X-Ray Induced Photodynamic Therapy: A Combination of Radiotherapy and Photodynamic Therapy

Ultrasound-activated nano-oxygen sensitizer for sonodynamic-radiotherapy of esophageal cancer

Background: owing to the intricate nature, variability, and persistent oxygen-deficient environment associated with esophageal cancer (EC) tissues, radiotherapy (RT) sometimes doesn't work as well because some cancer cells can resist the radiation to a certain extent. This can lead to the cancer coming back in the same spot or even making the treatment ineffective. The integration of RT with oxygenation strategies is a common approach in cancer treatment. The advent of oxygen-enhancing sonodynamic therapy (SDT), leveraging the cytotoxic effects of reactive oxygen species (ROS), has garnered significant attention as an innovative approach to inducing cell death. Methods: this study utilized nanobubbles (NBs) containing the acoustic sensitizer indocyanine green (ICG) to create a nanoplatform (ICG@O2 NBs) that incorporates oxygen-enhanced SDT and RT. Besides, NBs are paired with low-frequency ultrasound (LFUS), known as ultrasound-targeted nano-bubble destruction (UTND), for precise drug release and improved safety. Results: experimental findings, including JC-1/DCFH-DA assays, demonstrate that ICG@O2 NBs effectively enhance the performance of both RT and SDT. RNA sequencing (RNA-seq) demonstrated differential expression of mRNA and LncRNA prior to and after co-treatment. KEGG and GO pathway analysis were then conducted for enriching and recognizing target genes and pathways correlated with the sensitivity of RT, which were revealed to be remarkably clustered in RT-associated pathways. Conclusion: in vitro and in vivo investigations have indicated significant efficacy of synergistic treatments, highlighting the potential of combining NBs with SDT and RT for managing EC.

Activatable Photosensitizers: From Fundamental Principles to Advanced Designs

Photodynamic therapy (PDT) is a promising treatment that uses light to excite photosensitizers in target tissue, producing reactive oxygen species and localized cell death. It is recognized as a minimally invasive, clinically approved cancer therapy with additional preclinical applications in arthritis, atherosclerosis, and infection control. A hallmark of ideal PDT is delivering disease-specific cytotoxicity while sparing healthy tissue. However, conventional photosensitizers often suffer from non-specific photoactivation, causing off-target toxicity. Activatable photosensitizers (aPS) have emerged as more precise alternatives, offering controlled activation. Unlike traditional photosensitizers, they remain inert and photoinactive during circulation and off-target accumulation, minimizing collateral damage. These photosensitizers are designed to "turn on" in response to disease-specific biostimuli, enhancing therapeutic selectivity and reducing off-target effects. This review explores the principles of aPS, including quenching mechanisms stemming from activatable fluorescent probes and applied to activatable photosensitizers (RET, PeT, ICT, ACQ, AIE), as well as pathological biostimuli (pH, enzymes, redox conditions, cellular internalization), and bioresponsive constructs enabling quenching and activation. We also provide a critical assessment of unresolved challenges in aPS development, including limitations in targeting precision, selectivity under real-world conditions, and potential solutions to persistent issues (dual-lock, targeting moieties, biorthogonal chemistry and artificial receptors). Additionally, it provides an in-depth discussion of essential research design considerations needed to develop translationally relevant aPS with improved therapeutic outcomes and specificity.

Systemic antitumor immune response of doped yttria nanoscintillators under low-dose x-ray irradiation

Inadequate light penetration in tissues restricts photodynamic therapy to treating only superficial tumors. To enable x-ray-excited photodynamic therapy (XPDT) that targets deep-seated tumors, we synthesized a nanoscintillator-photosensitizer complex containing 5% Eu-doped Y2O3 fluorescing at 611 nanometers and decorated with SiO2 containing the scintillation-coupled photosensitizer methylene blue and a polyethylene glycol coating [PEGylated Y2O3:Eu@SiO2-methylene blue (pYSM)]. When irradiated, pYSMs generate singlet oxygen species in vitro, causing cytotoxicity with hallmarks of immunogenic cell death (calreticulin translocation to the cell membrane). Intravenously administered pYSMs home passively to pancreatic tumor xenografts and, upon 10 gray irradiation, cause significant tumor regression (P < 0.01). On combining XPDT with anti-PD1 immunotherapy, a distant nonirradiated tumor also regresses via an increase in intratumoral activated CD8+ cytotoxic T cells. Collectively, we advance a systemically delivered XPDT strategy that mediates an antitumor effect in both irradiated and nonirradiated (abscopal) tumors when coupled with immunotherapy, converting an immunologically "cold" tumor to an immunologically "hot" tumor.

Atomically-precise Au22(Lys-Cys-Lys)16 nanoclusters for radiation sensitization

Radiotherapy is a leading method for cancer treatment, effectively eliminating cancer cells but often causing collateral damage to surrounding healthy tissue. Radiosensitizers aim to enhance the therapeutic effects of radiotherapy while minimizing harm to normal cells. We recently reported atomically-precise gold nanoclusters, Au22(Lys-Cys-Lys)16, synthesized via a photochemical method coupled with a novel accelerated size-focusing procedure. These nanoclusters exhibit a distinct luminescence emission profile, reflecting exceptional optical purity and the absence of contamination from other nanocluster species. They demonstrate efficient oxygen radicals generation under light irradiation. In this study, we comprehensively evaluated the radiosensitization potential of Au22(Lys-Cys-Lys)16 nanoclusters in vitro and in vivo, alongside their pharmacokinetics, biodistribution and toxicity. The nanoclusters demonstrated high stability under physiological conditions and efficient internalization in tumor cells, achieving dose enhancement factors of 2.0 and 1.6 in KB and 4T1 tumor cells, respectively, under 225 kVp X-ray irradiation. Mechanistic investigations revealed enhanced radiation-induced DNA damage and disruption of DNA repair pathways. The radiosensitizing effects were further validated in radioresistant pancreatic ductal adenocarcinoma cells using the clonogenic assay and γH2AX analysis of double-strand breaks, as well as in a duck chorioallantoic membrane model. With ultra small size (~ 1.7 nm) and favorable surface framework, the nanoclusters exhibited relevant pharmacokinetics (circulation half-life, t₁/₂ = 10.4 h) and renal clearance. In a KB tumor-bearing mouse model, Au22(Lys-Cys-Lys)16 significantly delayed tumor progression and prolonged survival under 8 Gy irradiation without observed side-effects. These findings establish Au22(Lys-Cys-Lys)16 nanoclusters as a potentially translatable radiosensitizer, advancing cancer radiotherapy strategies.

A phase I clinical trial of sonodynamic therapy combined with radiotherapy for brainstem gliomas

Brainstem gliomas (BSGs) are a class of clinically refractory malignant tumors for which there is no uniform and effective treatment protocol. Ultrasound and radiation can activate hematoporphyrin and produce sonodynamic and radiodynamic effects to kill cancer cells. Therefore, we conducted the first phase I clinical trial of sonodynamic therapy (SDT) combined with radiotherapy (RT) for the treatment of BSGs to verify its safety and efficacy. We conducted a study of SDT combined with RT in 11 patients with BSGs who received SDT and RT after hematoporphyrin administration. Magnetic resonance imaging was performed during this period to assess the tumor, and adverse events were recorded. All adverse events recorded were grade 1-2; no grade 3 or more serious adverse events were observed. Treatment was well tolerated, and no dose-limiting toxicities were observed. There were no treatment-related deaths during the course of treatment. 8 of 11 patients (72.7%) maintained stable disease, 2 (18.2%) achieved partial response, and the tumors were still shrinking as of the last follow-up date. The median progression-free survival (PFS) for patients was 9.2 (95% confidence interval [CI] 6.2-12.2) months, and the median overall survival (OS) was 11.7 (95% CI 9.6-13.8) months. Therefore, SDT combined with RT has a favorable safety and feasibility and shows a preliminary high therapeutic potential.

Dual Porphyrin-Loaded Scintillating Nanoparticles Enhanced Photodynamic Therapy in Hypoxic Cancer Cells under X-ray Irradiation

Tumor hypoxia represents a major challenge to achieving successful therapy outcomes with photodynamic therapy (PDT). We hypothesized that systemic loading of dual porphyrins, protoporphyrin IX (PPIX) as a photosensitizer (PS) and hemin (Fe3+-PPIX) as an oxygen generator, onto Eu-doped NaYF4 scintillator (Sc), collectively terms as Eu-PPIX@Hemin, could enhance the activity of X-ray mediated PDT. Catalase-like property of hemin in the presence of H2O2 facilitated the production of oxygen molecules (3O2) in hypoxic cancer cells. The produced 3O2 reacts with nearby excited PPIX molecules (PPIX*) in the Sc-PS pairs to produce singlet oxygen (1O2), as cytotoxic reactive oxygen species (ROS) under X-ray irradiation. Eu-PPIX@Hemin nanoparticles (NPs) with a diameter of ~60 nm efficiently produced oxygen in the presence of H2O2, which its concentration in tumor cells is higher than that in normal cells. Eu-PPIX@Hemin generated similar amounts of ROS in hypoxic cultured cancer cells under low dose X-ray irradiation (0.5 Gy), compared to those in normoxic cancer cells. Notably, Eu-PPIX@Hemin exhibited similar cytotoxic effects in both hypoxic and normoxic cancer cells under X-ray irradiation. Overall, the mutual Sc-PS performance between PPIX and Eu was synergistically enhanced by hemin in Eu-PPIX@Hemin, which relieved hypoxia in the cancer cells under X-ray irradiation.

Ionizing radiation and photodynamic therapy lead to multimodal tumor cell death, synergistic cytotoxicity and immune cell invasion in human bladder cancer organoids

BACKGROUND

Photodynamic therapy (PDT) and radiotherapy using ionizing radiation (IR) are promising options for organ-preserving treatment of bladder cancer (BCa). A combination therapy (IR+PDT) could be beneficial for BCa treatment.

PURPOSE

For PDT, we used the near-infrared photosensitizer tetrahydroporphyrin-tetratosylate (THPTS) showing high therapeutic efficacy. Treatment responses were analyzed in BCa organoids.

METHODS

Organoids consisting of BCa cells lines, bladder fibroblasts and muscle cells were treated with IR (9 Gy) and/or PDT using THPTS (25, 50 μM; 20 J/cm2). Cytotoxicity was determined by microscopy, cell-based assays and histology. The cell death mode was analyzed by applying specific inhibitors followed by immunofluorescence or qPCR analyses of cell death markers. A matrix-based co-culture model was used to study T cell migration into the environment of treated organoids.

RESULTS

PDT and/or IR resulted in concentration-dependent reduction of metabolic activity, organoid diameter and integrity. Higher cytotoxicity of IR+PDT vs. monotherapies was observed after 72 h. Non-malignant organoids showed no cytotoxic effects. While apoptosis, necroptosis and ferroptosis were clearly involved in cell death of T-24 cells, cytotoxicity in RT-112 cells was probably provoked by apoptosis, ferroptosis and pyroptosis. IR+PDT resulted in significant migration of Jurkat cells into ECM-embedded organoids within 3 days after treatment.

CONCLUSION

Treatment with IR+PDT showed tumor-selective cytotoxicity with additive or synergistic effects in BCa organoids. Thereby, IR+PDT led to multimodal cell death depending on the cellular context. Migration of T cells into the organoid environment illustrates the immunogenic potential of IR+PDT. Therefore, it might be a promising approach for organ-preserving BCa treatment.

Modeling synergy and individual effects of X-ray induced photodynamic therapy components

X-ray induced photodynamic therapy (XPDT) utilizes self-lighting nanoparticles to combine the benefits of radiotherapy and photodynamic therapy. These nanomaterials transform X-ray to visible light that can be absorbed by nearby photosensitizers and in the presence of surrounding oxygen molecules generates reactive oxygen species, which are very toxic to the cells. Despite many studies conducted on modelling XPDT, little focused on the contribution of each component as well as their synergy effects. We developed a multiscale physicochemical model of XPDT to incorporate the key role of molecular oxygen in PDT component efficiency. Simultaneously, the effects of RT in the presence of TiO2 nanoscintillators evaluated experimentally on HT-29 cell line. Simulation results predicted necrosis and apoptosis death of cancerous cells and estimated the minimum XPDT efficiency under specific conditions. The calculated synergism index estimated a synergism ratio greater than one indicated that tumor growth inhibition in XPDT is greater than the sum of each treatment component alone.

Cuproptosis: a promising new target for breast cancer therapy

Breast cancer (BC) is the leading cause of cancer-related mortality among women globally, affecting approximately one-quarter of all female cancer patients and accounting for one-sixth of cancer-related deaths in women. Despite significant advancements in diagnostic and therapeutic approaches, breast cancer treatment remains challenging due to issues such as recurrence and metastasis. Recently, a novel form of regulated cell death, termed cuproptosis, has been identified. This process disrupts mitochondrial respiration by targeting the copper-dependent cellular pathways. The role of cuproptosis has been extensively investigated in various therapeutic contexts, including chemotherapy, immunotherapy, radiotherapy, and nanotherapy, with the development of novel drugs significantly improving clinical outcomes. This article aims to further elucidate the connection between cuproptosis and breast cancer, focusing on its therapeutic targets, signaling pathways, and potential biomarkers that could enhance treatment strategies. These insights may offer new opportunities for improved patient care and outcomes in breast cancer therapy.

Novel Flavin Mononucleotide-Functionalized Cerium Fluoride Nanoparticles for Selective Enhanced X-Ray-Induced Photodynamic Therapy

X-ray-induced photodynamic therapy (X-PDT) represents a promising new method of cancer treatment. A novel type of nanoscintillator based on cerium fluoride (CeF3) nanoparticles (NPs) modified with flavin mononucleotide (FMN) has been proposed. A method for synthesizing CeF3-FMN NPs has been developed, enabling the production of colloidal, spherical NPs with an approximate diameter of 100 nm, low polydispersity, and a high fluorescence quantum yield of 0.42. It has been demonstrated that CeF3-FMN NPs exhibit pH-dependent radiation-induced redox activity when exposed to X-rays. This activity results in the generation of reactive oxygen species, which is associated with the scintillation properties of cerium and the transfer of electrons to FMN. The synthesized NPs have been demonstrated to exhibit minimal cytotoxicity towards normal cells (NCTC L929 fibroblasts) but are more toxic to tumor cells (epidermoid carcinoma A431). Concurrently, the synthesized NPs (CeF3 and CeF3-FMN NPs) demonstrate a pronounced selective radiosensitizing effect on tumor cells at concentrations of 10-7 and 10-3 M, resulting in a significant reduction in their clonogenic activity, increasing radiosensitivity for cancer cells by 1.9 times following X-ray irradiation at a dose of 3 to 6 Gy. In the context of normal cells, these nanoparticles serve the function of antioxidants, maintaining a high level of clonogenic activity. Functional nanoscintillators on the basis of cerium fluoride can be used as part of the latest technologies for the treatment of tumors within the framework of X-PDT.

Recent Advances in Silica-Based Nanomaterials for Enhanced Tumor Imaging and Therapy

Cancer remains a formidable challenge, inflicting profound physical, psychological, and financial burdens on patients. In this context, silica-based nanomaterials have garnered significant attention for their potential in tumor imaging and therapy owing to their exceptional properties, such as biocompatibility, customizable porosity, and versatile functionalization capabilities. This review meticulously examines the latest advancements in the application of silica-based nanomaterials for tumor imaging and therapy. It underscores their potential in enhancing various cancer imaging modalities, including fluorescence imaging, magnetic resonance imaging, computed tomography, positron emission tomography, ultrasound imaging, and multimodal imaging approaches. Moreover, the review delves into their therapeutic efficacy in chemotherapy, radiotherapy, phototherapy, immunotherapy, gas therapy, sonodynamic therapy, chemodynamic therapy, starvation therapy, and gene therapy. Critical evaluations of the biosafety profiles and degradation pathways of these nanomaterials within biological environments are also presented. By discussing the current challenges and prospects, this review aims to provide a nuanced perspective on the clinical translation of silica-based nanomaterials, thereby highlighting their promise in revolutionizing cancer diagnostics, enabling real-time monitoring of therapeutic responses, and advancing personalized medicine.

Enhancing Cancer Treatment Through Combined Approaches: Photodynamic Therapy in Concert with Other Modalities

This review explores the role of photodynamic therapy (PDT) as an adjunctive treatment for cancers, with a focus on its potential to enhance the effects of established therapies like chemotherapy, surgery, and radiotherapy. Given the limitations of conventional cancer treatments, PDT's ability to improve therapeutic outcomes through combination strategies is examined. In cancers such as lung, breast, cholangiocarcinoma, and cervical, PDT shows promise in enhancing response rates, reducing recurrence, and minimizing adverse effects when used alongside standard modalities. This study highlights current findings on PDT's mechanisms in complementing chemotherapy, augmenting surgical precision, and enhancing radiotherapeutic effects, thus offering a multi-faceted approach to cancer treatment. Additionally, insights into the clinical application of PDT in these cancers emphasize its potential for reducing tumor resistance and supporting more effective, personalized care. By providing an overview of PDT's synergistic applications across diverse cancer types, this review underscores its emerging significance in oncology as a tool to address traditional treatment limitations. Ultimately, this review aims to inform and inspire researchers and clinicians seeking to refine and innovate cancer therapy strategies through PDT integration, contributing to the advancement of more effective, synergistic cancer treatments.

Aggregation-Induced Emission Luminogen Based Wearable Visible-Light Penetrator for Deep Photodynamic Therapy

Photodynamic therapy (PDT) has emerged as a preferred nonsurgical treatment in clinical applications due to its capacity to selectively eradicate diseased tissues while minimizing damage to normal tissue. Nevertheless, its clinical efficacy is constrained by the limited penetration of visible light. Although near-infrared (NIR) lasers offer enhanced tissue penetration, the dearth of suitable photosensitizers and a pronounced imaging-treatment disparity pose challenges. Additionally, clinical implementation via optical fiber implantation carries infection risks and necessitates minimally invasive surgery, contradicting PDT's noninvasive advantage. In this study, we introduce a brilliant approach utilizing aggregation-induced emission luminogens (AIEgen) to develop a visible-light penetrator (VLP), coupled with wireless light emitting diodes (LEDs), enabling deep photodynamic therapy. We validate the therapeutic efficacy of this visible-light penetrator in tissues inaccessible to conventional PDT, demonstrating significant suppression of inflammatory diffusion in vivo using AIEgen TBPPM loaded within the VLP, which exhibits a transmittance of 86% in tissues with a thickness of 3 mm. This innovative visible-light penetrator effectively overcomes the substantial limitations of PDT in clinical settings and holds promise for advancing phototherapy.

The wonders of X-PDT: an advance route to cancer theranostics

Global mortality data indicates cancer as the second-leading cause of death worldwide. Therefore, there's a pressing need to innovate effective treatments to address this significant medical and societal challenge. In recent years, X-ray-induced photodynamic therapy (X-PDT) has emerged as a promising advancement, revolutionizing traditional photodynamic therapy (PDT) for deeply entrenched malignancies by harnessing penetrating X-rays as external stimuli. Recent developments in X-ray photodynamic therapy have shown a trend toward minimizing radiation doses to remarkably low levels after the proof-of-concept demonstration. Early detection and real-time monitoring are crucial aspects of effective cancer treatment. Sophisticated X-ray imaging techniques have been enhanced by the introduction of X-ray luminescence nano-agents, alongside contrast nanomaterials based on X-ray attenuation. X-ray luminescence-based in vivo imaging offers excellent detection sensitivity and superior image quality in deep tissues at a reasonable cost, due to unhindered penetration and unimpeded auto-fluorescence of X-rays. This review emphasizes the significance of X-ray responsive theranostics, exploring their mechanism of action, feasibility, biocompatibility, and promising prospects in imaging-guided therapy for deep-seated tumors. Additionally, it discusses promising applications of X-PDT in treating breast cancer, liver cancer, lung cancer, skin cancer, and colorectal cancer.

Treating Deep-Seated Tumors with Radiodynamic Therapy: Progress and Perspectives

Radiodynamic therapy (RDT), as an emerging cancer treatment method, has attracted attention due to its remarkable therapeutic efficacy using low-dose, high-energy radiation (such as X-rays) and has shown significant potential in cancer treatment. The RDT system typically consists of scintillators and photosensitizers (PSs). Scintillators absorb X-rays and convert them to visible light, activating nearby PSs to generate cytotoxic reactive oxygen species (ROS). Challenges faced by the two-component strategy, including low loading capacity and inefficient energy transfer, hinder its final effectiveness. In addition, the tumor microenvironment (TME) with hypoxia and immunosuppression limits the efficacy of RDTs. Recent advances introduce one-component RDT systems based on nanomaterials with high-Z metal elements, which effectively inhibit deep-seated tumors. These novel RDT systems exhibit immune enhancement and immune memory, potentially eliminating both primary and metastatic tumors. This review comprehensively analyzes recent advances in the rational construction of RDTs, exploring their mechanisms and application in the treatment of deep-seated tumors. Aimed at providing a practical resource for oncology researchers and practitioners, the review offers new perspectives for potential future directions in RDT research.

Exploring the combined impact of cisplatin and copper-cysteamine nanoparticles through Chemoradiation: An in-vitro study

Copper-Cysteamine nanoparticles (Cu-Cy NPs) have emerged as promising radiosensitizers in cancer treatment. This study aims to investigate the combined therapeutic effect of these nanoparticles and cisplatin using a clinical linear accelerator to enhance the efficacy of chemoradiation therapy for cervical cancer. Following successful synthesis and characterization of Cu-Cy NPs, the cytotoxicity effect of these nanoparticles and cisplatin in various concentrations was evaluated on HeLa cancer cells, individually and in combination. Additionally, the radiobiological effects of these agents were investigated under a 6MV linear accelerator. At a concentration of 25 mg/L, Cu-Cy NPs displayed no significant cytotoxicity toward HeLa cancer cells. However, when combined with 2Gy X-ray irradiation at this concentration, the nanoparticles demonstrated a potent radiosensitizing effect. Notably, cell viability and migration rate in the combination group (Cu-Cy NPs + cisplatin + radiation) were significantly reduced compared to the radiation-alone group. Additionally, the combination treatment induced a significantly higher rate of apoptosis compared to the radiation-alone group. Overall, Cu-Cy NPs exhibited a significant dose-dependent synergistic enhancement of radiation efficacy when combined with cisplatin under X-ray exposure, and may provide a promising approach to improve the therapeutic effect of conventional radiation therapy.

Russell Mechanism-Mediated Cancer Therapy: A Minireview

The Russell mechanism, proposed by Russell, is a cyclic mechanism for the formation of linear tetroxide intermediates, which can spontaneously produce cytotoxic singlet oxygen (1O2) independent of oxygen, suggesting its anticancer potential. Compared with other mainstream anticancer strategies, the Russell mechanism employed for killing cancer cells does not require external energy input, harsh pH condition, and sufficient oxygen. However, up till now, the applications of Russell mechanism in antitumor therapy have been relatively rare, and there is almost no summary of the Russell mechanism in the cancer therapy field. This minireview introduces the different metal elements-based Russell mechanisms and the relevant research progress in Russell mechanism-based cancer therapy in recent years. At the same time, we briefly discussed the current challenges and future development regarding the applications of Russell mechanism. It is hoped that this review can further expand the research of Russell Mechanism in the biomedical field, and inspire researchers to extend its application fields to antibacterial, antiinflammatory, and wound healing uses.

Recent Advances in Photosensitizer Materials for Light-Mediated Tumor Therapy

Photodynamic therapy (PDT) as an emerging therapeutic method has drawn much attention in the treatment field for cancer. Photosensitizer, which can convert photon energy into cytotoxic species under light irradiation, is the core component in PDT. The design of photosensitizers still faces problems of light absorption, targeting, penetration and oxygen dependence. With the rapid progress of material science, various photosensitizers have been developed to produce cytotoxic species for treatment of tumor with high selectivity, safety, and noninvasiveness. Besides, the applications of photosensitizers have been expanded to diverse cancer treatments such as drug release, optogenetics and immune checkpoint blockade. In this review, we summarize the recent advances of photosensitizers in various therapeutic methods for cancer. Prevailing challenges and further prospects associated with photosensitizers are also discussed.

Development of Novel Bimodal Agents Based on Near-Infrared BODIPY-Conjugated Hoechst Derivatives for Combined Use in Auger Electron and Photodynamic Cancer Therapy

Auger electron therapy and photodynamic therapy (PDT) have attracted attention as powerful anticancer modalities. Herein, we report the development of novel bimodal agents for Auger electron therapy and PDT, and their application to combination therapy. [125I]NBH-1/NBH-1 and [125I]NBH-2/NBH-2, composing Hoechst and iodostyryl-BODIPY, were synthesized and evaluated regarding their usefulness as bimodal agents. [125I]NBH-1 showed significantly higher nuclear uptake than [125I]NBH-2 and radioactivity-dependent cytotoxicity induced by Auger electrons. In addition, NBH-1 exhibited photoinduced cytotoxicity. Combination therapy using [125I]NBH-1 and NBH-1 with light irradiation induced a superior cytotoxicity to these treatments alone. In tumor-bearing mice injected with NBH-1 or [125I]NBH-1/NBH-1 under light irradiation, significant tumor growth inhibition was observed compared with that of the control group. Especially, [125I]NBH-1/NBH-1 under light irradiation showed the strongest therapeutic effects among all treatments. These results suggest that [125I]NBH-1/NBH-1 is a potent bimodal agent for Auger therapy and PDT and that combination therapy using [125I]NBH-1 and NBH-1 shows enhanced therapeutic efficacy.

A first-in-class β-glucuronidase responsive conjugate for selective dual targeted and photodynamic therapy of bladder cancer

In this report, we present a novel prodrug strategy that can significantly improve the efficiency and selectivity of combined therapy for bladder cancer. Our approach involved the synthesis of a conjugate based on a chlorin-e6 photosensitizer and a derivative of the tyrosine kinase inhibitor cabozantinib, linked by a β-glucuronidase-responsive linker. Upon activation by β-glucuronidase, which is overproduced in various tumors and localized in lysosomes, this conjugate released both therapeutic modules within targeted cells. This activation was accompanied by the recovery of its fluorescence and the generation of reactive oxygen species. Investigation of photodynamic and dark toxicity in vitro revealed that the novel conjugate had an excellent safety profile and was able to inhibit tumor cells proliferation at submicromolar concentrations. Additionally, combined therapy effects were also observed in 3D models of tumor growth, demonstrating synergistic suppression through the activation of both photodynamic and targeted therapy.

Aggregation-Induced Emission Photosensitizer-Engineered Anticancer Nanomedicine for Synergistic Chemo/Chemodynamic/Photodynamic Therapy

Photodynamic therapy (PDT) with aggregation-induced emission (AIE) photosensitizers (PSs) is a promising therapeutic strategy to achieve better anticancer results. However, eradicating solid tumors completely by PDT alone can be difficult owing to the inherent drawbacks of this treatment, and the combination of PDT with other therapeutic modalities provides opportunities to achieve cooperative enhancement interactions among various treatments. Herein, this work presents the construction of a biocompatible nanocomposite, namely CaO2@DOX@ZIF@ASQ, featuring light-responsive reactive oxygen species (ROS) generation and tumor-targeting oxygen and hydrogen peroxide discharge, as well as controlled doxorubicin (DOX) and copper ion release, thus allowing the combined PDT/CT/CDT effect by AIE PS-enhanced PDT, DOX-based chemotherapy (CT), and copper-involved Fenton-like reaction-driven chemodynamic therapy (CDT). In vitro and in vivo studies verify that the generation of both ROS and O2 by this nanomedicine, stimulated by light, exhibits superior anticancer efficacy, alleviating tumor hypoxia and achieving synergistic PDT/CT/CDT therapeutic effect. This multifunctional nanomedicine remarkably suppresses the tumor growth with minimized systemic toxicity, providing a new strategy for constructing multimodal PDT/CT/CDT therapeutic systems to overcome hypoxia limitations, and potentially increase the antitumor efficacy at lower doses of PSs and chemotherapeutic drugs, thus minimizing potential toxicity to non-malignant tissues.

PEGylated Molybdenum-Iodine Nanocluster as a Promising Radiodynamic Agent against Prostatic Adenocarcinoma

The combination of photodynamic therapy and radiotherapy has given rise to a modality called radiodynamic therapy (RDT), based on reactive oxygen species-producing radiosensitizers. The production of singlet oxygen, O2(1Δg), by octahedral molybdenum (Mo6) clusters upon X-ray irradiation allows for simplification of the architecture of radiosensitizing systems. In this context, we prepared a radiosensitizing system using copper-free click chemistry between a Mo6 cluster bearing azido ligands and the homo-bifunctional linker bis-dPEG11-DBCO. The resulting compound formed nanoparticles, which featured production of O2(1Δg) and efficient cellular uptake, leading to remarkable photo- and radiotoxic effects against the prostatic adenocarcinoma TRAMP-C2 cell line. Spheroids of TRAMP-C2 cells were also used for evaluation of toxicity and phototoxicity. In vivo experiments on a mouse model demonstrated that subcutaneous injection of the nanoparticles is a safe administration mode at a dose of up to 0.08 g kg-1. The reported results confirm the relevancy of Mo6-based radiosensitizing nanosystems for RDT.

Design of a novel nanoparticle to use X-ray fluorescence of TiO2 to induce photodynamic effects in the presence of PpIX

BACKGROUND

Radiotherapy and photodynamic therapy are the methods of cancer treatment. Although one limitation of photodynamic therapy (PDT) is the limited penetration depth of light through tissue, using X-rays does not have this restriction. Self-lighting nanoparticles can convert X-rays into UV/visible. This study focuses on a newly designed nanostructure containing mesoporous silica nanoparticles (MSN), titanium dioxide nanoparticles (TiO2, anatase grade), and protoporphyrin IX (PpIX) as a photosensitizer to overcome the limitations of photodynamic therapy.

METHODS

After the synthesis and characterization of Ti-MSN/PpIX@PVP nanostructure, two ROSes (OH* and 1O2) were measured when the nanostructures were irradiated with 100 kV and 6 MV photons. The toxicity of Ti-MSN/PpIX@PVP nanostructure in presence and absence of radiation was investigated on DFW and HT-29 cell lines. The in-vitro experiments were analyzed using the MTT assay and colony count assay. Finally, the effect of light exposure in the presence of Ti-MSN/PpIX@PVP nanostructure on the two cell lines was studied. The in-vitro studies were evaluated using the Synergism Index (Syn) and Dose Enhancement Factor (DEF).

RESULTS

Based on the FESEM (field emission scanning electron Microscopy) images and DLS (dynamic light scattering) measurements, the size of Ti-MSN/PpIX nanostructure was determined as (35.2 nm) and (168.4 nm), respectively. Based on the spectrofluorimetry results, 100 kV photons produced more ROSes than 6 MV photons. The results of MTT assay and colony formation for X-PDT show Syn >1, except for 100 kV photons for HT-29 cell line. The nanostructure also reduced colony formation induced by X-PDT more effectively when irradiated by 100 kV photons on DFW cells. The results obtained from conventional PDT showed that the ED 50 of the HT-29 cell line was 6 times higher than that of the DFW cell line.

CONCLUSION

Designing and synthesizing Ti-MSN/PpIX@PVP nanostructures offer a promising strategy for reducing the current challenges in PDT and for developing and advancing X-PDT as an innovative cancer treatment technique.

Current Advances in Photodynamic Therapy (PDT) and the Future Potential of PDT-Combinatorial Cancer Therapies

Photodynamic therapy (PDT) is a two-stage treatment that implies the use of light energy, oxygen, and light-activated compounds (photosensitizers) to elicit cancerous and precancerous cell death after light activation (phototoxicity). The biophysical, bioengineering aspects and its combinations with other strategies are highlighted in this review, both conceptually and as they are currently applied clinically. We further explore the recent advancements of PDT with the use of nanotechnology, including quantum dots as innovative photosensitizers or energy donors as well as the combination of PDT with radiotherapy and immunotherapy as future promising cancer treatments. Finally, we emphasize the potential significance of organoids as physiologically relevant models for PDT.

Radiation-Activated Cobalamin-Kinase Inhibitors for Treatment of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most dismal diagnoses that a patient can receive. PDAC is extremely difficult to treat, as drug delivery is challenging in part due to the lack of vascularization, high stromal content, and high collagen content of these tumors. We have previously demonstrated that attaching drugs to the cobalamin scaffold provides selectivity for tumors over benign cells due to a high vitamin demand in these rapidly growing cells and an overexpression of transcobalamin receptors in a variety of cancer types. Importantly, we have shown the ability to deliver cobalamin derivatives to orthotopic pancreas tumors. Tyrosine kinase inhibitors have shown promise in treating PDAC as well as other cancer types. However, some of these inhibitors suffer from drug resistance, and as such, their success has been diminished. With this in mind, we synthesized the tyrosine kinase inhibitors erlotinib (EGFR) and dasatinib (Src) that are attached to this cobalamin platform. Both of these cobalamin-drug conjugates cause visible light-induced apoptosis, and the cobalamin-erlotinib conjugate (2) causes X-ray-induced apoptosis in MIA PaCa-2 cells. Both visible light and X-rays provide spatial control of drug release; however, utilizing X-ray irradiation offers the advantage of deeper tissue penetration. Therefore, we explored the utilization of 2 as a synergistic therapy with radiation in athymic nude mice implanted with MIA PaCa-2 tumors. We discovered that the addition of 2 caused an enhanced reduction in tumor margins in comparison with radiation therapy alone. In addition, treatment with 2 in the absence of radiation caused no significant reduction in tumor size in comparison with the controls. The cobalamin technology presented here allows for the spatial release of drugs in conjunction with external beam radiation therapy, potentially allowing for more effective treatment of deep-seated tumors with less systemic side effects.

Cuproptosis: A novel therapeutic target for overcoming cancer drug resistance

Cuproptosis is a newly identified form of cell death driven by copper. Recently, the role of copper and copper triggered cell death in the pathogenesis of cancers have attracted attentions. Cuproptosis has garnered enormous interest in cancer research communities because of its great potential for cancer therapy. Copper-based treatment exerts an inhibiting role in tumor growth and may open the door for the treatment of chemotherapy-insensitive tumors. In this review, we provide a critical analysis on copper homeostasis and the role of copper dysregulation in the development and progression of cancers. Then the core molecular mechanisms of cuproptosis and its role in cancer is discussed, followed by summarizing the current understanding of copper-based agents (copper chelators, copper ionophores, and copper complexes-based dynamic therapy) for cancer treatment. Additionally, we summarize the emerging data on copper complexes-based agents and copper ionophores to subdue tumor chemotherapy resistance in different types of cancers. We also review the small-molecule compounds and nanoparticles (NPs) that may kill cancer cells by inducing cuproptosis, which will shed new light on the development of anticancer drugs through inducing cuproptosis in the future. Finally, the important concepts and pressing questions of cuproptosis in future research that should be focused on were discussed. This review article suggests that targeting cuproptosis could be a novel antitumor therapy and treatment strategy to overcome cancer drug resistance.

Single-Stage Microfluidic Synthesis Route for BaGdF5:Tb3+-Based Nanocomposite Materials: Synthesis, Characterization and Biodistribution

Rare-earth-doped nanoscaled BaGdF5 is known as an efficient contrasting agent for X-ray micro-CT and NMR as well as a promising candidate for X-ray photodynamic therapy, thereby opening an opportunity for theragnostic applications. Conventional synthesis of Ln-doped BaGdF5 consider a long-lasting batch procedure, while a conjugation with photosensitizer usually implies a separate stage requiring active mixing. To the best of our knowledge, in this work, we for the first time obtain BaGdF5:Tb3+ nanophosphors in a microfluidic route at temperatures as low as 100 °C while decreasing the time of thermal treatment down to 6 min. The proposed synthesis route allows for the obtaining of single-phase and monodisperse BaGd1-xF5:Tbx3+ nanoparticles with an averaged particle size of ca. 7-9 nm and hydrodynamic radius around 22 nm, as estimated from TEM and DLS, respectively. In addition, X-ray-excited optical luminescence has been recorded in situ for the series of nanophosphors synthesis with varied flow rates of Tb3+ and Gd3+ stock solutions, thereby anticipating a possible application of microfluidics for screening a wide range of possible co-dopants and reaction conditions and its effect on the optical properties of the synthesized materials. Moreover, we demonstrated that BaGd1-xF5:Tbx3+@RoseBengal conjugates might be obtained in a single-stage route by implementing an additional mixer at the synthesis outcome, namely, by mixing the resulting reaction mixture containing nanoparticles with an equivalent flow of photosensitizer aqueous solution. In vitro cytotoxicity test declares moderate toxicity effect on different cell lines, while the results of flow cytometry indirectly confirm cellular uptake. Finally, we report long-term biodistribution monitoring of the synthesized nanocomposites assessed by X-ray micro-CT in the in vivo experiments on balb/c mice, which depicts an unusual character of agents' accumulation.

Inorganic Nanoparticles as Radiosensitizers for Cancer Treatment

Nanotechnology has expanded what can be achieved in our approach to cancer treatment. The ability to produce and engineer functional nanoparticle formulations to elicit higher incidences of tumor cell radiolysis has resulted in substantial improvements in cancer cell eradication while also permitting multi-modal biomedical functionalities. These radiosensitive nanomaterials utilize material characteristics, such as radio-blocking/absorbing high-Z atomic number elements, to mediate localized effects from therapeutic irradiation. These materials thereby allow subsequent scattered or emitted radiation to produce direct (e.g., damage to genetic materials) or indirect (e.g., protein oxidation, reactive oxygen species formation) damage to tumor cells. Using nanomaterials that activate under certain physiologic conditions, such as the tumor microenvironment, can selectively target tumor cells. These characteristics, combined with biological interactions that can target the tumor environment, allow for localized radio-sensitization while mitigating damage to healthy cells. This review explores the various nanomaterial formulations utilized in cancer radiosensitivity research. Emphasis on inorganic nanomaterials showcases the specific material characteristics that enable higher incidences of radiation while ensuring localized cancer targeting based on tumor microenvironment activation. The aim of this review is to guide future research in cancer radiosensitization using nanomaterial formulations and to detail common approaches to its treatment, as well as their relations to commonly implemented radiotherapy techniques.

Engineered Bacteria Labeled with Iridium(III) Photosensitizers for Enhanced Photodynamic Immunotherapy of Solid Tumors

Despite metal-based photosensitizers showing great potential in photodynamic therapy for tumor treatment, the application of the photosensitizers is intrinsically limited by their poor cancer-targeting properties. Herein, we reported a metal-based photosensitizer-bacteria hybrid, Ir-HEcN, via covalent labeling of an iridium(III) photosensitizer to the surface of genetically engineered bacteria. Due to its intrinsic self-propelled motility and hypoxia tropism, Ir-HEcN selectively targets and penetrates deeply into tumor tissues. Importantly, Ir-HEcN is capable of inducing pyroptosis and immunogenic cell death of tumor cells under irradiation, thereby remarkably evoking anti-tumor innate and adaptive immune responses in vivo and leading to the regression of solid tumors via combinational photodynamic therapy and immunotherapy. To the best of our knowledge, Ir-HEcN is the first metal complex decorated bacteria for enhanced photodynamic immunotherapy.

A physicochemical model of X-ray induced photodynamic therapy (X-PDT) with an emphasis on tissue oxygen concentration and oxygenation

X-PDT is one of the novel cancer treatment approaches that uses high penetration X-ray radiation to activate photosensitizers (PSs) placed in deep seated tumors. After PS activation, some reactive oxygen species (ROS) like singlet oxygen (1O2) are produced that are very toxic for adjacent cells. Efficiency of X-PDT depends on 1O2 quantum yield as well as X-ray mortality rate. Despite many studies have been modeled X-PDT, little is known about the investigation of tissue oxygen content in treatment outcome. In the present study, we predicted X-PDT efficiency through a feedback of physiological parameters of tumor microenvironment includes tissue oxygen and oxygenation properties. The introduced physicochemical model of X-PDT estimates 1O2 production in a vascularized and non-vascularized tumor under different tissue oxygen levels to predict cell death probability in tumor and adjacent normal tissue. The results emphasized the importance of molecular oxygen and the presence of a vascular network in predicting X-PDT efficiency.

Application of singlet oxygen-activatable nanocarriers to boost X-ray-induced photodynamic therapy and cascaded ferroptosis for breast cancer treatment

Ferroptosis has appealing antitumor potential that is mainly based on the accumulation of lipid peroxide to a lethal level. The cytotoxic singlet oxygen (1O2) generated from nanoscale X-ray-induced photodynamic therapy (X-PDT) may facilitate glutathione (GSH) depletion and further activate ferroptosis. To realize combined X-PDT and ferroptosis, a nanocarrier (D-NPVR) was engineered with a hyperbranched copolymer with 1O2-sensitive linkers, where both the photosensitizer (verteporfin) and ferroptosis inducer RAS-selective lethal small molecule 3 (RSL3) were encapsulated. Upon X-ray radiation, D-NPVR could produce a large amount of 1O2 for apoptosis. Subsequently, 1O2 triggered D-NP dissociation by cleavage of 1,2-bis(2-hydroxyethylthio)ethylene bonds to boost payload release and decrease levels of intracellular GSH via thiol oxidation. Liberated RSL3 is a covalent inhibitor for glutathione peroxide 4 (GPX4), which is responsible for detoxifying lipid peroxides to lipid alcohols with GSH assistance, and both 1O2-induced GSH depletion and GPX4 inactivation thereby produced ferroptotic cell death. Tumor growth inhibition in murine 4T1 tumor-bearing mice demonstrated that D-NPVR produced pronounced therapeutic efficiency where ferroptosis induction was supported by the GPX4 content and expression. This study highlights the contribution of 1O2-sensitive nanocarriers for promoting the potency of combined X-PDT and ferroptosis.

The use of nanomaterials in advancing photodynamic therapy (PDT) for deep-seated tumors and synergy with radiotherapy

Photodynamic therapy (PDT) has been under development for at least 40 years. Multiple studies have demonstrated significant anti-tumor efficacy with limited toxicity concerns. PDT was expected to become a major new therapeutic option in treating localized cancer. However, despite a shifting focus in oncology to aggressive local therapies, PDT has not to date gained widespread acceptance as a standard-of-care option. A major factor is the technical challenge of treating deep-seated and large tumors, due to the limited penetration and variability of the activating light in tissue. Poor tumor selectivity of PDT sensitizers has been problematic for many applications. Attempts to mitigate these limitations with the use of multiple interstitial fiberoptic catheters to deliver the light, new generations of photosensitizer with longer-wavelength activation, oxygen independence and better tumor specificity, as well as improved dosimetry and treatment planning are starting to show encouraging results. Nanomaterials used either as photosensitizers per se or to improve delivery of molecular photosensitizers is an emerging area of research. PDT can also benefit radiotherapy patients due to its complementary and potentially synergistic mechanisms-of-action, ability to treat radioresistant tumors and upregulation of anti-tumoral immune effects. Furthermore, recent advances may allow ionizing radiation energy, including high-energy X-rays, to replace external light sources, opening a novel therapeutic strategy (radioPDT), which is facilitated by novel nanomaterials. This may provide the best of both worlds by combining the precise targeting and treatment depth/volume capabilities of radiation therapy with the high therapeutic index and biological advantages of PDT, without increasing toxicities. Achieving this, however, will require novel agents, primarily developed with nanomaterials. This is under active investigation by many research groups using different approaches.

Radio- and Photosensitizing Os(II)-Based Nanocage for Combined Radio-/Chemo-/X-ray-Induced Photodynamic Therapies, NIR Imaging, and Drug Delivery

Integration of clinical imaging and collaborative multimodal therapies into a single nanomaterial for multipurpose diagnosis and treatment is of great interest to theranostic nanomedicine. Here, we report a rational design of a discrete Os-based metal-organic nanocage Pd6(OsL3)828+ (MOC-43) as a versatile theranostic nanoplatform to meet the following demands simultaneously: (1) synergistic treatments of radio-, chemo-, and X-ray-induced photodynamic therapies (X-PDT) for breast cancer, (2) NIR imaging for cancer cell tracking and tumor-targeting, and (3) anticancer drug transport through a host-guest strategy. The nanoscale MOC-43 incorporates high-Z Os-element to interact with X-ray irradiation for dual radiosensitization and photosensitization, showing efficient energy transfer to endogenous oxygen in cancer cells to enhance X-PDT efficacy. It also features intrinsic NIR emission originating from metal-to-ligand charge transfer (MLCT) as an excellent imaging probe. Meanwhile, its 12 pockets can capture and concentrate low-water-soluble molecules for anticancer drug delivery. These multifunctions are implemented and demonstrated by micellization of coumarin-loaded cages with DSPE-PEG2000 into coumarin ⊂ MOC-43 nanoparticles (CMNPs) for efficient subcellular endocytosis and uptake. The cancer treatments in vitro/in vivo show promising antitumor performance, providing a conceptual protocol to combine cage-cargo drug transport with diagnosis and treatment for collaborative cancer theranostics by virtue of multifunction synergism on a single-nanomaterial platform.

Ferroptosis as a promising therapeutic strategy for melanoma

Malignant melanoma (MM) is the most common and deadliest type of skin cancer and is associated with high mortality rates across all races and ethnicities. Although present treatment options combined with surgery provide short-term clinical benefit in patients and early diagnosis of non-metastatic MM significantly increases the probability of survival, no efficacious treatments are available for MM. The etiology and pathogenesis of MM are complex. Acquired drug resistance is associated with a pool prognosis in patients with advanced-stage MM. Thus, these patients require new therapeutic strategies to improve their treatment response and prognosis. Multiple studies have revealed that ferroptosis, a non-apoptotic form of regulated cell death (RCD) characterized by iron dependant lipid peroxidation, can prevent the development of MM. Recent studies have indicated that targeting ferroptosis is a promising treatment strategy for MM. This review article summarizes the core mechanisms underlying the development of ferroptosis in MM cells and its potential role as a therapeutic target in MM. We emphasize the emerging types of small molecules inducing ferroptosis pathways by boosting the antitumor activity of BRAFi and immunotherapy and uncover their beneficial effects to treat MM. We also summarize the application of nanosensitizer-mediated unique dynamic therapeutic strategies and ferroptosis-based nanodrug targeting strategies as therapeutic options for MM. This review suggests that pharmacological induction of ferroptosis may be a potential therapeutic target for MM.

High quantum efficiency ruthenium coordination complex photosensitizer for improved radiation-activated Photodynamic Therapy

Traditional external light-based Photodynamic Therapy (PDT)'s application is limited to the surface and minimal thickness tumors because of the inefficiency of light in penetrating deep-seated tumors. To address this, the emerging field of radiation-activated PDT (radioPDT) uses X-rays to trigger photosensitizer-containing nanoparticles (NPs). A key consideration in radioPDT is the energy transfer efficiency from X-rays to the photosensitizer for ultimately generating the phototoxic reactive oxygen species (ROS). In this study, we developed a new variant of pegylated poly-lactic-co-glycolic (PEG-PLGA) encapsulated nanoscintillators (NSCs) along with a new, highly efficient ruthenium-based photosensitizer (Ru/radioPDT). Characterization of this NP via transmission electron microscopy, dynamic light scattering, UV-Vis spectroscopy, and inductively coupled plasma mass-spectroscopy showed an NP size of 120 nm, polydispersity index (PDI) of less than 0.25, high NSCs loading efficiency over 90% and in vitro accumulation within the cytosolic structure of endoplasmic reticulum and lysosome. The therapeutic efficacy of Ru/radioPDT was determined using PC3 cell viability and clonogenic assays. Ru/radioPDT exhibited minimal cell toxicity until activated by radiation to induce significant cancer cell kill over radiation alone. Compared to protoporphyrin IX-mediated radioPDT (PPIX/radioPDT), Ru/radioPDT showed higher capacity for singlet oxygen generation, maintaining a comparable cytotoxic effect on PC3 cells.

Mechanisms and applications of radiation-induced oxidative stress in regulating cancer immunotherapy

Radiotherapy (RT) is an effective treatment option for cancer patients, which induces the production of reactive oxygen species (ROS) and causes oxidative stress (OS), leading to the death of tumor cells. OS not only causes apoptosis, autophagy and ferroptosis, but also affects tumor immune response. The combination of RT and immunotherapy has revolutionized the management of various cancers. In this process, OS caused by ROS plays a critical role. Specifically, RT-induced ROS can promote the release of tumor-associated antigens (TAAs), regulate the infiltration and differentiation of immune cells, manipulate the expression of immune checkpoints, and change the tumor immune microenvironment (TME). In this review, we briefly summarize several ways in which IR induces tumor cell death and discuss the interrelationship between RT-induced OS and antitumor immunity, with a focus on the interaction of ferroptosis with immunogenic death. We also summarize the potential mechanisms by which ROS regulates immune checkpoint expression, immune cells activity, and differentiation. In addition, we conclude the therapeutic opportunity improving radiotherapy in combination with immunotherapy by regulating OS, which may be beneficial for clinical treatment.

Flexible Quantum Dot Light-Emitting Device for Emerging Multifunctional and Smart Applications

Quantum dot light-emitting diodes (QLEDs), owing to their exceptional performances in device efficiency, color purity/tunability in the visible region and solution-processing ability on various substrates, become a potential candidate for flexible and ultrathin electroluminescent (EL) lighting and display. Moreover, beyond the lighting and display, flexible QLEDs are enabled with endless possibilities in the era of the internet of things and artificial intelligence by acting as input/output ports in wearable integrated systems. Challenges remain in the development of flexible QLEDs with the goals for high performance, excellent flexibility/even stretchability, and emerging applications. In this paper, the recent developments of QLEDs including quantum dot materials, working mechanism, flexible/stretchable strategies and patterning strategies, and highlight its emerging multifunctional integrations and smart applications covering wearable optical medical devices, pressure-sensing EL devices, and neural smart EL devices, are reviewed. The remaining challenges are also summarized and an outlook on the future development of flexible QLEDs made. The review is expected to offer a systematic understanding and valuable inspiration for flexible QLEDs to simultaneously satisfy optoelectronic and flexible properties for emerging applications.

Combinations of Photodynamic Therapy with Other Minimally Invasive Therapeutic Technologies against Cancer and Microbial Infections

The rapid rise in research and development following the discovery of photodynamic therapy to establish novel photosensitizers and overcome the limitations of the technology soon after its clinical translation has given rise to a few significant milestones. These include several novel generations of photosensitizers, the widening of the scope of applications, leveraging of the offerings of nanotechnology for greater efficacy, selectivity for the disease over host tissue and cells, the advent of combination therapies with other similarly minimally invasive therapeutic technologies, the use of stimulus-responsive delivery and disease targeting, and greater penetration depth of the activation energy. Brought together, all these milestones have contributed to the significant enhancement of what is still arguably a novel technology. Yet the major applications of photodynamic therapy still remain firmly located in neoplasms, from where most of the new innovations appear to launch to other areas, such as microbial, fungal, viral, acne, wet age-related macular degeneration, atherosclerosis, psoriasis, environmental sanitization, pest control, and dermatology. Three main value propositions of combinations of photodynamic therapy include the synergistic and additive enhancement of efficacy, the relatively low emergence of resistance and its rapid development as a targeted and high-precision therapy. Combinations with established methods such as chemotherapy and radiotherapy and demonstrated applications in mop-up surgery promise to enhance these top three clinical tools. From published in vitro and preclinical studies, clinical trials and applications, and postclinical case studies, seven combinations with photodynamic therapy have become prominent research interests because they are potentially easily applied, showing enhanced efficacy, and are rapidly translating to the clinic. These include combinations with chemotherapy, photothermal therapy, magnetic hyperthermia, cold plasma therapy, sonodynamic therapy, immunotherapy, and radiotherapy. Photochemical internalization is a critical mechanism for some combinations.

X-ray-responsive prodrugs and polymeric nanocarriers for multimodal cancer therapy

Radiotherapy as one of the most important cancer treatment modalities has been widely used in the therapy of various cancers. The clinically used radiation (e.g. X-ray) for radiotherapy has the advantages of precise spatiotemporal controllability and deep tissue penetration. However, traditional radiotherapy is frequently limited by the high side effects and tumor hypoxia. The combination of radiotherapy and other cancer treatment modalities may overcome the disadvantages of radiotherapy and improve the final therapeutic efficacy. In recent years, X-ray-activable prodrugs and polymeric nanocarriers have been extensively explored to introduce other treatment modalities in the precise position during radiotherapy, which can reduce the side toxicity of the drugs and improve the combination therapeutic efficacy. In this review, we focus on recent advances in X-ray-activable prodrugs and polymeric nanocarriers to boost X-ray-based multimodal synergistic therapy with reduced toxicity. The design strategies of prodrugs and polymeric nanocarriers are highlighted. Finally, challenges and outlooks of X-ray-activable prodrugs and polymeric nanocarriers are discussed.

Current Strategies in Photodynamic Therapy (PDT) and Photodynamic Diagnostics (PDD) and the Future Potential of Nanotechnology in Cancer Treatment

Photodynamic diagnostics (PDD) and photodynamic therapy (PDT) are well-established medical technologies used for the diagnosis and treatment of malignant neoplasms. They rely on the use of photosensitizers, light and oxygen to visualize or eliminate cancer cells. This review demonstrates the recent advancements in these modalities with the use of nanotechnology, including quantum dots as innovative photosensitizers or energy donors, liposomes and micelles. Additionally, this literature review explores the combination of PDT with radiotherapy, chemotherapy, immunotherapy, and surgery for treating various neoplasms. The article also focuses on the latest achievements in PDD and PDT enhancements, which seem to be very promising in the field of oncology.

Combining Pr3+-Doped Nanoradiosensitizers and Endogenous Protoporphyrin IX for X-ray-Mediated Photodynamic Therapy of Glioblastoma Cells

Glioblastoma multiforme is an aggressive type of brain cancer with high recurrence rates due to the presence of radioresistant cells remaining after tumor resection. Here, we report the development of an X-ray-mediated photodynamic therapy (X-PDT) system using NaLuF₄:25% Pr³⁺ radioluminescent nanoparticles in conjunction with protoporphyrin IX (PPIX), an endogenous photosensitizer that accumulates selectively in cancer cells. Conveniently, 5-aminolevulinic acid (5-ALA), the prodrug that is administered for PDT, is the only drug approved for fluorescence-guided resection of glioblastoma, enabling dual detection and treatment of malignant cells. NaLuF₄:Pr³⁺ nanoparticles were synthesized and spectroscopically evaluated at a range of Pr³⁺ concentrations. This generated radioluminescent nanoparticles with strong emissions from the ¹S₀ excited state of Pr³⁺, which overlaps with the Soret band of PPIX to perform photodynamic therapy. The spectral overlap between the nanoparticles and PPIX improved treatment outcomes for U251 cells, which were used as a model for the thin tumor margin. In addition to sensitizing PPIX to induce X-PDT, our nanoparticles exhibit strong radiosensitizing properties through a radiation dose-enhancement effect. We evaluate the effects of the nanoparticles alone and in combination with PPIX on viability, death, stress, senescence, and proliferation. Collectively, our results demonstrate this as a strong proof of concept for nanomedicine.

An X-ray activatable gold nanorod encapsulated liposome delivery system for mitochondria-targeted photodynamic therapy (PDT)

In this work, we developed a mitochondria-targeted nanomaterial for neoadjuvant X-ray-triggered photodynamic therapy of rectal cancer. Herein, we designed a biodegradable liposome incorporating a photosensitizer, verteporfin, to generate X-ray-induced reactive oxygen species, gold nanorods as radiation enhancers, and triphenylphosphonium as the mitochondrial targeting moiety. The average size of the nanocarrier was about 150 nm. Due to the synergetic effect between X-ray and a combination of verteporfin and gold nanorods, as well as precise site-targeted TPP-modified liposomal nanocarriers, our nanoconjugates generated sufficient cytotoxic singlet oxygen within the mitochondria under X-ray irradiation, triggering the loss of membrane potential and mitochondria-related apoptosis of cancer cells.

Combination of Two Photosensitisers in Anticancer, Antimicrobial and Upconversion Photodynamic Therapy

Photodynamic therapy (PDT) is a special form of phototherapy in which oxygen is needed, in addition to light and a drug called a photosensitiser (PS), to create cytotoxic species that can destroy cancer cells and various pathogens. PDT is often used in combination with other antitumor and antimicrobial therapies to sensitise cells to other agents, minimise the risk of resistance and improve overall outcomes. Furthermore, the aim of combining two photosensitising agents in PDT is to overcome the shortcomings of the monotherapeutic approach and the limitations of individual agents, as well as to achieve synergistic or additive effects, which allows the administration of PSs in lower concentrations, consequently reducing dark toxicity and preventing skin photosensitivity. The most common strategies in anticancer PDT use two PSs to combine the targeting of different organelles and cell-death mechanisms and, in addition to cancer cells, simultaneously target tumour vasculature and induce immune responses. The use of PDT with upconversion nanoparticles is a promising approach to the treatment of deep tissues and the goal of using two PSs is to improve drug loading and singlet oxygen production. In antimicrobial PDT, two PSs are often combined to generate various reactive oxygen species through both Type I and Type II processes.

Recent Advances in Hydrogel-Based Phototherapy for Tumor Treatment

Phototherapeutic agent-based phototherapies activated by light have proven to be safe modalities for the treatment of various malignant tumor indications. The two main modalities of phototherapies include photothermal therapy, which causes localized thermal damage to target lesions, and photodynamic therapy, which causes localized chemical damage by generated reactive oxygen species (ROS). Conventional phototherapies suffer a major shortcoming in their clinical application due to their phototoxicity, which primarily arises from the uncontrolled distribution of phototherapeutic agents in vivo. For successful antitumor phototherapy, it is essential to ensure the generation of heat or ROS specifically occurs at the tumor site. To minimize the reverse side effects of phototherapy while improving its therapeutic performance, extensive research has focused on developing hydrogel-based phototherapy for tumor treatment. The utilization of hydrogels as drug carriers allows for the sustained delivery of phototherapeutic agents to tumor sites, thereby limiting their adverse effects. Herein, we summarize the recent advancements in the design of hydrogels for antitumor phototherapy, offer a comprehensive overview of the latest advances in hydrogel-based phototherapy and its combination with other therapeutic modalities for tumor treatment, and discuss the current clinical status of hydrogel-based antitumor phototherapy.

The Promise of Nanoparticles-Based Radiotherapy in Cancer Treatment

Radiation has been utilized for a long time for the treatment of cancer patients. However, radiotherapy (RT) has many constraints, among which non-selectivity is the primary one. The implementation of nanoparticles (NPs) with RT not only localizes radiation in targeted tissue but also provides significant tumoricidal effect(s) compared to radiation alone. NPs can be functionalized with both biomolecules and therapeutic agents, and their combination significantly reduces the side effects of RT. NP-based RT destroys cancer cells through multiple mechanisms, including ROS generation, which in turn damages DNA and other cellular organelles, inhibiting of the DNA double-strand damage-repair system, obstructing of the cell cycle, regulating of the tumor microenvironment, and killing of cancer stem cells. Furthermore, such combined treatments overcome radioresistance and drug resistance to chemotherapy. Additionally, NP-based RT in combined treatments have shown synergistic therapeutic benefit(s) and enhanced the therapeutic window. Furthermore, a combination of phototherapy, i.e., photodynamic therapy and photothermal therapy with NP-based RT, not only reduces phototoxicity but also offers excellent therapeutic benefits. Moreover, using NPs with RT has shown promise in cancer treatment and shown excellent therapeutic outcomes in clinical trials. Therefore, extensive research in this field will pave the way toward improved RT in cancer treatment.

Catalytic nanotechnology of X-ray photodynamics for cancer treatments

Photodynamic therapy (PDT) has been applied in cancer treatment because of its high selectivity, low toxicity, and non-invasiveness. However, the limited penetration depth of the light still hampers from reaching deep-seated tumors. Considering the penetrating ability of high-energy radiotherapy, X-ray-induced photodynamic therapy (X-PDT) has evolved as an alternative to overcome tissue blocks. As the basic principle of X-PDT, X-rays stimulate the nanoparticles to emit scintillating or persistent luminescence and further activate the photosensitizers to generate reactive oxygen species (ROS), which would cause a series of molecular and cellular damages, immune response, and eventually break down the tumor tissue. In recent years, catalytic nanosystems with unique structures and functions have emerged that can enhance X-PDT therapeutic effects via an immune response. The anti-cancer effect of X-PDT is closely related to the following factors: energy conversion efficiency of the material, the radiation dose of X-rays, quantum yield of the material, tumor resistance, and biocompatibility. Based on the latest research in this field and the classical theories of nanoscience, this paper systematically elucidates the current development of the X-PDT and related immunotherapy, and highlights its broad prospects in medical applications, discussing the connection between fundamental science and clinical translation.

X-ray Activated Nanoplatforms for Deep Tissue Photodynamic Therapy

Photodynamic therapy (PDT), the use of light to excite photosensitive molecules whose electronic relaxation drives the production of highly cytotoxic reactive oxygen species (ROS), has proven an effective means of oncotherapy. However, its application has been severely constrained to superficial tissues and those readily accessed either endoscopically or laparoscopically, due to the intrinsic scattering and absorption of photons by intervening tissues. Recent advances in the design of nanoparticle-based X-ray scintillators and photosensitizers have enabled hybridization of these moieties into single nanocomposite particles. These nanoplatforms, when irradiated with diagnostic doses and energies of X-rays, produce large quantities of ROS and permit, for the first time, non-invasive deep tissue PDT of tumors with few of the therapeutic limitations or side effects of conventional PDT. In this review we examine the underlying principles and evolution of PDT: from its initial and still dominant use of light-activated, small molecule photosensitizers that passively accumulate in tumors, to its latest development of X-ray-activated, scintillator-photosensitizer hybrid nanoplatforms that actively target cancer biomarkers. Challenges and potential remedies for the clinical translation of these hybrid nanoplatforms and X-ray PDT are also presented.

Nanosensitizer-mediated unique dynamic therapy tactics for effective inhibition of deep tumors

X-ray and ultrasound waves are widely employed for diagnostic and therapeutic purposes in clinic. Recently, they have been demonstrated to be ideal excitation sources that activate sensitizers for the dynamic therapy of deep-seated tumors due to their excellent tissue penetration. Here, we focused on the recent progress in five years in the unique dynamic therapy strategies for the effective inhibition of deep tumors that activated by X-ray and ultrasound waves. The concepts, mechanisms, and typical nanosensitizers used as energy transducers are described as well as their applications in oncology. The future developments and potential challenges are also discussed. These unique therapeutic methods are expected to be developed as depth-independent, minimally invasive, and multifunctional strategies for the clinic treatment of various deep malignancies.

Recent Clinical and Preclinical Advances in External Stimuli-Responsive Therapies for Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) has long been one of the most prevalent cancers worldwide; even though treatments such as surgery, chemotherapy, radiotherapy and immunotherapy have been proven to benefit the patients and prolong their survival time, the overall five-year survival rate is still below 50%. Hence, the development of new therapies for better patient management is an urgent need. External stimuli-responsive therapies are emerging therapies with promising antitumor effects; therapies such as photodynamic (PDT) and photothermal therapies (PTT) have been tested clinically in late-stage HNSCC patients and have achieved promising outcomes, while the clinical translation of sonodynamic therapy (SDT), radiodynamic therapy (RDT), microwave dynamic/thermodynamic therapy, and magnetothermal/magnetodynamic therapy (MDT/MTT) still lag behind. In terms of preclinical studies, PDT and PTT are also the most extensively studied therapies. The designing of nanoparticles and combinatorial therapies of PDT and PTT can be referenced in designing other stimuli-responsive therapies in order to achieve better antitumor effects as well as less toxicity. In this review, we consolidate the advancements and limitations of various external stimuli-responsive therapies, as well as critically discuss the prospects of this type of therapies in HNSCC treatments.

Enhanced Photodynamic Therapy: A Review of Combined Energy Sources

Photodynamic therapy (PDT) has been used in recent years as a non-invasive treatment for cancer, due to the side effects of traditional treatments such as surgery, radiotherapy, and chemotherapy. This therapeutic technique requires a photosensitizer, light energy, and oxygen to produce reactive oxygen species (ROS) which mediate cellular toxicity. PDT is a useful non-invasive therapy for cancer treatment, but it has some limitations that need to be overcome, such as low-light-penetration depths, non-targeting photosensitizers, and tumor hypoxia. This review focuses on the latest innovative strategies based on the synergistic use of other energy sources, such as non-visible radiation of the electromagnetic spectrum (microwaves, infrared, and X-rays), ultrasound, and electric/magnetic fields, to overcome PDT limitations and enhance the therapeutic effect of PDT. The main principles, mechanisms, and crucial elements of PDT are also addressed.