You-Di Shi

D–A–D type chromophores with aggregation-induced emission and two-photon absorption: synthesis, optical characteristics and cell imaging

Three novel D–A–D type chromophores, consisting of substituted triphenylamine and aggregation-induced emission (AIE)-active tetraphenylethylene moieties, 1 (with two ethoxy groups), 2 (with two hydroxyl groups), 3 (non-substituted), were synthesized and characterized. Their one-photon excited fluorescence (OPEF) quantum yields (ΦF) and lifetimes (τ) in organic solutions increased with the increase of the electron-donating ability of the substituents on the triphenylamine unit, i.e., 1 > 2 > 3. By means of dynamic light scattering and scanning electron microscopy, it was found that the higher hydrophobicity of 1 resulted in larger particle sizes and a strong AIE effect. 1 and 2 showed good two-photon excited fluorescence (TPEF) and two-photon absorption cross-sections (σ) (4230 and 4004, respectively) and proved to have good biocompatibility. Both compounds 1 and 2 were successfully applied in cell imaging based on their OPEF and TPEF properties. This work clearly implies that these chromophores can be finely tuned for different optical properties and applications through varying the electron-donating ability, hydrophobicity, and cytotoxicity of the substituents.

Fluorescent sensors based on [12]aneN3-modified BODIPY: Discrimination of different biological thiols in aqueous solution and living cells.

Two fluorescent probes, 1 and 2, derived from borondipyrromethene (BODIPY) modified with macrocyclic polyamine [12]aneN3, were synthesized and applied in the discrimination of cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) with absorption and fluorescent spectroscopy in comparison. It was found that Boc-protected 1 showed highly sensitive and selective recognition of GSH over Cys and Hcy; while probe 2 was able to distinguish the three different thiols due to their different reactivities. With its water-solubility, rapid responsiveness, high sensitivity and low cytotoxicity, probe 2 was successfully applied in the fast detection of three biothiols in living cells.

Gemini-Type Tetraphenylethylene Amphiphiles Containing [12]aneN3 and Long Hydrocarbon Chains as Nonviral Gene Vectors and Gene Delivery Monitors

Four gemini amphiphiles decorated with triazole-[12]aneN3 as the hydrophilic moiety and various long hydrocarbons as hydrophobic moieties, 1-4, were designed to form micelles possessing the aggregation-induced emission (AIE) property for gene delivery and tracing. All four amphiphiles give ultralow critical micelle concentrations, are pH-/photostable and biocompatible, and completely retard the migration of plasmid DNAs at low concentrations. The DNA-binding abilities of the micelles were fully assessed. The coaggregated nanoparticles of 1-4 with DNAs could convert back into AIE micelles. In vitro transfections indicated that lipids 1 and 2 and their originated liposomes bearing decent delivering abilities have great potentials as nonviral vectors. Finally, on the basis of the transfection and the transitions between condensates and micelles, lipid 2 was singled out as the first example for real-time tracing of the intracellular deliveries of nonlabeled DNA, which provides spatiotemporal messages about the processes of condensate uptake and DNA release.

[12]aneN3 Modified Tetraphenylethene Molecules as High-Performance Sensing, Condensing, and Delivering Agents toward DNAs

Four [12]aneN3 modified tetraphenylethene (TPE) compounds with different numbers of polyamine units and structure configurations, namely 1, 2, 3, and 4, were designed and synthesized. All compounds showed strong aggregation-induced emission (AIE) features. Compounds 2 and 4 showed significant emission enhancement after the addition of ssDNAs and dsDNAs of different lengths as well as calf thymus DNA (ctDNA). Compounds 1 and 3 showed very poor fluorescent responses toward DNAs. Gel electrophoresis demonstrated the abilities of 1-4 to condense DNA effectively. Complete retardation of plasmid DNA can be achieved at a concentration of 25 μM (1), 8 μM (for 2 and 3) and 4 μM (4). Experiments including fluorescent contrastive titrations, scanning electron microscopy, dynamic laser scattering, EB displacement, and gel electrophoresis demonstrated that the four compounds were able to integrate with DNA through electrostatic interactions and supramolecular stacking. A vicinal configuration around TPE (2) and more triazole-[12]aneN3 recognition sites (4) evidently enhanced the sensing capability toward oligonucleotides, and the TPE unit played an important role in the plasmid DNA condensation process because of its strong binding. With the advantages of low cytotoxicity, effective DNA sensing, and DNA condensing properties, compound 4 was successfully applied as a nonviral DNA vector and fluorescent tracer for label-free gene delivery, which is the first example of a nonviral gene vector with AIE activity.

[12]aneN3-based lipid with naphthalimide moiety for enhanced gene transfection efficiency

Three cationic lipids derived from [12]aneN3 modified with naphthalimide (1a), oleic acid (1b) and octadecylamine (1c) were designed and synthesized. In vitro transfection showed that all these liposomes can deliver plasmid DNA into the tested cell lines. Among these liposomes, 1a gave the best transfection efficiency (TE) in A549 cells, which was higher than that of lipofectamine 2000. More importantly, the TE of 1a was dramatically increased in the presence of 10% serum. These results suggested that 1a might be a promising non-viral gene vector, and also give further insight for developing novel high performance gene delivery agents.

A novel non-viral gene vector for hepatocyte-targeting and in situ monitoring of DNA delivery in single cells

A macrocyclic polyamine lipid bearing both fluorescent naphthalimide and targeting cholic acid moieties, 1, was designed and synthesized as a novel non-viral gene vector. Plasmid DNA was completely condensed at 10 μM of 1 (N/P = 3.6) in 5 minutes at 37 °C. The process of DNA uptake process by 1 in a single cell was clearly investigated through time-dependent fluorescence microscopy assay. Flow cytometry experiments of liposome 1 clearly proved its targeting activity toward HepG2 cells. Luciferase gene expression transfected by the DNA complex of 1/DOPE gave a higher transfection efficiency in HepG2, A549, HeLa, U2OS and CCC-HPF-1 cells than by lipofectamine 2000. The present work demonstrated that the designed multifunctional organic molecule is able to fluorescently track the gene delivery process at a single-cell level for the first time. This will greatly aid mechanistic studies of gene transfection and further development of new gene vectors for biomedical applications.