Direct Synthesis of Photosensitizable Bacterial Cellulose as Engineered Living Material for Skin Wound Repair.

Living materials based on bacterial cellulose (BC) represent a natural and promising candidate for wound dressing. Both physical adsorption and chemical methods have been applied to BC for realizing antibacterial function. However, effective and long-lasting incorporation of bactericidal moieties to BC remains challenging. Herein, a Komagataeibacter sucrofermentans-based direct synthetic method to fabricate photosensitizer-grafted BC through in situ bacterial metabolism in the presence of TPEPy-modified glucose is explored. The results verify that the direct biosynthesis method is efficient and convenient to endow BC with outstanding fluorescence and light-triggered photodynamic bactericidal activity for skin wound repair. This work presents a new approach to fabricate eco-friendly and active wound dressing with light-controlled bactericidal activity by microbial metabolism. The successful modification of the glucose carbon source of microorganisms also offers insights for biosyntheses of other living materials through microbial metabolism.

Metabolically engineered bacteria as light-controlled living therapeutics for anti-angiogenesis tumor therapy.

A living therapeutic system based on attenuated Salmonella was developed via metabolic engineering using an aggregation-induced emission (AIE) photosensitizer MA. The engineered bacteria could localize in the tumor tissues and continue to colonize and express exogenous genes. Under light irradiation, the encoded VEGFR2 gene was released and expressed in tumor tissues, which can suppress angiogenesis induced by a T cell-mediated autoimmune response and inhibit tumor growth.

Nanobody modified high-performance AIE photosensitizer nanoparticles for precise photodynamic oral cancer therapy of patient-derived tumor xenograft.

Photodynamic therapy (PDT) is a promising noninvasive treatment option for patients suffering from superficial tumors, such as oral cancer. However, for photosensitizers (PSs), it remains a grand challenge to simultaneously excel in all the key performance indicators including effective singlet oxygen (1O2) generation under clinical laser, specific targeting function and stable far-red (FR)/near-infrared (NIR) emission with low dark toxicity. In addition, traditional PS nanoparticles (NPs) for clinical use suffer from quenched fluorescence and reduced 1O2 production caused by molecular aggregation. To address these issues, AIEPS5 with aggregation-induced FR/NIR emission and effective 1O2 generation under 532 nm laser irradiation is designed by precise optimization of the chemical structure. By attaching a polyethylene glycol (PEG) chain onto AIEPS5, the yielded amphiphilic AIEPS5-PEG2000 can spontaneously self-assemble into water dispersible NPs, which are further endowed with targeted delivery function via the decoration of anti-Her-2 nanobody (NB). The bespoke AIEPS5-NPs-NB exhibit effective 1O2 generation capability, bright FR/NIR emission centered at 680 nm, and negligible dark toxicity, which outperform Heimbofen, a clinically approved PS in PDT using a patient-derived tumor xenograft model.

Stereoisomerization during Molecular Packing.

Isomerization is an essential chemical process that often evokes dramatic change of chemical, physical, or biological properties. For a long time, isomerization has been known as a transformation that is induced by certain external energy such as light, heat, or mechanical force. Herein, a new isomerization phenomenon is described, which does not require external energy but simply occurs during molecular packing. The proposed isomerization is demonstrated by a series of symmetric donor-acceptor-donor (D-A-D) molecules, the donor of which may adopt two different stereoisomeric forms. Based on the evidence of the asymmetric isomers in crystals, the occurrence of isomerization during molecular packing is proved. Moreover, the unique asymmetric geometry in the solid state favors the restriction of intramolecular motion, resulting in highly efficient organic solids with quantum yields approaching unity.

Activation of Pyroptosis by Membrane-Anchoring AIE Photosensitizer Design: New Prospect for Photodynamic Cancer Cell Ablation.

Pyroptosis as a lytic and inflammatory form of cell death is a powerful tool to fight against cancer. However, pyroptosis is usually activated by chemotherapeutic drugs, which limits its anti-tumor applications due to drug resistance and severe side effects. Herein, we demonstrate that membrane targeting photosensitizers can induce pyroptosis for cancer cell ablation with noninvasiveness and low side effects. A series of membrane anchoring photosensitizers (TBD-R PSs) with aggregation-induced emission (AIE) characteristics were prepared through conjugation of TBD and phenyl ring with cationic chains. Upon light irradiation, cytotoxic ROS were produced in situ, resulting in direct membrane damage and superior cancer cell ablation. Detailed study revealed that pyroptosis gradually became the dominant cell death pathway along with the increase of TBD-R PSs membrane anchoring capability. This study offers a photo-activated pyroptosis-based intervention strategy for cancer cell ablation.

Carrier-Free Hybrid DNA Nanoparticles for Light-Induced Self-Delivery of Functional Nucleic Acid Enzymes.

Herein, we developed hybrid DNAzyme nanoparticles (NPs) to achieve light-induced carrier-free self-delivery of DNAzymes with sufficient cofactor supply and lysosome escape capacity. In this system, aggregation-induced emission (AIE) photosensitizer (PS) (TBD-Br) was grafted onto a phosphorothiolated DNAzyme backbone, which automatically self-assembled to form NPs and the surface phosphorothioate group could easily coordinate with the cofactor Zn2+ in the buffer. When the yielded hybrid DNAzyme NPs were located inside tumor cell lysosomes, the 1O2 from TBD-Br under light illumination could destroy lysosome structure and promote the Zn2+ coordinated DNAzyme NPs escape. Both in vitro and in vivo results demonstrated that the hybrid DNAzyme NPs could downregulate the early growth response factor-1 protein (EGR-1) to inhibit tumor cell growth in addition to induce tumor cell apoptosis by AIE PS (TBD-Br) under light irradiation.

AIEgen-Lipid Conjugate for Rapid Labeling of Neutrophils and Monitoring of Their Behavior.

Studies on neutrophil-based nanotherapeutic engineering have shown great potentials in treating infection and inflammation disorders. Conventional neutrophil labeling methods are time-consuming and often result in undesired contamination and activation since neutrophils are terminal-differentiated cells with a half-life span of only 7 h. A simple, fast, and biocompatible strategy to construct engineered neutrophils is highly desirable but remains difficult to achieve. In this study, we present an AIEgen-lipid conjugate, which can efficiently label harvested neutrophils in 30 s with no washing step required. This fast labeling method does not affect the activation and transmigration property of neutrophils, which has been successfully used to monitor neutrophil behaviors such as the chemotaxis process and migrating function towards inflammation sites both in vitro and in vivo, offering a tantalizing prospect for neutrophil-based nanotherapeutics studies.

HClO-Activated Fluorescence and Photosensitization from an AIE Nanoprobe for Image-Guided Bacterial Ablation in Phagocytes.

Bacteria hiding in host phagocytes are difficult to kill, which can cause phagocyte disorders resulting in local and systemic tissue damage. Effective accumulation of activatable photosensitizers (PSs) in phagocytes to realize selective imaging and on-demand photodynamic ablation of bacteria is of great scientific and practical interests for precise bacteria diagnosis and treatment. Herein, HClO-activatable theranostic nanoprobes, DTF-FFP NPs, for image-guided bacterial ablation in phagocytes are introduced. DTF-FFP NPs are prepared by nanoprecipitation of an HClO-responsive near-infrared molecule FFP and an efficient PS DTF with aggregation-induced emission characteristic using an amphiphilic polymer Pluronic F127 as the encapsulation matrix. As an energy acceptor, FFP can quench both fluorescence and production of reactive oxygen species (ROS) of DTF, thus eliminating the phototoxicity of DTF-FFP NPs in normal cells and tissues. Once delivered to the infection sites, DTF-FFP NPs light up with red fluorescence and efficiently generate ROS owing to the degradation of FFP by the stimulated release of HClO in phagocytes. The selective activation of fluorescence and photosensitization is successfully confirmed by both in vitro and in vivo results, demonstrating the effectiveness and theranostic potential of DTF-FFP NPs in precise bacterial therapy.

Light-Induced Self-Escape of Spherical Nucleic Acid from Endo/Lysosome for Efficient Non-Cationic Gene Delivery.

Developing non-cationic gene carriers and achieving efficient endo/lysosome escape of functional nucleic acids in cytosol are two major challenges faced by the field of gene delivery. Herein, we demonstrate the concept of self-escape spherical nucleic acid (SNA) to achieve light controlled non-cationic gene delivery with sufficient endo/lysosome escape capacity. In this system, Bcl-2 antisense oligonucleotides (OSAs) were conjugated onto the surface of aggregation-induced emission (AIE) photosensitizer (PS) nanoparticles to form core-shell SNA. Once the SNAs were taken up by tumor cells, and upon light irradiation, the accumulative 1 O2 produced by the AIE PSs ruptured the lysosome structure to promote OSA escape. Prominent in vitro and in vivo results revealed that the AIE-based core-shell SNA could downregulate the anti-apoptosis protein (Bcl-2) and induce tumor cell apoptosis without any transfection reagent.

Reprogramming Tumor Microenvironment with Photothermal Therapy.

The tumor microenvironment significantly influences cancer progression and therapeutic response. Reprogramming of tumor microenvironment has emerged as a strategy to assist conventional cancer treatment. In recent years, photothermal therapy has received considerable attention owing to its noninvasiveness, high temporal-spatial resolution, and minimal drug resistance. Apart from ablating cancer cells by generating heat upon light irradiation, photothermal therapy can also affect the tumor microenvironment, such as disrupting the tumor extracellular matrix and tumor vasculature. Moreover, cancer cell death by hyperthermia could potentially activate the immune system to fight against tumor. In this topical review, we focus on the recent progress of photothermal therapy based on tumor microenvironment remodeling, aiming to better guide the design of nanoparticles for cancer photoimmunotherapy.

Specific Near-Infrared Probe for Ultrafast Imaging of Lysosomal ß-Galactosidase in Ovarian Cancer Cells.

Reactivity based fluorescent probes have been widely investigated as a powerful and noninvasive tool for disease diagnosis in recent years. ß-Galactosidase (ß-gal), one of the typical lysosomal glycosidases, is reported to be a vital biomarker overexpressed in primary ovarian cancer cells. Fluorescent probes with excellent performance for endogenous ß-gal detection offer a unique option for visualization and diagnosis of primary ovarian cancer cells. Herein, a near-infrared fluorescent probe Lyso-Gal with lysosome-targeting ability was developed for lysosomal ß-gal detection and imaging in ovarian cancer cells (SKOV-3 cells). Lyso-Gal exhibits weak fluorescence in aqueous solution but emits bright NIR fluorescence at 725 nm after incubation with ß-gal. Highly selective imaging of ovarian cancer cells has been achieved upon incubation with Lyso-Gal for only 1 min. The detection time is extremely short. In comparison with a similar hemicyanine probe, Hx-Gal, without lysosome-targeting ability, Lyso-Gal realizes endogenous ß-gal visualization in lysosomes and shows brighter fluorescence than Hx-Gal in SKOV-3 cells. This work demonstrates the potential of Lyso-Gal for detection of primary ovarian cancer cells by using ß-gal as the biomarker.

Hybrid Nanospheres to Overcome Hypoxia and Intrinsic Oxidative Resistance for Enhanced Photodynamic Therapy.

Photodynamic therapy (PDT) has been a well-accepted clinical treatment for malignant tumors owing to its noninvasiveness and high spatiotemporal selectivity. However, the efficiency of PDT is still severely hindered by an inherent aggregation-caused quenching (ACQ) effect of traditional photosensitizers (PSs), the presence of B-cell lymphoma 2 (Bcl-2), an antiapoptosis protein in cells, and hypoxia in the tumor microenvironment. To address these issues, hybrid nanospheres containing Fe3+, aggregation-induced emission (AIE) PS, and Bcl-2 inhibitor of sabutoclax were constructed via coordination-driven self-assembly in aqueous media. Once the hybrid nanospheres are taken up by tumor cells, intracellular O2 concentration is observed to increase via Fenton reaction driven by Fe3+, whereas intracellular PDT resistance of the AIE PS was mitigated by sabutoclax. The design of the multifunctional hybrid nanospheres demonstrates a prospective nanoplatform for image-guided enhanced PDT of tumors.

Color-Tunable Light-up Bioorthogonal Probes for In Vivo Two-Photon Fluorescence Imaging.

Light-up bioorthogonal probes have attracted increasing attention recently due to their capability to directly image diverse biomolecules in living cells without washing steps. The development of bioorthogonal probes with excellent fluorescent properties suitable for in vivo imaging, such as long excitation/emission wavelength, high fluorescence turn-on ratio, and deep penetration, has been rarely reported. Herein, a series of azide-based light-up bioorthogonal probes with tunable colors based on a weak fluorescent 8-aminoquinoline (AQ) scaffold were designed and synthesized. The azido quinoline derivatives are able to induce large fluorescence enhancement (up to 1352-fold) after click reaction with alkynes. In addition, the probes could be engineered to exhibit excellent two-photon properties (δ=542 GM at 780 nm) after further introducing different styryl groups into the AQ scaffold. Subsequent detailed bioimaging experiments demonstrated that these versatile probes can be successfully used for live cell/zebrafish imaging without washing steps. Further in vivo two-photon imaging experiments demonstrated that these light-up biorthogonal probe outperformed conventional fluorophores, for example, high signal-to-noise ratio and deep tissue penetration. The design strategy reported in this study is a useful approach to realize diverse high-performance biorthogonal light-up probes for in vivo studying.

Precise Molecular Design for High-Performance Luminogens with Aggregation-Induced Emission.

Precise design of fluorescent molecules with desired properties has enabled the rapid development of many research fields. Among the different types of optically active materials, luminogens with aggregation-induced emission (AIEgens) have attracted significant interest over the past two decades. The negligible luminescence of AIEgens as a molecular species and high brightness in aggregate states distinguish them from conventional fluorescent dyes, which has galvanized efforts to bring AIEgens to a wide array of multidisciplinary applications. Herein, the useful principles and emerging structure-property relationships for precise molecular design toward AIEgens with desirable properties using concrete examples are revealed. The cutting-edge applications of AIEgens and their excellent performance in enabling new research directions in biomedical theranostics, optoelectronic devices, stimuli-responsive smart materials, and visualization of physical processes are also highlighted.

Recent advances of AIE dots in NIR imaging and phototherapy.

Nanomaterials are indispensable tools for imaging and therapy. Organic dots with aggregation-induced emission characteristics (AIE dots) have emerged as a new nanolight for their ultra-brightness, excellent photostability and biocompatibility. Due to the rotor structures, most of the reported AIE luminogens show short wavelength absorption and emission, an intrinsic disadvantage for their biomedical applications. Recently, more exciting examples reveal that properly designed AIE dots can easily reach NIR emission, excitable by near-infrared (NIR) light via multiphoton processes, which also have great potentials in photoacoustic imaging (PAI) and phototherapy. In this review, we summarize the recent advances of AIE nanomaterials for NIR fluorescence imaging, PAI, image-guided photodynamic and photothermal therapy (PDT and PTT). We highlight various strategies to improve the energy conversion efficiency of AIE dots through controlling different energy decay pathways. With this review, we hope to encourage more precise design of organic nanomaterials for biomedical applications.

Photoacoustic and Magnetic Resonance Imaging Bimodal Contrast Agent Displaying Amplified Photoacoustic Signal.

Progress in photoacoustic (PA) and magnetic resonance imaging (MRI) bimodal contrast agents has been achieved mainly by utilizing the imaging capability of single or multiple components and consequently realizing the desired application for both imaging modalities. However, the mechanism of the mutual influence between components within a single nanoformulation, which is the key to developing high-performance multimodal contrast agents, has yet to be fully understood. Herein, by integrating conjugated polymers (CPs) with iron oxide (IO) nanoparticles using an amphiphilic polymer, a bimodal contrast agent named CP-IO is developed, displaying 45% amplified PA signal intensity as compared to bare CP nanoparticle, while the performance of MRI is not affected. Further experimental and theoretical simulation results reveal that the addition of IO nanoparticles in CP-IO nanocomposites contributes to this PA signal amplification through a synergistic effect of additional heat generation and faster heat dissipation. Besides, the feasibility of CP-IO nanocomposites acting as PA-MRI bimodal contrast agents is validated through in vivo tumor imaging using mice models. From this study, it is demonstrated that a delicately designed structural arrangement of various components in a contrast agent could potentially lead to a superior performance in the imaging capability.

Recent Advances of Optical Imaging in the Second Near-Infrared Window.

The near-infrared window between 1000 and 1700 nm, commonly termed the "second near-infrared (NIR-II) window," has quickly emerged as a highly attractive optical region for biological imaging. In contrast to conventional imaging in the visible region between 400 and 700 nm, as well as in the first NIR (NIR-I) window between 700 and 900 nm, NIR-II biological imaging offers numerous merits, including higher spatial resolution, deeper penetration depth, and lower optical absorption and scattering from biological substrates with minimal tissue autofluorescence. Noninvasive imaging techniques, specifically NIR-II fluorescence and photoacoustic (PA) imaging, have embodied the attractiveness of NIR-II optical imaging, with several NIR-II contrast agents demonstrating superior performance to the clinically approved NIR-I agents. Consequently, NIR-II biological imaging has been increasingly explored due to its tremendous potential for preclinical studies and clinical utility. Herein, the progress of optical imaging in the NIR-II window is reported. Starting with highlighting the importance of biological imaging in the NIR-II spectral region, the emergence and latest development of various NIR-II fluorescence and PA imaging probes and their applications are then discussed. Perspectives on the promises and challenges facing this nascent yet exciting field are then given.

Shaping Gold Nanocrystals in Dimethyl Sulfoxide: Toward Trapezohedral and Bipyramidal Nanocrystals Enclosed by {311} Facets.

The remarkable synthetically tunable structural, electronic, and optical properties of gold nanocrystals have attracted increasing interest and enabled multidisciplinary applications. Over the past decades, nearly all the possible fundamental shapes of faceted Au nanocrystals have been synthesized, except for only one missing-the trapezohedron enclosed by {hkk} facets. In this report, the unprecedented synthesis of trapezohedral Au nanocrystals with {311} crystal facets was realized. Dimethyl sulfoxide (DMSO) was discovered as a solvent for shaping Au nanocrystals with {311} crystal facets for the first time. Mechanistic studies, together with previous DFT and STM studies, attribute the unique role of DMSO to its ambidentate nature, where both sulfur and oxygen of DMSO can coordinate to gold surface, endowing its unique role in stabilizing high-index {311} facets through a "two center bonding" mode. The DMSO-based synthesis provides a new synthetic tool toward the synthesis of a series of unreported Au nanocrystals with new structures. In particular, a new type of gold bipyramids, the octagonal bipyramids, was first synthesized with additional plasmonic tunability while simultaneously retaining their {311} facets. The application of these new Au nanocrystals in surface-enhanced Raman scattering spectroscopy was investigated, and their shape-dependent performances were demonstrated. These results highlight the tremendous potential of using ambidentate molecules as shape- and surface-directing agents for metal nanocrystals and offer the promise of enabling new synthetic tools toward atomically precise control of surface structures of metal nanocrystals.