Publications by authors named "Jacky W Y Lam"

257 Publications

A biocompatible dual-AIEgen system without spectral overlap for quantitation of microbial viability and monitoring of biofilm formation.

Mater Horiz 2021 Jun 23;8(6):1816-1824. Epub 2021 Apr 23.

Department of Chemistry, Department of Chemical and Biological Engineering, Hong Kong Branch of Chinese Nation-al Engineering Research Center for Tissue Restoration and Reconstruction, Institute of Advanced Study and Division of Life Science The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

The lack of rapid and reliable microbial detection and sensing platforms and insufficient understanding of microbial behavior may delay precautions that could be made, which is a great threat to human life and increases the heavy financial burden on society. In this contribution, a dual-aggregation-induced emission luminogen (AIEgen) system is successfully developed for microbial imaging and metabolic status sensing. This system consists of two AIEgens (DCQA and TPE-2BA) that bear positively charged groups or boronic acid groups, providing universal microbial staining ability and specific affinity for dead microbes, respectively. Based on the distinctive fluorescence response produced by the diverse interaction of AIEgens with live or dead microbes, this dual-AIEgen system can detect all the microbes and identify their viabilities. Furthermore, the morphology and metabolic status of a sessile biofilm can also be imaged and monitored. The system exhibits rapid labelling properties that suitable for various microbes, and good biocompatibilities.
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http://dx.doi.org/10.1039/d1mh00149cDOI Listing
June 2021

Augmenting photosynthesis through facile AIEgen-chloroplast conjugation and efficient solar energy utilization.

Mater Horiz 2021 May 26;8(5):1433-1438. Epub 2021 Apr 26.

Department of Chemical and Biological Engineering, Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Division of Life Science and Institute of Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Photosynthesis is regarded as the foundation for sustaining life on our planet. Light-harvesting is the initial step that activates the subsequent photochemical reactions. In the photosystems, chloroplast is the basic light-driven metabolic factory of higher plant cells. However, there is an incomplete match between the solar radiation spectrum and absorption profile of chloroplasts. It is hard for the photosynthetic pigments to fully utilize the sunlight energy. Here, we designed two new aggregation-induced emission (AIE) molecules with activated alkyl groups (TPE-PPO and TPA-TPO). Via a facile metal-free "Click" reaction, we realized the substantial manipulation of live chloroplasts with the AIE luminogens (AIEgens). Owing to the matched photophysical properties, the AIEgens could harvest harmful ultraviolet radiation (HUVR) and photosynthetically inefficient radiation (PIR), and further convert them into photosynthetically active radiation (PAR) for chloroplast absorption. As a result, the conjugated AIEgen-chloroplast exhibited better capability of water splitting and electron separation. It promoted the generation of adenosine triphosphate (ATP), which is an important product of photosynthesis. This work provides an effective strategy for improving plant photosynthesis.
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http://dx.doi.org/10.1039/d1mh00012hDOI Listing
May 2021

Metal-Based Aggregation-Induced Emission Theranostic Systems.

ChemMedChem 2021 Nov 27. Epub 2021 Nov 27.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Guangdong-Hong Kong-Macau Joint Laboratory of Optoelectronic and Magnetic Functional Materials, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Efficient theranostic systems can realize better outcomes in disease treatment because of precise diagnosis and the concomitant effective therapy. Aggregation-induced emission luminogens (AIEgens) are a unique type of organic emitters with intriguing photophysical properties in the aggregate state. Among the AIEgens studied for biomedical applications, so far, metal-based AIE systems have shown great potential in theranostics due to the enhanced multimodal bioimaging ability and therapeutic effect. This research field has been growing rapidly, and many rationally designed systems with promising activities to cancer and other diseases have been reported recently. In this review, we summarized the recent progress of metal-based AIE materials in bioimaging and biological theranostics, and deciphered the pertinent design strategies. We hope that this review can offer new insights into the development of this growing field.
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http://dx.doi.org/10.1002/cmdc.202100578DOI Listing
November 2021

A synergy between the push-pull electronic effect and twisted conformation for high-contrast mechanochromic AIEgens.

Mater Horiz 2021 Feb 15;8(2):630-638. Epub 2020 Dec 15.

AIE Research Center, Shaanxi Key Laboratory of Phytochemistry, College of Chemistry and Chemical Engineering, Baoji University of Arts and Sciences, Baoji 721013, China.

Mechanochromic (MC) luminogens in response to external stimulus have shown promising applications as pressure sensors and memory devices. Meanwhile, research on their underlying mechanism is still in the initial stage. Here, three pyridinium-functionalized tetraphenylethylenes bearing n-pentyloxy, hydrogen and nitro groups, namely TPE-OP, TPE-H and TPE-NO, are designed to systematically investigate the influence of the push-pull electronic effect and molecular conformation on MC luminescence. Upon anisotropic grinding and isotropic hydrostatic compression, TPE-OP with strong intramolecular charge transfer (ICT) affords the best MC behavior among them. Analysis of three polymorphs of TPE-H clearly indicates that planarization of the molecular conformation plays an important role in their bathochromic shifts under mechanical stimuli. Theoretical calculations also verify that high twisting stress of AIEgens can be released under high pressure. This study presents a mechanistic insight into MC behaviour and an effective strategy to achieve high-contrast MC luminescence.
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http://dx.doi.org/10.1039/d0mh01251cDOI Listing
February 2021

Vision redemption: Self-reporting AIEgens for combined treatment of bacterial keratitis.

Biomaterials 2021 Dec 22;279:121227. Epub 2021 Oct 22.

Department of Chemical and Biological Engineering, Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Division of Life Science and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, 999077, China; Shenzhen Institute of Molecular Aggregate Science and Engineering, School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, 518172, China. Electronic address:

Bacterial keratitis (BK) is one of the most commonly leading causes of visual impairment and blindness worldwide, and suffers the risk of drug-resistant infections due to the abuse of antibiotics. Herein, we report a cationic diphenyl luminogen with aggregation-induced emission called IQ-Cm containing isoquinolinium and coumarin units for theranostic study of BK. IQ-Cm has no obvious cytotoxicity to mammalian cells below a certain concentration, and could preferentially bind to bacteria over mammalian cells. IQ-Cm can be used as a sensitive self-reporting probe to rapidly discriminate live and dead bacteria by the visual emission colors. The intrinsic dark toxicity to bacteria and generation of reactive oxygen species under light irradiation endow IQ-Cm with excellent antibacterial activity in vitro and in BK rabbit models infected with S. aureus. The present study provides a sensitive and efficient theranostic strategy for rapid discrimination of various bacterial states and the combined treatment of BK based on the intrinsic dark antibacterial activity and photodynamic therapy effect.
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http://dx.doi.org/10.1016/j.biomaterials.2021.121227DOI Listing
December 2021

Mechanistic connotations of restriction of intramolecular motions (RIM).

Natl Sci Rev 2021 Jun 11;8(6):nwaa260. Epub 2021 Jun 11.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study and Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, China.

Restriction of intramolecular motion (RIM) is the widely-accpeted mechanism of aggregation-induced emission (AIE). In this concise and comprehensive perspective, four mechanistic models related to different nonradiative pathways are summarized with examples to disclose the connotation of RIM, and meaningful mechanistic topics for future researches are advised.
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http://dx.doi.org/10.1093/nsr/nwaa260DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8288185PMC
June 2021

In Situ Generation of Heterocyclic Polymers by Triple-Bond Based Polymerizations.

Macromol Rapid Commun 2021 Oct 15:e2100524. Epub 2021 Oct 15.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, and Institute of Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Stemming from unique ring structures, heterocyclic polymers exhibit distinguished electrical, mechanical, and photophysical properties and have been widely used in a variety of important applications. Along with the technological significance are the challenges in their synthesis. Traditional synthetic strategies toward heterocyclic polymers often require the direct attachment of heterocycles to polymer backbones, which are generally limited by the lack of suitable and low-cost heterocyclic monomers, tedious reaction process, difficulties in incorporation of multiple substitutents, etc. Alternatively, in situ construction of heterocyclic polymers via triple-bond based polymerization offers promising prospects. This review summarized the recent progress on polymerizations of triple-bond based monomers including alkynes, nitriles, and isonitriles that can in situ generate heterocyclic polymers. The properties and advanced applications of the derived heterocyclic polymers will also be discussed. Finally, the future perspectives and challenges in this field will be addressed.
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http://dx.doi.org/10.1002/marc.202100524DOI Listing
October 2021

Phototriggered Aggregation-Induced Emission and Direct Generation of 4D Soft Patterns.

Adv Mater 2021 Dec 4;33(48):e2105113. Epub 2021 Oct 4.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology (HKUST), Clear Water Bay, Kowloon, Hong Kong, 999077, China.

Microscopic control of macroscopic phenomena is one of the core subjects in materials science. Particularly, the spatio-temporal control of material behaviors through a non-contact way is of fundamental importance but is difficult to accomplish. Herein, a strategy to realize remote spatio-temporal control of luminescence behaviors is reported. A multi-arm salicylaldehyde benzoylhydrazone-based aggregation-induced emission luminogen (AIEgen)/metal-ion system, of which the fluorescence can be gated by the UV irradiation with time dependency, is developed. By changing the metal-ion species, the fluorescence emission and the intensity can also be tuned. The mechanism of the UV-mediated fluorescence change is investigated, and it is revealed that a phototriggered aggregation-induced emission (PTAIE) process contributes to the behaviors. The AIEgen is further covalently integrated into a polymeric network and the formed gel/metal-ion system can achieve laser-mediated mask-free writing enabled by the PTAIE process. Moreover, by further taking advantage of the time-dependent self-healing property of hydrazone-based dynamic covalent bond, transformable 4D soft patterns are generated. The findings and the strategy increase the ways to manipulate molecules on the supramolecule or aggregate level. They also show opportunities for the development of controllable smart materials and expand the scope of the materials in advanced optoelectronic applications.
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http://dx.doi.org/10.1002/adma.202105113DOI Listing
December 2021

Highly efficient photothermal nanoparticles for the rapid eradication of bacterial biofilms.

Nanoscale 2021 Aug 3;13(32):13610-13616. Epub 2021 Aug 3.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Biofilm-related infections, such as dental plaque, chronic sinusitis, native valve endocarditis, and chronic airway infections in cystic fibrosis have brought serious suffering to patients and financial burden to society. Materials that can eliminate mature biofilms without developing drug resistance are promising tools to treat biofilm-related infections, and thus they are in urgent demand. Herein, we designed and readily prepared organic nanoparticles (NPs) with highly efficient photothermal conversion by harvesting energy via excited-state intramolecular motions and enlarging molar absorptivity. The photothermal NPs can sufficiently eliminate mature bacterial biofilms upon low-power near-infrared laser irradiation. NPs hold great promise for the rapid eradication of bacterial biofilms by photothermal therapy.
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http://dx.doi.org/10.1039/d1nr03471eDOI Listing
August 2021

Catalyst-Free Spontaneous Polymerization with 100% Atom Economy: Facile Synthesis of Photoresponsive Polysulfonates with Multifunctionalities.

JACS Au 2021 Mar 19;1(3):344-353. Epub 2021 Feb 19.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Photoresponsive polymers have attracted extensive attention due to their tunable functionalities and advanced applications; thus, it is significant to develop facile synthesis strategies, extend polymers family, and establish various applications for photoresponsive polymers. Herein, we develop a catalyst-free spontaneous polymerization of dihaloalkynes and disulfonic acids without photosensitive monomers for the synthesis of photoresponsive polysulfonates at room temperature in air with 100% atom economy in high yields. The resulting polysulfonates could undergo visible photodegradation with strong photoacid generation, leading to various applications including dual-emissive or 3D photopatterning, and practical broad-spectrum antibacterial activity. The halogen-rich polysulfonates also exhibit a high and photoswitched refractive index and could undergo efficient postfunctionalizations to further expand the variety and functionality of photoresponsive heteroatom-containing polyesters.
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http://dx.doi.org/10.1021/jacsau.0c00100DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8395608PMC
March 2021

Recent Advances in Aggregation-Induced Emission Materials and Their Biomedical and Healthcare Applications.

Adv Healthc Mater 2021 Aug 21:e2101055. Epub 2021 Aug 21.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

The emergence of the concept of aggregation-induced emission (AIE) has opened new opportunities in many research areas, such as biopsy analysis, biological processes monitoring, and elucidation of key physiological and pathological behaviors. As a new class of luminescent materials, AIE luminogens (AIEgens) possess many prominent advantages such as tunable molecular structures, high molar absorptivity, high brightness, large Stokes shift, excellent photostability, and good biocompatibility. The past two decades have witnessed a dramatic growth of research interest in AIE, and many AIE-based bioprobes with excellent performance have been widely explored in biomedical fields. This review summarizes some of the latest advancements of AIE molecular probes and AIE nanoparticles (NPs) with regards to biomedical and healthcare applications. According to the research areas, the review is divided into five sections, which are imaging and identification of cells and bacteria, photodynamic therapy, multimodal theranostics, deep tissue imaging, and fluorescence-guided surgery. The challenges and future opportunities of AIE materials in the advanced biomedical fields are briefly discussed. In perspective, the AIE-based bioprobes play vital roles in the exploration of advanced bioapplications for the ultimate goal of addressing more healthcare issues by integrating various cutting-edge modalities and techniques.
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http://dx.doi.org/10.1002/adhm.202101055DOI Listing
August 2021

Hydrophilicity-Hydrophobicity Transformation, Thermoresponsive Morphomechanics, and Crack Multifurcation Revealed by AIEgens in Mechanically Strong Hydrogels.

Adv Mater 2021 Oct 4;33(39):e2101500. Epub 2021 Aug 4.

Department of Chemistry, the Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, The Hong Kong University of Science and Technology, Guangdong-Hong Kong-Macro Joint Laboratory of Optoelectronic and Magnetic Functional Materials, Clear Water Bay, Kowloon, Hong Kong, 999077, China.

Biomimetic exploration of stimuli-responsive and crack-resistant hydrogels is of great academic and practical significance, although the rational design of tough hydrogels is limited by insufficient mechanism study due to the lack of imaging techniques to "see" hydrogels at mesoscale level. A series of composite hydrogels with compartmentalized thermal response is designed by incorporating aggregation- and polarity-sensitive fluorescent probes in a poly(N-isopropylacrylamide) (PNIPAM) network grafted with poly(N,N-dimethylacrylamide) side-chains. The fluorescence technique is explored as a powerful tool to directly visualize their hydrophilicity-hydrophobicity transformation and the composition-dependent microphase separation. Based on the morphological observation and mechanical measurements, the concept of morphomechanics with a comprehensive mechanism clarification is proposed. In this regard, the thermoresponsive toughening is attributed to the formation of multiple noncovalent interactions and the conformational changes of PNIPAM chains. The enhanced fracture energy by crack multifurcation is related to the tearing-like disruption of weak interfaces between the separated phases.
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http://dx.doi.org/10.1002/adma.202101500DOI Listing
October 2021

Real-Time Visualization and Monitoring of Physiological Dynamics by Aggregation-Induced Emission Luminogens (AIEgens).

Annu Rev Anal Chem (Palo Alto Calif) 2021 07 27;14(1):413-435. Epub 2021 Jul 27.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Centre for Tissue Restoration and Reconstruction, Institute for Advanced Study, Division of Life Science and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China; email:

Physiological dynamics in living cells and tissues are crucial for maintenance and regulation of their normal activities and functionalities. Tiny fluctuations in physiological microenvironments can leverage significant influences on cell growth, metabolism, differentiation, and apoptosis as well as disease evolution. Fluorescence imaging based on aggregation-induced emission luminogens (AIEgens) exhibits superior advantages in real-time sensing and monitoring of the physiological dynamics in living systems, including its unique properties such as high sensitivity and rapid response, flexible molecular design, and versatile nano- to mesostructural fabrication. The introduction of canonic AIEgens with long-wavelength, near-infrared, or microwave emission, persistent luminescence, and diversified excitation source (e.g., chemo- or bioluminescence) offers researchers a tool to evaluate the resulting molecules with excellent performance in response to subtle fluctuations in bioactivities with broader dimensionalities and deeper hierarchies.
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http://dx.doi.org/10.1146/annurev-anchem-090420-101149DOI Listing
July 2021

Side Area-Assisted 3D Evaporator with Antibiofouling Function for Ultra-Efficient Solar Steam Generation.

Adv Mater 2021 Sep 26;33(36):e2102258. Epub 2021 Jul 26.

Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, 999077, China.

Solar-driven interfacial steam generation (SISG) has been recognized as a promising strategy to solve water shortages in an eco-friendly and low-cost way. However, the practical application of SISG is vitally restricted by some inherent limits, especially for finite evaporation rate and insufficient working life of evaporator. Herein, a novel SISG system involving an all-fiber porous cylinder-like foam 3D evaporator, side area-assisted evaporation protocol, and aggregation-induced-emission-active solar absorber with "one stone two birds" function is explored. The solar absorber exhibits efficient photothermal conversion, endowing the side area-assisted evaporator with as high as 3.6 kg m h of solar evaporation rate, which is highly desirable for SISG under 1 sun of irradiation. Moreover, the solar absorber is capable of powerfully producing reactive oxygen species upon sunlight irradiation, which results in extraordinary photodynamic killing of bacteria nearby the fiber to prevent biofouling, consequently improving the working life of evaporator.
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http://dx.doi.org/10.1002/adma.202102258DOI Listing
September 2021

How Do Molecular Motions Affect Structures and Properties at Molecule and Aggregate Levels?

J Am Chem Soc 2021 08 22;143(30):11820-11827. Epub 2021 Jul 22.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China.

Molecular motions are essential natures of matter and play important roles in their structures and properties. However, owing to the diversity and complexity of structures and behaviors, the study of motion-structure-property relationships remains a challenge, especially at all levels of structural hierarchy from molecules to macro-objects. Herein, luminogens showing aggregation-induced emission (AIE), namely, 9-(pyrimidin-2-yl)-carbazole (PyCz) and 9-(5-R-pyrimidin-2-yl)-carbazole [R = Cl (ClPyCz), Br (BrPyCz), and CN (CyPyCz)], were designed and synthesized, to decipher the dependence of materials' structures and properties on molecular motions at the molecule and aggregate levels. Experimental and theoretical analysis demonstrated that the active intramolecular motions in the excited state of all molecules at the single-molecule level endowed them with more twisted structural conformations and weak emission. However, owing to the restriction of intramolecular motions in the nano/macroaggregate state, all the molecules assumed less twisted conformations with bright emission. Unexpectedly, intermolecular motions could be activated in the macrocrystals of ClPyCz, BrPyCz, and CyPyCz through the introduction of external perturbations, and synergic strong and weak intermolecular interactions allowed their crystals to undergo reversible deformation, which effectively solved the problem of the brittleness of organic crystals, while endowing them with excellent elastic performance. Thus, the present study provided insights on the motion-structure-property relationship at each level of structural hierarchy and offered a paradigm to rationally design multifunctional AIE-based materials.
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http://dx.doi.org/10.1021/jacs.1c05647DOI Listing
August 2021

Mitochondria-Specific Aggregation-Induced Emission Luminogens for Selective Photodynamic Killing of Fungi and Efficacious Treatment of Keratitis.

ACS Nano 2021 Jun 28. Epub 2021 Jun 28.

Department of Chemistry, Department of Chemical and Biological Engineering, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, and SCUT-HKUST Joint Research Laboratory, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong China.

The development of effective antifungal agents remains a big challenge in view of the close evolutionary relationship between mammalian cells and fungi. Moreover, rapid mutations of fungal receptors at the molecular level result in the emergence of drug resistance. Here, with low tendency to develop drug-resistance, the subcellular organelle mitochondrion is exploited as an alternative target for efficient fungal killing by photodynamic therapy (PDT) of mitochondrial-targeting luminogens with aggregation-induced emission characteristics (AIEgens). With cationic isoquinolinium (IQ) moiety and proper hydrophobicity, three AIEgens, namely, IQ-TPE-2O, IQ-Cm, and IQ-TPA, can preferentially accumulate at the mitochondria of fungi over the mammalian cells. Upon white light irradiation, these AIEgens efficiently generate reactive O, which causes irreversible damage to fungal mitochondria and further triggers the fungal death. Among them, IQ-TPA shows the highest PDT efficiency against fungi and negligible toxicity to mammalian cells, achieving the selective and highly efficient killing of fungi. Furthermore, we tested the clinical utility of this PDT strategy by treating fungal keratitis on a fungus-infected rabbit model. It was demonstrated that IQ-TPA presents obviously better therapeutic effects as compared with the clinically used rose bengal, suggesting the success of this PDT strategy and its great potential for clinical treatment of fungal infections.
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http://dx.doi.org/10.1021/acsnano.1c03508DOI Listing
June 2021

Unusual light-driven amplification through unexpected regioselective photogeneration of five-membered azaheterocyclic AIEgen.

Chem Sci 2020 Oct 19;12(2):709-717. Epub 2020 Oct 19.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, State Key Laboratory of Molecular Nanoscience, Division of Life Science, Department of Chemical and Biomedical Engineering and Institute for Advanced Study, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China

Developing versatile synthetic methodologies with merits of simplicity, efficiency, and environment friendliness for five-membered heterocycles is of incredible importance to pharmaceutical and material science, as well as a huge challenge to synthetic chemistry. Herein, an unexpected regioselective photoreaction to construct a fused five-membered azaheterocycle with an aggregation-induced emission (AIE) characteristic is developed under mild conditions. The formation of the five-membered ring is both thermodynamically and kinetically favored, as justified by theoretical calculation and experimental evidence. Markedly, a light-driven amplification strategy is proposed and applied in selective mitochondria-targeted cancer cell recognition and fluorescent photopattern fabrication with improved resolution. The work not only delivers the first report on efficiently generating a fused five-membered azaheterocyclic AIE luminogen under mild conditions photoreaction, but also offers deep insight into the essence of the photosynthesis of fused five-membered azaheterocyclic compounds.
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http://dx.doi.org/10.1039/d0sc04725bDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8179000PMC
October 2020

Structural and process controls of AIEgens for NIR-II theranostics.

Chem Sci 2020 Jun 12;12(10):3427-3436. Epub 2020 Jun 12.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering, Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China

Aggregation-induced emission (AIE) is a cutting-edge fluorescence technology, giving highly-efficient solid-state photoluminescence. Particularly, AIE luminogens (AIEgens) with emission in the range of second near-infrared window (NIR-II, 1000-1700 nm) have displayed salient advantages for biomedical imaging and therapy. However, the molecular design strategy and underlying mechanism for regulating the balance between fluorescence (radiative pathway) and photothermal effect (non-radiative pathway) in these narrow bandgap materials remain obscure. In this review, we outline the latest achievements in the molecular guidelines and photophysical process control for developing highly efficient NIR-II emitters or photothermal agents with aggregation-induced emission (AIE) attributes. We provide insights to optimize fluorescence efficiency by regulating multi-hierarchical structures from single molecules (flexibilization) to molecular aggregates (rigidification). We also discuss the crucial role of intramolecular motions in molecular aggregates for balancing the functions of fluorescence imaging and photothermal therapy. The superiority of the NIR-II region is demonstrated by fluorescence/photoacoustic imaging of blood vessels and the brain as well as photothermal ablation of the tumor. Finally, a summary of the challenges and perspectives of NIR-II AIEgens for theranostics is given.
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http://dx.doi.org/10.1039/d0sc02911dDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8179408PMC
June 2020

Visualization and Manipulation of Solid-State Molecular Motions in Cocrystallization Processes.

J Am Chem Soc 2021 06 21;143(25):9468-9477. Epub 2021 Jun 21.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Department of Chemical and Biomedical Engineering, Institute for Advanced Study, and Guangdong Hong Kong Macro Joint Laboratory of Optoelectronic and Magnetic Functional Materials, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Solid-state molecular motions (SSMM) play a critical role in adjusting behaviors and properties of materials. However, research on SSMM, especially for multicomponent systems, suffers from various problems and is rarely explored. Herein, through collaboration with cocrystal engineering, visualization and manipulation of SSMM in two-component systems, namely, FSBO (()-2-(4-fluorostyryl)benzo[]oxazole)/TCB (1,2,4,5-tetracyanobenzene) and PVBO (()-2-(2-(pyridin-4-yl)vinyl)benzo[]oxazole)/TCB, were realized. The obtained yellow-emissive F/T (FSBO/TCB) cocrystal displayed turn-on fluorescence, and the green-emissive P/T (PVBO/TCB) cocrystal presented redder emission, both of which exhibited an aggregation-induced emission property. At varied pressure and temperature, the grinding mixtures of FSBO/TCB and PVBO/TCB displayed different molecular motions that were readily observed through the fluorescence signal. Notably, even without grinding, FSBO and TCB molecules could move over for 4 mm in a 1D tube. The unique emission changes induced by SSMM were applied in information storage and dynamic anticounterfeiting. This work not only visualized and manipulated SSMM but offered more insights for multicomponent study in aggregate science.
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http://dx.doi.org/10.1021/jacs.1c02594DOI Listing
June 2021

Stimuli-Responsive AIEgens.

Adv Mater 2021 Aug 17;33(32):e2008071. Epub 2021 Jun 17.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, 999077, China.

The unique advantages and the exciting application prospects of AIEgens have triggered booming developments in this area in recent years. Among them, stimuli-responsive AIEgens have received particular attention and impressive progress, and they have been demonstrated to show tremendous potential in many fields from physical chemistry to materials science and to biology and medicine. Here, the recent achievements of stimuli-responsive AIEgens in terms of seven most representative types of stimuli including force, light, polarity, temperature, electricity, ion, and pH, are summarized. Based on typical examples, it is illustrated how each type of systems realize the desired stimuli-responsive performance for various applications. The key work principles behind them are ultimately deciphered and figured out to offer new insights and guidelines for the design and engineering of the next-generation stimuli-responsive luminescent materials for more broad applications.
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http://dx.doi.org/10.1002/adma.202008071DOI Listing
August 2021

Simultaneously boosting the conjugation, brightness and solubility of organic fluorophores by using AIEgens.

Chem Sci 2020 Jul 27;11(32):8438-8447. Epub 2020 Jul 27.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Centre for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering, Institute of Molecular Functional Materials, The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China

Organic near-infrared (NIR) emitters hold great promise for biomedical applications. Yet, most organic NIR fluorophores face the limitations of short emission wavelengths, low brightness, unsatisfactory processability, and the aggregation-caused quenching effect. Therefore, development of effective molecular design strategies to improve these important properties at the same time is a highly pursued topic, but very challenging. Herein, aggregation-induced emission luminogens (AIEgens) are employed as substituents to simultaneously extend the conjugation length, boost the fluorescence quantum yield, and increase the solubility of organic NIR fluorophores, being favourable for biological applications. A series of donor-acceptor type compounds with different substituent groups (, hydrogen, phenyl, and tetraphenylethene (TPE)) are synthesized and investigated. Compared to the other two analogs, with TPE substituents exhibits the reddest fluorescence, highest brightness, and best solubility. Both the conjugated structure and twisted conformation of TPE groups endow the resulting compounds with improved fluorescence properties and processability for biomedical applications. The and applications reveal that the NIR nanoparticles function as a potent probe for tumour imaging. This study would provide new insights into the development of efficient building blocks for improving the performance of organic NIR emitters.
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http://dx.doi.org/10.1039/d0sc03423aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8163428PMC
July 2020

How to Manipulate Through-Space Conjugation and Clusteroluminescence of Simple AIEgens with Isolated Phenyl Rings.

J Am Chem Soc 2021 Jun 11;143(25):9565-9574. Epub 2021 Jun 11.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China.

Apart from the traditional through-bond conjugation (TBC), through-space conjugation (TSC) is gradually proved as another important interaction in photophysical processes, especially for the recent observation of clusteroluminescence from nonconjugated molecules. However, unlike TBC in conjugated chromophores, it is still challenging to manipulate TSC and clusteroluminescence. Herein, simple and nonconjugated triphenylmethane (TPM) and its derivatives with electron-donating and electron-withdrawing groups were synthesized, and their photophysical properties were systematically studied. TPM was characterized with visible clusteroluminescence due to the intramolecular TSC. Experimental and theoretical results showed that the introduction of electron-donating groups into TPM could red-shift the wavelength and increase the efficiency of clusteroluminescence simultaneously, due to the increased electronic density and stabilization of TSC. However, TPM derivatives with electron-withdrawing groups showed inefficient or even quenched clusteroluminescence caused by the vigorous excited-state intramolecular motion and intermolecular photoinduced electron transfer process. This work provides a reliable strategy to manipulate TSC and clusteroluminescence.
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http://dx.doi.org/10.1021/jacs.1c03882DOI Listing
June 2021

An Air-Stable Organic Radical from a Controllable Photoinduced Domino Reaction of a Hexa-aryl Substituted Anthracene.

J Org Chem 2021 Jun 25;86(11):7359-7369. Epub 2021 May 25.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering, Division of Life Science, State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Air-stable organic radicals and radical ions have attracted great attention for their far-reaching application ranging from bioimaging to organic electronics. However, because of the highly reactive nature of organic radicals, the design and synthesis of air-stable organic radicals still remains a challenge. Herein, an air-stable organic radical from a controllable photoinduced domino reaction of a hexa-aryl substituted anthracene is described. The domino reaction involves a photoinduced [4 + 2] cycloaddition reaction, rearrangement, photolysis, and an elimination reaction; H/C NMR spectroscopy, high resolution mass spectrometry, single-crystal X-ray diffraction, and EPR spectroscopy were exploited for characterization. Furthermore, a photoinduced domino reaction mechanism is proposed according to the experimental and theoretical studies. In addition, the effects of employing push and pull electronic groups on the controllable photoinduced domino reaction were investigated. This article not only offers a new blue emitter and novel air-stable organic radical compound for potential application in organic semiconductor applications, but also provides a perspective for understanding the fundamentals of the reaction mechanism on going from anthracene to semiquinone in such anthracene systems.
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http://dx.doi.org/10.1021/acs.joc.1c00233DOI Listing
June 2021

Cobalt-Mediated Switchable Catalysis for the One-Pot Synthesis of Cyclic Polymers.

Angew Chem Int Ed Engl 2021 Jul 24;60(31):16974-16979. Epub 2021 Jun 24.

Department of Chemistry, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China.

A cobalt salen pentenoate complex [salen=(R,R)-N,N'-bis(3,5-di-tertbutylsalicylidene)-1,2-cyclohexanediamine] is rationally designed as the catalyst for the ring-opening copolymerization (ROCOP) of epoxides/anhydrides/CO . Via migratory insertion of carbon monoxide (CO) into the Co-O bonds, the ROCOP-active species α-alkene-ω-O-Co (salen) can be rapidly and quantitatively transformed into α-alkene-ω-O C-Co (salen) telechelic linear precursors. Upon dilution of reaction mixtures, the homolytic cleavage of Co-C bonds induced by visible light generates α-alkene acyl radicals that spontaneously undergo intramolecular radical addition to afford organocobalt-functionalized cyclic polyesters and CO -based polycarbonates with excellent regioselectivity. The cyclic products can either react with radical scavengers to generate metal-free cyclic polymers or serve as photo-initiators for organometallic-mediated radical polymerization (OMRP) to produce tadpole-shaped copolymers.
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http://dx.doi.org/10.1002/anie.202106285DOI Listing
July 2021

Heteroaromatic Hyperbranched Polyelectrolytes: Multicomponent Polyannulation and Photodynamic Biopatterning.

Angew Chem Int Ed Engl 2021 08 17;60(35):19222-19231. Epub 2021 Jun 17.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Division of Biomedical Engineering, Division of Life Science, and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

We reported an efficient multicomponent polyannulation for in situ generation of heteroaromatic hyperbranched polyelectrolytes by using readily accessible internal diynes and low-cost, commercially available arylnitriles, NaSbF , and H O/AcOH. The polymers were obtained in excellent yields (up to 99 %) with extraordinary high molecular weights (M up to 1.011×10 ) and low polydispersity indices. The resulting polymers showed good processibility and high quantum yields with tunable emission in the solid state, making them ideal materials for highly ordered fluorescent photopatterning. These hyperbranched polyelectrolytes also possessed strong ability to generate reactive oxygen species, which allowed their applications in efficient bacterial killing and customizable photodynamic patterning of living organisms in a simple and cost-effective way.
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http://dx.doi.org/10.1002/anie.202104709DOI Listing
August 2021

Making Aggregation-Induced Emission Luminogen More Valuable by Gold: Enhancing Anticancer Efficacy by Suppressing Thioredoxin Reductase Activity.

ACS Nano 2021 05 3;15(5):9176-9185. Epub 2021 May 3.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong 999077, China.

Gold complexes have been recognized as potential anticancer agents against various kinds of diseases due to their inherent suppressions of antioxidant thioredoxin reductase (TrxR) activity. Herein, a powerful aggregation-induced emission luminogen (AIEgen), TBP-Au, was designed and synthesized by integrating an anticancer Au(I) moiety with an AIE-active photosensitizer (TBP), in which both the production and consumption routes of reactive oxygen species (ROS) were elaborately considered simultaneously to boost the anticancer efficacy. It has been demonstrated that TBP-Au could realize superior two-photon fluorescence imaging in tumor tissues with high resolution and deep penetration as well as long-term imaging in live animals due to its AIE property. In addition, the introduction of a special Au(I) moiety could tune the organelle specificity and efficiently facilitate the ROS-determined photodynamic therapy (PDT). More impressively, TBP-Au could efficiently eliminate cancer cells under light irradiation through the preconceived synergetic approaches from the PDT and the effective suppression of TrxR, demonstrating that TBP-Au holds great potential for precise cancer theranostics.
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http://dx.doi.org/10.1021/acsnano.1c02882DOI Listing
May 2021

Clusteroluminescence from Cluster Excitons in Small Heterocyclics Free of Aromatic Rings.

Adv Sci (Weinh) 2021 04 11;8(7):2004299. Epub 2021 Feb 11.

Department of Chemistry The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong 999077 China.

The study of nonconventional luminescence is important for revealing the luminescence of natural systems and has gradually drawn the attention of researchers in recent years. However, the underlying mechanism is still inexplicable. Herein, the luminescence behavior of two series of simple, heteroatom-containing small molecules without aromatic rings, i.e., maleimide and succinimide derivatives, are studied to gain further mechanistic insight into the nonconventional luminescence process. It has been unveiled that all the molecules exhibit bright and visible luminescence in concentrated solution and solid state and the formation of clusters is the root cause for such behaviors, which can effectively increase the possibility of both the nonradiative n-* and favorable -* transitions and stabilize the excitons formed in the excited state. The distinctive luminescent phenomena and intriguing mechanism presented in this work will be significant for understanding the mechanism of clusteroluminescence and provide new strategies for the rational design of novel luminescent materials.
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http://dx.doi.org/10.1002/advs.202004299DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8025018PMC
April 2021

Functionalization of Silk by AIEgens through Facile Bioconjugation: Full-Color Fluorescence and Long-Term Bioimaging.

Angew Chem Int Ed Engl 2021 05 28;60(22):12424-12430. Epub 2021 Apr 28.

Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Division of Life Science and State Key Laboratory of Molecular Neuroscience, Institute for Advanced Study and Department of Chemical and Biomedical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China.

Silkworm silk is a promising natural biopolymer for textile and biomedical applications for its remarkable flexibility, excellent biocompatibility and controllable biodegradability. The functionalization of silks makes them more versatile for flexible displays and visible bioscaffolds. However, fluorescent silks are normally fabricated through unstable physical absorption or complicated chemical reactions under harsh conditions. Herein, we developed a simple strategy for preparing fluorescent silks. Five aggregation-induced emission luminogens (AIEgens) with activated alkynes were synthesized by rational molecular design, and then reacted with silk fibers through facile metal-free click bioconjugation. The resulting conjugates show bright full-color emissions and high stability. A white light-emitting silk was fabricated by simultaneous bioconjugation with red-, green- and blue-emissive AIEgens. The red-emissive AIEgen-functionalized silks were successfully applied for long-term cell tracking and two-photon bioimaging, demonstrating great potential for tissue engineering and bioscaffold monitoring.
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http://dx.doi.org/10.1002/anie.202015592DOI Listing
May 2021

Biologically Excretable Aggregation-Induced Emission Dots for Visualizing Through the Marmosets Intravitally: Horizons in Future Clinical Nanomedicine.

Adv Mater 2021 Apr 19;33(17):e2008123. Epub 2021 Mar 19.

State Key Laboratory of Modern Optical Instrumentations, Centre for Optical and Electromagnetic Research, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou, 310058, China.

Superb reliability and biocompatibility equip aggregation-induced emission (AIE) dots with tremendous potential for fluorescence bioimaging. However, there is still a chronic lack of design instructions of excretable and bright AIE emitters. Here, a kind of PEGylated AIE (OTPA-BBT) dots with strong absorption and extremely high second near-infrared region (NIR-II) PLQY of 13.6% is designed, and a long-aliphatic-chain design blueprint contributing to their excretion from an animal's body is proposed. Assisted by the OTPA-BBT dots with bright fluorescence beyond 1100 nm and even 1500 nm (NIR-IIb), large-depth cerebral vasculature (beyond 600 µm) as well as real-time blood flow are monitored through a thinned skull, and noninvasive NIR-IIb imaging with rich high-spatial-frequency information gives a precise presentation of gastrointestinal tract in marmosets. Importantly, after intravenous or oral administration, the definite excretion of OTPA-BBT dots from the body is demonstrated, which provides influential evidence of biosafety.
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http://dx.doi.org/10.1002/adma.202008123DOI Listing
April 2021

Facilitation of molecular motion to develop turn-on photoacoustic bioprobe for detecting nitric oxide in encephalitis.

Nat Commun 2021 02 11;12(1):960. Epub 2021 Feb 11.

Department of Chemistry, The Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Institute for Advanced Study, Department of Chemical and Biological Engineering and Institute of Molecular Functional Materials, The Hong Kong University of Science and Technology, Kowloon, Hong Kong, China.

Nitric oxide (NO) is an important signaling molecule overexpressed in many diseases, thus the development of NO-activatable probes is of vital significance for monitoring related diseases. However, sensitive photoacoustic (PA) probes for detecting NO-associated complicated diseases (e.g., encephalitis), have yet to be developed. Herein, we report a NO-activated PA probe for in vivo detection of encephalitis by tuning the molecular geometry and energy transformation processes. A strong donor-acceptor structure with increased conjugation can be obtained after NO treatment, along with the active intramolecular motion, significantly boosting "turn-on" near-infrared PA property. The molecular probe exhibits high specificity and sensitivity towards NO over interfering reactive species. The probe is capable of detecting and differentiating encephalitis in different severities with high spatiotemporal resolution. This work will inspire more insights into the development of high-performing activatable PA probes for advanced diagnosis by making full use of intramolecular motion and energy transformation processes.
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http://dx.doi.org/10.1038/s41467-021-21208-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7878857PMC
February 2021
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