Fang Hu

Pd(II)-catalyzed alkoxylation of unactivated C(sp3)–H and C(sp2)–H bonds using a removable directing group: efficient synthesis of alkyl ethers

The Pd(II)-catalyzed alkoxylation of unactivated C(sp3)–H and C(sp2)–H bonds using a new bidentate directing group has been developed. Alkoxylation occurs selectively at the β position with broad substrate scope and high tolerance of functional groups (chloro, cyano, ether, ester, olefin, amino, etc.). Besides alkoxylation of the β-C–H bonds, γ-alkoxylation of C(sp2)–H bonds could also be achieved, provided that no reactive β-C–H bonds were present. In addition, this DG is readily available and removable.

Pd(II)-catalyzed alkylation of unactivated C(sp3)–H bonds: efficient synthesis of optically active unnatural α-amino acids

A palladium-catalyzed alkylation of primary and secondary C(sp3)–H bonds with alkyl iodides and/or bromides for the synthesis of optically active unnatural α-amino acids (α-AAs) is described. This process is scalable and tolerates a variety of functional groups with complete retention of chirality, providing an efficient new strategy for the synthesis of various unnatural α-amino acid derivatives.

Identification of Bacteria in Water by a Fluorescent Array

We report a method for the rapid and efficient identification of bacteria making use of five probes having fluorescent characteristics (F-array) and subsequent statistical analysis. Eight kinds of bacteria, including normal and multidrug-resistant bacteria, are differentiated successfully. Our easy-to-perform and time-saving method consists of mixing bacteria and probes, recording fluorescent intensity data by automated flow cytometry, and statistical analysis. No washing steps are required in order to identify the different bacteria simultaneously.

Manipulation of the Aggregation and Deaggregation of Tetraphenylethylene and Silole Fluorophores by Amphiphiles: Emission Modulation and Sensing Applications

In this Feature Article, we have summarized the recent advances in the fluorescence modulation of tetraphenylethylene and silole fluorophores by manipulating the respective aggregation/deaggregation with amphiphiles. These include (i) the assembly of neutral tetraphenylethylene analogues with the aid of an ionic amphiphile, (ii) the aggregation of ionic tetraphenylethylene and silole induced by amphiphiles, and (iii) bio/chemosensors based on the aggregation/deaggregation of AIE fluorophores tuned by ionic amphiphiles.

Highly Solid-State Emissive Pyridinium-Substituted Tetraphenylethylene Salts: Emission Color-Tuning with Counter Anions and Application for Optical Waveguides

In this paper seven salts of pyridinium-substituted tetraphenylethylene with different anions are reported. They show typical aggregation-induced emission. Crystal structures of three of the salts with (CF(3)SO(2))(2) N(-), CF(3) SO(3)(-), and SbF(6)(-) as the respective counter anions, are determined. The emission behavior of their amorphous and crystalline solids is investigated. Both amorphous and crystalline solids, except for the one with I(-), are highly emissive. Certain amorphous solids are red-emissive with almost the same quantum yields and fluorescence life-times. However, some crystalline solids are found to show different emission colors varying from green to yellow. Thus, their emission colors can be tuned by the counter anions. Furthermore, certain crystalline solids are highly emissive compared to the respective amorphous solids. Such solid-state emission behavior of these pyridinium-substituted tetraphenylethylene salts is interpreted on the basis of their crystal structures. In addition, optical waveguiding behavior of fabricated microrods is presented.

Organelle-specific bioprobes based on fluorogens with aggregation-induced emission (AIE) characteristics

Bioprobes based on fluorogens with aggregation-induced emission (AIE) characteristics have been increasingly used in chemosensing and bioimaging due to their high sensitivity, photostability and biocompatibility. In this review, we summarize the design of cellular organelle specific (cytoplasm membrane, mitochondria, lysosomes, lipid droplets and nucleus) AIE bioprobes and their applications in organelle imaging, organelle bioactivity monitoring, and image-guided cancer cell ablation.

A Highly Efficient and Photostable Photosensitizer with Near-Infrared Aggregation-Induced Emission for Image-Guided Photodynamic Anticancer Therapy

Photodynamic therapy (PDT), which relies on photosensitizers (PS) and light to generate reactive oxygen species to kill cancer cells or bacteria, has attracted much attention in recent years. PSs with both bright emission and efficient singlet oxygen generation have also been used for image-guided PDT. However, simultaneously achieving effective 1 O2 generation, long wavelength absorption, and stable near-infrared (NIR) emission with low dark toxicity in a single PS remains challenging. In addition, it is well known that when traditional PSs are made into nanoparticles, they encounter quenched fluorescence and reduced 1 O2 production. In this contribution, these challenging issues have been successfully addressed through designing the first photostable photosensitizer with aggregation-induced NIR emission and very effective 1 O2 generation in aggregate state. The yielded nanoparticles show very effective 1 O2 generation, bright NIR fluorescence centered at 820 nm, excellent photostability, good biocompatibility, and negligible dark in vivo toxicity. Both in vitro and in vivo experiments prove that the nanoparticles are excellent candidates for image-guided photodynamic anticancer therapy.

Metal-Ion-Promoted Electron Transfer between Tetrathiafulvalene and Quinone Units Within a Calix[4]arene Framework and Tuning through Coordination of the Neighboring Crown Ether with a Sodium Cation

A new calix[4]arene 1 with tetrathiafulvalene (TTF), quinone, and crown ether units in the lower rim was designed and synthesized with the aim to investigate the possibility to tune the metal-ion promoted electron transfer by coordination of the crown ether unit with additional metal ions. Both absorption and electron spin resonance (ESR) spectroscopic studies clearly indicate that electron transfer occurs efficiently from TTF to the quinone units in the presence of Sc(3+)/Pb(2+)/Zn(2+). Moreover, the intramolecular electron transfer within 1 induced by Zn(2+) can be switched off by addition of Na(+) and further turned on by addition of either Sc(3+) or Pb(2+).

Metal–Organic-Framework-Assisted In Vivo Bacterial Metabolic Labeling and Precise Antibacterial Therapy

Bacterial infection is one of the most serious physiological conditions threatening human health. There is an increasing demand for more effective bacterial diagnosis and treatment through noninvasive theranostic approaches. Herein, a new strategy is reported to achieve in vivo metabolic labeling of bacteria through the use of MIL-100 (Fe) nanoparticles (NPs) as the nanocarrier for precise delivery of 3-azido-d-alanine (d-AzAla). After intravenous injection, MIL-100 (Fe) NPs can accumulate preferentially and degrade rapidly within the high H2 O2 inflammatory environment, releasing d-AzAla in the process. d-AzAla is selectively integrated into the cell walls of bacteria, which is confirmed by fluorescence signals from clickable DBCO-Cy5. Ultrasmall photosensitizer NPs with aggregation-induced emission characteristics are subsequently designed to react with the modified bacteria through in vivo click chemistry. Through photodynamic therapy, the amount of bacteria on the infected tissue can be significantly reduced. Overall, this study demonstrates the advantages of metal-organic-framework-assisted bacteria metabolic labeling strategy for precise bacterial detection and therapy guided by fluorescence imaging.

Specific Light-Up Probe with Aggregation-Induced Emission for Facile Detection of Chymase

Human chymases are important proteases abundant in mast cell granules. The elevated level of chymases and other serine proteases is closely related to inflammatory and immunoregulatory functions. Monitoring of the chymase level is very important, however, the existing methods remain limited and insufficient. In this work, a light-up probe of TPETH-2(CFTERD3) (where CFTERD is Cys-Phe-Thr-Glu-Arg-Asp) was developed for chymase detection. The probe has low fluorescent signal in aqueous media, but its solubility can be changed after hydrolysis by chymase, giving significant fluorescence turn-on with a high signal-to-noise (S/N) ratio. The probe has excellent selectivity to chymase compared to other proteins and can effectively differentiate chymase from other enzymes (e.g., chymotrypsin and trypsin) in the same family (E.C. 3.4.21). The detection limit is calculated to be 0.1 ng/mL in PBS buffer with a linear range of 0-9.0 ng/mL. A comparison study using TPETH-2(CFTERD2) as the probe reveals the importance of molecular design in realizing the high S/N ratio. TPETH-2(CFTERD3) thus represents a simple turn-on probe for chymase detection, with real-time and direct readout and also excellent sensitivity and selectivity.