AIE Multinuclear Ir(III) Complexes for Biocompatible Organic Nanoparticles with Highly Enhanced Photodynamic Performance

Leveraging the Photofunctions of Transition Metal Complexes for the Design of Innovative Phototherapeutics

Despite the advent of various medical interventions for cancer treatment, the disease continues to pose a formidable global health challenge, necessitating the development of new therapeutic approaches for more effective treatment outcomes. Photodynamic therapy (PDT), which utilizes light to activate a photosensitizer to produce cytotoxic reactive oxygen species (ROS) for eradicating cancer cells, has emerged as a promising approach for cancer treatment due to its high spatiotemporal precision and minimal invasiveness. However, the widespread clinical use of PDT faces several challenges, including the inefficient production of ROS in the hypoxic tumor microenvironment, the limited penetration depth of light in biological tissues, and the inadequate accumulation of photosensitizers at the tumor site. Over the past decade, there has been increasing interest in the utilization of photofunctional transition metal complexes as photosensitizers for PDT applications due to their intriguing photophysical and photochemical properties. This review provides an overview of the current design strategies used in the development of transition metal complexes as innovative phototherapeutics, aiming to address the limitations associated with PDT and achieve more effective treatment outcomes. The current challenges and future perspectives on the clinical translation of transition metal complexes are also discussed.

Self-Chemiluminescence-Triggered Ir(III) Complex Photosensitizer for Photodynamic Therapy against Hypoxic Tumor

The limited optical penetration depth and hypoxic tumor microenvironment (TME) are key factors that hinder the practical applications of conventional photodynamic therapy (PDT). To fundamentally address these issues, self-luminescent photosensitizers (PSs) can achieve efficient PDT. Herein, a self-chemiluminescence (CL)-triggered Ir complex PS, namely, IrL2, with low-O2-dependence type I photochemical processes is reported for efficient PDT. The rational design achieves efficient chemiluminescence resonance energy transfer (CRET) from covalently bonded luminol units to the Ir complex in IrL2 under the catalysis of H2O2 and hemoglobin (Hb) to generate O2•- and 1O2. Liposome IrL2H nanoparticles (NPs) are constructed by loading IrL2 and Hb. The intracellular H2O2 and loaded Hb catalyze the luminol part of IrL2H, and the Ir2 part is then excited to produce types I and II reactive oxygen species (ROS) through CRET, inducing cell death, even under hypoxic conditions, and promoting cell apoptosis. IrL2H is used for tumor imaging and inhibits tumor growth in 4T1-bearing mouse models through intratumoral injection without external light sources. This work provides new designs for transition metal complex PSs that conquer the limitations of external light sources and the hypoxic TME in PDT.

Reviewing the evolutive ACQ-to-AIE transformation of photosensitizers for phototheranostics

Photodynamic therapy (PDT) represents an emerging noninvasive treatment technique for cancers and various nonmalignant diseases, including infections. During the process of PDT, the physical and chemical properties of photosensitizers (PSs) critically determine the effectiveness of PDT. Traditional PSs have made great progress in clinical applications. One of the challenges is that traditional PSs suffer from aggregation-caused quenching (ACQ) due to their discotic structures. Recently, aggregation-induced emission PSs (AIE-PSs) with a twisted propeller-shaped conformation have been widely concerned because of high reactive oxygen species (ROS) generation efficiency, strong fluorescence efficiency, and resistance to photobleaching. However, AIE-PSs also have some disadvantages, such as short absorption wavelengths and insufficient molar absorption coefficient. When the advantages and disadvantages of AIE-PSs and ACQ-PSs are complementary, combining ACQ-PSs and AIE-PSs is a "win-to-win" strategy. As far as we know, the conversion of traditional representative ACQ-PSs to AIE-PSs for phototheranostics has not been reviewed. In the review, we summarize the recent progress on the ACQ-to-AIE transformation of PSs and the strategies to achieve desirable theranostic applications. The review would be helpful to design more efficient ACQ-AIE-PSs in the future and to accelerate the development and clinical application of PDT.

Near-Infrared Afterglow ONOO--Triggered Nanoparticles for Real-Time Monitoring and Treatment of Early Ischemic Stroke

Early detection and drug intervention with the appropriate timing and dosage are the main clinical challenges for ischemic stroke (IS) treatment. The conventional therapeutic agents relay fluorescent signals, which require real-time external light excitation, thereby leading to inevitable autofluorescence and poor tissue penetration. Herein, we report endogenous peroxynitrite (ONOO-)-activated BDP-4/Cur-CL NPs that release NIR afterglow signals (λmax 697 nm) for real-time monitoring of the progression of ischemia reperfusion (I/R) brain injury while releasing curcumin for the safe treatment of IS. The BDP-4/Cur-CL NPs exhibited bright NIR afterglow luminescence (maximum 732-fold increase), superb sensitivity (LOD = 82.67 nM), high energy-transfer efficiency (94.6%), deep tissue penetration (20 mm), outstanding antiapoptosis, and anti-inflammatory effects. The activated NIR afterglow signal obtained in mice with middle cerebral artery occlusion (MCAO) showed three functions: (i) the BDP-4/Cur-CL NPs are rapidly activated by endogenous ONOO-, instantly illuminating the lesion area, distinguishing I/R damage from normal areas, which can be successfully used for endogenous ONOO- detection in the early stage of IS; (ii) real-time reporting of in situ generation and dynamic fluctuations of endogenous ONOO- levels in the lesion area, which is of great value in monitoring the evolutionary mechanisms of IS; and (iii) dynamic monitoring of the release of curcumin drug for safe treatment. Indeed, the released curcumin effectively decreased apoptosis, enhanced survival, alleviated neuroinflammation, reduced brain tissue loss, and improved the cognition of MCAO stroke mice. This work is the first example of afterglow luminescence for early diagnosis, real-time reporting, drug tracing, and treatment for IS.

Cyclometalated Ir(III) Complexes as Lysosome-Targeted Photodynamic Anticancer Agents

We have designed and synthesized two Ir(III) complexes (Ir1 and Ir2) coordinated with an 8-sulfonamidoquinoline derivative ligand as photosensitizers, which exhibit strong red phosphorescence emission and a long phosphorescence lifetime. The Ir(III) complexes exhibit a high population of triplet states, which enable red phosphorescence and efficient singlet oxygen generation. Ir1 and Ir2 rapidly enter the cancer cells and accumulate in lysosomes, producing large amounts of intracellular singlet oxygen when exposed to light irradiation, eventually leading to cancer cell death, and the phototoxic indexes of complexes Ir1 and Ir2 against cancer cells are in the range of 76-228. Overall, our studies indicate that the synthesized Ir(III) complexes with quinoline ligands exhibit photosensitizing properties, effectively inducing cancer cell death when exposed to light. These promising results suggest their potential application in photodynamic therapy.

Aggregation-Induced Near-Infrared Emission and Electrochemiluminescence of an Iridium(III) Complex for Ampicillin Sodium Sensing

A new iridium(III) complex was synthesized and characterized. Its photophysical properties and aggregation-induced emission and electrochemiluminescence in the near-infrared range were studied. The large conjugated cyclometallic ligand 1,2-phenylbenzoquinoline (pbq) was selected to form the Ir-C bond with the metal iridium(III) center and provide near-infrared emission of the complex. The auxiliary ligand 4,4'-diamino-2,2'-bipyridine (dabpy) can form hydrogen bonds, which was beneficial for the generation of aggregation-induced emission. The complex was aggregated into small spherical nanoparticles in 80% water and fascinating nanorings in 90% water. The sensing of ampicillin sodium (AMP) antibiotic by the iridium(III) complex were also investigated by photoluminescent and electrochemiluminescent methods. The complex showed a good selectivity toward AMP antibiotic compared to sodium phenylacetate and other eight antibiotics. The detection limits for AMP antibiotic was 0.76 μg/mL. This work provided a new strategy for the design of iridium(III) complex-based aggregation-induced emission and electrochemiluminescence probes for the sensing application.

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.

Immunotoxicity of metal and metal oxide nanoparticles: from toxic mechanisms to metabolism and outcomes

The influence of metal and metal oxide nanomaterials on various fields since their discovery has been remarkable. They have unique properties, and therefore, have been employed in specific applications, including biomedicine. However, their potential health risks cannot be ignored. Several studies have shown that exposure to metal and metal oxide nanoparticles can lead to immunotoxicity. Different types of metals and metal oxide nanoparticles may have a negative impact on the immune system through various mechanisms, such as inflammation, oxidative stress, autophagy, and apoptosis. As an essential factor in determining the function and fate of immune cells, immunometabolism may also be an essential target for these nanoparticles to exert immunotoxic effects in vivo. In addition, the biodegradation and metabolic outcomes of metal and metal oxide nanoparticles are also important considerations in assessing their immunotoxic effects. Herein, we focus on the cellular mechanism of the immunotoxic effects and toxic effects of different types of metal and metal oxide nanoparticles, as well as the metabolism and outcomes of these nanoparticles in vivo. Also, we discuss the relationship between the possible regulatory effect of nanoparticles on immunometabolism and their immunotoxic effects. Finally, we present perspectives on the future research and development direction of metal and metal oxide nanomaterials to promote scientific research on the health risks of nanomaterials and reduce their adverse effects on human health.

Mitochondria-Targeting and Multiresponsive Nanoplatform Based on AIEgens for Synergistic Chemo-Photodynamic Therapy and Enhanced Immunotherapy

Although photodynamic therapy (PDT) has become an attractive strategy for cancer treatment, its clinical application still suffers from some limitations, including insufficient delivery of photosensitizers, hypoxic tumor environment, and the development of PDT resistance. To address these limitations, a new class of mitochondria-targeting and fluorinated polymer with aggregation-induced emission characteristics was fabricated to sensitize PDT and co-deliver chemotherapeutic drugs. The amphiphilic fluoropolymer was able to efficiently carry oxygen and SN-38 (the active metabolite of irinotecan) and self-assemble into multifunctional micellar nanoparticles (SN-38-TTCF@O₂ NPs). Upon internalization into tumor cells, these NPs could successfully escape lysosomes, selectively target mitochondria, efficiently produce reactive oxygen species (ROS) under light irradiation, and release drugs in response to ROS. In the HCT116 tumor xenograft model, they preferentially accumulated in tumor tissue and significantly alleviated tumor hypoxia, resulting in synergistic chemo-PDT efficacy without distinct toxicity. Furthermore, the nanoscale chemo-PDT induced immunogenic cell death, promoted the recruitment and activation of cytotoxic T lymphocytes, and ultimately augmented the anti-tumor efficacy of anti-PD-1 antibody in the murine CT26 tumor model. These results may provide novel insights into the development of efficient chemo-PDT nanomedicine to improve the outcome of immunotherapy.

Apoptotic Induction of Mitochondria-Anchored Aggregation-Induced Emission Luminogens through the Intrinsic Mitochondrial Pathway

Gastric cancer has the third highest mortality rate globally. Chemotherapy is the primary treatment used in advanced gastric cancer. Aggregation-induced emission luminogens (AIEgens) have been exploited as non-toxic and efficient chemotherapy agents for the treatment of cancer. Our previous research demonstrated that tetraphenylethene-substituted pyridinium salt (TPE-Py) is a kind of AIEgen that had the ability to lead to apoptosis in gastric cancer cells. However, it is currently unknown whether TPE-Py induced apoptosis in gastric cancer cells by the mitochondria-mediated pathway. This research confirmed that TPE-Py could target mitochondria and induce apoptotic cell death. In addition, several well-recognized indicators were detected to investigate the functional and morphological changes of mitochondria. We found that TPE-Py could diminish the mitochondrial membrane potential and increase the accumulation of reactive oxygen species and the discharge of cytochrome c, which was related to the mitochondrial apoptotic pathway. Meanwhile, morphological changes in mitochondria were also observed by transmission electron microscopy in gastric cancer cells after incubation with TPE-Py. In conclusion, we provided insights into the mechanism regulating apoptosis in gastric cancer cells and elucidated the mechanism of apoptosis induced by TPE-Py via the intrinsic mitochondrial pathway.

Short-Wavelength Aggregation-Induced Emission Photosensitizers for Solid Tumor Therapy: Enhanced with White-Light Fiber Optic

Background

White-light photodynamic therapy (wPDT) has been used in the treatment of cancer due to its convenience, effectiveness and less painful. However, the limited penetration of white-light into the tissues leads to a reduced effectiveness of solid tumor treatment.

Methods

Two short-wavelength aggregation-induced emission (AIE) nanoparticles were prepared, PyTPA@PEG and TB@PEG, which have excitation wavelengths of 440 nm and 524 nm, respectively. They were characterized by UV, fluorescence, particle size and TEM. The ability of nanoparticles to produce reactive oxygen species (ROS) and kill cancer cells under different conditions was investigated in vitro, including white-light, after white-light penetrating the skin, laser. A white-light fiber for intra-tumor irradiation was customized. Finally, induced tumor elimination with fiber-mediated wPDT was confirmed in vivo.

Results

In vitro, both PyTPA@PEG and TB@PEG are more efficient in the production ROS when exposed to white-light compared to laser. However, wPDT also has a fatal flaw in that its level of ROS production after penetrating the skin is reduced to 20-40% of the original level. To this end, we have customized a white-light fiber for intra-tumor irradiation. In vivo, the fiber-mediated wPDT significantly induces tumor elimination with maximized therapeutic outcomes by irradiating the interior of the tumor. In addition, wPDT also has the advantage that its light source can be adapted to a wide range of photosensitizers (wavelength range 400-700 nm), whereas a laser of single wavelength can only target a specific photosensitizer.

Conclusion

This method of using optical fiber to increase the tissue penetration of white light can greatly improve the therapeutic effect of AIE photosensitizers, which is needed for the treatment of large/deep tumors and holds great promise in cancer treatment.

Self-Amplifying Iridium(III) Photosensitizer for Ferroptosis-Mediated Immunotherapy Against Transferrin Receptor-Overexpressing Cancer

Photoimmunotherapy is attractive for cancer treatment due to its spatial controllability and sustained responses. This work presents a ferrocene-containing Ir(III) photosensitizer (IrFc1) that can bind with transferrin and be transported into triple-negative breast cancer (TNBC) cells via a transferrin receptor-mediated pathway. When the ferrocene in IrFc1 is oxidized by reactive oxygen species, its capability to photosensitize both type I (electron transfer) and type II (energy transfer) pathways is activated through a self-amplifying process. Upon irradiation, IrFc1 induces the generation of lipid oxidation to cause ferroptosis in TNBC cells, which promotes immunogenic cell death (ICD) under both normoxia and hypoxia. In vivo, IrFc1 treatment elicits a CD8⁺ T-cell response, which activates ICD in TNBC resulting in enhanced anticancer immunity. In summary, this work reports a small molecule-based photosensitizer with enhanced cancer immunotherapeutic properties by eliciting ferroptosis through a self-amplifying process.

Ir(III) Complexes with AIE Characteristics for Biological Applications

Both biological process detection and disease diagnosis on the basis of luminescence technology can provide comprehensive insights into the mechanisms of life and disease pathogenesis and also accurately guide therapeutics. As a family of prominent luminescent materials, Ir(III) complexes with aggregation-induced emission (AIE) tendency have been recently explored at a tremendous pace for biological applications, by virtue of their various distinct advantages, such as great stability in biological media, excellent fluorescence properties and distinctive photosensitizing features. Significant breakthroughs of AIE-active Ir(III) complexes have been achieved in the past few years and great progress has been witnessed in the construction of novel AIE-active Ir(III) complexes and their applications in organelle-specific targeting imaging, multiphoton imaging, biomarker-responsive bioimaging, as well as theranostics. This review systematically summarizes the basic concepts, seminal studies, recent trends and perspectives in this area.

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.

Recent advances in photothermal therapy-based multifunctional nanoplatforms for breast cancer

Breast cancer (BC) is one of the most common cancers in women worldwide; however, the successful treatment of BC, especially triple-negative breast cancer (TNBC), remains a significant clinical challenge. Recently, photothermal therapy (PTT), which involves the generation of heat under irradiation to achieve photothermal ablation of BC with minimal invasiveness and outstanding spatial–temporal selectivity, has been demonstrated as a novel therapy that can overcome the drawbacks of chemotherapy or surgery. Significantly, when combining PTT with chemotherapy and/or photodynamic therapy, an enhanced synergistic therapeutic effect can be achieved in both primary and metastatic BC tumors. Thus, this review discusses the recent developments in nanotechnology-based photothermal therapy for the treatment of BC and its metastasis to provide potential strategies for future BC treatment.

3D CNT/MXene microspheres for combined photothermal/photodynamic/chemo for cancer treatment

MXene nanosheets have shown exciting potential in nanomedicine because of their large surface area, intense near-infrared (NIR) absorbance, and good biocompatibility. However, their development in the direction of treating tumors is constrained by the limitations of existing design methodologies. These methodologies lack control over the size and distribution of tumors. Moreover, their photodynamic therapy (PDT) effect is poor. To address this unmet medical need, a simple strategy that processes MXene with carbon nanotube (CNT) into a three-dimensional (3D) honeycomb structure having anti aggregation capacity was established. The structure can be used in disease phototherapy against tumors, bacteria, and viruses, such as photothermal therapy (PTT), photodynamic therapy (PDT), and multimodal synergistic therapy. In the present study, 3D CNT/MXene microspheres were obtained by the template method and spray-drying method. The microspheres possessed special photothermal effects and photothermal stability under NIR laser irradiation. Furthermore, the developed microspheres could achieve a maximum of 85.6% drug loading capability of doxorubicin (DOX). Under light irradiation at 650 and 808 nm, 3D CNT/MXene microspheres could efficiently produce singlet oxygen due to the effectiveness of CNTs as carries for Titanium Dioxide (TiO₂) photosensitizers present on the MXene surface. Furthermore, in vitro studies had showed that 3D CNT/MXene-DOX effectively inhibited the proliferation of HeLa cells. Hence, this study provides a promising platform for future clinical applications to realize PTT/PDT/chemotherapy combination cancer treatment based on MXene.

Lysosome-targeted cyclometalated iridium(III) complexes: JMJD inhibition, dual induction of apoptosis and autophagy

A series of cyclometalated iridium(III) complexes with the formula [Ir(C^N)2 L](PF6) (C^N = 2-phenylpyridine (ppy, in Ir-1), 2-(2-thienyl)pyridine (thpy, in Ir-2), 2-(2,4-difluorophenyl)pyridine (dfppy, in Ir-3), L = 2-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)quinolin-8-ol) were designed and synthesized, which utilize 8-hydroxyquinoline derivative as N^N ligands to chelate the cofactor Fe2+ of the Jumonji domain-containing protein (JMJD) histone demethylase. As expected, the results of UV/Vis titration analysis confirm the chelating capabilities of Ir-1-3 for Fe2+, and molecular docking studies also show that Ir-1-3 can interact with the active pocket of JMJD protein, and treatment of cells with Ir-1-3 results in significant upregulation of trimethylated histone 3 lysine 9 (H3K9Me3), indicating the inhibition of JMJD activity. Meanwhile, Ir-1-3 exhibit much higher cytotoxicity against the tested tumor cell lines compared with the clinical chemotherapeutic agent cisplatin. And Ir-1-3 can block the cell cycle at G2/M phase and inhibit cell migration and colony formation. Further studies show that Ir-1-3 can specifically accumulate in lysosomes, damage the integrity of lysosomes, and induce apoptosis and autophagy. Reduction of mitochondrial membrane potential (MMP) and elevation of reactive oxygen species (ROS) also contribute to the antitumor effects of Ir-1-3. Finally, Ir-1 can inhibit tumor growth effectively in vivo and increase the expression of H3K9Me3 in tumor tissues. Our study demonstrates that these iridium(III) complexes are promising anticancer agents with multiple functions, including the inhibition of JMJD and induction of apoptosis and autophagy.

AIE-active iridium(III) complex integrated with upconversion nanoparticles for NIR-irradiated photodynamic therapy

The integration of an aggregation induced emission (AIE)-active Ir(III) complex and upconversion nanoparticles (UCNPs) has achieved a NIR-irradiated photosensitizer (PS), UCNPs@Ir-2-N. This PS has satisfactory biocompatibility, excellent phototoxicity, good accumulation in cells and high ¹O₂ generation ability, thereby effectively killing 4T1 mouse cancer cells in vitro. This work has potential for future photodynamic therapy (PDT) applications.

Luminescent and Photofunctional Transition Metal Complexes: From Molecular Design to Diagnostic and Therapeutic Applications

There has been emerging interest in the exploitation of the photophysical and photochemical properties of transition metal complexes for diagnostic and therapeutic applications. In this Perspective, we highlight the major recent advances in the development of luminescent and photofunctional transition metal complexes, in particular, those of rhenium(I), ruthenium(II), osmium(II), iridium(III), and platinum(II), as bioimaging reagents and phototherapeutic agents, with a focus on the molecular design strategies that harness and modulate the interesting photophysical and photochemical behavior of the complexes. We also discuss the current challenges and future outlook of transition metal complexes for both fundamental research and clinical applications.

Aggregation-induced emission (AIE)-Based nanocomposites for intracellular biological process monitoring and photodynamic therapy

As a non-invasive visualization technique, photoluminescence imaging (PLI) has found its huge value in many biological applications associated with intracellular process monitoring and early and accurate diagnosis of diseases. PLI can also be combined with therapeutics to build imaging-guided theragnostic platforms for achieving early and precise treatment of diseases. Photodynamic therapy (PDT) as a quintessential phototheranostics technology has gained great benefits from the combination with PLI. Recently, aggregation-induced emission (AIE)-active materials have emerged as one of the most promising bioimaging and phototheranostic agents. Most of AIEgens, however, need to be chemically engineered to form versatile nanocomposites with improved their photophysical property, photochemical activity, biocompatibility, etc. In this review, we focus on three categories of AIE-active nanocomposites and highlight their application progresses in the intracellular biological process monitoring and PLI-guided PDT. We hope this review can guide further development of AIE-active nanocomposites and promote their practical applications for monitoring intracellular biological processes and imaging-guided PDT.

Aggregation-induced emission photosensitizer-based photodynamic therapy in cancer: from chemical to clinical

Cancer remains a serious threat to human health owing to the lack of effective treatments. Photodynamic therapy (PDT) has emerged as a promising non-invasive cancer treatment that consists of three main elements: photosensitizers (PSs), light and oxygen. However, some traditional PSs are prone to aggregation-caused quenching (ACQ), leading to reduced reactive oxygen species (ROS) generation capacity. Aggregation-induced emission (AIE)-PSs, due to their distorted structure, suppress the strong molecular interactions, making them more photosensitive in the aggregated state instead. Activated by light, they can efficiently produce ROS and induce cell death. PS is one of the core factors of efficient PDT, so proceeding from the design and preparation of AIE-PSs, including how to manipulate the electron donor (D) and receptor (A) in the PSs configuration, introduce heavy atoms or metal complexes, design of Type I AIE-PSs, polymerization-enhanced photosensitization and nano-engineering approaches. Then, the preclinical experiments of AIE-PSs in treating different types of tumors, such as ovarian cancer, cervical cancer, lung cancer, breast cancer, and its great potential clinical applications are discussed. In addition, some perspectives on the further development of AIE-PSs are presented. This review hopes to stimulate the interest of researchers in different fields such as chemistry, materials science, biology, and medicine, and promote the clinical translation of AIE-PSs.

AIE-based gold nanostar-berberine dimer nanocomposites for PDT and PTT combination therapy toward breast cancer

We designed and synthesized three new berberine-based compounds, namely, pyridine-2,6-dimethyl-/2,2'-bipyridine-3,3'-dimethyl-tethered berberine dimers BD1 and BD2, and a tetrakis(4-benzyl)ethylene linked berberine tetramer BD4. We identified that the dimer BD2 and tetramer BD4, as well as 1,10-phenanthroline-2,9-dimethyl-linked berberine dimer BD3 previously reported by us, showed remarkable aggregation-induced emission (AIE) properties which endowed them with higher singlet oxygen (¹O₂) production ability than berberine. Of the four compounds, BD3 exhibits the lowest ΔE_ST energy with the highest ¹O₂ generation ability and thus was selected for further construction of AuNSs-BD3@HA (denoted as ABH, AuNSs = gold nanostars; HA = hyaluronic acid). The nanosystem of ABH shows a remarkable therapeutic effect toward breast cancer by combining photodynamic therapy (PDT) from BD3, photothermal therapy (PTT) from AuNSs, and the CD44-targeting capability of HA. The synergistically enhanced PDT and PTT induce superior cancer cell apoptosis/necrosis in vitro and anti-breast cancer activity in vivo. This study provides a new concept for PDT using natural product derivatives and their combination with PTT for efficient treatment of tumors.

Single-Cell Quantification of a Highly Biocompatible Dinuclear Iridium(III) Complex for Photocatalytic Cancer Therapy

Quantifying the content of metal-based anticancer drugs within single cancer cells remains a challenge. Here, we used single-cell inductively coupled plasma mass spectrometry to study the uptake and retention of mononuclear (Ir1) and dinuclear (Ir2) Ir^III photoredox catalysts. This method allowed rapid and precise quantification of the drug in individual cancer cells. Importantly, Ir2 showed a significant synergism but not an additive effect for NAD(P)H photocatalytic oxidation. The lysosome-targeting Ir2 showed low dark toxicity in vitro and in vivo. Ir2 exhibited high photocatalytic therapeutic efficiency at 525 nm with an excellent photo-index in vitro and in tumor-bearing mice model. Interestingly, the photocatalytic anticancer profile of the dinuclear Ir2 was much better than the mononuclear Ir1, indicating for the first time that dinuclear metal-based photocatalysts can be applied for photocatalytic anticancer treatment.

A biocompatible photosensitizer with a high intersystem crossing efficiency for precise two-photon photodynamic therapy

Photodynamic efficiency is strongly dependent on the generation rate of reactive oxygen species (ROS) and the tissue penetration depth. Recent advances in materials science reveal that organic molecules with room-temperature phosphorescence (RTP) can potentially serve as efficient photosensitizers owing to their limited dark cytotoxicity and abundant triplet excitons upon light irradiation. In this study, we combine RTP materials with two-photon excitation to improve the ROS generation, therapeutic precision, and tissue penetration of photodynamic therapy. We successfully prepared a novel RTP-based photosensitizer (BF₂DCz) with a high photoluminescence quantum yield of 47.7 ± 3% and a remarkable intersystem crossing efficiency of ∼90.3%. By encapsulation into the bovine serum albumin (BSA) matrix, BF₂DCz-BSA exhibits excellent biocompatibility, negligible dark toxicity, and superior photostability. Excitation using a femtosecond laser causes BF2DCz-BSA to efficiently generate ROS and precisely exert cell damage at the desired location.

Cascade-activatable NO release based on GSH-detonated "nanobomb" for multi-pathways cancer therapy

Therapeutic approaches of combining conventional photodynamic therapy (PDT) with other adjuvant treatments to sensitize PDT represent an appealing strategy. Herein, a novel synergetic "nanobomb" strategy based on glutathione (GSH)-responsive biodegradation was proposed to effectively destroy tumors expeditiously and accurately. This "nanobomb" was rationally constructed via the simultaneous encapsulation of methylene blue (MB) and l-arginine (L-Arg) into polyethylene glycol (PEG) modified mesoporous organosilicon nanoparticles (MON). The resulting L-Arg/MB@MP initially exhibited prolonged blood circulation, improved bioavailability, and enhanced tumor accumulation in mice after tail vein injection according to the pharmacokinetic investigations, before the nanoparticles were entirely excreted. Under laser irradiation, L-Arg/MB@MP produced remarkable reactive oxygen species (ROS) directly for PDT therapy, while a portion of ROS may oxidize L-Arg to generate nitric oxide (NO) not only for gas therapy (GT) but also serve as a biological messenger to regulate vasodilation to alleviate the tumor hypoxia. Subsequently, the rapidly released NO was further oxidized to reactive nitrogen species, which together with ROS promote immunogenic cell death by inducing G2/M cell-cycle arrest and apoptosis in cancer cells, and eventually resulting in enhanced anti-tumor immune responses. Moreover, the GSH depletion in tumor tissues induced by L-Arg/MB@MP biodegradation can cooperate with GT to amplify the therapeutic effect of PDT. These results demonstrate that this "nanobomb" provides new ideas for clinical translation to treat tumor patients in terms of synergistic PDT-GT nanotherapy in hypoxic-solid tumors.

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.

Effective topical treatments of innovative NNO-tridentate vanadium (IV) complexes-mediated photodynamic therapy in psoriasis-like mice model

Psoriasis is a chronic inflammatory skin disease that can significantly impact the quality of human life. Various drug treatments with long-term severe side effects limit those drugs usage. Photodynamic therapy...

AIE-active Ir(iii) complexes functionalised with a cationic Schiff base ligand: synthesis, photophysical properties and applications in photodynamic therapy

Two AIE-active Ir(iii) cationic complexes containing Schiff base ligands were synthesised. Ir-2-N+ NPs are shown to be good PSs in vitro for PDT.

Photodynamic therapy: A next alternative treatment strategy for hepatocellular carcinoma?

Liver cancer is one of the most common cancers in the world. Of all types of liver cancer, hepatocellular carcinoma (HCC) is known to be the most frequent primary liver malignancy and has seriously compromised the health status of the general population. Locoregional thermal ablation techniques such as radiofrequency and microwave ablation, have attracted attention in clinical practice as an alternative strategy for HCC treatment. However, their aggressive thermal effect may cause undesirable complications such as hepatic decompensation, hemorrhage, bile duct injury, extrahepatic organ injuries, and skin burn. In recent years, photodynamic therapy (PDT), a gentle locoregional treatment, has attracted attention in ablation therapy for patients with superficial or luminal tumors as an alternative treatment strategy. However, some inherent defects and extrinsic factors of PDT have limited its use in clinical practice for deep-seated HCC. In this contribution, the aim is to summarize the current status and challenges of PDT in HCC treatment and provide potential strategies to overcome these deficiencies in further clinical translational practice.

Phosphorescent NIR emitters for biomedicine: applications, advances and challenges

Application of NIR (near-infrared) emitting transition metal complexes in biomedicine is a rapidly developing area of research. Emission of this class of compounds in the "optical transparency windows" of biological tissues and the intrinsic sensitivity of their phosphorescence to oxygen resulted in the preparation of several commercial oxygen sensors capable of deep (up to whole-body) and quantitative mapping of oxygen gradients suitable for in vivo experimental studies. In addition to this achievement, the last decade has also witnessed the increased growth of successful alternative applications of NIR phosphors that include (i) site-specific in vitro and in vivo visualization of sophisticated biological models ranging from 3D cell cultures to intact animals; (ii) sensing of various biologically relevant analytes, such as pH, reactive oxygen and nitrogen species, RedOx agents, etc.; (iii) and several therapeutic applications such as photodynamic (PDT), photothermal (PTT), and photoactivated cancer (PACT) therapies as well as their combinations with other therapeutic and imaging modalities to yield new variants of combined therapies and theranostics. Nevertheless, emerging applications of these compounds in experimental biomedicine and their implementation as therapeutic agents practically applicable in PDT, PTT, and PACT face challenges related to a critically important improvement of their photophysical and physico-chemical characteristics. This review outlines the current state of the art and achievements of the last decade and stresses the most promising trends, major development prospects, and challenges in the design of NIR phosphors suitable for biomedical applications.

Recent Advances in AIEgen-Based Photodynamic Therapy and Immunotherapy

Cancer, one of the leading causes of death, has seriously threatened public health. However, there is still a lack of effective treatments. Nowadays, photodynamic therapy (PDT), relying on photosensitizers to trigger the generation of reactive oxygen species (ROS) for killing cancer cells, has been emerging as a noninvasive anti-cancer strategy. To enhance the overall anti-cancer efficacy of PDT, various approaches including molecular design and combination with other therapeutic techniques have been proposed and implemented. Especially, photodynamic immunotherapy that can effectively evoke the body's immune response has attracted much attention. Recently, a class of photosensitizers with aggregation-induced emission (AIE) character have shown unique promises, taking advantage of their profound fluorescence and ROS-generating ability in the aggregation state. Despite the promising results demonstrated by several groups, the associated studies are few and the mechanism of such AIEgen-based photodynamic immunotherapy has not been fully understood. This review discusses the recent advances in the AIEgen-based enhanced PDT with a special focus on the AIE photosensitizers for photodynamic immunotherapy, aiming to inspire more opportunities for in-depth investigation of the working principles in this emerging anti-cancer approach.

PEG-Polymer Encapsulated Aggregation-Induced Emission Nanoparticles for Tumor Theranostics

In the field of tumor imaging and therapy, the aggregation-caused quenching (ACQ) effect of fluorescent dyes at high concentration is a great challenge. In this regard, the aggregation-induced emission luminogens (AIEgens) show great potential, since AIEgens effectively overcome the ACQ effect and have better fluorescence quantum yield, photobleaching resistance, and photosensitivity. Polyethylene glycol (PEG)-polymer is the most commonly used carrier to prepare nanoparticles (NPs). The advantage of PEGylation is that it can greatly prolong the metabolic half-life and reduce immunogenicity and toxicity. Considering that the hydrophobicity of most AIEgens hinders their application in organisms, the use of PEG-polymer encapsulation is an effective strategy to overcome this obstacle. Importantly, bioactive functional groups can be modified on PEG-polymers to enhance the biological effect of NPs. The combination of powerful AIEgens and PEG-polymers provides a new strategy for tumor imaging and therapy, which is promising for clinical application.

Fluorescence Imaging and Photodynamic Inactivation of Bacteria Based on Cationic Cyclometalated Iridium(III) Complexes with Aggregation-Induced Emission Properties

Antibacterial photodynamic therapy (PDT) is one of the emerging methods for curbing multidrug-resistant bacterial infections. Effective fluorescent photosensitizers with dual functions of bacteria imaging and PDT applications are highly desirable. In this study, three cationic and heteroleptic cyclometalated Ir(III) complexes with the formula of [Ir(CˆN)₂ (NˆN)][PF₆ ] are prepared and characterized. These Ir(III) complexes named Ir(ppy)₂ bP, Ir(1-pq)₂ bP, and Ir(2-pq)₂ bP are comprised of three CˆN ligands (i.e., 2-phenylpyridine (ppy), 1-phenylisoquinoline (1-pq), and 2-phenylquinoline (2-pq)) and one NˆN bidentate co-ligand (bP). The photophysical characterizations demonstrate that these Ir(III) complexes are red-emitting, aggregation-induced emission active luminogens. The substitution of phenylpyridine with phenylquinoline isomers in the molecules greatly enhances their UV and visible-light absorbance as well as the photoinduced reactive oxygen species (ROS) generation ability. All three Ir(III) complexes can stain both Gram-positive and Gram-negative bacteria efficiently. Interestingly, even though Ir(1-pq)₂ bP and Ir(2-pq)₂ bP are constitutional isomers with very similar structures and similar ROS generation ability in buffer, the former eradicates bacteria much more effectively than the other through white light-irradiated photodynamic inactivation. This work will provide valuable information on the rational design of Ir(III) complexes for fluorescence imaging and efficient photodynamic inactivation of bacteria.

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

This review presents a robust strategy to design photosensitizers (PSs) for various species. Photodynamic therapy (PDT) is a photochemical-based treatment approach that involves the use of light combined with a light-activated chemical, referred to as a PS. Attractively, PDT is one of the alternatives to conventional cancer treatment due to its noninvasive nature, high cure rates, and low side effects. PSs play an important factor in photoinduced reactive oxygen species (ROS) generation. Although the concept of photosensitizer-based photodynamic therapy has been widely adopted for clinical trials and bioimaging, until now, to our surprise, there has been no relevant review article on rational designs of organic PSs for PDT. Furthermore, most of published review articles in PDT focused on nanomaterials and nanotechnology based on traditional PSs. Therefore, this review aimed at reporting recent strategies to develop innovative organic photosensitizers for enhanced photodynamic therapy, with each example described in detail instead of providing only a general overview, as is typically done in previous reviews of PDT, to provide intuitive, vivid, and specific insights to the readers.

Recent advances in assembled AIEgens for image-guided anticancer therapy

Image-guided therapy, with simultaneous imaging and therapy functions, has the potential to greatly enhance the therapeutic efficacy of anticancer therapy, and reduce the incidence of side effects. Fluorescence imaging has the advantages of easy operation, abundant signal, high contrast, and fast response for real-time and non-invasive tracking. Luminogens with aggregation-induced emission characteristics (AIEgens) can emit strong luminescence in an aggregate state, which makes them ideal materials to construct applicative fluorophores for fluorescence imaging. The opportunity for image-guided cancer treatment has inspired researchers to explore the theranostic application of AIEgens combined with other therapy methods. In recent years, many AIEgens with efficient photosensitizing or photothermal abilities have been designed by precise molecular engineering, with superior performance in image-guided anticancer therapy. Owing to the hydrophobic property of most AIEgens, an assembly approach has been wildly utilized to construct biocompatible AIEgen-based nanostructures in aqueous systems, which can be used for image-guided anticancer therapy. In the present review, we summarize the recent advances in the assembled AIEgens for image-guided anticancer therapy. Five types of image-guided anticancer therapy using assembled AIEgens are included: chemotherapy, photodynamic therapy, photothermal therapy, gene therapy, and synergistic therapy. Moreover, a brief conclusion with the discussion of current challenges and future perspectives in this area is further presented.

Ir(III) Complex Dimer Nanoparticles for Photodynamic Therapy

Iridium compounds are versatile in catalysis and photodynamic therapy. We present two Ir(III) complex dimers that can self-assemble into nanoparticles in the absence of adjuvant or surfactants. The formed nanoparticles possess a spherical morphology and robust colloidal stability and could be internalized by cancer cells. The Ir(III) complex nanoparticles have relatively strong photodynamic activity upon irradiation, which includes type I and type II reactive oxygen species. The generated reactive oxygen species could effectively induce cell death upon irradiation. This work highlights the potential of metal complexes and their nanoparticles in cancer treatment.

Developing Efficient Dinuclear Pt(II) Complexes Based on the Triphenylamine Core for High-Efficiency Solution-Processed OLEDs

The various applications of dinuclear complexes have attracted increasing attention. However, the electroluminescence efficiencies of dinuclear Pt(II) complexes are far from satisfactory. Herein, based on the triphenylamine core, we develop four dinuclear Pt(II) complexes that cover the emission colors from yellow to red with high photoluminescence quantum efficiencies of up to 0.79 in doped films. The solid-state structure of PyDPt is revealed by the single-crystal X-ray diffraction investigation. Besides, solution-processed OLEDs have been fabricated with different electron transport materials. With higher electron mobility and excellent hole-blocking ability, 1,3,5-tri(m-pyridin-3-ylphenyl)benzene (TmPyPB) can help to realize good charge balance in related OLEDs. In addition, angle-dependent PL spectra reveal the preferentially horizontal orientation of these dinuclear Pt(II) complexes in doped CBP films, which benefits the outcoupling efficiencies. Therefore, the yellow OLED based on PyDPt shows unexpected high performance with a peak current efficiency of up to 78.7 cd/A and an external quantum efficiency of up to 22.4%, which is the highest EQE reported for OLEDs based on dinuclear Pt(II) complexes so far. This study demonstrates the great potential of developing dinuclear Pt(II) complexes for achieving excellent electroluminescence efficiencies.

Hyaluronic Acid Coated Liposomes Co-Delivery of Natural Cyclic Peptide RA-XII and Mitochondrial Targeted Photosensitizer for Highly Selective Precise Combined Treatment of Colon Cancer

Background

Natural cyclopeptide RA-XII, isolated from Rubia yunnanensis, is a promising chemotherapeutic agent for colon cancer. The photosensitizer protoporphyrin-IX attached with triphenylphosphonium (TPP) could possess mitochondria targeting capacity and exert photodynamic therapy (PDT) by inducing oxidizing damage to the mitochondria and cell apoptosis eventually. In this work, pH-sensitive liposomes were constructed to simultaneously deliver RA-XII as a chemotherapeutic drug and modified porphyrin as a mitochondria-targeting photosensitizer to treat colon cancer, and verified its mechanism of action and antitumor therapeutic efficacy.

Methods

The colon cancer targeting liposome nanoparticle RA/TPPP-Lip was synthesized using thin film hydration. The therapeutic effect and targeting ability of RA/TPPP-Lip was investigated in vitro. And use HCT116 cell allogeneic subcutaneous transplantation tumor model to investigate the anti-tumor and targeting effects of RA/TPPP-Lip in vivo.

Results

RA/TPPP-Lip gained the targeting ability through surface-modified HA to increase the accumulation of RA-XII and TPPP in colon cancer cells. A series of in vitro experimental results showed that TPPP produced cytotoxic ROS under laser irradiation to directly damage cell mitochondria and played a combined role with RA-XII, making RA/TPPP-Lip the best colon cancer cell growth inhibitory effect. Furthermore, in vivo antitumor experiments showed that the RA/TPPP-Lip substantially accumulated at the tumor site and efficiently repressed tumor growth in nude mice.

Conclusion

We have successfully designed a new cancer-targeted nanomedicine platform (RA/TPPP-Lip) for the collaborative treatment of colon cancer, which can achieve the targeted continuous release of multiple therapeutic drugs. This work provides a new strategy for precise combination therapy, which may promote the further development of collaborative cancer treatment platforms.

AIE material for photodynamic therapy

Photodynamic therapy (PDT) is emerging as an excellent strategy to treat different types of cancers. The advantages of using PDT over other cancer treatment modalities are owing to its non-invasive nature, spatiotemporal precession, controllable photoactivity, and least side effects. The photosensitization ability of traditional photosensitizers (PSs) are severely curtailed by aggregation-induced quenching (ACQ). On the contrary, aggregation induced emission (AIE) molecules/fluorogens (AIEgens) show enhanced fluorescence emission and high reactive oxygen species (ROS)/singlet oxygen (¹O₂) production capability in the aggregated state. These unique characteristics of AIEgens make them potential AIE-PSs for fluorescence/luminescence image-guided combination PDT. In this chapter, we discussed the strategies that are developed to synthesize small molecule-based AIE-PSs, metal complex-based AIE-PSs, and AIE-PSs with two-photon absorbance (TPA) properties, polymer-based AIE-PSs, and nanoparticles based AIE-PSs for PDT. We have also discussed the rational design of targeting peptide conjugated AIE-PSs to selective target cancer cells over normal cells. Furthermore, recent findings on nanoparticle-based combination AIE-PSs are also discussed, where the combination AIE-PSs show synergistically improved anticancer activity and overcome the drug resistance. Finally, we shed light on the recent development, ongoing challenges, and future directions for designing better AIE-PS for PDT.

A new near-infrared phosphorescent iridium(III) complex conjugated to a xanthene dye for mitochondria-targeted photodynamic therapy

Iridium(iii) complexes are potent candidates for photodynamic therapy (PDT), but some key drawbacks still hamper clinical translation, such as poor operability in the phototherapeutic window, high dark toxicity, and low reactive oxygen species (ROS) production efficiency. In this work, a near-infrared phosphorescent Ir(iii) complex conjugated to a xanthene dye, NIR-Ir-XE, is reported with highly favourable properties for mitochondria-targeted imaging and cancer phototherapy. The generation of the triplet excited state of a xanthene moiety endows the NIR-Ir-XE to form singlet oxygen (1O2) for use as a photodynamic therapy agent after irradiation with visible light. Compared with the xanthene-free Ir(iii) counterpart (NIR-Ir-bpy), the xanthene-modified cyclometalated Ir(iii) photosensitizer NIR-Ir-XE exhibits higher 1O2 generation efficiency, negligible dark toxicity and a better therapeutic effect. Importantly, a clear correlation between cell death and intracellular generation of 1O2 derived from NIR-Ir-XE after light irradiation was demonstrated. The corresponding in vivo photo-antitumor performance was further demonstrated to be effective in tumor-bearing mice. The observed properties of NIR-Ir-XE qualify it as a promising PDT agent.

Versatile gadolinium(III)-phthalocyaninate photoagent for MR/PA imaging-guided parallel photocavitation and photodynamic oxidation at single-laser irradiation

Current light-mediated photodynamic therapy (PDT) is far underutilized in clinical cancer treatment due to its low pharmacological effect. We herein proposed a new gadolinium(III)-phthalocyanine (GdPc)-enabled phototherapeutics, photoacoustic/dynamic therapy (PADT), towards in vivo solid tumors via parallel-produced photocavitation and photodynamic oxidation with excitation by a single pulsed laser. We demonstrated that pulsed irradiation of GdPc could simultaneously produce an intense acoustic effect and a high-level ¹O₂ quantum yield to afford mitochondrial damage and initiate programmed cell death. Under the guidance of magnetic resonance/photoacoustic dual-modal imaging, the mechanical oxygen-independent destruction of acoustic cavitation and the chemical damage of ¹O₂ were validated to afford combinatorial inhibition of tumors under either normal or hypoxic conditions after the agent delivered into the cancer cells by a pH-sensitive nanomicelle. The single-laser initiated PADT using GdPc as a versatile photoagent maximizes the use of light energy to minimize the dose requirement of oxygen and agent towards high therapeutic efficacy, surpassing dramatically over conventional PDT.

Multistage-responsive nanovehicle to improve tumor penetration for dual-modality imaging-guided photodynamic-immunotherapy

The exploration of an intelligent multifunctional imaging-guided therapeutic platform is of great significance because of its ideal delivery efficiency and controlled release. In this work, a tumor microenvironment (TME)-responsive nanocarrier (denoted as MB@MSP) is designed for on-demand, sequentially release of a short D-peptide antagonist of programmed cell death-ligand 1 (named as P^DPPA-1) and a photosensitizer methylene blue (MB). Fe₃O₄-Au located in the core of MB@MSP is used as a magnetic resonance imaging and micro-computed tomography imaging contrast agent for noninvasive diagnosis of solid tumors and simultaneous monitoring of drug delivery. The P^DPPA-1 coated on MB@MSP can be shed due to the cleavage of the peptide substrate by matrix metalloproteinase-2 (MMP-2) that is highly expressed in the tumor stroma, and disulfide bonding is further broken when it encounters high levels of glutathione (GSH) in TME, which finally leads to significant size reduction and charge-reversal. These transitions facilitate penetration and uptake of nanocarriers against tumors. Noticeably, the released P^DPPA-1 can block the immune checkpoint to create an environment that favors the activation of cytotoxic T lymphocytes and augment the antitumor immune response elicited by photodynamic therapy, thus significantly improving therapeutic outcomes. Studies of the underlying mechanisms suggest that the designed MMP-2 and GSH-sensitive delivery system not only induce apoptosis of tumor cells but also modulate the immunosuppressive tumor microenvironment to eventually augment the suppression tumor metastasis effect of CD8⁺ cytotoxic T cells. Overall, the visualization of the therapeutic processes with comprehensive information renders MB@MSP an intriguing platform to realize the combined treatment of metastatic tumors.

Rational design of iridium-porphyrin conjugates for novel synergistic photodynamic and photothermal therapy anticancer agents

Near-infrared (NIR) emitters are important probes for biomedical applications. Nanoparticles (NPs) incorporating mono- and tetranuclear iridium(iii) complexes attached to a porphyrin core have been synthesized. They possess deep-red absorbance, long-wavelength excitation (635 nm) and NIR emission (720 nm). TD-DFT calculations demonstrate that the iridium-porphyrin conjugates herein combine the respective advantages of small organic molecules and transition metal complexes as photosensitizers (PSs): (i) the conjugates retain the long-wavelength excitation and NIR emission of porphyrin itself; (ii) the conjugates possess highly effective intersystem crossing (ISC) to obtain a considerably more long-lived triplet photoexcited state. These photoexcited states do not have the usual radiative behavior of phosphorescent Ir(iii) complexes, and they play a very important role in promoting the singlet oxygen (1O2) and heat generation required for photodynamic therapy (PDT) and photothermal therapy (PTT). The tetranuclear 4-Ir NPs exhibit high 1O2 generation ability, outstanding photothermal conversion efficiency (49.5%), good biocompatibility, low half-maximal inhibitory concentration (IC50) (0.057 μM), excellent photothermal imaging and synergistic PDT and PTT under 635 nm laser irradiation. To our knowledge this is the first example of iridium-porphyrin conjugates as PSs for photothermal imaging-guided synergistic PDT and PTT treatment in vivo.

BSA-encapsulated cyclometalated iridium complexes as nano-photosensitizers for photodynamic therapy of tumor cells

Photodynamic therapy is a promising treatment method. The development of suitable photosensitizers can improve therapeutic efficacy. Herein, we report three iridium complexes (Ir1, Ir2, and Ir3), and encapsulate them within bovine serum albumin (BSA) to form nano-photosensitizers (Ir1@BSA, Ir2@BSA, and Ir3@BSA) for photodynamic therapy (PDT) of tumor cells. In the structures of Ir(iii) complexes, we use the pyrazine heterocycle as part of the C^N ligands and explore the effect of different ligands on the ability to generate singlet oxygen (¹O₂) by changing the conjugation length of the ligand and increasing the coplanarity of the ligand. Besides, the fabricated nano-photosensitizers are beneficial to improve water dispersibility and increase cellular uptake ability. Through studying photophysical properties, ¹O₂ generation capacity, and cellular uptake performance, the results show that Ir1@BSA has the best photodynamic therapeutic effect on 4T1 tumor cells. This study provides an effective research basis for the further design of new nano-photosensitizers.

Three new iridium complexes were synthesized and fabricated with BSA to form nano-photosensitizers, which can catalyze oxygen to produce singlet oxygen to achieve photodynamic therapy of tumor cells.

Boosting Wide-Range Tunable Long-Afterglow in 1D Metal-Organic Halide Micro/Nanocrystals for Space/Time-Resolved Information Photonics

Molecular afterglow materials with ultralong-lived excited states have attracted considerable interest owing to their promise for light-emitting devices, optical imaging, and anti-counterfeiting applications. However, the realization of ultralong afterglow emission in low-dimensional micro/nanostructures has remained an open challenge, limiting progress toward new-generation photonic applications. In this work, new types of mono/binuclear metal-organic halide micro/nanocrystals with tunable afterglow properties, made possibly by the rational control over both ultralong-lived room-temperature phosphorescence and thermally activated delayed fluorescence, are developed. Interestingly, the mono/binuclear coordination complexes present excitation-dependent luminescence across a wide range (wavelength > 150 nm) with broad emission color differences from blue to yellow owing to the multiple long-lived excited states. The 1D binuclear metal-organic microrods further exhibit excitation-dependent optical waveguide and space/time dual-resolved afterglow emission properties, endowing them with great potential in wavelength-division multiplexing information photonics and logic gates. Therefore, this work not only communicates the first example of wide-range tunable ultralong afterglow of low-dimensional metal-organic micro/nanocrystals under ambient conditions but also provides a new route to achieve optical communications and photonic logic compilation at the micro/nanoscale.

Multifunctional Organic Fluorescent Probe with Aggregation-Induced Emission Characteristics: Ultrafast Tumor Monitoring, Two-Photon Imaging, and Image-Guide Photodynamic Therapy

The development of multifunctional photosensitizers (PSs) with aggregation-induced emission (AIE) properties plays a critical role in promoting the progress of the photodynamic therapy (PDT). In this work, a multifunctional PS (named DSABBT NPs) with AIE activity has been designed and prepared to carry out ultrafast staining, excellent two-photon bioimaging, and high-efficiency image-guided PDT. Simply, DSABBT with AIE characteristic was synthesized by one-step Schiff reaction of 4-(diethylamino)-salicylaldehyde (DSA) and 4,7-bis(4-aminophenyl)-2,1,3-benzothiadiazole (BBT). Then, DSABBT and DSPE-PEG₂₀₀₀-cRGD generate nanoparticles (NPs) easily in an ultrapure water/tetrahydrofuran mixture through a facile nanoprecipitation at room temperature. We found that DSABBT NPs exhibit bright solid-state fluorescence with large stokes shifts (180 nm) and two-photon absorption cross-section (1700 GM). Importantly, DSABBT NPs exhibited excellent ability of ultrafast staining and two-photon imaging, which can readily label suborganelles by subtly shaking the living cells for 5 s under mild conditions. Moreover, DSABBT NPs displayed high singlet oxygen (¹O₂) generation capacity and remarkable image-guided PDT efficiency. Therefore, DSABBT NPs can act as the promising candidate for multifunctional PSs, which can destroy cancer cells and block malignant tumor growth via the production of reactive oxygen species upon irradiation conditions. These outcomes provide us with a selectable strategy for developing multifunctional theranostic systems.