23 ]; (ii) SBBF-encapsulated silica: the silica wrapping can help to compensate the drawbacks of the SBBF; and (iii) readily scalable and facile synthesis: a simple one-pot reaction using commercially available and inexpensive starting materials.…”

“…APTES (3 eq) was added to the ethanol solution (5 mL) containing DCD (0.4382 mmol) and acetic acid (50 μL, 2 eq). The mixture was then refluxed for 18 h under an open-air atmosphere [ 23 ]. After the reaction, the mixture was cooled down to room temperature and filtrated.…”

“…1-propylamine (4 eq) was added to the ethanol solution (5 mL) containing DCD (0.219 mmol) and acetic acid (50 μL, 2 eq). The mixture was refluxed for 18 h under an open-air atmosphere and then was cooled down to room temperature and filtrated [ 23 ]. Red solid compound (50 mg) was obtained and rinsed three times with deionized water (DI.H 2 O) and acetone.…”

A New Lipid‐Droplets‐Targeted Fluorescence Probe with Dual‐Reactive Sites for Specific Detection of ClO− in Living Cells

“…[17,18] The traditional imaging techniques, such as Raman microscopy, transmission electron microscopy, and immunofluorescence microscopy, [19][20][21] have been employed for the purpose to visualize lipid droplets, but some challenges have still been existed, such as complicated procedures and poor cellular permeability and thus may disturb the functions of cells. [22][23][24] Keeping these disadvantages in mind, in recent years, fluorescence imaging has been disclosed as a reliable tool for visualizing the localization and the dynamics of cellular compartments. [25][26][27] Especially, by utilizing the aggregationinduced emission (AIE) active dyes (named as AIEgens), the cell imaging could be accomplished with excellent selectivity, remarkable sensitivity, and extraordinary temporal spatial resolution.…”

“…[32][33][34] However, there is a main issue for lipophilic organic dyes is their low cell penetrability, which can be excluded from cells due to the absence of cell interface-targeting segments, such as cationic charges, which is detrimental for designing specific fluorescent probes, as it has a tendency to provoke attraction toward negatively charged biomolecules (proteins and biomembranes) by opposite charge attractions. [35][36][37] Therefore, the imbalance between hydrophobicity and cell penetrability should be considered in the context of probe designing.…”