Sulfonate‐Functionalized AIEgens: Strategic Approaches Beyond Water Solubility for Sensing and Imaging Applications

Abstract

The development of water-soluble aggregation-induced emission (AIE)-active "light-up" probes for sensing and imaging purposes has drawn immense research attention in the recent past. One strategy has been to introduce À SO 3 À groups in AIEgens (AIE-sulfonates) to increase their hydrophilic properties, and the ionic nature of the corresponding compounds also paves the way for electrostatic interaction with various analytes, in particular, with several biospecies having positively charged surfaces. A significant number of AIE-sulfonates, many among them having a tetraphenylethylene (TPE) moiety, have been designed and synthesized for the selective detection of a variety of analytes, such as metal ions, small molecules, enzymes, proteins, and bacteria. The strategies for selective detection include, for example, spontaneous complex formation with cations, electrostatic interaction with target-specific units in the biospecies, and strong hydrophobic interactions. In addition, these AIEgens are used in cell imaging and OLED applications. This Review attempts to provide a summary and discuss recent developments in sulfonate-functionalized AIEactive "light-up" probes in sensing and imaging applications with a focus on the role of the sulfonate functionality in the design and sensing processes.

Emission‐Tunable Nanofluorophores through Self‐assembly of Amphiphilic Block Copolymers: toward Application in Cell Imaging

“…[ 30‐33 ] Incorporating AIE fluorophores into amphiphilic molecules to construct water‐soluble aggregates is a feasible way to solve the above problem. [ 34‐40 ] Many fabrication strategies, such as atom transfer radical polymerization (ATRP), reversible addition‐fragmentation chain transfer (RAFT) polymerization, multicomponent reaction (MCR) and surfactant encapsulation, have been developed for the synthesis of water‐soluble AIE fluorescent probes for biomedical applications. [ 41‐43 ] However, drawbacks also exist in these methods.…”

A Highly Water‐Soluble Aggregation‐Induced Emission Luminogen with Anion‐π+ Interactions for Targeted NIR Imaging of Cancer Cells and Type I Photodynamic Therapy

“…Although the water solubility of PSs can be effectively improved by introducing multiple quaternary ammonium salts or sulfonates into the molecule, the synthetic procedures always suffer from multiple/complex operations and difficult purification bottlenecks [36–38] . Despite some water soluble or amphiphilic AIE molecules have been developed, most of them suffer from short emission wavelengths, weak ROS production and difficulties in purification [39–44] . Undoubtedly, the pursuit of a more manageable and user‐friendly approach to fabricate highly water‐soluble type I PSs with AIE feature and NIR emission holds immense potential for clinical application, but yet is quite challenging.…”

Tetraphenylethene–anthracene-based fluorescence emission sensor for the detection of water with photo-induced electron transfer and aggregation-induced emission characteristics

“…Meanwhile, as another fluorescence enhancement system for the detection of water, there is aggregation-induced emission (AIE) of organic fluorophores; that is, emission enhancement induced by aggregate formation of the organic fluorophores usually upon the addition of water into the solutions. 48–71 Tetraphenylethene (TPE), diphenyldibenzofulvene (DPDBF), and their derivatives are typical AIE-active fluorophores. 56–71 TPE- or DPDBF-based compounds in dilute solutions exhibited almost no emission due to the radiationless relaxation of the excitons by dynamic rotation of the phenyl groups.…”

“…48–71 Tetraphenylethene (TPE), diphenyldibenzofulvene (DPDBF), and their derivatives are typical AIE-active fluorophores. 56–71 TPE- or DPDBF-based compounds in dilute solutions exhibited almost no emission due to the radiationless relaxation of the excitons by dynamic rotation of the phenyl groups. Upon aggregate formation by the addition of large amounts of water (over 60 wt% in almost every case) into the solutions, on the other hand, the TPE- or DPDBF-based compounds exhibited AIE characteristics due to the restricted intramolecular rotation (RIR) of the phenyl groups, which eliminates the radiationless (non-emissive) relaxation of the photoexcited fluorophores.…”