NIR-II emissive multifunctional AIEgen with single laser-activated synergistic photodynamic/photothermal therapy of cancers and pathogens

Aggregation-induced emission-based phototheranostics to combat bacterial infection at wound sites: A review

The healing of chronic wounds infected by bacteria has attracted increasing global concerns. In the past decades, antibiotics have certainly brought hope to cure bacteria-infected chronic wounds. However, the misuse of antibiotics leads to the emergence of numerous multidrug-resistant bacteria, which aggravate the health threat to clinical patients. To address these increasing challenges, scientists are committed to creating novel non-antibiotic strategies to kill bacteria and promote bacteria-infected chronic wound healing. Fortunately, with the quick development of nanotechnology, the representatives of phototherapy, such as photothermal therapy (PTT) and photodynamic therapy (PDT), exhibit promising possibilities in promoting bacteria-infected wound healing. Well-known, photothermal agents and photosensitizers largely determine the effects of PTT and PDT. A common problem for these molecules is the aggregation-induced quenching effect, which highly limits their further applicability in biomedical and clinical fields. Fortunately, the occurrence of aggregation-induced emission luminogens (AIEgens) efficiently overcomes the photobleaching and exhibit advantages, such as strongly aggregated emission, superior photostability, aggregation-enhanced reactive oxygen species (ROS), and heat generation, which makes great sense to the development of PTT and PDT. This article reviews various studies conducted on novel AIEgen-based materials that can mediate potent PDT, PTT, and a combination of PDT and PTT to promote bacteria-infected chronic wound healing.

Electrostatic Co-Assembly of Cyanine Pair for Augmented Photoacoustic Imaging and Photothermal Therapy

Molecular phototheranostic dyes are of eminent interest for oncological diagnosis and imaging-guided phototherapy. However, it remains challenging to develop photosensitizers (PSs) that simultaneously integrate high-contrast photoacoustic imaging and efficient therapeutic capabilities. In this work, a supramolecular strategy is employed to construct a molecular pair phototheranostic agent via the direct self-assembly of two cyanines, C5TNa (anionic) and Cy-Et (cationic). The Coulombic interactions between C5TNa and Cy-Et facilitate the formation of a complementary cyanine pair (C5T-ET) and the creation of supramolecular CT-J-type aggregates in water. This complementary cyanine pair (C5T-ET) results in completely quenched fluorescence and significantly enhances nonradiative deactivation (≈22 ps), leading to a 3.3-fold increase in photothermal conversion efficiency and a 7.1-fold enhancement in photoacoustic response compared to indocyanine green (ICG). As a result, the J-type aggregate cyanine pair (C5T-ET) demonstrates high photoacoustic imaging capability and remarkable antitumor phototheranostic efficacy in vivo, highlighting its potential for clinical applications. This work provides strong experimental evidence for the superior performance of the complementary cyanine pair (C5T-ET) in enhancing photosensitization and photoacoustic response. It is believed that this strategy will propel the advancement of controllable dye J-aggregates and contribute to the practical implementation of photoacoustic imaging and phototherapy in vivo.

Biomimetic NIR-II aggregation-induced emission nanoparticles for targeted photothermal therapy of ovarian cancer

Photothermal therapy (PTT) is a cutting-edge technique that harnesses light energy and converts it into heat for precise tumor ablation. By employing photothermal agents to selectively generate heat and target cancer cells, PTT has emerged as a promising cancer treatment strategy. Notably, therapies conducted in the second near-infrared (NIR-II) window exhibit superior therapeutic outcomes, owing to deeper tissue penetration and reduced light scattering. In this study, we developed biomimetic NIR-II aggregation-induced emission (AIE) nanoparticles (2TB-NPs@TM) for high-efficiency NIR-II imaging and targeted phototherapy of ovarian cancer. The core nanoparticle aggregates (2TB-NPs) display strong NIR-II fluorescence and high photothermal conversion efficiency, while the outer tumor cell membrane coating facilitates active targeting and precise recognition of tumor tissues. This design imparts excellent biocompatibility and enhances drug delivery efficiency, leading to potent synergistic therapeutic effects. Our findings open new avenues for advancing targeted, high-performance phototherapy diagnostics in cancer treatment.

Nanophotonic-enhanced photoacoustic imaging for brain tumor detection

Photoacoustic brain imaging (PABI) has emerged as a promising biomedical imaging modality, combining high contrast of optical imaging with deep tissue penetration of ultrasound imaging. This review explores the application of photoacoustic imaging in brain tumor imaging, highlighting the synergy between nanomaterials and state of the art optical techniques to achieve high-resolution imaging of deeper brain tissues. PABI leverages the photoacoustic effect, where absorbed light energy causes thermoelastic expansion, generating ultrasound waves that are detected and converted into images. This technique enables precise diagnosis, therapy monitoring, and enhanced clinical screening, specifically in the management of complex diseases such as breast cancer, lymphatic disorder, and neurological conditions. Despite integration of photoacoustic agents and ultrasound radiation, providing a comprehensive overview of current methodologies, major obstacles in brain tumor treatment, and future directions for improving diagnostic and therapeutic outcomes. The review underscores the significance of PABI as a robust research tool and medical method, with the potential to revolutionize brain disease diagnosis and treatment.

Integration of Motion and Stillness: A Paradigm Shift in Constructing Nearly Planar NIR-II AIEgen with Ultrahigh Molar Absorptivity and Photothermal Effect for Multimodal Phototheranostics

The two contradictory entities in nature often follow the principle of unity of opposites, leading to optimal overall performance. Particularly, aggregation-induced emission luminogens (AIEgens) with donor-acceptor (D-A) structures exhibit tunable optical properties and versatile functionalities, offering significant potential to revolutionize cancer treatment. However, trapped by low molar absorptivity (ε) owing to the distorted configurations, the ceilings of their photon-harvesting capability and the corresponding phototheranostic performance still fall short. Therefore, a research paradigm from twisted configuration to near-planar structure featuring a high ε is urgently needed for AIEgens development. Herein, by introducing the strategy of "motion and stillness" into a highly planar A-D-A skeleton, we successfully developed a near-infrared (NIR)-II AIEgen of Y5-2BO-2BTF, which boasts an impressive ε of 1.06 × 105 M-1 cm-1 and a photothermal conversion efficiency (PCE) of 77.8%. The modification of steric hindrance on the benzene ring in the acceptor unit of the aggregation-caused quenching counterpart Y5-2BO, to a meta-CF3-substituted naphthyl, leads to reversely staggered packing and various intermolecular noncovalent conformational locks in Y5-2BO-2BTF ("stillness"). Furthermore, the -CF3 moiety acted as a flexible motion unit with an ultralow energy barrier, significantly facilitating the photothermal process in loose Y5-2BO-2BTF aggregates ("motion"). Accordingly, Y5-2BO-2BTF nanoparticles enabled tumor eradication and pulmonary metastasis inhibition through NIR-II fluorescence-photoacoustic-photothermal imaging-navigated type I photodynamic-photothermal therapy. This work provides the first evidence that the highly planar conformation with a reversely staggered stacking arrangement could serve as a novel molecular design direction for AIEgens, shedding new light on constructing superior phototheranostic agents for bioimaging and cancer therapy.

NIR-II AIEgens for Infectious Diseases Phototheranostics

Pathogenic infectious diseases have persistently posed significant threats to public health. Phototheranostics, which combines the functions of diagnostic imaging and therapy, presents an extremely promising solution to block the spread of pathogens as well as the outbreak of epidemics owing to its merits of a wide-spectrum of activity, high controllability, non-invasiveness, and difficult to acquire resistance. Among multifarious phototheranostic agents, second near-infrared (NIR-II, 1000-1700 nm) aggregation-induced emission luminogens (AIEgens) are notable by virtue of their deep penetration depth, excellent biocompatibility, balanced radiative and nonradiative decay and aggregation-enhanced theranostic performance, making them an ideal option for combating pathogens. This minireview provides a systematical summary of the latest advancements in NIR-II AIEgens with emphasis on the molecular design and nanoplatform formulation to fulfill high-efficiency in treating bacterial and viral pathogens, classified by disease models. Then, the current challenges, potential opportunities, and future research directions are presented to facilitate the further progress of this emerging field.

Enhancing Photothermal Energy Transduction through Inter- and Intramolecular Interactions of Multiple Two-Photon Dyes Appended onto Calix[4]arene

Organic dyes-based photothermal agents (OPTAs) have received increasing attention as alternative to inorganic materials due to their higher biocompatibility and extensive diversification. Maximizing nonradiative deexcitation channels is crucial to improve the photothermal conversion efficiency (PCE) of OPTAs. This is typically achieved through individual molecular design or collective enhancement using supramolecular strategies. Furthermore, photothermal therapy (PTT) generally relies on linear one-photon absorption of the light source by the OPTA, with less consideration given to nonlinear two-photon absorption (2PA) strategies, despite their potential benefits. Here, a synergistic strategy, which combines intramolecular and intermolecular quenching, is employed to maximize the photothermal efficiency of diphenylamino-substituted distyryl dicyanobenzene (DSB), an outstanding two-photon-absorbing chromophore. One to three DSB units have been introduced on the conic p-tert-butyl-calix[4]arene (CX), serving as a preorganizing platform to allow aggregate formation and promote intramolecular quenching within the multichromophoric systems. Importantly, the multichromophoric molecules had very high two-photon absorption capabilities with cross sections (δ2PA) reaching maximal values of 3290 GM at 810 nm. Experimental data accompanied by large-scale molecular dynamics simulations and time-dependent density functional theory calculations shed light onto the interaction mechanism in those multiple DSB-appended CX compounds to rationalize their optical properties. Then, the formulation with Pluronic F127 amphiphile yields water-dispersible nanoprecipitates (Nps), in which the PCE is further maximized and the photobleaching is reduced due to the combination of intra- and intermolecular quenching. The high two-photon absorption in the near-infrared (NIR) window associated with the high PCE of these nanosized OPTAs could serve as a basis to future in vivo 2P-PTT applications.

Expanding Our Horizons: AIE Materials in Bacterial Research

Bacteria share a longstanding and complex relationship with humans, playing a role in protecting gut health and sustaining the ecosystem to cause infectious diseases and antibiotic resistance. Luminogenic materials that share aggregation-induced emission (AIE) characteristics have emerged as a versatile toolbox for bacterial studies through fluorescence visualization. Numerous research efforts highlight the superiority of AIE materials in this field. Recent advances in AIE materials in bacterial studies are categorized into four areas: understanding bacterial interactions, antibacterial strategies, diverse applications, and synergistic applications with bacteria. Initial research focuses on visualizing the unseen bacteria and progresses into developing strategies involving electrostatic interactions, amphiphilic AIE luminogens (AIEgens), and various AIE materials to enhance bacterial affinity. Recent progress in antibacterial strategies includes using photodynamic and photothermal therapies, bacterial toxicity studies, and combined therapies. Diverse applications from environmental disinfection to disease treatment, utilizing AIE materials in antibacterial coatings, bacterial sensors, wound healing materials, etc., are also provided. Finally, synergistic applications combining AIE materials with bacteria to achieve enhanced outcomes are explored. This review summarizes the developmental trend of AIE materials in bacterial studies and is expected to provide future research directions in advancing bacterial methodologies.

High-Performance NIR-II Fluorescent Type I/II Photosensitizer Enabling Augmented Mild Photothermal Therapy of Tumors by Disrupting Heat Shock Proteins

NIR-II fluorescent photosensitizers as phototheranostic agents hold considerable promise in the application of mild photothermal therapy (MPTT) for tumors, as the reactive oxygen species generated during photodynamic therapy can effectively disrupt heat shock proteins. Nevertheless, the exclusive utilization of these photosensitizers to significantly augment the MPTT efficacy has rarely been substantiated, primarily due to their insufficient photodynamic performance. Herein, the utilization of high-performance NIR-II fluorescent type I/II photosensitizer (AS21:4) is presented as a simple but effective nanoplatform derived from molecule AS2 to enhance the MPTT efficacy of tumors without any additional therapeutic components. By taking advantage of heavy atom effect, AS21:4 as a type I/II photosensitizer demonstrates superior efficacy in producing 1O2 (1O2 quantum yield = 12.4%) and O2 •- among currently available NIR-II fluorescent photosensitizers with absorption exceeding 800 nm. In vitro and in vivo findings demonstrate that the 1O2 and O2 •- generated from AS21:4 induce a substantial reduction in the expression of HSP90, thereby improving the MPTT efficacy. The remarkable phototheranostic performance, substantial tumor accumulation, and prolonged tumor retention of AS21:4, establish it as a simple but superior phototheranostic agent for NIR-II fluorescence imaging-guided MPTT of tumors.

Peptide-IR820 Conjugate: A Promising Strategy for Efficient Vascular Disruption and Hypoxia Induction in Melanoma

Photothermal therapy (PTT) has emerged as a noninvasive and precise cancer treatment modality known for its high selectivity and lack of drug resistance. However, the clinical translation of many PTT agents is hindered by the limited biodegradability of inorganic nanoparticles and the instability of organic dyes. In this study, a peptide conjugate, IR820-Cys-Trp-Glu-Trp-Thr-Trp-Tyr (IR820-C), was designed to self-assemble into nanoparticles for both potent PTT and vascular disruption in melanoma treatment. When co-assembled with the poorly soluble vascular disrupting agent (VDA) combretastatin A4 (CA4), the resulting nanoparticles (IR820-C@CA4 NPs) accumulate efficiently in tumors, activate systemic antitumor immune responses, and effectively ablate melanoma with a single treatment and near-infrared irradiation, as confirmed by our in vivo experiments. Furthermore, by exploiting the resulting tumor hypoxia, we subsequently administered the hypoxia-activated prodrug tirapazamine (TPZ) to capitalize on the created microenvironment, thereby boosting therapeutic efficacy and antimetastatic potential. This study showcases the potential of short-peptide-based nanocarriers for the design and development of stable and efficient photothermal platforms. The multifaceted therapeutic strategy, which merges photothermal ablation with vascular disruption and hypoxia-activated chemotherapy, holds great promise for advancing the efficacy and scope of cancer treatment modalities.

Lutetium Texaphyrin-Celecoxib Conjugate as a Potential Immuno-Photodynamic Therapy Agent

Immuno-photodynamic therapy (IPDT) has emerged as a new modality for cancer treatment. Novel photosensitizers can help achieve the promise inherent in IPDT, namely, the complete eradication of a tumor without recurrence. We report here a small molecule photosensitizer conjugate, LuCXB. This IPDT agent integrates a celecoxib (cyclooxygenase-2 inhibitor) moiety with a near-infrared absorbing lutetium texaphyrin photocatalytic core. In aqueous environments, the two components of LuCXB are self-associated through inferred donor-acceptor interactions. A consequence of this intramolecular association is that upon photoirradiation with 730 nm light, LuCXB produces superoxide radicals (O2-•) via a type I photodynamic pathway; this provides a first line of defense against the tumor while promoting IPDT. For in vivo therapeutic applications, we prepared a CD133-targeting, aptamer-functionalized exosome-based nanophotosensitizer (Ex-apt@LuCXB) designed to target cancer stem cells. Ex-apt@LuCXB was found to display good photosensitivity, acceptable biocompatibility, and robust tumor targetability. Under conditions of photoirradiation, Ex-apt@LuCXB acts to amplify IPDT while exerting a significant antitumor effect in both liver and breast cancer mouse models. The observed therapeutic effects are attributed to a synergistic mechanism that combines antiangiogenesis and photoinduced cancer immunotherapy.

A New Theranostic Platform Against Gram-Positive Bacteria Based on Near-Infrared-Emissive Aggregation-Induced Emission Nanoparticles

Infections induced by Gram-positive bacteria pose a great threat to public health. Antibiotic therapy, as the first chosen strategy against Gram-positive bacteria, is inevitably associated with antibiotic resistance selection. Novel therapeutic strategies for the discrimination and inactivation of Gram-positive bacteria are thus needed. Here, a specific type of aggregation-induced emission luminogen (AIEgen) with near-infrared fluorescence emission as a novel antibiotic-free therapeutic strategy against Gram-positive bacteria is proposed. With the combination of a positively charged group into a highly twisted architecture, self-assembled AIEgens (AIE nanoparticles (NPs)) at a relatively low concentration (5 µm) exhibited specific binding and photothermal effect against living Gram-positive bacteria both in vitro and in vivo. Moreover, toxicity assays demonstrated excellent biocompatibility of AIE NPs at this concentration. All these properties make the AIE NPs as a novel generation of theranostic platform for combating Gram-positive bacteria and highlight their promising potential for in vivo tracing of such bacteria.

Comparison of the Differences between Two-Photon Excitation, Upconversion, and Conventional Photodynamic Therapy on Cancers in In Vitro and In Vivo Studies

Photodynamic therapy (PDT) is a minimally invasive treatment for several diseases. It combines light energy with a photosensitizer (PS) to destroy the targeted cells or tissues. A PS itself is a non-toxic substance, but it becomes toxic to the target cells through the activation of light at a specific wavelength. There are some limitations of PDT, although it has been used in clinical studies for a long time. Two-photon excitation (TPE) and upconversion (UC) for PDT have been recently developed. A TPE nanoparticle-based PS combines the advantages of TPE and nanotechnology that has emerged as an attractive therapeutic agent for near-infrared red (NIR) light-excited PDT, whilst UC is also used for the NIR light-triggered drug release, activation of 'caged' imaging, or therapeutic molecules during PDT process for the diagnosis, imaging, and treatment of cancers.

METHODS

Nine electronic databases were searched, including WanFang Data, PubMed, Science Direct, Scopus, Web of Science, Springer Link, SciFinder, and China National Knowledge Infrastructure (CNKI), without any language constraints. TPE and UCNP were evaluated to determine if they had different effects from PDT on cancers. All eligible studies were analyzed and summarized in this review.

RESULTS

TPE-PDT and UCNP-PDT have a high cell or tissue penetration ability through the excitation of NIR light to activate PS molecules. This is much better than the conventional PDT induced by visible or ultraviolet (UV) light. These studies showed a greater PDT efficacy, which was determined by enhanced generation of reactive oxygen species (ROS) and reduced cell viability, as well as inhibited abnormal cell growth for the treatment of cancers.

CONCLUSIONS

Conventional PDT involves Type I and Type II reactions for the generation of ROS in the treatment of cancer cells, but there are some limitations. Recently, TPE-PDT and UCNP-PDT have been developed to overcome these problems with the help of nanotechnology in in vitro and in vivo studies.

Thiophene π-Bridge Manipulation of NIR-II AIEgens for Multimodal Tumor Phototheranostics

The fabrication of a multimodal phototheranostic platform on the basis of single-component theranostic agent to afford both imaging and therapy simultaneously, is attractive yet full of challenges. The emergence of aggregation-induced emission luminogens (AIEgens), particularly those emit fluorescence in the second near-infrared window (NIR-II), provides a powerful tool for cancer treatment by virtue of adjustable pathway for radiative/non-radiative energy consumption, deeper penetration depth and aggregation-enhanced theranostic performance. Although bulky thiophene π-bridges such as ortho-alkylated thiophene, 3,4-ethoxylene dioxythiophene and benzo[c]thiophene are commonly adopted to construct NIR-II AIEgens, the subtle differentiation on their theranostic behaviours has yet to be comprehensively investigated. In this work, systematical investigations discovered that AIEgen BT-NS bearing benzo[c]thiophene possesses acceptable NIR-II fluorescence emission intensity, efficient reactive oxygen species generation, and high photothermal conversion efficiency. Eventually, by using of BT-NS nanoparticles, unprecedented performance on NIR-II fluorescence/photoacoustic/photothermal imaging-guided synergistic photodynamic/photothermal elimination of tumors was demonstrated. This study thus offers useful insights into developing versatile phototheranostic systems for clinical trials.

An NIR-II Excitable AIE Small Molecule with Multimodal Phototheranostic Features for Orthotopic Breast Cancer Treatment

One-for-all phototheranostics, referring to a single component simultaneously exhibiting multiple optical imaging and therapeutic modalities, has attracted significant attention due to its excellent performance in cancer treatment. Benefitting from the superiority in balancing the diverse competing energy dissipation pathways, aggregation-induced emission luminogens (AIEgens) are proven to be ideal templates for constructing one-for-all multimodal phototheranostic agents. However, to this knowledge, the all-round AIEgens that can be triggered by a second near-infrared (NIR-II, 1000-1700 nm) light have not been reported. Given the deep tissue penetration and high maximum permissible exposure of the NIR-II excitation light, herein, this work reports for the first time an NIR-II laser excitable AIE small molecule (named BETT-2) with multimodal phototheranostic features by taking full use of the advantage of AIEgens in single molecule-facilitated versatility as well as synchronously maximizing the molecular donor-acceptor strength and conformational distortion. As formulated into nanoparticles (NPs), the high performance of BETT-2 NPs in NIR-II light-driven fluorescence-photoacoustic-photothermal trimodal imaging-guided photodynamic-photothermal synergistic therapy of orthotopic mouse breast tumors is fully demonstrated by the systematic in vitro and in vivo evaluations. This work offers valuable insights for developing NIR-II laser activatable one-for-all phototheranostic systems.

A Single NIR-II Laser-Triggered Self-Enhancing Photo/Enzyme-coupled Three-in-One Nanosystems for Breast Cancer Phototheranostics

Multifunctional phototheranostics, employing precise and non-invasive techniques, is widely developed to enhance theranostic efficiency of breast cancer (BC), reduce side-effects, and improve quality of life. Integrating all phototheranostic modalities into a single photosensitizer for highly effective BC treatment is particularly challenging due to the potential inefficiency and time consumption associated with repeated switching of multiple-wavelength lasers. Herein, a novel single NIR-II laser-triggered three-in-one nanosystem(PdCu NY) is rationally designed, which enables dual-modal (NIR-II FL/NIR-II PA) imaging-guided self-enhancing photothermal-photodynamic therapy (PTT-PDT) in NIR-II window. The PdCu NY based on optimal Pd/Cu molar-ratio(1:11) can be easily fabricated and large-scale production for simultaneous PTT-PDT against BC under a single 1064nm laser irradiation. Significantly, the PdCu NY acted as a promising photocatalyst for decomposition of H2O into O2 upon the same laser irradiation. In addition, the inherent catalase (CAT)-like activity of PdCu NYs enables photo-enzyme dual-catalytic O2 supply to effectively alleviate hypoxia, achieving self-enhanced PDT efficiency. These PTT-PDT self-enhanced nanosystems demonstrate precise lesion localization and complete tumor ablation using a single 1064nm laser source by "one-laser, multi-functions" strategy. More importantly, this study not only reports a three-in-one PdCu-based phototheranostic agent, but also sheds light on the exploration of versatile biosafety nanosystems for clinical applications.

A COX2-targeting cancer-specific fluorescent probe for hydrogen sulfide detection in living cells, Caenorhabditis elegans, and zebrafish

A novel cyclooxygenase-2 (COX-2) targeted H2S-activated cancer-specific fluorescent probe, namely, COX2-H2S, was designed and synthesized, with naphthalimide as the fluorophore and indomethacin as the targeting group. This H2S-sensing probe was developed to differentiate tumor cells from normal cells and was tested in living cells, Caenorhabditis elegans (C. elegans), and zebrafish. The probe could successfully be used for imaging endogenous and exogenous H2S in living cells, demonstrating high sensitivity and specificity and strong anti-interference. COX2-H2S had the ability to not only discern cancer cells from normal cells but also specifically recognize 9L/lacZ cells from other glioblastoma cells (U87-MG and LN229). It could also be successfully applied for the fluorescent live imaging of H2S in both C. elegans and zebrafish.

Thiophene Stability in Photodynamic Therapy: A Mathematical Model Approach

Thiophene-containing photosensitizers are gaining recognition for their role in photodynamic therapy (PDT). However, the inherent reactivity of the thiophene moiety toward singlet oxygen threatens the stability and efficiency of these photosensitizers. This study presents a novel mathematical model capable of predicting the reactivity of thiophene toward singlet oxygen in PDT, using Conceptual Density Functional Theory (CDFT) and genetic programming. The research combines advanced computational methods, including various DFT techniques and symbolic regression, and is validated with experimental data. The findings underscore the capacity of the model to classify photosensitizers based on their photodynamic efficiency and safety, particularly noting that photosensitizers with a constant rate 1000 times lower than that of unmodified thiophene retain their photodynamic performance without substantial singlet oxygen quenching. Additionally, the research offers insights into the impact of electronic effects on thiophene reactivity. Finally, this study significantly advances thiophene-based photosensitizer design, paving the way for therapeutic agents that achieve a desirable balance between efficiency and safety in PDT.

Benzobisthiadiazole-Based Small Molecular Near-Infrared-II Fluorophores: From Molecular Engineering to Nanophototheranostics

Organic fluorescent molecules with emission in the second near-infrared (NIR-II) biological window have aroused increasing investigation in cancer phototheranostics. Among these studies, Benzobisthiadiazole (BBT), with high electron affinity, is widely utilized as the electron acceptor in constructing donor-acceptor-donor (D-A-D) structured fluorophores with intensive near-infrared (NIR) absorption and NIR-II fluorescence. Until now, numerous BBT-based NIR-II dyes have been employed in tumor phototheranostics due to their exceptional structure tunability, biocompatibility, and photophysical properties. This review systematically overviews the research progress of BBT-based small molecular NIR-II dyes and focuses on molecule design and bioapplications. First, the molecular engineering strategies to fine-tune the photophysical properties in constructing the high-performance BBT-based NIR-II fluorophores are discussed in detail. Then, their biological applications in optical imaging and phototherapy are highlighted. Finally, the current challenges and future prospects of BBT-based NIR-II fluorescent dyes are also summarized. This review is believed to significantly promote the further progress of BBT-derived NIR-II fluorophores for cancer phototheranostics.

Dual/Multi-Modal Image-Guided Diagnosis and Therapy Based on Luminogens with Aggregation-Induced Emission

The combination of multiple imaging methods has made an indelible contribution to the diagnosis, surgical navigation, treatment, and prognostic evaluation of various diseases. Due to the unique advantages of luminogens with aggregation-induced emission (AIE), their progress has been significant in the field of organic fluorescent contrast agents. Herein, this manuscript summarizes the recent advancements in AIE molecules as contrast agents for optical image-based dual/multi-modal imaging. We particularly focus on the exceptional properties of each material and the corresponding application in the diagnosis and treatment of diseases.

Near-Infrared-II Fluorophore with Inverted Dependence of Fluorescence Quantum Yield on Polarity as Potent Phototheranostics for Fluorescence-Image-Guided Phototherapy of Tumors

Organic phototheranostics simultaneously having fluorescence in the second near-infrared (NIR-II, 1000-1700 nm) window, and photothermal and photodynamic functions possess great prospects in tumor diagnosis and therapy. However, such phototheranostics generally suffer from low brightness and poor photodynamic performance due to severe solvatochromism. Herein, an organic NIR-II fluorophore AS1, which possesses an inverted dependence of fluorescence quantum yield on polarity, is reported to serve as potent phototheranostics for tumor diagnosis and therapy. After encapsulation of AS1 into nanostructures, the obtained phototheranostics (AS1R ) exhibit high extinction coefficients (e.g., 68200 L mol-1  cm-1 at 808 nm), NIR-II emission with high fluorescence quantum yield up to 4.7% beyond 1000 nm, photothermal conversion efficiency of ≈65%, and 1 O2 quantum yield up to 4.1%. The characterization of photophysical properties demonstrates that AS1R is superior to other types of organic phototheranostics in brightness, photothermal effect, and photodynamic performance at the same mass concentration. The excellent phototheranostic performance of AS1R enables clear visualization and complete elimination of tumors using a single and low injection dose. This study demonstrates the merits and prospects of NIR-II fluorophore with inverted polarity dependence of fluorescence quantum yield as high-performance phototheranostic agents for fluorescence imaging and phototherapy of tumors.

Recent advances of AIE-active materials for orthotopic tumor phototheranostics

Cancer ranks as a leading threat to human life and health. Compared to conventional cancer treatments, phototheranostics shares the advantages of integrated diagnosis and therapy, outstanding therapeutic performance and good controllability. Amid diverse phototheranostic agents, small organic luminogens with aggregation-induced emission (AIEgen) tendency show predominant advantages in terms of superior photostability, large Stokes shifts, and boosted theranostic capacity as aggregates. In the past two decades, AIE-active materials have demonstrated formidable applications in disease theranostics, especially for tumors. This review mainly highlights the recent advances of orthotopic tumor phototheranostics mediated by AIEgens with a classification of different organs. Additionally, a brief discussion of current bottlenecks and future directions is outlined. We believe this review can deepen the understanding and spur more innovations on tumor theranostics by employing AIEgens. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging.

Engineering of a GSH activatable photosensitizer for enhanced photodynamic therapy through disrupting redox homeostasis

Although disrupted redox homeostasis has emerged as a promising approach for tumor therapy, most existing photosensitizers are not able to simultaneously improve the reactive oxygen species level and reduce the glutathione (GSH) level. Therefore, designing photosensitizers that can achieve these two aspects of this goal is still urgent and challenging. In this work, an organic activatable near-infrared (NIR) photosensitizer, CyI-S-diCF₃, is developed for GSH depletion-assisted enhanced photodynamic therapy. CyI-S-diCF₃, composed of an iodinated heptamethine cyanine skeleton linked with a recognition unit of 3,5-bis(trifluoromethyl)benzenethiol, can specifically react with GSH by nucleophilic substitution, resulting in intracellular GSH depletion and redox imbalance. Moreover, the activated photosensitizer can produce abundant singlet oxygen (¹O₂) under NIR light irradiation, further heightening the cellular oxidative stress. By this unique nature, CyI-S-diCF₃ exhibits excellent toxicity to cancer cells, followed by inducing earlier apoptosis. Thus, our study may propose a new strategy to design an activatable photosensitizer for breaking the redox homeostasis in tumor cells.

Multifunctional Nanoprobe Based on Fluorescence Resonance Energy Transfer for Furin Detection and Drug Delivery

Triple-negative breast cancer is particularly difficult to treat because of its high degree of malignancy and poor prognosis. A fluorescence resonance energy transfer (FRET) nanoplatform plays a very important role in disease diagnosis and treatment due to its unique detection performance. Combining the properties of agglomeration-induced emission fluorophore and FRET pair, a FRET nanoprobe (HMSN/DOX/RVRR/PAMAM/TPE) induced by specific cleavage was designed. First, hollow mesoporous silica nanoparticles (HMSNs) were used as drug carriers to load doxorubicin (DOX). HMSN nanopores were coated with the RVRR peptide. Then, polyamylamine/phenylethane (PAMAM/TPE) was combined in the outermost layer. When Furin cut off the RVRR peptide, DOX was released and adhered to PAMAM/TPE. Finally, the TPE/DOX FRET pair was constituted. The overexpression of Furin in the triple-negative breast cancer cell line (MDA-MB-468 cell) can be quantitatively detected by FRET signal generation, so as to monitor cell physiology. In conclusion, the HMSN/DOX/RVRR/PAMAM/TPE nanoprobes were designed to provide a new idea for the quantitative detection of Furin and drug delivery, which is conducive to the early diagnosis and treatment of triple-negative breast cancer.

Neutrophil-like Biomimic AIE Nanoparticles with High-Efficiency Inflammatory Cytokine Targeting Enable Precise Photothermal Therapy and Alleviation of Inflammation

Although photothermal therapy (PTT) has thrived as a promising treatment for drug-resistant bacterial infections by avoiding the abuse of antibiotics, the remaining challenges that limit the treatment efficiency are the poor targeting properties of infected lesions and low penetration to the cell membrane of Gram-negative bacteria. Herein, we developed a biomimetic neutrophil-like aggregation-induced emission (AIE) nanorobot (CM@AIE NPs) for precise inflammatory site homing and efficient PTT effects. Due to their surface-loaded neutrophil membranes, CM@AIE NPs can mimic the source cell and thus interact with immunomodulatory molecules that would otherwise target endogenous neutrophils. Coupled with the secondary near-infrared region absorption and excellent photothermal properties of AIE luminogens (AIEgens), precise localization, and treatment in inflammatory sites can be achieved, thereby minimizing damage to surrounding normal tissues. Moreover, CM@AIE NP-mediated PTT was stimulated in vivo by a 980 nm laser irradiation, which contributed to the extent of the therapeutic depth and limited the damage to skin tissues. The good biocompatibility and excellent in vitro and in vivo antibacterial effects prove that CM@AIE NPs can provide a strategy for broad-spectrum antibacterial applications.

Recent Advances in Synthetic Routes to Azacycles

A heterocycle is an important structural scaffold of many organic compounds found in pharmaceuticals, materials, agrochemicals, and biological processes. Azacycles are one of the most common motifs of a heterocycle and have a variety of applications, including in pharmaceuticals. Therefore, azacycles have received significant attention from scientists and a variety of methods of synthesizing azacycles have been developed because their efficient synthesis plays a vital role in the production of many useful compounds. In this review, we summarize recent approaches to preparing azacycles via different methods as well as describe plausible reaction mechanisms.

Dendritic Plasmonic CuPt Alloys for Closed-Loop Multimode Cancer Therapy with Remarkably Enhanced Efficacy

The outcome of laser-triggered plasmons-induced phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is significantly limited by the hypoxic tumor microenvironment and the upregulation of heat shock proteins (HSPs) in response to heat stress. Mitochondria, the biological battery of cells, can serve as an important breakthrough to overcome these obstacles. Herein, dendritic triangular pyramidal plasmonic CuPt alloys loaded with heat-sensitive NO donor N, N'-di-sec-butyl-N, N'-dinitroso-1,4-phenylenediamine (BNN) is developed. Under 808 nm laser irradiation, plasmonic CuPt can generate superoxide anion free radicals (·O₂ ^- ) and heat simultaneously. The heat generated can then trigger the release of NO gas, which not only enables gas therapy but also damages the mitochondrial respiratory chain. Impaired mitochondrial respiration leads to reduced oxygen consumption and insufficient intracellular ATP supply, which effectively alleviates tumor hypoxia and undermines the synthesis of HSPs, in turn boosting plasmonic CuPt-based PDT and mild PTT. Additionally, the generated NO and ·O₂ ^- can react to form more cytotoxic peroxynitrite (ONOO^- ). This work describes a plasmonic CuPt@BNN (CPB) triggered closed-loop NO gas, free radicals, and mild photothermal therapy strategy that is highly effective at reciprocally promoting antitumor outcomes.

Design of an Injectable Magnetic Hydrogel Based on the Tumor Microenvironment for Multimodal Synergistic Cancer Therapy

Conventional tumor chemotherapy is limited by its low therapeutic efficacy and side effects, which severely hold back its further application. Drug delivery systems (DDSs) based on nanomaterials have attracted wide interest in cancer treatment; especially, the system can realize efficient synergistic therapies. Here, we designed a smart hydrogel drug delivery system with multiple responses to enhance the tumor treatment effect. By cross-linking oxidized hydroxypropyl cellulose with carboxymethyl chitosan, an injectable hydrogel was obtained, into which artesunate (ART), ferroferric oxide (Fe₃O₄) nanoparticles, and black phosphorus nanosheets (BPs) were preloaded. This DDS has multiple functions including magnetic targeting, pH sensitivity, chemodynamic therapy, and photothermal response. This nanoparticle-composited hydrogel not only preserved excellent rheological properties but also allowed for an accurate stable drug release at tumor sites and synergistic effects of multiple therapies. The in vitro and in vivo experiments revealed that this DDS could efficiently eliminate the HepG2 tumor with good biocompatibility. Taken together, this study clarifies the possible antitumor mechanism of this ART-loaded nanoparticle-composited hydrogel and provides a new strategy for synergistic photothermal-chemo-chemodynamic therapy.

A rationally designed cancer vaccine based on NIR-II fluorescence image-guided light-triggered remote control of antigen cross-presentation and autophagy

Cancer vaccines represent a promising immunotherapeutic treatment modality. The promotion of cross-presentation of extracellular tumor-associated antigens on the major histocompatibility complex (MHC) class I molecules and dendritic cell maturation at the appropriate time and place is crucial for cancer vaccines to prime cytolytic T cell response with reduced side effects. Current vaccination strategies, however, are not able to achieve the spatiotemporal control of antigen cross-presentation. Here, we report a liposomal vaccine loading the second near-infrared window (NIR-II, 1000-1700 nm) fluorophore BPBBT with an efficient photothermal conversion effect that offers an NIR-light-triggered endolysosomal escape under the imaging guidance. The NIR-II image-guided vaccination strategy specifically controls the cytosolic delivery of antigens for cross-presentation in the draining lymph nodes (DLNs). Moreover, the photothermally induced endolysosomal rupture initiates autophagy. We also find that the adjuvant simvastatin acts as an autophagy activator through inhibiting the PI3K/AKT/mTOR pathway. The light-induced autophagy in the DLNs together with simvastatin treatment cooperatively increase MHC class II expression by activating autophagy machinery for dendritic cell maturation. This study presents a paradigm of NIR-II image-guided light-triggered vaccination. The approach for remote control of antigen cross-presentation and autophagy represents a new strategy for vaccine development.

Aggregation-Induced Emission Luminogens for Enhanced Photodynamic Therapy: From Organelle Targeting to Tumor Targeting

Photodynamic therapy (PDT) has attracted much attention in the field of anticancer treatment. However, PDT has to face challenges, such as aggregation caused by quenching of reactive oxygen species (ROS), and short 1O2 lifetime, which lead to unsatisfactory therapeutic effect. Aggregation-induced emission luminogen (AIEgens)-based photosensitizers (PSs) showed enhanced ROS generation upon aggregation, which showed great potential for hypoxic tumor treatment with enhanced PDT effect. In this review, we summarized the design strategies and applications of AIEgen-based PSs with improved PDT efficacy since 2019. Firstly, we introduce the research background and some basic knowledge in the related field. Secondly, the recent approaches of AIEgen-based PSs for enhanced PDT are summarized in two categories: (1) organelle-targeting PSs that could cause direct damage to organelles to enhance PDT effects, and (2) PSs with tumor-targeting abilities to selectively suppress tumor growth and reduce side effects. Finally, current challenges and future opportunities are discussed. We hope this review can offer new insights and inspirations for the development of AIEgen-based PSs for better PDT effect.

D-A Type NIR-II Organic Molecules: Strategies for the Enhancement Fluorescence Brightness and Applications in NIR-II Fluorescence Imaging-Navigated Photothermal Therapy

NIR-II fluorescence imaging (NIR-II FI) and photothermal therapy (PTT) have received broad attentions in precise tumor diagnosis and effective treatment attributed to high-resolution and deep tissue imaging, negligible invasivity, and high-efficiency treatment. Although many fluorescent molecules have been designed and conducted for NIR-II FI and PTT, it is still an enormous challenge for researchers to pioneer some rational design guidelines to improve fluorescence brightness. Organic D-A-type molecules, including small molecules and conjugated polymers, can be designed and developed to improve fluorescence brightness due to their tunable and easy functionalized chemical structures, allowing molecules tailored photophysical properties. In this review, some approaches to the development and design strategies of D-A type small molecules and conjugated polymers for the enhancement of fluorescence brightness are systemically introduced. Meanwhile, some applications of PTT and PTT-based combination therapy (such as PDT, chemotherapy, or gas therapy) assisted by NIR-II FI-based single or multiimaging technologies are classified and represented in detail as well. Finally, the current issues and challenges of NIR-II organic molecules in NIR-II FI-navigated PTT are summarized and discussed, which gives some guidelines for the future development direction of NIR-II organic molecules for NIR-II FI-navigated PTT.

NIR-II AIEgens with Photodynamic Effect for Advanced Theranostics

Phototheranostics that concurrently integrates accurate diagnosis (e.g., fluorescence and photoacoustic (PA) imaging) and in situ therapy (e.g., photodynamic therapy (PDT) and photothermal therapy (PTT)) into one platform represents an attractive approach for accelerating personalized and precision medicine. The second near-infrared window (NIR-II, 1000-1700 nm) has attracted considerable attention from both the scientific community and clinical doctors for improved penetration depth and excellent spatial resolution. NIR-II agents with a PDT property as well as other functions are recently emerging as a powerful tool for boosting the phototheranostic outcome. In this minireview, we summarize the recent advances of photodynamic NIR-II aggregation-induced emission luminogens (AIEgens) for biomedical applications. The molecular design strategies for tuning the electronic bandgaps and photophysical energy transformation processes are discussed. We also highlight the biomedical applications, such as image-guided therapy of both subcutaneous and orthotopic tumors, and multifunctional theranostics in combination with other treatment methods, including chemotherapy and immunotherapy; and the precise treatment of both tumor and bacterial infection. This review aims to provide guidance for PDT agents with long-wavelength emissions to improve the imaging precision and treatment efficacy. We hope it will provide a comprehensive understanding about the chemical structure-photophysical property-biomedical application relationship of NIR-II luminogens.

NIR-II bioimaging of small molecule fluorophores: From basic research to clinical applications

Due to the low autofluorescence and deep-photo penetration, the second near-infrared region fluorescence imaging technology (NIR-II, 1000-2000 nm) has been widely utilized in basic scientific research and preclinical practice throughout the past decade. The most attractive candidates for clinical translation are organic NIR-II fluorophores with a small-molecule framework, owing to their low toxicity, high synthetic repeatability, and simplicity of chemical modification. In order to enhance the translation of small molecule applications in NIR-II bioimaging, NIR-II fluorescence imaging technology has evolved from its usage in cells to the diagnosis of diseases in large animals and even humans. Although several examples of NIR-II fluorescence imaging have been used in preclinical studies, there are still many challenges that need to be addressed before they can finally be used in clinical settings. In this paper, we reviewed the evolution of the chemical structures and photophysical properties of small-molecule fluorophores, with an emphasis on their biomedical applications ranging from small animals to humans. We also explored the potential of small-molecule fluorophores.

Long wavelength-emissive Ru(II) metallacycle-based photosensitizer assisting in vivo bacterial diagnosis and antibacterial treatment

Ruthenium (Ru) complexes are developed as latent emissive photosensitizers for cancer and pathogen photodiagnosis and therapy. Nevertheless, most existing Ru complexes are limited as photosensitizers in terms of short excitation and emission wavelengths. Herein, we present an emissive Ru(II) metallacycle (herein referred to as 1) that is excited by 808-nm laser and emits at a wavelength of ∼1,000 nm via coordination-driven self-assembly. Metallacycle 1 exhibits good optical penetration (∼7 mm) and satisfactory reactive oxygen species production properties. Furthermore, 1 shows broad-spectrum antibacterial activity (including against drug-resistant Escherichia coli) as well as low cytotoxicity to normal mammalian cells. In vivo studies reveal that 1 is employed in precise, second near-infrared biomedical window fluorescent imaging-guided, photo-triggered treatments in Staphylococcus aureus-infected mice models, with negligible side effects. This work thus broads the applications of supramolecular photosensitizers through the strategy of lengthening their wavelengths.

Organic single molecule based nano-platform for NIR-II imaging and chemo-photothermal synergistic treatment of tumor

Integrating multiple functionalities of near-infrared second window fluorescence imaging (NIR-Ⅱ FLI), chemotherapy, and photothermal treatment (PTT) into a single molecule is desirable but still a highly challenging task. Herein, inspired by the results that hyperthermia can enhance the cytotoxicity of some alkylating agents, we designed and synthesized the novel compound NM. By introducing nitrogen mustard's active moiety bis(2-chlorethyl)amino into Donor-Acceptor-Donor (D-A-D) electronic structure, the unimolecular system not only behaviored as a chemotherapeutic agent but also exhibited good PTT and NIR-Ⅱ FLI abilities. The hydrophobic agent NM was encapsulated by DSPE-PEG2000 to generate the nano-platform NM-NPs. The current study on in vitro and in vivo experiments indicated that NM-NPs make vessels visualize clearly in the NIR-II zone and achieve complete tumor elimination through chemo-photothermal synergistic treatment. Overall, this study provides a new innovative strategy for developing superior, versatile phototheranostics for cancer theranostics.

Immunosonodynamic Therapy Designed with Activatable Sonosensitizer and Immune Stimulant Imiquimod

Sonodynamic therapy (SDT) has garnered extensive attention as a noninvasive treatment for deep tumors. Furthermore, imiquimod (R837), an FDA-approved toll-like receptor 7 agonist, is commonly used in clinical settings as an immune adjuvant. We prepared an activatable sonodynamic sensitizer platform (MR) based on glutathione-sensitive disulfide bonds linking Leu-MB, the reduced form of methylene blue (MB), and R837 to achieve efficient combinatory SDT and immunotherapy for tumors without harming normal tissues. We also used the amphiphilic polymer C₁₈PMH-PEG to create self-assembled MB-R837-PEG (MRP) nanoparticles for immunosonodynamic therapy (iSDT). iSDT is a cancer treatment that combines activatable SDT and immunotherapy. Our iSDT demonstrated an excellent sonodynamic effect only at the tumor site, demonstrating high specificity in killing tumor cells when compared to SDT reported in the literature. The iSDT improves its tumor-killing effect by inducing an immune response, which is accomplished by secreted immune adjuvants in the tumor site. MRP was selectively activated by glutathione in the tumor microenvironment to release MB and R837, exhibiting excellent antitumor sonodynamic and immune responses. In addition, when combined with an α-PD-L1 antibody for immune checkpoint blockade, this therapy effectively inhibited tumor metastasis. Furthermore, mice treated with iSDT and α-PD-L1 antibody did not develop tumors even after tumor reinoculation, indicating that long-term immune memory was achieved. The concept of sonodynamic sensitizer preparation as a next-generation iSDT based on a noninvasive synergistic therapeutic modality applicable in the near future is presented in this study.

An AIE photosensitizer with unquenched fluorescence based on nitrobenzoic acid for tumor-targeting and image-guided photodynamic therapy

Fluorescence quenching occurs in most nitroaromatic compounds due to photoinduced electron transfer (PET) effects, limiting their use as image-guided photosensitizers for anticancer photodynamic therapy (PDT) or as probes for nitroreductase in hypoxic cells. Herein, we developed a tumor-targeting aggregation-induced emission photosensitizer (AIE-PS), Biotin-TTVBA, by binding TTVBA (a nitrobenzoic acid-based AIE-PS with a free carboxylic acid group) to biotin. Biotin-TTVBA has near-infrared emission characteristics in DMSO containing 99% toluene, a large Stoke's shift (210 nm), high photostability, wash-free cell staining ability and type I/II photosensitivity. Compared with TTVBA, Biotin-TTVBA significantly increased cellular uptake (a 60-fold increase) and selective uptake of tumor cells (a 250% increase in the ratio of tumor cells to normal cells), resulting in enhanced antitumor activity against tumor cells (HeLa and MCF-7) and a decreased IC₅₀ value (from >40 μM to 2.5 μM). Taken together, the results of this study call attention to AIE-PSs based on nitroaromatic groups because of their strong fluorescence and ROS generation ability, which can be used in image-guided photodynamic therapy and provide a new approach for tumor-targeting design of AIE-PSs.

Photothermal agents based on small organic fluorophores with intramolecular motion

Photothermal therapy (PTT) has attracted great attention due to its noninvasive and low side effects. Photothermal agents (PTAs) which could convert absorbing light into heat play a critical role in PTT. For conventional small organic PTAs, the photothermal conversion ability is mainly achieved by intermolecular noncovalent interactions such as π-π interactions. However, in terms of organic fluorophores with rotator or vibrator segments, the balance between fluorescence emission and heat generation is mainly regulated by intramolecular motions which could be mediated by molecular engineering. Following this designing principle, various fluorophores with intramolecular motions for effective PTT have been reported. In this review, we highlight the recent progress of PTAs based on small organic fluorophores with intramolecular motions for enhanced PTT. Designing tactics of these fluorophores to afford long-wavelength absorption, high photothermal conversion ability, and effective accumulation capability are emphasized. Finally, one-for-all phototheranostics achieved by mediating intramolecular motions of these fluorophores are highlighted. We hope this review could pave a new avenue to developing fluorophores with intramolecular motion as PTAs to advance their clinical transition. STATEMENT OF SIGNIFICANCE: Recent progress of photothermal agents (PTAs) based on small organic fluorophores with intramolecular motion is summarized in this review. Molecular engineering of these small organic fluorophores to afford long-wavelength absorption, high photothermal conversion ability, and effective accumulation at tumor sites for enhanced photothermal therapy (PTT) is highlighted. Strategies to tune the intramolecular motions of these fluorophores to achieve multimodal phototherapy are emphasized as well.

Organic photosensitizers for antimicrobial phototherapy

Microbial infectious diseases, especially those caused by new and antibiotic-resistant pathogenic microbes, have become a significant threat to global human health. As an antibiotic-free therapy, phototherapy is a promising approach to treat microbial infections due to its spatiotemporal selectivity, non-invasiveness, minimal side effects, and broad antimicrobial spectrum. Although organic photosensitizer-based antimicrobial phototherapy has been extensively studied over the last decade, there has been no specific review article on this topic yet. It is important and timely to summarize recent research progress in this field. This tutorial review highlights the concept and significance of phototherapy and summarizes innovative types of organic photosensitizers with design strategies to deal with microbial infections. In addition, examples of organic antimicrobial photosensitizers, including antibacterial photosensitizers, antiviral photosensitizers, and antifungal photosensitizers are discussed. Finally, current challenges and future directions of organic photosensitizer-based phototherapy for clinical antimicrobial applications are presented. We believe that this tutorial review will provide general guidance for the future development of efficient photosensitizers and encourage preclinical and clinical studies for phototherapy-mediated antimicrobial treatments.

Deep learning aided quantitative analysis of anti-tuberculosis fixed-dose combinatorial formulation by terahertz spectroscopy

Anti-tuberculosis fixed-dose combinatorial formulation (FDCs) is an effective drug for the treatment of tuberculosis. As a compound medicine, its efficacy is based on the comprehensive action of multiple main ingredients. If the content of an active ingredient is insufficient, not only will it reduce the curative effect, but it also causes patients to develop drug resistance and leads to the evolution of drug-resistant strains of tuberculosis, which hamper the treatment of the disease. Thus accurate detection of the contents of active components in the anti-tuberculosis FDC is the key link of its quality control. For the first time, convolutional neural networks (CNN), one of the most popular deep learning methods, is adopted to develop a quantitative calibration model based on terahertz time-domain spectroscopy (THz-TDS) for the accurate detection of the content of each active component in the anti-tuberculosis FDCs. For comparison with CNN, partial least squares regression (PLSR) was also introduced to build a reference quantitative calibration model. For CNN modeling, the raw THz spectral is fed to the model directly; While for PLSR, prior to the spectrum feeding to the model, the raw spectral data are processed by multiple different combinations of preprocessing. Experimental and simulation results demonstrate that although preprocessing techniques can improve the prediction performance of PLSR, its prediction capabilities is still inferior to CNN based on raw spectrum. Therefore, for the quantitative analysis of the content of each active component in the anti-tuberculosis FDCs, CNN appears to be an ideal modeling method.

The fast-growing field of photo-driven theranostics based on aggregation-induced emission

Photo-driven theranostics, also known as phototheranostics, relying on the diverse excited-state energy conversions of theranostic agents upon photoexcitation represents a significant branch of theranostics, which ingeniously integrate diagnostic imaging and therapeutic interventions into a single formulation. The combined merits of photoexcitation and theranostics endow photo-driven theranostics with numerous superior features. The applications of aggregation-induced emission luminogens (AIEgens), a particular category of fluorophores, in the field of photo-driven theranostics have been intensively studied by virtue of their versatile advantageous merits of favorable biocompatibility, tuneable photophysical properties, unique aggregation-enhanced theranostic (AET) features, ideal AET-favored on-site activation ability and ready construction of one-for-all multimodal theranostics. This review summarised the significant achievements of photo-driven theranostics based on AIEgens, which were detailedly elaborated and classified by their diverse theranostic modalities into three groups: fluorescence imaging-guided photodynamic therapy, photoacoustic imaging-guided photothermal therapy, and multi-modality theranostics. Particularly, the tremendous advantages and individual design strategies of AIEgens in pursuit of high-performance photosensitizing output, high photothermal conversion and multimodal function capability by adjusting the excited-state energy dissipation pathways are emphasized in each section. In addition to highlighting AIEgens as promising templates for modulating energy dissipation in the application of photo-driven theranostics, current challenges and opportunities in this field are also discussed.

A multimodal fluorescent probe for portable colorimetric detection of pH and it's application in mitochondrial bioimaging

Mitochondria, as vital energy supplying organelles, play important roles in cellular metabolism, which are closely related with mitochondrial pH (∼8.0). In this work, a novel multimodal fluorescent probe was employed for ratiometric and colorimetric detection of pH. The probe is designed to work by controlling benzothiazole phenol-hemicyanine system as the interaction site and hemicyanine connected by conjugate bonds as the mitochondrial targeting, which also could make the fluorescence of probe red-shifted. This system results in a perfect ratiometric fluorescent response, whose emission changed from red to blue under pH 2.0-10.0, having a broad linear range (pH = 3.0-10.0). And the marked colour change (light yellow to deep purple via naked eye under pH 2.0-11.0) could be used to construct the test strip colorimetry and smartphone APP detection method, realizing the fast, portable, and accurate detection of pH in vitro and environment. Besides, the probe owns the characteristics of easy loading, high selectivity and staining ability of mitochondria, and low cytotoxicity, thereby allowing imaging of pH values and real-time monitor the subcellular mitochondria pH changes caused by drugs in living cells. It thus could be used to monitor the organ-specific dynamics related to transitions between pathological and physiological states.

A Glutathione Activatable Photosensitizer for Combined Photodynamic and Gas Therapy under Red Light Irradiation

Although photodynamic therapy (PDT) is a promising approach for cancer therapy, most existing photosensitizers lack selectivity for tumor cells and the overexpressed glutathione (GSH) in tumor cells reduces the PDT efficiency. Therefore, designing photosensitizers that can be selectively activated within tumor cells and combine PDT with other therapeutic modalities represents a route for precise and efficient anticancer treatment. Herein, an organic activatable photosensitizer, CyI-DNBS, bearing 2,4-dinitrobenzenesulfonate (DNBS) as the cage group is reported. CyI-DNBS can be uptaken by cancer cells after which the cage group is selectively removed by the intracellular GSH, resulting in the generation of SO₂ for gas therapy. The reaction also releases the activated photosensitizer, CyI-OH, that can produce singlet oxygen (¹ O₂ ) under red light irradiation. Therefore, CyI-DNBS targets cancer cells for both photodynamic and SO₂ gas therapy treatments. The activatable photosensitizer provides a new approach for PDT and SO₂ gas synergistic therapy and demonstrates excellent anticancer effect in vivo.

Design of a Metallacycle-Based Supramolecular Photosensitizer for In Vivo Image-Guided Photodynamic Inactivation of Bacteria

Bacterial infection is one of the greatest threats to public health. In vivo real-time monitoring and effective treatment of infected sites through non-invasive techniques, remain a challenge. Herein, we designed a PtII metallacycle-based supramolecular photosensitizer through the host-guest interaction between a pillar[5]arene-modified metallacycle and 1-butyl-4-[4-(diphenylamino)styryl]pyridinium. Leveraging the aggregation-induced emission supramolecular photosensitizer, we improved fluorescence performance and antimicrobial photodynamic inactivation. In vivo studies revealed that it displayed precise fluorescence tracking of S. aureus-infected sites, and in situ performed image-guided efficient PDI of S. aureus without noticeable side effects. These results demonstrated that metallacycle combined with host-guest chemistry could provide a paradigm for the development of powerful photosensitizers for biomedicine.