AIE-active luminogens as highly efficient free-radical ROS photogenerator for image-guided photodynamic therapy

A General Strategy for Enhanced Photodynamic Antimicrobial Therapy with Perylenequinonoid Photosensitizers Using a Macrocyclic Supramolecular Carrier

Perylenequinonoid natural products are a class of photosensitizers (PSs) that exhibit high reactive oxygen species (ROS) generation and excellent activity for Type I/Type II dual photodynamic therapy. However, their limited activity against gram-negative bacteria and poor water solubility significantly restrict their potential in broad-spectrum photodynamic antimicrobial therapy (PDAT). Herein, a general approach to overcome the limitations of perylenequinonoid photosensitizers (PQPSs) in PDAT by utilizing a macrocyclic supramolecular carrier is presented. Specifically, AnBox·4Cl, a water-soluble cationic cyclophane, is identified as a universal macrocyclic host for PQPSs such as elsinochrome C, hypocrellin A, hypocrellin B, and hypericin, forming 1:1 host-guest complexes with high binding constants (≈107 m -1) in aqueous solutions. Each AnBox·4Cl molecule carries four positive charges that promote strong binding with the membrane of gram-negative bacteria. As a result, the AnBox·4Cl-PQPS complexes can effectively anchor on the surfaces of gram-negative bacteria, while the PQPSs alone cannot. In vitro and in vivo experiments demonstrate that these supramolecular PSs have excellent water solubility and high ROS generation, with broad-spectrum PDAT effect against both gram-negative and gram-positive bacteria. This work paves a new path to enhance PDAT by showcasing an efficient approach to improve PQPSs' water solubility and killing efficacy for gram-negative bacteria.

Molecular engineering to elevate reactive oxygen species generation for synergetic damage on lipid droplets and mitochondria

Photodynamic therapy (PDT), characterized by high treatment efficiency, absence of drug resistance, minimal trauma, and few side effects, has gradually emerged as a novel and alternative clinical approach compared to traditional surgical resection, chemotherapy and radiation. Whereas, considering the limited diffusion distance and short lifespan of reactive oxygen species (ROS), as well as the hypoxic tumor microenvironment, it is crucial to design photosensitizers (PSs) with suborganelle specific targeting ability and low-oxygen dependence for accurate and highly efficient photodynamic therapy. In this study, we have meticulously designed three PSs, namely CIH, CIBr, and CIPh, based on molecular engineering. Theoretical calculation demonstrate that the three compounds possess good molecular planarity with calculated S1-T1 energy gaps (ΔES1-T1) of 1.04 eV for CIH, 0.92 eV for CIBr, and 0.84 eV for CIPh respectively. Notably, CIPh showcases remarkable dual subcellular targeting capability towards lipid droplets (LDs) and mitochondria owing to the synergistic effect of lipophilicity derived from coumarin's inherent properties combined with electropositivity conferred by indole salt cations. Furthermore, CIPh demonstrates exclusive release of singlet oxygen (1O2)and highly efficient superoxide anion free radicals(O2⦁-) upon light irradiation supported by its smallest S1-T1 energy gap (ΔES1-T1 = 0.84 eV). This leads to compromised integrity of LDs along with mitochondrial membrane potential, resulting in profound apoptosis induction in HepG2 cells. This successful example of molecular engineering guided by density functional theory (DFT) provides valuable experience for the development of more effective PSs with superior dual targeting specificity. It also provides a new idea for the development of advanced PSs with efficient and accurate ROS generation ability towards fluorescence imaging-guided hypoxic tumor therapy.

Aggregation-Induced Emission Photosensitizer with Ag(I)-π Interaction-Enhanced Reactive Oxygen Species for Eliminating Multidrug Resistant Bacteria

Multidrug-resistant (MDR) bacteria pose serious threats to public health due to the lack of effective and biocompatible drugs to kill MDR bacteria. Photodynamic antibacterial therapy has been widely studied due to its low induction of resistance. However, photosensitizers that can efficiently generate reactive oxygen species (ROS) through both type I and type II mechanisms and that have the capability of multiple modes of action are rarely reported. Addressing this issue, we developed a near-infrared-emitting triphenylamine indole iodoethane (TTII) and its silver(I) self-assembled (TTIIS) aggregation-induced emission (AIE) photosensitizer for multimode bacterial infection therapy. TTII can efficiently produce both Type I ROS •OH and Type II ROS 1O2. Interestingly, the Ag(I)-π interaction contributed in TTIIS efficiency promotion of the generation of 1O2. Moreover, by releasing Ag+, TTIIS enabled photodynamic-Ag(I) dual-mode sterilization. As a result, TTIIS achieved an effective enhancement of antibacterial activity, with a 1-2-fold boost against multidrug-resistant Escherichia coli (MDR E. coli). Both TTII and TTIIS at a concentration as low as 0.55 μg mL-1 can kill more than 98% of methicillin resistant Staphylococcus aureus (MRSA) on MRSA-infected full-thickness defect wounds of a mouse, and both TTII and TTIIS were effective in eliminating the bacteria and promoting wound healing.

Membrane-Anchored Aggregation-Induced Emission Luminogens: Accurate Labeling and Efficient Photodynamic Inactivation of Streptococcus mutans in Anticaries Therapy

Dental caries is a widespread bacterial infectious disease that imposes a significant public health burden globally. The primary culprits in caries development are cariogenic bacteria, notably Streptococcus mutans (S. mutans), due to their robust biofilm-forming capabilities. To address this issue, a series of cationic pyridinium-substituted photosensitizers with aggregation-induced emission have been designed. All of these aggregation-induced emission luminogens (AIEgens) exhibit outstanding microbial visualization and photodynamic killing of S. mutans, thanks to their luminous fluorescence and efficient singlet oxygen generation ability. Notably, one of the membrane-anchored AIEgens (TDTPY) can inactivate planktic S. mutans and its biofilm without causing significant cytotoxicity. Importantly, application of TDTPY-mediated photodynamic treatment on in vivo rodent models has yielded commendable imaging results and effectively slowed down caries progression with assured biosafety. Unlike traditional single-mode anticaries materials, AIEgens integrate the dual functions of detecting and removing S. mutans and are expected to build a new caries management diagnosis and treatment platform. To the best of our knowledge, this is also the first report on the use of AIEgens for anticaries studies both in vitro and in vivo.

Extensive optical and DFT studies on novel AIE active fluorescent sensor for Colorimetric and fluorometric detection of nitrobenzene in Solid, solution and vapor phase

An electron rich isophthalamide based sensor IPA has been synthesized through a simple two-step reaction, containing noteworthy aggregation induced emission (AIE) properties. Considering the significant emission with λmax at 438 nm, sensor IPA has been employed for the sensing of nitrobenzene (NB) in solid, solution and vapor state with high sensitivity and selectivity. Sensor IPA showed noteworthy colorimetric and fluorometric quenching in fluorescence emission when exposed to NB. Small size of NB and involvement of photoinduced electron transfer (PET) lead to detection of NB down to 60 nM. IPA-NB interaction was studied through UV-Vis. spectroscopic studies along with fluorescence spectroscopy. Moreover, 1H and 13C NMR titration experiments provided additional support for determination of interaction type. Furthermore, by using density functional theory (DFT) calculations, thermodynamic stability was studied. Additionally, non-covalent interactions (NCI), frontier molecular orbitals (FMO), density of states (DOS), were investigated for providing further evidence of nitrobenzene sensing and its interaction with sensor. Natural bond orbital (NBO) analysis was carried out for charge transfer studies. Quantum theory of atom in molecule (QTAIM) and SAPT0 studies provided information about interaction points and binding energy. Additionally, IPA was investigated for NB sensing in real water samples, and its effective participation in solid state on-site detection as well as in solution phase was brought to light along with logic gate construction.

Anion-π+ AIEgens for Fluorescence Imaging and Photodynamic Therapy

Fluorescence imaging-guided photodynamic therapy (PDT) has attracted extensive attention due to its potential of real-time monitoring the lesion locations and visualizing the treatment process with high sensitivity and resolution. Aggregation-induced emission luminogens (AIEgens) show enhanced fluorescence and reactive oxygen species (ROS) generation after cellular uptake, giving them significant advantages in bioimaging and PDT applications. However, most AIEgens are unfavorable for the application in organisms due to their severe hydrophobicity. Anion-π+ type AIEgens carry intrinsic charges that can effectively alleviate their hydrophobicity and improve their binding capability to cells, which is expected to enhance the bioimaging quality and PDT performance. This concept summarizes the applications of anion-π+ type AIEgens in fluorescence imaging, fluorescence imaging-guided photodynamic anticancer and antimicrobial therapy in recent years, hoping to provide some new ideas for the construction of robust photosensitizers. Finally, the current problems and future challenges of anion-π+ AIEgens are discussed.

Two-Photon-Responsive "TICT + AIE" Active Naphthyridine-BF2 Photoremovable Protecting Group: Application for Specific Staining and Killing of Cancer Cells

The combined effects of twisted intramolecular charge transfer (TICT) and aggregation-induced emission (AIE) phenomena have demonstrated a significant influence on excited-state chemistry. These combined TICT and AIE features have been extensively utilized to enhance photodynamic and photothermal therapy. Herein, we demonstrated the synergistic capabilities of TICT and AIE phenomena in the design of the photoremovable protecting group (PRPG), namely, NMe2-Napy-BF2. This innovative PRPG incorporates TICT and AIE characteristics, resulting in four remarkable properties: (i) red-shifted absorption wavelength, (ii) strong near-infrared (NIR) emission, (iii) viscosity-sensitive emission property, and (iv) accelerated photorelease rate. Inspired by these intriguing attributes, we developed a nanodrug delivery system (nano-DDS) using our PRPG for cancer treatment. In vitro studies showed that our nano-DDS manifested effective cellular internalization, specific staining of cancer cells, high-resolution confocal imaging of cancerous cells in the NIR region, and controlled release of the anticancer drug chlorambucil upon exposure to light, leading to cancer cell eradication. Most notably, our nano-DDS exhibited a substantially increased two-photon (TP) absorption cross section (435 GM), exhibiting its potential for in vivo applications. This development holds promise for significant advancements in cancer treatment strategies.

Molecular engineering to design a bright near-infrared red photosensitizer: cellular bioimaging and phototherapy

Near-infrared red (NIR) fluorescence imaging guide phototherapeutic therapy (PDT) has the advantages of deep tissue penetration, real-time monitoring of drug treatment and disease, little damage to normal tissue, low cytotoxicity and almost no side effects, and thus, it is attracting increasing research attention and is expected to show promising potential for clinical tumor treatment. The photosensitizer (PS), light source and oxygen are the three basic and important factors to construct PDT technology, and highly efficient PSs are still being passionately pursued because they determine the PDT efficiency. Ideal PSs should have properties such as good biocompatibility, deep tissue penetration, and highly efficient reactive oxygen species (ROS) generation despite the hypoxic environment. Therefore, pure organic type I PSs with NIR fluorescence have been receiving increasing attention due to their deep penetration and hypoxia resistance. However, reported NIR-active type I PSs usually require complex synthetic procedures, which presents a challenge for mass production. In this research work, based on the molecular design ideas of introducing the heavy atom effect and intramolecular charge transfer, we prepared three NIR-active type I PSs (TNZ, TNZBr, and TNZCHO) using a very simple method with one or two synthetic steps. Clear characterizations of photophysical properties, ROS performance tests, and fluorescent imaging of human umbilical vein endothelial (HUVE) cells and PDT treatment of HepG2 cells were carried out. The results revealed that the heavy atom and intramolecular charge transfer (ICT) effects could obviously enhance the ROS efficiency, and both PSs produce only type I ROS without any type II ROS (1O2) generation. The good NIR fluorescence brightness and type I ROS efficiency ensure satisfactory bioimaging and PDT outcomes. This research provides the possibility of preparing NIR-active type I PSs via mass production.

Rational design of type-I photosensitizer molecules for mitochondrion-targeted photodynamic therapy

Photodynamic therapy (PDT) has emerged as a promising approach for tumor treatment. However, traditional type II PDT faces limitations due to its oxygen-dependent nature. Type-I photosensitizers (PSs) exhibit superiority over conventional type-II PSs owing to their diminished oxygen dependence. Nevertheless, designing effective type-I PSs remains a significant challenge. In this work, we provide a novel strategy to tune the PDT mechanism of an excited photosensitizer through aryl substituent engineering. Using S-rhodamine as the base structure, three PSs were synthesized by incorporating phenyl, furyl, or thienyl groups at the meso position. Interestingly, furyl- or thienyl-substituted S-rhodamine are type-I-dominated PSs that produce O2˙-, while phenyl S-rhodamine results in O2˙- and 1O2 through type-I and type-II mechanisms, respectively. Experimental analyses and theoretical calculations showed that the introduction of a five-membered heterocycle at the meso position promoted intersystem crossing (ISC) and electron transfer, facilitating the production of O2˙-. Furthermore, furyl- or thienyl-substituted S-rhodamine exhibited high phototoxicity at ultralow concentrations. Thienyl-substituted S-rhodamine showed promising PDT efficacy against hypoxic solid tumors. This innovative strategy provides an alternative approach to developing new type-I PSs without the necessity for creating entirely new skeletons.

Dual-Functional AIE Fluorescent Probe for Visualization of Lipid Droplets and Photodynamic Therapy of Cancer

Abnormal lipid droplets (LDs) are known to be intimately bound with the occurrence and development of cancer, allowing LDs to be critical biomarkers for cancers. Aggregation-induced emission luminogens (AIEgens), with efficient reactive oxygen species (ROS) production performance, are prime photosensitizers (PSs) for photodynamic therapy (PDT) with imaging. Therefore, the development of dual-functional fluorescent probes with aggregation-induced emission (AIE) characteristics that enable both simultaneous LD monitoring and imaging-guided PDT is essential for concurrent cancer diagnosis and treatment. Herein, we reported the development of a novel LD-targeting fluorescent probe (TDTI) with AIE performance, which was expected to realize the integration of cancer diagnosis through LD visualization and cancer treatment via PDT. We demonstrated that TDTI, with typical AIE characteristics and excellent photostability, could target LDs with high specificity, which enables the dynamic tracking of LDs in living cells, specific imaging of LDs in zebrafish, and the differentiation of cancer cells from normal cells for cancer diagnosis. Meanwhile, TDTI exhibited fast ROS generation ability (achieving equilibrium within 60 s) under white light irradiation (10 mW/cm2). The cell apoptosis assay revealed that TDTI effectively induced growth inhibition and apoptosis of HeLa cells. Further, the results of PDT in vivo indicated that TDTI had a good antitumor effect on the tumor-bearing mice model. Collectively, these results highlight the potential utility of the dual-functional fluorescent probe TDTI in the integrated diagnosis and treatment of cancer.

A smart cysteine-activated and heavy-atom-free nano-photosensitizer for photodynamic therapy to treat cancers

A smart and heavy-atom-free photoinactive nano-photosensitizer capable of being activated by cysteine at the tumor site to generate highly photoactive nano-photosensitizers that show strong NIR absorption and fluorescence with a good singlet oxygen quantum yield (16.8%) for photodynamic therapy is reported.

Photo-Induced Disproportionation-Mediated Photodynamic Therapy: Simultaneous Oxidation of Tetrahydrobiopterin and Generation of Superoxide Radicals

We herein present an approach of photo-induced disproportionation for preparation of Type-I photodynamic agents. As a proof of concept, BODIPY-based photosensitizers were rationally designed and prepared. The photo-induced intermolecular electron transfer between homotypic chromophores leads to the disproportionation reaction, resulting in the formation of charged intermediates, cationic and anionic radicals. The cationic radicals efficiently oxidize the cellularimportant coenzyme, tetrahydrobiopterin (BH4 ), and the anionic radicals transfer electrons to oxygen to produce superoxide radicals (O2 - ⋅). One of our Type-I photodynamic agents not only self-assembles in water but also effectively targets the endoplasmic reticulum. It displayed excellent photocytotoxicity even in highly hypoxic environments (2 % O2 ), with a half-maximal inhibitory concentration (IC50 ) of 0.96 μM, and demonstrated outstanding antitumor efficacy in murine models bearing HeLa tumors.

Type I photodynamic antimicrobial therapy: Principles, progress, and future perspectives

The emergence of drug-resistant bacteria has significantly diminished the efficacy of existing antibiotics in the treatment of bacterial infections. Consequently, the need for finding a strategy capable of effectively combating bacterial infections has become increasingly urgent. Photodynamic therapy (PDT) is considered one of the most promising emerging antibacterial strategies due to its non-invasiveness, low adverse effect, and the fact that it does not lead to the development of drug resistance. However, bacteria at the infection sites often exist in the form of biofilm instead of the planktonic form, resulting in a hypoxic microenvironment. This phenomenon compromises the treatment outcome of oxygen-dependent type-II PDT. Compared to type-II PDT, type-I PDT is not constrained by the oxygen concentration in the infected tissues. Therefore, in the treatment of bacterial infections, type-I PDT exhibits significant advantages over type-II PDT. In this review, we first introduce the fundamental principles of type-I PDT in details, including its physicochemical properties and how it generates reactive oxygen species (ROS). Next, we explore several specific antimicrobial mechanisms utilized by type-I PDT and summarize the recent applications of type-I PDT in antimicrobial treatment. Finally, the limitations and future development directions of type-I photosensitizers are discussed. STATEMENT OF SIGNIFICANCE: The misuse and overuse of antibiotics have accelerated the development of bacterial resistance. To achieve the effective eradication of resistant bacteria, pathfinders have devised various treatment strategies. Among these strategies, type I photodynamic therapy has garnered considerable attention owing to its non-oxygen dependence. The utilization of non-oxygen-dependent photodynamic therapy not only enables the effective elimination of drug-resistant bacteria but also facilitates the successful eradication of hypoxic biofilms, which exhibits promising prospects for treating biofilm-associated infections. Based on the current research status, we anticipate that the novel type I photodynamic therapy agent can surmount the biofilm barrier, enabling efficient treatment of hypoxic biofilm infections.

Biocompatible N-carbazoleacetic acid decorated CuxO nanoparticles as self-cascading platforms for synergistic single near-infrared triggered phototherapy treating microbial infections

In this work, positively charged N-carbazoleacetic acid decorated CuxO nanoparticles (CuxO-CAA NPs) as novel biocompatible nanozymes have been successfully prepared through a one-step hydrothermal method. CuxO-CAA can serve as a self-cascading platform through effective GSH-OXD-like and POD-like activities, and the former can induce continuous generation of H2O2 through the catalytic oxidation of overexpressed GSH in the bacterial infection microenvironment, which in turn acts as a substrate for the latter to yield ˙OH via Fenton-like reaction, without introducing exogenous H2O2. Upon NIR irradiation, CuxO-CAA NPs possess a high photothermal conversion effect, which can further improve the enzymatic activity for increasing the production rate of H2O2 and ˙OH. Besides, the photodynamic performance of CuxO-CAA NPs can produce 1O2. The generated ROS and hyperthermia have synergetic effects on bacterial mortality. More importantly, CuxO-CAA NPs are more stable and biosafe than Cu2O, and can generate electrostatic adsorption with negatively charged bacterial cell membranes and accelerate bacterial death. Antibacterial results demonstrate that CuxO-CAA NPs are lethal against methicillin-resistant Staphylococcus aureus (MRSA) and ampicillin-resistant Escherichia coli (AREC) through destroying the bacterial membrane and disrupting the bacterial biofilm formation. MRSA-infected animal wound models show that CuxO-CAA NPs can efficiently promote wound healing without causing toxicity to the organism.

Combining Multiple Photosensitizer Modules into One Supramolecular System for Synergetic Enhanced Photodynamic Therapy

Photodynamic therapy (PDT), as an emerging cancer treatment, requires the development of highly desirable photosensitizers (PSs) with integrated functional groups to achieve enhanced therapeutic efficacy. Coordination-driven self-assembly (CDSA) would provide an alternative approach for combining multiple PSs synergistically. Here, we demonstrate a simple yet powerful strategy of combining conventional chromophores (tetraphenylethylene, porphyrin, or Zn-porphyrin) with pyridinium salt PSs together through condensation reactions, followed by CDSA to construct a series of novel metallo-supramolecular PSs (S1-S3). The generation of reactive oxygen species (ROS) is dramatically enhanced by the direct combination of two different PSs, and further reinforced in the subsequent ensembles. Among all the ensembles, S2 with two porphyrin cores shows the highest ROS generation efficiency, specific interactions with lysosome, and strong emission for probing cells. Moreover, the cellular and living experiments confirm that S2 has excellent PDT efficacy, biocompatibility, and biosafety. As such, this study will enable the development of more efficient PSs with potential clinical applications.

Construction of gelatin/alginate hydrogels doped hemicyanine derivatives for photodynamic antibacterial application

Hydrogel systems based on natural polymer materials have provided alternative opportunities for preparing antimicrobial dressings. A composite antibacterial hydrogel system containing gelatin (Gel), alginate (Alg) and hemicyanine derivatives with different chain lengths (C3, C6 and C10) was constructed. The composite hydrogels have excellent swelling ability and low degradability due to the classical three-dimensional network structure. Because of the photosensitization ability of C3, C6 and C10, hydrogels containing these molecules can also effectively produce reactive oxygen species (ROS) under light. Importantly, the hydrogel containing C3 molecules that have higher spatial extension structure and shorter alkyl chain than C6 and C10 shows better photo-responsive antibacterial effect against drug-resistant Escherichia coli. The bacterial killing activity of the composite hydrogel system could be regulated by changing the alkyl chain length of the photosensitizers. This effective and photo-responsive composite hydrogel system is expected to be used for bacteria-infected wound repair and promoting wound healing.

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.

An Activatable Phototheranostic Probe for Anti-hypoxic Type I Photodynamic- and Immuno-Therapy of Cancer

Photodynamic therapy (PDT), which utilizes type I photoreactions, has great potential as an effective cancer treatment because of its hypoxia-tolerant superiority over the commonly used type II pathway. A few type I photosensitizers are exploited; however, they majorly induce cytotoxicity and possess poor tumor specificity and low-efficient theranostics. To resolve this issue, herein an aminopeptidase N (APN)-activated type I phototheranostic probe (CyA) is reported for anti-hypoxic PDT in conjunction with immunotherapy for effective cancer treatment. CyA can specifically activate near-infrared fluorescence, photoacoustic signals, and phototoxicity following APN-induced substrate cleavage and the subsequent generation of active phototheranostic molecules (such as CyBr). CyA endows specific imaging capabilities and effective phototoxicity toward tumor cells overexpressing APN under both normoxia and hypoxia. In addition, the locally activatable PDT induces systemic antitumor immune responses. More importantly, the integration of localized activated PDT and systemic immunotherapy evokes enhanced therapeutic effects with improved tumor inhibition efficiency in live mice compared with individual treatments. This study aims to present an activatable phototheranostic probe for effective hypoxia-tolerant PDT and combination therapy.

Type I Photosensitizer Targeting Glycans: Overcoming Biofilm Resistance by Inhibiting the Two-Component System, Quorum Sensing, and Multidrug Efflux

Stubborn biofilm infections pose serious threats to human health due to the persistence, recurrence, and dramatically magnified antibiotic resistance. Photodynamic therapy has emerged as a promising approach to combat biofilm. Nevertheless, how to inhibit the bacterial signal transduction system and the efflux pump to conquer biofilm recurrence and resistance remains a challenging and unaddressed issue. Herein, a boric acid-functionalized lipophilic cationic type I photosensitizer, ACR-DMP, is developed, which efficiently generates •OH to overcome the hypoxic microenvironment and photodynamically eradicates methicillin-resistant Staphylococcus aureus (MRSA) and biofilms. Furthermore, it not only alters membrane potential homeostasis and osmotic pressure balance due to its strong binding ability with plasma membrane but also inhibits quorum sensing and the two-component system, reduces virulence factors, and regulates the activity of the drug efflux pump attributed to the glycan-targeting ability, helping to prevent biofilm recurrence and conquer biofilm resistance. In vivo, ACR-DMP successfully obliterates MRSA biofilms attached to implanted medical catheters, alleviates inflammation, and promotes vascularization, thereby combating infections and accelerating wound healing. This work not only provides an efficient strategy to combat stubborn biofilm infections and bacterial multidrug resistance but also offers systematic guidance for the rational design of next-generation advanced antimicrobial materials.

Functional fluorescent nanomaterials for the detection, diagnosis and control of bacterial infection and biofilm formation: Insight towards mechanistic aspects and advanced applications

Infectious diseases resulting from the high pathogenic potential of several bacteria possesses a major threat to human health and safety. Traditional methods used for screening of these microorganisms face major issues with respect to detection time, selectivity and specificity which may delay treatment for critically ill patients past the optimal time. Thus, a convincing and essential need exists to upgrade the existing methodologies for the fast detection of bacteria. In this context, increasing number of newly emerging nanomaterials (NMs) have been discovered for their effective use and applications in the area of diagnosis in bacterial infections. Recently, functional fluorescent nanomaterials (FNMs) are extensively explored in the field of biomedical research, particularly in developing new diagnostic tools, nanosensors, specific imaging modalities and targeted drug delivery systems for bacterial infection. It is interesting to note that organic fluorophores and fluorescent proteins have played vital role for imaging and sensing technologies for long, however, off lately fluorescent nanomaterials are increasingly replacing these due to the latter's unprecedented fluorescence brightness, stability in the biological environment, high quantum yield along with high sensitivity due to enhanced surface property etc. Again, taking advantage of their photo-excitation property, these can also be used for either photothermal and photodynamic therapy to eradicate bacterial infection and biofilm formation. Here, in this review, we have paid particular attention on summarizing literature reports on FNMs which includes studies detailing fluorescence-based bacterial detection methodologies, antibacterial and antibiofilm applications of the same. It is expected that the present review will attract the attention of the researchers working in this field to develop new engineered FNMs for the comprehensive diagnosis and treatment of bacterial infection and biofilm formation.

Assessment of Photosensitizer Concentration Effects on the Efficacy of Photodynamic Therapy

Introduction: Photodynamic therapy (PDT) is an attractive approach in medicine. Due to its noninvasive nature and low side effects, PDT has been developed quickly. In the present study, the gene expression profiles of the human cell line that was treated via PDT in the sub-lethal concentration (LC50) and super-lethal concentration (LC90) of a photosensitizer (PS) from Gene Expression Omnibus (GEO) were extracted and the common differentially expressed genes (DEGs) were investigated. Methods: The gene expression profiles of the treated cells were compared with a control, and the common DEGs were determined. The common DEGs were assessed via protein-protein interaction (PPI) network analysis, and gene ontology enrichment was evaluated. The related biological terms for the common genes were identified. Results: Ninety-four common DEGs were selected to be analyzed. It appeared that the activation and increment of gene expression were prominent processes. Jun, Dusp1, Atf4, and Atf3 as four critical genes were highlighted. "Chromosomal and microsatellite instability in colorectal cancer" was identified as the main class of biological terms related to the assessed DEGs. Conclusion: The major molecular events which happened in both analyses indicated that PDT, independent from the concentration of PS, induced gross molecular changes such as the upregulation of Jun and Dusp1.

Research Progress of Photodynamic Therapy in Wound Healing: A Literature Review

Light is an efficient technique that has a significant influence on contemporary medicine. Photodynamic therapy (PDT), which involves the combined action of photosensitizers (PSs), oxygen, and light, has emerged as a therapeutically promising method for treating a broad variety of solid tumors and infectious diseases. Photodynamic therapy is minimally invasive, has few side effects, lightens scars, and reduces tissue loss while preserving organ structure and function. In particular, PDT has a high healing potential for wounds (PDT stimulates wound healing by enhancing re-epithelialization, promoting angiogenesis as well as modulating skin homeostasis). Wound healing involves interactions between many different processes, including coagulation, inflammation, angiogenesis, cellular migration, and proliferation. Poor wound healing with diabetes or extensive burns remains a difficult challenge. This review emphasizes PDT as a potential research field and summarizes PDT's role in wound healing, including normal wounds, chronic wounds, and aging wounds.

Towards bioresource-based aggregation-induced emission luminogens from lignin β-O-4 motifs as renewable resources

One-pot synthesis of heterocyclic aromatics with good optical properties from phenolic β-O-4 lignin segments is of high importance to meet high value added biorefinery demands. However, executing this process remains a huge challenge due to the incompatible reaction conditions of the depolymerization of lignin β-O-4 segments containing γ-OH functionalities and bioresource-based aggregation-induced emission luminogens (BioAIEgens) formation with the desired properties. In this work, benzannulation reactions starting from lignin β-O-4 moieties with 3-alkenylated indoles catalyzed by vanadium-based complexes have been successfully developed, affording a wide range of functionalized carbazoles with up to 92% yield. Experiments and density functional theory calculations suggest that the reaction pathway involves the selective cleavage of double C-O bonds/Diels-Alder cycloaddition/dehydrogenative aromatization. Photophysical investigations show that these carbazole products represent a class of BioAIEgens with twisted intramolecular charge transfer. Distinctions of emission behavior were revealed based on unique acceptor-donor-acceptor-type molecular conformations as well as molecular packings. This work features lignin β-O-4 motifs with γ-OH functionalities as renewable substrates, without the need to apply external oxidant/reductant systems. Here, we show a concise and sustainable route to functional carbazoles with AIE properties, building a bridge between lignin and BioAIE materials.

Modulating the Luminescence, Photosensitizing Properties, and Mitochondria-Targeting Ability of D-π-A-Structured Dihydrodibenzo[a,c]phenazines

Herein, pyridinium and 4-vinylpyridinium groups are introduced into the VIE-active N,N'-disubstituted-dihydrodibenzo[a,c]phenazines (DPAC) framework to afford a series of D-π-A-structured dihydrodibenzo[a,c]phenazines in consideration of the aggregation-benefited performance of the DPAC module and the potential mitochondria-targeting capability of the resultant pyridinium-decorated DPACs (DPAC-PyPF6 and DPAC-D-PyPF6). To modulate the properties and elucidate the structure-property relationship, the corresponding pyridinyl/4-vinylpyridinyl-substituted DPACs, i.e., DPAC-Py and DPAC-D-Py, are designed and studied as controls. It is found that the strong intramolecular charge transfer (ICT) effect enables the effective separation of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of DPAC-PyPF6 and DPAC-D-PyPF6, which is conducive to the generation of ROS. By adjusting the electron-accepting group and the π-bridge, the excitation, absorption, luminescence, photosensitizing properties as well as the mitochondria-targeting ability can be finely tuned. Both DPAC-PyPF6 and DPAC-D-PyPF6 display large Stokes shifts (70-222 nm), solvent-dependent absorptions and emissions, aggregation-induced emission (AIE), red fluorescence in the aggregated state (λem = 600-650 nm), aggregation-promoted photosensitizing ability with the relative singlet-oxygen quantum yields higher than 1.10, and a mitochondria-targeting ability with the Pearson coefficients larger than 0.85. DPAC-D-PyPF6 shows absorption maximum at a longer wavelength, slightly redder fluorescence and better photosensitivity as compared to DPAC-PyPF6, which consequently leads to the higher photocytotoxicity under the irradiation of white light as a result of the larger π-conjugation.

A photo-triggered self-accelerated nanoplatform for multifunctional image-guided combination cancer immunotherapy

Precise and efficient image-guided immunotherapy holds great promise for cancer treatment. Here, we report a self-accelerated nanoplatform combining an aggregation-induced emission luminogen (AIEgen) and a hypoxia-responsive prodrug for multifunctional image-guided combination immunotherapy. The near-infrared AIEgen with methoxy substitution simultaneously possesses boosted fluorescence and photoacoustic (PA) brightness for the strong light absorption ability, as well as amplified type I and type II photodynamic therapy (PDT) properties via enhanced intersystem crossing process. By formulating the high-performance AIEgen with a hypoxia-responsive paclitaxel (PTX) prodrug into nanoparticles, and further camouflaging with macrophage cell membrane, a tumor-targeting theranostic agent is built. The integration of fluorescence and PA imaging helps to delineate tumor site sensitively, providing accurate guidance for tumor treatment. The light-induced PDT effect could consume the local oxygen and lead to severer hypoxia, accelerating the release of PTX drug. As a result, the combination of PDT and PTX chemotherapy induces immunogenic cancer cell death, which could not only elicit strong antitumor immunity to suppress the primary tumor, but also inhibit the growth of distant tumor in 4T1 tumor-bearing female mice. Here, we report a strategy to develop theranostic agents via rational molecular design for boosting antitumor immunotherapy.

Mitochondrial DNA-targeted therapy: A novel approach to combat cancer

Mitochondrial DNA (mtDNA) encodes proteins and RNAs that are essential for mitochondrial function and cellular homeostasis, and participates in important processes of cellular bioenergetics and metabolism. Alterations in mtDNA are associated with various diseases, especially cancers, and are considered as biomarkers for some types of tumors. Moreover, mtDNA alterations have been found to affect the proliferation, progression and metastasis of cancer cells, as well as their interactions with the immune system and the tumor microenvironment (TME). The important role of mtDNA in cancer development makes it a significant target for cancer treatment. In recent years, many novel therapeutic methods targeting mtDNA have emerged. In this study, we first discussed how cancerogenesis is triggered by mtDNA mutations, including alterations in gene copy number, aberrant gene expression and epigenetic modifications. Then, we described in detail the mechanisms underlying the interactions between mtDNA and the extramitochondrial environment, which are crucial for understanding the efficacy and safety of mtDNA-targeted therapy. Next, we provided a comprehensive overview of the recent progress in cancer therapy strategies that target mtDNA. We classified them into two categories based on their mechanisms of action: indirect and direct targeting strategies. Indirect targeting strategies aimed to induce mtDNA damage and dysfunction by modulating pathways that are involved in mtDNA stability and integrity, while direct targeting strategies utilized molecules that can selectively bind to or cleave mtDNA to achieve the therapeutic efficacy. This study highlights the importance of mtDNA-targeted therapy in cancer treatment, and will provide insights for future research and development of targeted drugs and therapeutic strategies.

Synthesis and properties of novel type I photosensitizer polycyclic amide

Herein, we have designed and synthesized a novel type-I photosensitizer (PhPA) via Rh-catalyzed oxidative cyclization of diacetoxyterephthalamide with alkynes. The photoelectric properties, photosensitivity and photodegradation process of PhPA have been systematically investigated. The remarkable fluorescence quenching effect (Φ_PL < 0.01) of PhPA suggests that the intersystem crossing from the singlet excited state to the reactive triplet state is enhanced by the enlarged conjugated backbone. Additionally, the ability of superoxide radical (O₂^-˙) generation was confirmed by electron paramagnetic resonance spectroscopy. Finally, the mechanism of PhPA photo-oxidative degradation via the structure of two metabolites is proposed.

Near-infrared AIEgens with high singlet-oxygen yields for mitochondria-specific imaging and antitumor photodynamic therapy

AIE-active photosensitizers (PSs) are promising for antitumor therapy due to their advantages of aggregation-promoted photosensitizing properties and outstanding imaging ability. High singlet-oxygen (¹O₂) yield, near-infrared (NIR) emission, and organelle specificity are vital parameters to PSs for biomedical applications. Herein, three AIE-active PSs with D-π-A structures are rationally designed to realize efficient ¹O₂ generation, by reducing the electron-hole distribution overlap, enlarging the difference on the electron-cloud distribution at the HOMO and LUMO, and decreasing the ΔE_ST. The design principle has been expounded with the aid of time-dependent density functional theory (TD-DFT) calculations and the analysis of electron-hole distributions. The ¹O₂ quantum yields of AIE-PSs developed here can be up to 6.8 times that of the commercial photosensitizer Rose Bengal under white-light irradiation, thus among the ones with the highest ¹O₂ quantum yields reported so far. Moreover, the NIR AIE-PSs show mitochondria-targeting capability, low dark cytotoxicity but superb photo-cytotoxicity, and satisfactory biocompatibility. The in vivo experimental results demonstrate good antitumor efficacy for the mouse tumour model. Therefore, the present work will shed light on the development of more high-performance AIE-PSs with high PDT efficiency.

Recent advances in type I organic photosensitizers for efficient photodynamic therapy for overcoming tumor hypoxia

Photodynamic therapy (PDT) with an oxygen-dependent character is a noninvasive therapeutic method for cancer treatment. However, its clinical therapeutic effect is greatly restricted by tumor hypoxia. What's more, both PDT-mediated oxygen consumption and microvascular damage aggravate tumor hypoxia, thus, further impeding therapeutic outcomes. Compared to type II PDT with high oxygen dependence and high oxygen consumption, type I PDT with less oxygen consumption exhibits great potential to overcome the vicious hypoxic plight in solid tumors. Type I photosensitizers (PSs) are significantly important for determining the therapeutic efficacy of PDT, which performs an electron transfer photochemical reaction with the surrounding oxygen/substrates to generate highly cytotoxic free radicals such as superoxide radicals (˙O₂^-) as type I ROS. In particular, the primary precursor (˙O₂^-) would progressively undergo a superoxide dismutase (SOD)-mediated disproportionation reaction and a Haber-Weiss/Fenton reaction, yielding higher cytotoxic species (˙OH) with better anticancer effects. As a result, developing high-performance type I PSs to treat hypoxic tumors has become more and more important and urgent. Herein, the latest progress of organic type I PSs (such as AIE-active cationic/neutral PSs, cationic/neutral PSs, polymer-based PSs and supramolecular self-assembled PSs) for monotherapy or synergistic therapeutic modalities is summarized. The molecular design principles and strategies (donor-acceptor system, anion-π⁺ incorporation, polymerization and cationization) are highlighted. Furthermore, the future challenges and prospects of type I PSs in hypoxia-overcoming PDT are proposed.

Chemiluminescent carbon nanodots for dynamic and guided antibacteria

Advanced antibacterial technologies are needed to counter the rapid emergence of drug-resistant bacteria. Image-guided therapy is one of the most promising strategies for efficiently and accurately curing bacterial infections. Herein, a chemiluminescence (CL)-dynamic/guided antibacteria (CDGA) with multiple reactive oxygen species (ROS) generation capacity and chemiexcited near-infrared emission has been designed for the precise theranostics of bacterial infection by employing near-infrared emissive carbon nanodots (CDs) and peroxalate as CL fuels. Mechanistically, hydrogen peroxide generated in the bacterial microenvironment can trigger the chemically initiated electron exchange between CDs and energy-riched intermediate originated from the oxidized peroxalate, enabling bacterial induced inflammation imaging. Meanwhile, type I/II photochemical ROS production and type III ultrafast charge transfer from CDs under the self-illumination can inhibit the bacteria proliferation efficiently. The potential clinical utility of CDGA is further demonstrated in bacteria infected mice trauma model. The self-illuminating CDGA exhibits an excellent in vivo imaging quality in early detecting wound infections and internal inflammation caused by bacteria, and further are proven as efficient broad-spectrum antibacterial nanomedicines without drug-resistance, whose sterilizing rate is up to 99.99%.

Molecular Charge and Antibacterial Performance Relationships of Aggregation-Induced Emission Photosensitizers

Bacterial infections remain a major cause of morbidity worldwide due to drug resistance of pathogenic bacteria. Photodynamic therapy (PDT) has emerged as a promising approach to overcome this drug resistance. However, existing photosensitizers (PSs) are broad-spectrum antibacterial agents that dysregulate the microflora balance resulting in undesirable side effects. Herein, we synthesized a series of aggregation-induced emission (AIE)-active PSs with a lipophilic cationic AIE core with varying charges, named TBTCP and its derivatives. The association of the difference in their molecular charge with the antibacterial effects was systemically investigated. Among the derivatives presented, TBTCP-SF with the electronegative sulfonate group nulled its ability to bind to and ablate Gram-positive (G+) or Gram-negative (G-) bacteria. TBTCP-QY modified by electropositive quaternary ammonium facilitated binding and augmented the photodynamic antibacterial activity for both G+ and G- bacteria. TBTCP-PEG with hydrophilic neutral ligands selectively bound and inactivated G+ bacteria. Under white-light illumination, TBTCP-PEG ablated 99.9% methicillin-resistant Staphylococcus aureus (MRSA) and promoted wound healing in MRSA-infected mice, eliminating MRSA infection both in vitro and in vivo. Our work provides unprecedented insight into the utility of AIE-active PSs for highly targeted and efficient photodynamic ablation of either G+ or G- bacteria that can be translated to next-generation antibacterial materials.

A hypochlorite-activated strategy for realizing fluorescence turn-on, type I and type II ROS-combined photodynamic tumor ablation

The combination of cancer cell-activated fluorescence and the advantages of both type I and type II photodynamic therapy (PDT) capabilities to achieve a synergistic therapeutic effect in a complex tumor environment is highly desirable. Herein, we report an approach by means of tumor intracellular hypochlorite (ClO^-) to turn on fluorescence integrated with type I and II ROS generation for imaging-guided PDT. The resultant PTZSPy functions as a type II photosensitizer with mitochondria-targeting capability. In the presence of ClO^-, PTZSPy is transformed into its oxidized counterpart SPTZSPy, turns on an orange-red fluorescence and triggers the type I ROS generation ability. Biological studies revealed that PTZSPy can accurately distinguishes tumor cells from normal cells, dynamically monitors the cell ablation process and be utilized for theranostics in MCF-7 tumor-bearing nude mice in vivo. This work provides an innovative strategy exploiting the highly abundant ClO^- in tumor cells for the type I and II ROS two-pronged and imaging-guided PDT.

Fluorescent Probes Based on AIEgen-Mediated Polyelectrolyte Assemblies for Manipulating Intramolecular Motion and Magnetic Relaxivity

Uniting photothermal therapy (PTT) with magnetic resonance imaging (MRI) holds great potential in nanotheranostics. However, the extensively utilized hydrophobicity-driven assembling strategy not only restricts the intramolecular motion-induced PTT, but also blocks the interactions between MR agents and water. Herein, we report an aggregation-induced emission luminogen (AIEgen)-mediated polyelectrolyte nanoassemblies (APN) strategy, which bestows a unique "soft" inner microenvironment with good water permeability. Femtosecond transient spectra verify that APN well activates intramolecular motion from the twisted intramolecular charge transfer process. This de novo APN strategy uniting synergistically three factors (rotational motion, local motion, and hydration number) brings out high MR relaxivity. For the first time, APN strategy has successfully modulated both intramolecular motion and magnetic relaxivity, achieving fluorescence lifetime imaging of tumor spheroids and spatio-temporal MRI-guided high-efficient PTT.

Acceptor engineering of metallacycles with high phototoxicity indices for safe and effective photodynamic therapy

Although metallacycle-based photosensitizers have attracted increasing attention in biomedicine, their clinical application has been hindered by their inherent dark toxicity and unsatisfactory phototherapeutic efficiency. Herein, we employ a π-expansion strategy for ruthenium acceptors to develop a series of Ru(ii) metallacycles (Ru1-Ru4), while simultaneously reducing dark toxicity and enhancing phototoxicity, thus obtaining a high phototoxicity index (PI). These metallacycles enable deep-tissue (∼7 mm) fluorescence imaging and reactive oxygen species (ROS) production and exhibit remarkable anti-tumor activity even under hypoxic conditions. Notably, Ru4 has the lowest dark toxicity, highest ROS generation ability and an optimal PI (∼146). Theoretical calculations verify that Ru4 exhibits the largest steric bulk and the lowest singlet-triplet energy gap (ΔE _ST, 0.62 eV). In vivo studies confirm that Ru4 allows for effective and safe phototherapy against A549 tumors. This work thus is expected to open a new avenue for the design of high-performance metal-based photosensitizers for potential clinical applications.

Structural optimization of BODIPY photosensitizers for enhanced photodynamic antibacterial activities

Enhancing the interactions between photosensitizers and bacteria is key to developing effective photodynamic antibacterial agents. However, the influence of different structures on the therapeutic effects has not been systematically investigated. Herein, 4 BODIPYs with distinct functional groups, including the phenylboronic acid (PBA) group and pyridine (Py) cations, were designed to explore their photodynamic antibacterial activities. The BODIPY with the PBA group (IBDPPe-PBA) exhibits potent activity against planktonic Staphylococcus aureus (S. aureus) upon illumination, while the BODIPY with Py cations (IBDPPy-Ph) or both the PBA group and Py cations (IBDPPy-PBA) can significantly minimize the growth of both S. aureus and Escherichia coli (E. coli). In particular, IBDPPy-Ph can not only eliminate the mature S. aureus biofilm and E. coli biofilm in vitro, but also promote the healing of the infected wound. Our work provides an alternative for reasonable design of photodynamic antibacterial materials.

Single aromatics sulfonamide substituted dibenzothiazole squaraines for tumor NIR imaging and efficient photodynamic therapy at low drug dose

On the base of the zwiterionic dibenzothiazole squaraine SQ, five cationic aromatics sulfonamide substituted dibenzothiazole squaraines SQ-D1 ∼ 5 have been designed and synthesized. Through the formation of the cationic compound, a higher rigid structure and the addition of the strong electron-withdrawing group (-CN), an ideal photosensitizer SQ-D2 has been gotten. In all the sulfonaminosquaraines, compound SQ-D2 exhibited the highest ROS generation efficacy and photostability. It also showed the highest photo-cytotoxicity (IC₅₀ = 0.25 ± 0.08 μM), very low dark-cytotoxicity and the excellent cell uptake. In animal study, it not only showed the effective tumor retention and the easy removal from the body, but also exhibited the effective PDT efficacy at low drug dose (0.15 mg/kg) and the good biocompatibility. Furthermore, photosensitizer SQ-D2 as a single component exhibited greater potential than clinically approved photosensitizer m-THPC and some nanomaterials with photosensitizers in PDT therapy towards human breast cancer. This work provides a new perspective to develop the ideal photosensitizer of the squaraine dyes.

Room-Temperature Phosphorescence and Cellular Phototoxicity Activated by Triplet Dynamics in Aggregates of Push-Pull Phenothiazine-Based Isomers

In this study, we report a comprehensive time-resolved spectroscopic investigation of the excited-state deactivation mechanism in three push-pull isomers characterized by a phenothiazine electron donor, a benzothiazole electron acceptor, and a phenyl π-bridge where the connection is realized at the relative ortho, meta, and para positions. Spin-orbit charge-transfer-induced intersystem crossing takes place with high yield in these all-organic donor-acceptor compounds, leading also to efficient production of singlet oxygen. Our spectroscopic results give clear evidence of room-temperature phosphorescence not only in solid-state host-guest matrices but also in highly biocompatible aggregates of these isomers produced in water dispersions, as rarely reported in the literature. Moreover, aggregates of the isomers could be internalized by lung cancer and melanoma cells and display bright luminescence without any dark cytotoxic effect. On the other hand, the isomers showed significant cellular phototoxicity against the tumor cells due to light-induced reactive oxygen species generation. Our findings strongly suggest that nanoaggregates of the investigated isomers are promising candidates for imaging-guided photodynamic therapy.

Mitochondria-targeted iridium-based photosensitizers enhancing photodynamic therapy effect by disturbing cellular redox balance

Photodynamic therapy (PDT) is a non-invasive, light-activated treatment approach that has been broadly employed in cancer. Cyclometallic iridium (Ш) complexes are candidates for ideal photosensitizers due to their unique photophysical and photochemical features, such as high quantum yield, large Stokes shift, strong resistance to photobleaching, and high cellular permeability. We evaluated a panel of iridium complexes and identified PC9 as a powerful photosensitizer to kill cancer cells. PC9 shows an 8-fold increase of cytotoxicity to HeLa cells under light irradiation. Further investigation discloses that PC9 has a strong mitochondrial-targeting ability and can inhibit the antioxidant enzyme thioredoxin reductase, which contributes to improving PDT efficacy. Our data indicate that iridium complexes are efficient photosensitizers with distinct physicochemical properties and cellular actions, and deserve further development as promising agents for PDT.

AIE-active Ir(III) complexes as type-I dominant photosensitizers for efficient photodynamic therapy

The ability of a photosensitizer (PS) to generate reactive oxygen species (ROS) including type I oxygen free radicals and type II ¹O₂ is pivotal for photodynamic therapy. Luminescent Ir(III) complexes are effective PSs with high ¹O₂ generation ability owing to their high intersystem crossing ability and effective energy transfer to ³O₂. However, so far, reports on type I ROS based on ˙OH generation induced by Ir(III) PS are still rare. In this work, four novel aggregation-induced emission (AIE)-active Ir(III) PSs, namely MFIriqa, MFIrqa, SFIriqa, and SFIrqa have been designed and synthesized, which show highly efficient emission in the aggregated state. Cell imaging experiment results indicate that all four Ir(III) PSs can effectively improve the signal-to-noise ratio of imaging by reducing the interference from the background due to their fascinating AIE properties. Importantly, in vitro, Ir(III) PSs MFIrqa, SFIriqa, and SFIrqa nanoparticles show obvious photodynamic activity toward cancer cells upon irradiation accompanied by type I ˙OH generation, which may be attributed to the unique excited-state characteristics of Ir(III) complexes. This work will provide guidance for the construction of a type I photosensitizer based on the AIE-active Ir(III) complex, which offers great advantages for potential clinical applications under hypoxic conditions.

Family of hNQO1 Activatable Near-Infrared Fluoro-Photoacoustic Probes for Diagnosis of Wound Infection and Ulcerative Colitis

Bacterial infections can easily occur when patients mishandle wounds or eat moldy food. The prompt diagnosis of a bacterial infection could effectively reduce the risk of possible anatomical damage. However, non-invasive early detection of bacterial infections is difficult to achieve due to the lack of favorable tools. Here, we designed two hNQO1 fluorescent probes (RX2 and RX3) to visualize bacterial infection after deep learning on the pathogenesis of bacterial infection. RX2 and RX3 enable early detection of bacterial infection and are verified to be, respectively, suitable for fluorescence imaging (FLI) and photoacoustic imaging (PAI) by comparing the signal-to-background ratio of both probes in a mouse model of myositis caused by Escherichia coli infection. In view of the difference in penetration depth between the two imaging modalities, we further applied RX2 for FLI of E. coli-infected wounds and RX3 for PAI of E. coli-infected inflammatory bowel disease, suggesting the great potential of both probes for early diagnosis of bacterial infections.

Boosting Type-I and Type-II ROS Production of Water-Soluble Porphyrin for Efficient Hypoxic Tumor Therapy

As the most successful clinically approved photosensitizers, porphyrins have been extensively employed in the photodynamic therapy (PDT) of cancers. However, their poor water solubility, aggregation-induced self-quenching on ROS generation, and a low tolerance for a hypoxic condition usually result in unsatisfied therapeutic outcomes. Therefore, great efforts have been dedicated to improving the PDT efficacy of porphyrin-type photosensitizers in treating hypoxic tumors, including combination with additional active components or therapies, which can significantly complicate the therapeutic process. Herein, we report a novel water-soluble porphyrin with O-linked cationic side chains, which exhibits good water solubility, high photostability, and significantly enhanced ROS generation efficacy in both type-I and type-II photodynamic pathways. We have also found that the end charges of side chains can dramatically affect the ROS generation of the porphyrin. The cationic porphyrin exhibited high in vitro PDT efficacy with low IC₅₀ values both in normoxia and hypoxia. Hence, during in vivo PDT study, the cationic porphyrin displayed highly effective tumor ablation capability. This study demonstrates the power of side-chain chemistry in tuning the photodynamic property of porphyrin, which offers a new effective strategy to enhance the anticancer performance of photosensitizers for fulfilling the increasing demands for cancer therapy in clinics.

Molecular engineering to red-shift the absorption band of AIE photosensitizers and improve their ROS generation ability

Increasing the number of acceptors and extending their π-conjugation will red-shift the absorption-emission band, increase the maximum molar extinction coefficient, and improve the ROS generation ability of AIE-photosensitizers.

Recent Progress in Type I Aggregation-Induced Emission Photosensitizers for Photodynamic Therapy

In modern medicine, precision diagnosis and treatment using optical materials, such as fluorescence/photoacoustic imaging-guided photodynamic therapy (PDT), are becoming increasingly popular. Photosensitizers (PSs) are the most important component of PDT. Different from conventional PSs with planar molecular structures, which are susceptible to quenching effects caused by aggregation, the distinct advantages of AIE fluorogens open up new avenues for the development of image-guided PDT with improved treatment accuracy and efficacy in practical applications. It is critical that as much of the energy absorbed by optical materials is dissipated into the pathways required to maximize biomedical applications as possible. Intersystem crossing (ISC) represents a key step during the energy conversion process that determines many fundamental optical properties, such as increasing the efficiency of reactive oxygen species (ROS) production from PSs, thus enhancing PDT efficacy. Although some review articles have summarized the accomplishments of various optical materials in imaging and therapeutics, few of them have focused on how to improve the phototherapeutic applications, especially PDT, by adjusting the ISC process of organic optics materials. In this review, we emphasize the latest advances in the reasonable design of AIE-active PSs with type I photochemical mechanism for anticancer or antibacterial applications based on ISC modulation, as well as discuss the future prospects and challenges of them. In order to maximize the anticancer or antibacterial effects of type I AIE PSs, it is the aim of this review to offer advice for their design with the best energy conversion.

Synergistically Enhancing Tumor Chemotherapy Using an Aggregation-Induced Emission Photosensitizer on Covalently Conjugated Molecularly Imprinted Polymer Nanoparticles

Due to the polygenic and heterogeneous nature of the tumorigenesis process, traditional chemotherapy is far from desirable. Fabricating multifunctional nanoplatforms integrating photodynamic effect can synergistically enhance chemotherapy because they can make the cancer cells much sensitive to chemotherapeutics. However, how to assemble different units in nanoplatforms and minimize side effects caused by chemodrugs and photosensitizers (PSs) still needs to be explored. Herein, a nanoplatform CPP/PS-MIP@DOX is developed using a simultaneously covalently conjugated new aggregation-induced emission (AIE) PS and a cell-penetrating peptide (CPP) on the surface of silica-based molecularly imprinted polymer (MIP) nanoparticles, prepared with doxorubicin (DOX) as the template in the water system via a sol-gel technique. CPP/PS-MIP@DOX has good biocompatibility, high DOX-loading ability, promoted cellular uptake, and sustained and pH-sensitive drug release capability. Furthermore, it can efficiently penetrate into tumor tissue, accurately home to, and accumulate at the tumor site. As a result, a better efficacy with lower cytotoxicity is achieved with a smaller dosage of DOX by utilizing either the photodynamic effect or unique characteristics of the MIP. It is the first nanoplatform fabricated by chemically conjugating AIE PSs directly on the surface of the scaffold via the surface-decorated strategy and successfully applied in cancer therapy. This work provides an effective strategy by constructing AIE PS-based cancer nanomedicines with MIPs as scaffolds.

Tricyano-Methylene-Pyridine Based High-Performance Aggregation-Induced Emission Photosensitizer for Imaging and Photodynamic Therapy

Photosensitizers equipped with high reactive oxygen species (ROS) generation capability and bright emission are essential for accurate tumor imaging and precise photodynamic therapy (PDT). However, traditional aggregation-caused quenching (ACQ) photosensitizers cannot simultaneously produce desirable ROS and bright fluorescence, resulting in poor image-guided therapy effect. Herein, we report an aggregation-induced emission (AIE) photosensitizer TCM-Ph with a strong donor-π-acceptor (D-π-A) structure, which greatly separates the HOMO-LUMO distribution and reduces the ΔE_ST, thereby increasing the number of triplet excitons and producing more ROS. The AIE photosensitizer TCM-Ph has bright near-infrared emission, as well as a higher ROS generation capacity than the commercial photosensitizers Bengal Rose (RB) and Chlorine e6 (Ce6), and can effectively eliminate cancer cells under image guidance. Therefore, the AIE photosensitizer TCM-Ph has great potential to replace the commercial photosensitizers.

Self-cleaning wearable masks for respiratory infectious pathogen inactivation by type I and type II AIE photosensitizer

Although face masks as personal protective equipment (PPE) are recommended to control respiratory diseases with the on-going COVID-19 pandemic, improper handling and disinfection increase the risk of cross-contamination and compromise the effectiveness of PPE. Here, we prepared a self-cleaning mask based on a highly efficient aggregation-induced emission photosensitizer (TTCP-PF₆) that can destroy pathogens by generating Type I and Type II reactive oxygen species (ROS). The respiratory pathogens, including influenza A virus H1N1 strain and Streptococcus pneumoniae (S. pneumoniae) can be inactivated within 10 min of ultra-low power (20 W/m²) white light or simulated sunlight irradiation. This TTCP-PF₆-based self-cleaning strategy can also be used against other airborne pathogens, providing a strategy for dealing with different microbes.