Far Red/Near-Infrared AIE Dots for Image-Guided Photodynamic Cancer Cell Ablation

Red-emissive azabenzanthrone derivatives for photodynamic therapy irradiated with ultralow light power density and two-photon imaging

Photodynamic therapy has proved to be an effective strategy for cancer therapy, and advanced photosensitizers for image-guided photodynamic therapy require biocompatibility, intense absorption, high ROS generation efficiency, phototoxicity, low irradiation power density and efficient emission. In this work, four red emissive azabenzanthrone derivatives have been designed and synthesized, which generally exhibit efficient aggregated state emission. Through structural optimization, 3-diphenylamino-11-azabenzanthrone was found to show satisfactory photo-induced ROS generation and high emission efficiency in the aggregated state. Under the irradiation of a white LED lamp with an ultralow power density of 1.67 mW cm-2, this compound demonstrates significant photo-induced cytotoxicity toward HeLa cells. Moreover, deep tissue penetration can be realized by two-photon imaging of mouse brain vessels with these azabenzanthrone derivatives at vertical depths of up to 280 μm, attributed to the large emission wavelength and efficient emission.

Aggregation-Induced Emission (AIE) Dots: Emerging Theranostic Nanolights

Theranostic nanolights refer to luminescent nanoparticles possessing both imaging and therapeutic functions. Their shape, size, surface functions, and optical properties can be precisely manipulated through integrated efforts of chemistry, materials, and nanotechnology for customized applications. When localized photons are used to activate both imaging and therapeutic functions such as photodynamic or photothermal therapy, these theranostic nanolights increase treatment efficacy with minimized damage to surrounding healthy tissues, which represents a promising noninvasive nanomedicine as compared to conventional theranostic approaches. As one of the most promising theranostic nanolights, organic dots with aggregation-induced emission (AIE dots) are biocompatible nanoparticles with a dense core of AIE fluorogens (AIEgens) and protective shells, whose sizes are in the range of a few to tens of nanometers. Different from conventional fluorophores that suffer from aggregation-caused quenching (ACQ) due to π-π stacking interaction in the aggregate state, AIEgens emit strongly as nanoaggregates due to the restriction of intramolecular motions. Through precise molecular engineering, AIEgens could also be designed to show efficient photosensitizing or photothermal abilities in the aggregate state. Different from ACQ dyes, AIEgens allow high loading in nanoparticles without compromised performance, which makes them the ideal cores for theranostic nanolights to offer high brightness for imaging and strong photoactivities for theranostic applications. In this Account, we summarize the recent advance of AIE dots and highlight their great potential as theranostic nanolights in biomedical applications. Starting from the design of AIEgens, the fabrication of AIE dots and their bioimaging applications are discussed. The exceptional advantages of superbrightness, high resistance to photobleaching, lack of emission intermittency, and excellent biocompatibility have made them reliable cross platform contrast agents for different imaging techniques such as confocal microscopy, multiphoton fluorescence microscopy, super-resolution nanoscopy, and light-sheet ultramicroscopy, which have been successfully applied for cell tracking, vascular disease diagnosis, and image-guided surgery. The integration of therapeutic functions with customized AIEgens has further empowered AIE dots as an excellent theranostic platform for image-guided phototherapy. Of particular interest is AIE photosensitizer dots, which simultaneously show bright fluorescence and high photosensitization, yielding superior performance to commercial photosensitizer nanoparticles in image-guided therapy. Further development in multiphoton excited photodynamic therapy has offered precise treatment with up to 5 μm resolution at 200 μm depth, while chemiexcited photodynamic therapy has completely eliminated the limitation of penetration depth to realize power-free imaging and therapy. With this Account, we hope to stimulate more collaborative research interests from different fields of chemistry, materials, biology, and medicine to promote translational research of AIE dots as the theranostic nanolights.

Unveiling the Different Emission Behavior of Polytriazoles Constructed from Pyrazine-Based AIE Monomers by Click Polymerization

Polymers with aggregation-induced emission (AIE) characteristics have aroused tremendous interest because of their potential applications in large-area flexible display and luminescent self-assembling, and as stimuli-responsive and porous materials. However, the design of AIE-active polymers is always not as easy as that of small molecules because their properties are hard to predict. In some cases, the polymers prepared from the AIE-active monomers show the aggregation-caused quenching (ACQ) instead of AIE effect. To understand the structure-property relationship of the polymers constructed from the AIE monomers, in this paper, two pyrazine-containing AIE monomers were utilized to construct luminescent polymers by click polymerization. The photophysical property investigation indicates that the polytriazole containing tetraphenylpyrazine units is AIE-active, whereas that bearing 2,3-dicyano-5,6-diphenylpyrazine units suffers from the ACQ effect. Through systematical investigation, the cause for such difference was unveiled. Thus, this work provides a useful guidance for further design of AIE-active polymers.

AIEgen-Based Fluorescent Nanomaterials: Fabrication and Biological Applications

In recent years, luminogens with the feature of aggregation-induced emission (AIEgen) have emerged as advanced luminescent materials for fluorescent nanomaterial preparation. AIEgen-based nanomaterials show enhanced fluorescence efficiency and superior photostability, which thusly offer unique advantages in biological applications. In this review, we will summarize the fabrication methods of AIEgen-based nanomaterials and their applications in in vitro/in vivo imaging, cell tracing, photodynamic therapy and drug delivery, focusing on the recent progress.

PL-W18O49-TPZ Nanoparticles for Simultaneous Hypoxia-Activated Chemotherapy and Photothermal Therapy

The combination of W₁₈O₄₉ and tirapazamine (TPZ) core has been first introduced into the preparation of poly(ε-caprolactone)-poly(ethylene glycol) (PL) surrounded nanoparticles (NPs). The aim of using W₁₈O₄₉ is employing its capability of reacting with the absorbed O₂ to generate reactive oxygen species (ROS) when exposed to a long-wavelength laser at 808 nm to increase skin penetration and body tolerance. In this work, we have demonstrated that W₁₈O₄₉ unit gives rise to more hypoxic tumor microenvironment and activates the prodrug TPZ to achieve hypoxia-activated chemotherapy, which could be monitored by the intracellular ROS/hypoxia detection and in vivo positron emission tomography imaging. In addition, the successful introduction of W₁₈O₄₉ into PL-W₁₈O₄₉-TPZ NPs could render the photothermal therapy under the irradiation of an 808 nm laser. As a result, in vivo antitumor results have clearly shown that PL-W₁₈O₄₉-TPZ NPs could efficiently erase the solid tumor tissues by means of simultaneous hypoxia-activated chemotherapy and photothermal therapy. In comparison to the costly small-molecule photosensitizer chlorine e6 used in hypoxia-activated chemotherapy, W₁₈O₄₉ NPs have two advantages of large-scale preparation and additional photothermal therapy effect, which could provide new insight into future clinical applications.

Construction of emission-tunable nanoparticles based on a TICT-AIEgen: impact of aggregation-induced emission versus twisted intramolecular charge transfer

AIE dot-doped silica nanoparticles, were constructed by combining AIE dots with the dye-doping silica nanoparticle method, exhibited tunable persistent emissions.

A far-red-emissive AIE active fluorescent probe with large stokes shift for detection of inflammatory bowel disease in vivo

Inflammatory bowel disease (IBD) is a group of chronic remittent or progressive inflammatory gastrointestinal tract diseases, accompanying impaired barrier function.

A simple mitochondrial targeting AIEgen for image-guided two-photon excited photodynamic therapy

Two-photon excited photodynamic therapy (TP-PDT) is not only able to offer deeper penetration depth but also much more precise 3D treatment than traditional one-photon excited PDT. However, the achievement of TP-PDT requires photosensitizers with large two-photon absorption cross sections, efficient generation of reactive oxygen species, and bright two-photon fluorescence. In this work, we present a simple AIE luminogen (AIEgen), IQ-TPA, with mitochondrial targeting and susceptible two-photon excitation for image-guided photodynamic therapy in cancer cells. This feasibility of utilizing small molecular multifunctional AIEgens for TP-PDT was demonstrated together with the merits of tiny size, good cell permeability, low dark cytotoxicity and easy synthesis, showing great potential for the development of future theranostic systems.

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.

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.

Aggregation-induced emission enhancement and aggregation-induced circular dichroism of chiral pentaphenylpyrrole derivatives and their helical self-assembly

AIEE-active chiral pentaphenylpyrrole derivatives possess AICD and circularly polarized luminescence features with self-assembling to regular nanofibers.

Selective visualization of endogenous hydrogen sulfide in lysosomes using aggregation induced emission dots

The AIE dots (AIED) with superior sensor properties have been developed for selective imaging of lysosomal H₂S in living cells.

Low-power white light triggered AIE polymer nanoparticles with high ROS quantum yield for mitochondria-targeted and image-guided photodynamic therapy

AIE nanoparticles show mitochondrial targeting, harvest FR/NIR emission and exert severe ROS cytotoxicity under ultralow-power-intensity (10 mW cm⁻²) light irradiation.

Highly efficient photosensitizers with aggregation-induced emission characteristics obtained through precise molecular design

Through precise molecular design, predictable properties including photosensitizing efficacy, tunable absorption and emission wavelengths and aggregation-induced emission characteristics were achieved.

A novel single-fluorophore-based ratiometric fluorescent probe for direct detection of isocyanates in air

Airborne isocyanates were conveniently detected by a test paper loaded with a novel single fluorophore ratiometric fluorescent probe.