Manipulate tumor hypoxia for improved photodynamic therapy using nanomaterials

Advances of functional nanomaterials as either therapeutic agents or delivery systems in the treatment of periodontitis

Periodontitis is a common chronic inflammatory disease primarily caused by pathogenic microorganisms in the oral cavity. Without appropriate treatments, it may lead to the gradual destruction of the supporting tissues of the teeth. While current treatments can alleviate symptoms, they still have limitations, particularly in eliminating pathogenic bacteria, promoting periodontal tissue regeneration, and avoiding antibiotic resistance. In recent years, functional nanomaterials have shown great potential in the treatment of periodontitis due to their unique physicochemical and biological properties. This review summarizes various functionalization strategies of nanomaterials and explores their potential applications in periodontitis treatment, including metal-based nanoparticles, carbon nanomaterials, polymeric nanoparticles, and exosomes. The mechanisms and advances in antibacterial effects, immune regulation, reactive oxygen species (ROS) scavenging, and bone tissue regeneration are discussed in detail. In addition, the challenges and future directions of applying nanomaterials in periodontitis therapy are also discussed.

Molecular engineering strategies for fabricating type-I mitochondria-targeted aggregation-induced emission photosensitizers for apoptosis-ferroptosis synergistically boosting photodynamic therapy

The precise distribution and subcellular localization of photosensitizers (PSs) play a crucial role in maximizing the utilization of reactive oxygen species (ROS) and enhancing photodynamic therapy (PDT). However, the therapeutic efficacy of PDT is significantly compromised by the hypoxic microenvironment, particularly in malignant tumors. To address these challenges, we designed and synthesized three donor-donor-π-bridge-acceptor (D-D-π-A) type aggregation-induced emission (AIE) PSs: TCM-OTs, TCM-OH, and TCPy-OH. By fine-tuning the acceptor and donor substituents, we successfully modulated organelle-targeting specificity and ROS generation to mitigate hypoxia-related limitations. Among these compounds, TCM-OH emerged as a highly promising PS, exhibiting selective mitochondrial targeting and efficient type-I ROS generation. To further enhance its pharmacological properties, we encapsulated each PS into DSPE-PEG2k to form nanoparticles (NPs). Notably, TCM-OH NPs facilitated the production of superoxide (•O2-) and hydroxyl radicals (•OH) within mitochondria, leading to mitochondrial dysfunction and subsequent cell death via a synergistic ferroptosis-apoptosis pathway under light irradiation. Both in vitro and in vivo experiments demonstrated the potent therapeutic efficacy of this strategy, with minimal toxicity, underscoring its potential for hypoxic cancer treatment. Overall, this study provides a rational design framework for developing potent type-I PSs with multimodal capabilities for biomedical applications.

Nanoparticles for Photodynamic Therapy of Breast Cancer: A Review of Recent Studies

Photodynamic therapy (PDT) is a therapeutic method based on the interaction between light and a photosensitizer. Supported by nanoparticles, this method represents a promising interdisciplinary approach for the treatment of many diseases. This article reviews the latest 2024 developments in the design and applications of nanoparticles dedicated to stand-alone PDT of breast cancer. Strategies to improve therapeutic efficacy by enhancing reactive oxygen species (ROS) production, precise delivery of photosensitizers and their stabilization in the systemic circulation are discussed, among others. Results from preclinical studies indicate significant improvements in therapeutic efficacy, including inhibition of tumor growth, reduction in metastasis and improvement of the immune microenvironment. The potential of these technologies to expand PDT applications in medicine and the need for further clinical trials to confirm their safety and efficacy are highlighted.

New horizons for the therapeutic application of nanozymes in cancer treatment

The advent of nanozymes has revolutionized approaches to cancer diagnosis and therapy, introducing innovative strategies that address the limitations of conventional treatments. Nanozyme nanostructures with enzyme-mimicking catalytic abilities exhibit exceptional stability, biocompatibility, and customizable functions, positioning them as promising tools for cancer theranostics. By emulating natural enzyme reactions, nanozymes can selectively target and eradicate cancer cells, minimizing harm to adjacent healthy tissues. Nanozymes can also be functionalized with specific targeting ligands, allowing for the precise delivery and regulated release of therapeutic agents, improving treatment effectiveness and reducing adverse effects. However, issues such as biocompatibility, selectivity, and regulatory compliance remain critical challenges for the clinical application of nanozymes. This review provides an overview of nanozymes, highlighting their unique properties, various classifications, catalytic activities, and diverse applications in cancer treatments. The strategic oncological deployment of nanozymes could profoundly impact future advancements in personalized medicine, highlighting recent progress and prospective directions in enzyme-mimetic approaches for cancer treatment. This review summarizes an overview of nanozymes, highlighting their unique properties, various classifications, catalytic activities, and diverse applications in cancer treatments.

A novel cyanine photosensitizer for sequential dual-site GSH depletion and ROS-potentiated cancer photodynamic therapy

The efficacy of photodynamic therapy (PDT) is often limited by the reductive microenvironment in tumor cells due to the high level of glutathione (GSH) and glutathione peroxidase 4 (GPX4), which maintain redox homeostasis. Therefore, designing a GSH-responsive photosensitizer that depletes intracellular GSH is a promising strategy to enhance PDT selectivity and efficacy. Herein, we present a GSH-selective sequentially responsive theranostic photosensitizer, Cy-Res. This cyanine agent targeting mitochondria effectively depletes two GSH molecules, leading to the generation of abundant ROS and exacerbating oxidative stress. Additionally, it achieves an 80-fold fluorescence enhancement upon response to GSH, enabling selective imaging of tumor cells. By mitigating GSH's impact on PDT, Cy-ResNPs achieves synergistic and efficient PDT treatment of invasive melanoma under low-power irradiation (808 nm, 80 mW/cm2). The inhibitory processes downregulate GPX4, increase apoptotic proteins like Bax, and promote mixed cell death involving both ferroptosis and apoptosis. Overall, this study offers new insights and strategies for the development of GSH-responsive theranostic agents, highlighting their potential for application in tumor diagnosis and therapy.

Recent advances in reactive oxygen species (ROS)-responsive drug delivery systems for photodynamic therapy of cancer

Reactive oxygen species (ROS)-responsive drug delivery systems (DDSs) have garnered significant attention in cancer research because of their potential for precise spatiotemporal drug release tailored to high ROS levels within tumors. Despite the challenges posed by ROS distribution heterogeneity and endogenous supply constraints, this review highlights the strategic alliance of ROS-responsive DDSs with photodynamic therapy (PDT), enabling selective drug delivery and leveraging PDT-induced ROS for enhanced therapeutic efficacy. This review delves into the biological importance of ROS in cancer progression and treatment. We elucidate in detail the operational mechanisms of ROS-responsive linkers, including thioether, thioketal, selenide, diselencide, telluride and aryl boronic acids/esters, as well as the latest developments in ROS-responsive nanomedicines that integrate with PDT strategies. These insights are intended to inspire the design of innovative ROS-responsive nanocarriers for enhanced cancer PDT.

EGFR-targeting oxygen-saturated nanophotosensitizers for orchestrating multifaceted antitumor responses by counteracting immunosuppressive milieu

High Epidermal growth factor receptor (EGFR) in Cutaneous Squamous Cell Carcinoma (cSCC) is associated with poor prognosis and advanced metastatic stages, severely impeding the efficacy of EGFR-targeting immunotherapy. This is commonly attributed to the combinatory outcomes of hypoxic tumor microenvironment (TME) and immunosuppressive effector cells together. Herein, a novel paradigm of EGFR-targeting oxygen-saturated nanophotosensitizers, designated as CHPFN-O2, has been specifically tailored to mitigate tumor hypoxia in EGFR-positive cSCC and achieve Cetuximab (CTX)-mediated immunotherapy (CIT). The conjugated CTX in CHPFN-O2 serves to initiate immune responses by recruiting Fc receptor (FcR)-expressing immune effector cells towards tumor cells, thereby eliciting antibody-dependent cellular phagocytosis (ADCP), antibody-dependent cellular trogocytosis (ADCT) and antibody-dependent cellular cytotoxicity (ADCC). Besides, CHPFN-O2 can engender a shift from a tumor-friendly to a tumor-hostile one through improved tumor oxygenation, contributing to oxygen-elevated photodynamic therapy (oxPDT). Notably, the combination of oxPDT and CIT eventually promotes T-cell-mediated antitumor activity and successfully inhibits the growth of EGFR-expressing cSCC with good safety profiles. This comprehensive oxPDT/CIT integration aims not only to enhance therapeutic efficacy against EGFRhigh cSCC but also to extend its applicability to other EGFRhigh malignancies, thus delineating a new avenue for the highly efficient synergistic treatment of EGFR-expressing malignancies.

Light enhanced cytotoxicity and antitumoral effect of a ruthenium-based photosensitizer inspired from natural alkaloids

In this work, we report on the synthesis and properties of a new sensitizer for photodynamic therapy applications, constituted by a ruthenium(ii) complex (1) featuring a ligand inspired from natural isoquinoline alkaloids. The spectroscopic analysis revealed that 1 is characterized by an intense red emission (λ em = 620 nm, Φ = 0.17) when excited at 550 nm, a low energy radiation warranting for a safe therapeutic approach. The phototoxicity of 1 on human breast cancer (Hs578T) and melanoma (A375) cell lines was assessed after irradiation using a LED lamp (525 nm, total fluence 10 J cm-2). In vitro biological assays indicated that the cytotoxicity of 1 was significantly enhanced by light reaching IC50 values below the micromolar threshold. The cell damage induced by 1 proved to be strictly connected with the overproduction of reactive oxygen species (ROS) responsible for mitochondrial dysfunction leading to the activation of caspases and then to apoptosis, and for DNA photocleavage leading to cell cycle arrest.

Towards chlorocytes for therapeutic intravascular photosynthesis

Aerobic metabolism relies on external oxygen production through photosynthesis and its subsequent transport into each cell of the body via the cardiorespiratory system. This mechanism has successfully evolved over millions of years, enabling animals to inhabit most environments on Earth. However, the insufficient oxygen supply leads to several clinical problems, ranging from non-healing wounds to tumor resistance to therapy. Given that photosynthetic microorganisms are capable of producing oxygen and removing carbon dioxide from the environment, over the last decade, several groups worldwide have proposed their potential use as an alternative tissue oxygenation approach. While most studies have demonstrated safety and efficacy after local tissue administration, recent studies have also suggested that systemic administration could trigger intravascular photosynthesis. If successful, the development of a new generation of circulating cells, known as chlorocytes, may partially replace the role of erythrocytes in gas exchange within the body, without relying on external supply and vascular flow. This work reviews the existing literature on local and systemic administration of photosynthetic microorganisms, highlighting the main challenges in the field and potential solutions to unleash the enormous potential clinical impact of chlorocytes and intravascular photosynthesis. KEY POINTS: • Circulating photosynthetic microorganisms could deliver oxygen to tissues • Microalgae and cyanobacteria have shown safety and efficacy for oxygen delivery • Several key challenges need to be addressed for the clinical success of chlorocytes.

Effect of oxygen generating nanozymes on indocyanine green and IR 820 mediated phototherapy against oral cancer

The hypoxic environment within a solid tumor is a limitation to the effectiveness of photodynamic therapy. Here, we demonstrate the use of oxygen generating nanozymes (CeO2, Fe3O4, and MnO2) to improve the photodynamic effect. The optimized combination of process parameters for irradiation was obtained using the Box Behnken experimental design. Indocyanine green, IR 820, and their different combinations with oxygen generators were studied for their effect on oral carcinoma. Dynamic light scattering technique showed the average particle size of CeO2, MnO2, and Fe3O4 to be 211 ± 16, and 157 ± 28, 143 ± 19 nm with PDI of 0.23, 0.28 and 0.20 and a zeta potential of -2.6 ± 0.45, -2.4 ± 0.60 and  -6.1 ± 0.23 mV, respectively. The formation of metal oxides was confirmed using UV-visible, FTIR, and X-ray photon spectroscopies. The amount of dissolved oxygen produced by CeO2, MnO2, and Fe3O4 in the presence of H2O2 within 2 min was 1.7 ± 0.15, 1.7 ± 0.16, and 1.4 ± 0.12 mg/l, respectively. Growth inhibition studies in the FaDu oral carcinoma spheroid model showed a significant (P < 0.05) increase in growth reduction from 81 ± 2.9 and 88 ± 2.1% to 97 ± 1.2 and 99 ± 1.0% for ICG and IR 820, respectively, after irradiation (808 nm laser, 1 W/cm2, 5 min) in the presence of CeO2 (25 μg/ml). In conclusion, oxygen-generating nanozymes can improve the photodynamic effect of ICG and IR 820.

Nanosized Porphyrin-Containing Covalent Organic Polymer to Enhance Ferroptosis in Photodynamic Treatment of Tumor Cells via Glutathione Depletion

A porphyrin-containing nanoscale covalent organic polymer (COP) was fabricated from 5,10,15,20-tetra(4-carboxyphenyl)porphyrin (TCPP) and cystamine via an acylation reaction. On the one hand, TCPP can induce tumor cell death by laser irradiation. Due to the presence of disulfide bonds of cystamine which can react with glutathione, it exhibits depletion of glutathione and accumulation of peroxides in tumor cells. Ultimately by the hyaluronic acid to encapsulate the COP to get S-COP@HA, the nanoparticle with a size of 168.6 nm also exhibits good tumor accumulation and biosafety. Significant inhibition of tumor cell growth was observed after two consecutive doses of S-COP@HA at relatively low laser densities. This combination therapy was proved to reduce the level of reduced glutathione in tumor cells, where ferroptosis occurs after photodynamic treatment. Overall, this study presents a potent, good therapeutic option for the effective enhancement of photodynamic therapy by glutathione depletion.

Abscopal effect: from a rare phenomenon to a new frontier in cancer therapy

Radiotherapy (RT) controls local lesions, meantime it has the capability to induce systemic response to inhibit distant, metastatic, non-radiated tumors, which is referred to as the "abscopal effect". It is widely recognized that radiotherapy can stimulate systemic immune response. This provides a compelling theoretical basis for the combination of immune therapy combined with radiotherapy(iRT). Indeed, this phenomenon has also been observed in clinical treatment, bringing significant clinical benefits to patients, and a series of basic studies are underway to amplify this effect. However, the molecular mechanisms of immune response induced by RT, determination of the optimal treatment regimen for iRT, and how to amplify the abscopal effect. In order to amplify and utilize this effect in clinical management, these key issues require to be well addressed; In this review, we comprehensively summarize the growing consensus and emphasize the emerging limitations of enhancing the abscopal effect with radiotherapy or immunotherapy. Finally, we discuss the prospects and barriers to the current clinical translational applications.

Cyanine dyes in the mitochondria-targeting photodynamic and photothermal therapy

Mitochondrial dysregulation plays a significant role in the carcinogenesis. On the other hand, its destabilization strongly represses the viability and metastatic potential of cancer cells. Photodynamic and photothermal therapies (PDT and PTT) target mitochondria effectively, providing innovative and non-invasive anticancer therapeutic modalities. Cyanine dyes, with strong mitochondrial selectivity, show significant potential in enhancing PDT and PTT. The potential and limitations of cyanine dyes for mitochondrial PDT and PTT are discussed, along with their applications in combination therapies, theranostic techniques, and optimal delivery systems. Additionally, novel approaches for sonodynamic therapy using photoactive cyanine dyes are presented, highlighting advances in cancer treatment.

Photodynamic therapy for cancer: mechanisms, photosensitizers, nanocarriers, and clinical studies

Photodynamic therapy (PDT) is a temporally and spatially precisely controllable, noninvasive, and potentially highly efficient method of phototherapy. The three components of PDT primarily include photosensitizers, oxygen, and light. PDT employs specific wavelengths of light to active photosensitizers at the tumor site, generating reactive oxygen species that are fatal to tumor cells. Nevertheless, traditional photosensitizers have disadvantages such as poor water solubility, severe oxygen-dependency, and low targetability, and the light is difficult to penetrate the deep tumor tissue, which remains the toughest task in the application of PDT in the clinic. Here, we systematically summarize the development and the molecular mechanisms of photosensitizers, and the challenges of PDT in tumor management, highlighting the advantages of nanocarriers-based PDT against cancer. The development of third generation photosensitizers has opened up new horizons in PDT, and the cooperation between nanocarriers and PDT has attained satisfactory achievements. Finally, the clinical studies of PDT are discussed. Overall, we present an overview and our perspective of PDT in the field of tumor management, and we believe this work will provide a new insight into tumor-based PDT.

Enhancing cancer immunotherapy with photodynamic therapy and nanoparticle: making tumor microenvironment hotter to make immunotherapeutic work better

Cancer immunotherapy has made tremendous advancements in treating various malignancies. The biggest hurdle to successful immunotherapy would be the immunosuppressive tumor microenvironment (TME) and low immunogenicity of cancer cells. To make immunotherapy successful, the 'cold' TME must be converted to 'hot' immunostimulatory status to activate residual host immune responses. To this end, the immunosuppressive equilibrium in TME should be broken, and immunogenic cancer cell death ought to be induced to stimulate tumor-killing immune cells appropriately. Photodynamic therapy (PDT) is an efficient way of inducing immunogenic cell death (ICD) of cancer cells and disrupting immune-restrictive tumor tissues. PDT would trigger a chain reaction that would make the TME 'hot' and have ICD-induced tumor antigens presented to immune cells. In principle, the strategic combination of PDT and immunotherapy would synergize to enhance therapeutic outcomes in many intractable tumors. Novel technologies employing nanocarriers were developed to deliver photosensitizers and immunotherapeutic to TME efficiently. New-generation nanomedicines have been developed for PDT immunotherapy in recent years, which will accelerate clinical applications.

Salvianolic acid B as a potent nano-agent for enhanced ALA-PDT of oral cancer and leukoplakia cells

BACKGROUND

Photodynamic therapy (PDT) relies on the light activation of a photosensitizers to generate reactive oxygen species such as singlet oxygen, but its effect on cancer therapy is limited dramatically by hypoxia in the tumor microenvironment.

OBJECTIVES

To determine the potential of a nano-photosensitizer loaded salvianolic acid B (SalB) and 5-aminolevulinic acid (ALA) for enhancing the efficacy of PDT in oral squamous cell carcinoma Cal27 cells and leukoplakia Leuk1 cells.

RESULTS

Singlet oxygen sensor green (SOSG) assay showed that nano-SalB-ALA generated higher levels of singlet oxygen, compared to nano-SalB and nano-ALA. Cellular uptake assay showed that nano-SalB-ALA effectively absorbed by Leuk1 cells. Importantly, cell counting kit-8 and flow cytometry revealed that PDT with nano-SalB-ALA effectively inhibited the viability and induced the apoptosis of Cal27 and Leuk1 cells, respectively. Moreover, the tumor xenograft study revealed that PDT with nano-SalB-ALA had a stronger inhibitory effect on tumor growth of nude mice, compared to control groups.

CONCLUSIONS

The novel photosensitizer nano-SalB-ALA remarkably enhanced the efficacy of PDT by improving singlet oxygen production, inhibiting cell proliferation, promoting cell apoptosis, and suppressing tumor growth. These suggest PDT with nano-SalB-ALA could be a clinically significant and potent treatment for oral cancer and leukoplakia.

pH-responsive Photinia glabra-zinc oxide-protoporphyrin IX nanoconjugates with enhanced cellular uptake for photodynamic therapy towards cancer cells

Background: Photodynamic therapy (PDT) of cancer has been limited by the poor solubility of most photosensitizers, use of high drug dosages, and the pH difference between the tumor tissue microenvironment (slightly acidic) and the bloodstream. These affect cellular uptake, selectivity and singlet oxygen generation. Materials & methods: We formulated Photinia glabra-green synthesized zinc oxide-protoporphyrin IX (PG-ZnO-PP) nanoconjugates by conjugating the ZnO nanoparticles enriched with amino groups and PP. Results: PG-ZnO-PP nanoconjugates showed higher rate of reactive oxygen species generation, improved cellular uptake in the acidic pH and lower IC50 toward Eca-109 cells for PDT. Conclusion: PG-ZnO-PP nanoconjugates are a potential solution to reducing drug dosage of PP through improved drug uptake, for enhanced targetability and reduced skin photosensitivity with improved PDT efficacy.

Cascade strategy for glucose oxidase-based synergistic cancer therapy using nanomaterials

Nanomaterial-based cancer therapy faces significant limitations due to the complex nature of the tumor microenvironment (TME). Starvation therapy is an emerging therapeutic approach that targets tumor cell metabolism using glucose oxidase (GOx). Importantly, it can provide a material or environmental foundation for other diverse therapeutic methods by manipulating the properties of the TME, such as acidity, hydrogen peroxide (H2O2) levels, and hypoxia degree. In recent years, this cascade strategy has been extensively applied in nanoplatforms for ongoing synergetic therapy and still holds undeniable potential. However, only a few review articles comprehensively elucidate the rational designs of nanoplatforms for synergetic therapeutic regimens revolving around the conception of the cascade strategy. Therefore, this review focuses on innovative cascade strategies for GOx-based synergetic therapy from representative paradigms to state-of-the-art reports to provide an instructive, comprehensive, and insightful reference for readers. Thereafter, we discuss the remaining challenges and offer a critical perspective on the further advancement of GOx-facilitated cancer treatment toward clinical translation.

A supramolecular nanoplatform for imaging-guided phototherapies via hypoxia tumour microenvironment remodeling

Photodynamic therapy (PDT) has emerged as an invasive and promising antitumour treatment, however, the hypoxia in deep tumour tissues and the poor water-solubility of photosensitizers as bottlenecks greatly hinder PDT efficiency. Herein, a tumour microenvironment (TME) activated supramolecular nanoplatform consisting of the pillar[5]arene-based amphiphilic polymer POPD, the phototherapeutic agent Cy7-CN, respiratory medication atovaquone (ATO) and chemotherapeutic drug pyridinyl camptothecin (CPT-Py) was constructed for imaging-guided hypoxia-ameliorated phototherapies. Owing to host-guest interaction, the photochemical and photophysical properties of cyanine were improved exceedingly due to the suppression of π-π stacking. Triggered by the acidic microenvironment in tumour sites, the supramolecular nanoplatform would dissociate and release CPT-Py and ATO which inhibits mitochondria-associated oxidative phosphorylation (OXPHOS) and encourages more oxygen to be used in enhanced PDT. In vitro and in vivo studies verified that the rational combination of ATO-enhanced PDT and PTT overcame the disadvantages of single phototherapy and formed mutual promotion, and simultaneously sensitized chemotherapeutic drugs, which resulted in high tumour inhibition. It is hoped that the supramolecular nanoplatform could shed light on the development of phototherapeutic agents.

Thiocarbonyl Derivatives of Natural Chlorins: Synthesis Using Lawesson's Reagent and a Study of Their Properties

The development of sulfur-containing pharmaceutical compounds is important in the advancement of medicinal chemistry. Photosensitizers (PS) that acquire new properties upon incorporation of sulfur-containing groups or individual sulfur atoms into their structure are not neglected, either. In this work, a synthesis of sulfur-containing derivatives of natural chlorophyll a using Lawesson's reagent was optimized. Thiocarbonyl chlorins were shown to have a significant bathochromic shift in the absorption and fluorescence bands. The feasibility of functionalizing the thiocarbonyl group at the macrocycle periphery by formation of a Pt(II) metal complex in the chemotherapeutic agent cisplatin was shown. The chemical stability of the resulting conjugate in aqueous solution was studied, and it was found to possess a high cytotoxic activity against sarcoma S37 tumor cells that results from the combined photodynamic and chemotherapeutic effect on these cells.

"Domino" cascade reactor based on DNA hydrogel for synergistic treatment of malignant tumor

The action pathways of starvation therapy and photodynamic therapy (PDT) do not exist in isolation and are usually related to tumor cell metabolism and immune regulation, which are of great significance in the treatment of malignant tumors. Here, a cancer-targeted "domino" cascade reactor is constructed for synergistic starvation therapy and amplifies photodynamic therapy by assembling hemin and glucose oxidase (GOx) into DNA hydrogel load with hypoxia-inducible factor 1α (HIF-1α) and photosensitizer chlorin e6 (Ce6). The cascade reactor has excellent biocompatibility and tumor targeting, which promotes PDT by reducing HIF-1α. At the same time, the G-quadruplex of AS1411 combined with hemin (AH) catalyzes the generation of oxygen from hydrogen peroxide to further improve the efficiency of PDT. The synergistic therapeutic effect of the cascade reactor is evaluated through in vivo and in vitro experiments, indicating that this cascade reactor has great potential advantages in the synergistic treatment of cancer.