Guanxin Zhang

Fluorescent bio/chemosensors based on silole and tetraphenylethene luminogens with aggregation-induced emission feature

New fluorescent sensors have been developed, utilizing the aggregation-induced emission (AIE) attribute of silole and tetraphenylethene luminogens. In this feature article, we briefly summarize recent progress in the development of AIE-based bio/chemosensors for assays of nuclease and AChE activities, screening of inhibitors, and detection of various analytes including charged biopolymers, ionic species, volatile and explosive organic compounds.

Multistimuli Responsive Organogels Based on a New Gelator Featuring Tetrathiafulvalene and Azobenzene Groups: Reversible Tuning of the Gel−Sol Transition by Redox Reactions and Light Irradiation

For the development of multistimuli responsive organogels, the new organic gelator LMWG 1, featuring electroactive TTF and photoresponsive azobenzene groups, was designed and studied. By manipulating the redox state of the TTF group in LMWG 1, the gel-sol transition for organogels with the LMWG 1 can be reversibly tuned by either chemical or electrochemical oxidation/reduction reactions. Alternatively, the photoisomerization of the azobenzene group in LMWG 1 can also trigger the gel-sol transition. Therefore, organogels with LMWG 1 respond not only to thermal stimuli but also to redox reactions and light irradiation.

Convenient and Continuous Fluorometric Assay Method for Acetylcholinesterase and Inhibitor Screening Based on the Aggregation-Induced Emission

A new convenient and continuous fluorometric assay method for acetylcholinesterase (AChE) and its inhibitor screening is successfully established with the ensemble of 1 [a TPE (tetraphenylethylene) compound with two sulfonate (-SO(3)(-)) units] and myristoylcholine (an amphiphilic compound as a good substrate of AChE). This new assay method is designed by making use of the aggregation-induced emission (AIE) feature of TPE compounds. Both dynamic light scattering (DLS) and fluorescence confocal microscopic measurements indicated the formation of aggregation complex for the ensemble of 1 and myristoylcholine and further disassembly of the aggregation complex after introducing AChE. The analysis for AChE can be carried out continuously, and AChE with concentration as low as 0.5 U/mL can be assayed. The results also clearly demonstrate the usefulness of this convenient assay method for kinetic study of AChE-catalyzed myristoylcholine hydrolysis and screening inhibitors of AChE. Given its simplicity and easy operation, this method may extend to high-throughput screening of AChE inhibitors and relevant Alzheimers disease (AD) drug discovery.

Stimuli responsive gels based on low molecular weight gelators

In this feature article we summarize the recent developments of stimuli responsive gels based on low molecular weight gelators (LMWGs) for which the gel-sol transitions can be triggered by other stimuli besides heating. These include gels responsive to redox reactions and light irradiations. Chemoresponsive gels are also introduced, including those for which the gel-sol transitions can be induced by reactions with neutral molecules and those for which the gel strength is improved following the addition of neutral molecules. Perspectives for such stimuli responsive gels are discussed with regard to their potential applications and remaining challenging issues.

Fluorescence turn-on detection of DNA and label-free fluorescence nuclease assay based on the aggregation-induced emission of silole.

By making use of the aggregation-induced emission feature of silole, compound 1 with an ammonium group is designed and synthesized with a view to developing a new optical probe for fluorescence turn-on detection of DNA and label-free fluorescence nuclease assay. The fluorescence of 1 increases largely upon mixing with DNA, in particular for long DNA, indicating that 1 can be used for fluorescence turn-on detection of DNA. More interestingly, 1 can be employed to follow the DNA cleavage process by nuclease. Therefore, a label-free fluorescence nuclease assay method is successfully established with 1. Furthermore, this label-free fluorescence assay can also be used for inhibitor screening of nucleases. Given its simplicity, easy operation, sensitivity and cost-effectiveness, this method can be extended to other nuclease assays and high-throughput screening of nuclease inhibitors.

A Fluorescence Turn-on Detection of Cyanide in Aqueous Solution Based on the Aggregation-Induced Emission

The nucleophilic addition of cyanide to the trifluoroacetylamino group in 2 yields an amphiphilic species which would induce the aggregation of silole 1, and as a result, the fluorescence of the ensemble increases largely. Accordingly, a fluorescence turn-on detection of cyanide in aqueous solution can be established with the ensemble of silole 1 and compound 2. Also, this ensemble displays good selectivity toward cyanide over other common inorganic anions.

Targeted bioimaging and photodynamic therapy of cancer cells with an activatable red fluorescent bioprobe.

A new red-emissive bioprobe TPE-red-2AP2H was developed by taking advantage of the unique emission feature of tetraphenylethylene and a cancer cell-specific peptide. By responding to the target protein and the acidic microenvironment of tumor cells, activated fluorescence bioimaging was achieved with high signal-to-noise ratio and without involving mutiple washing steps. Apart from targeting the membrane-anchored LAPTM4B proteins, TPE-red-2AP2H was successfully utilized to trace the intracellular movement of LAPTM4B protein. The generation of (1)O2 under visible light irradiation makes this bioprobe also promising for targeted-photodynamic therapy. By discriminating the expression level of the target protein, TPE-red-2AP2H can respond to the progression status of tumors with different photodynamic therapy effect.

New Organic Semiconductors with Imide/Amide‐Containing Molecular Systems

Due to their high electron affinities, chemical and thermal stabilities, π-conjugated molecules with imide/amide frameworks have received considerable attentions as promising candidates for high-performance optoelectronic materials, particularly for organic semiconductors with high carrier mobilities. The purpose of this Research News is to give an overview of recent advances in development of high performance imide/amide based organic semiconductors for field-effect transistors. It covers naphthalene diimide-, perylene diimide- and amide-based conjugated molecules and polymers for organic semiconductors.

Continuous Colorimetric Assay for Acetylcholinesterase and Inhibitor Screening with Gold Nanoparticles

We report herein a new colorimetric assay method for acetylcholinesterase (AChE) activity and its inhibitor screening by making use of the following facts: (1) the aggregation of gold nanoparticles (Au-NPs) results in the red-shift of the plasmon absorption due to interparticle plasmon interactions and (2) AChE can catalyze the hydrolysis of acetylthiocholine into thiocholine which can induce the aggregation of Au-NPs. With this convenient method, the activity of AChE with a concentration as low as 0.6 mU/mL can be assayed. Moreover, this assay method is also useful for screening inhibitors of AChE. Given its simplicity and easy-operation, this method may extend to high-throughput screening of AChE inhibitors and relevant drug discovery.

Aqueous fluorescence turn-on sensor for Zn2+ with a tetraphenylethylene compound.

A new sensitive and selective fluorescence turn-on sensor for Zn(2+) (1) was developed by taking advantage of the aggregation-induced emission of the tetraphenylethylene framework. In addition, the corresponding ester precursor of 1 was successfully used for intracellular Zn(2+) imaging.