Recent Strategies to Address Hypoxic Tumor Environments in Photodynamic Therapy

Oxygen-Releasing Nanodroplets Relieve Intratumoral Hypoxia and Potentiate Photodynamic Therapy in 3D Head and Neck Cancer Spheroids

Hypoxia in solid tumors, including head and neck cancer (HNC), contributes to treatment resistance, aggressive tumor phenotypes, and poorer clinical outcomes. Perfluorocarbon nanodroplets have emerged as promising drugs to alleviate tumor hypoxia. These versatile nanocarriers can also encapsulate and deliver various therapeutic agents, offering a multifunctional approach to cancer treatment. However, a detailed characterization of hypoxia alleviation, particularly the duration of hypoxia treatment drug residence, has not been thoroughly investigated. In this study, we developed and characterized perfluoropentane nanodroplets (PFP NDs) for the codelivery of oxygen and the photoactivatable drug benzoporphyrin derivative (BPD) to hypoxic HNC spheroids. The PFP NDs exhibited excellent stability, efficient oxygen loading/release, and biocompatibility. Using 3D multicellular tumor spheroids of FaDu and SCC9 HNC cells, we investigated the spatiotemporal dynamics of hypoxia within these spheroids and the ability of oxygenated PFP NDs to alleviate hypoxia. Our results showed that oxygen-loaded PFP NDs effectively penetrated the core of tumor spheroids, significantly reducing hypoxia, as evidenced by the downregulation of hypoxia-inducible factors HIF-1α and HIF-2α. Importantly, we demonstrated sustained hypoxia alleviation for up to 3 h post-treatment with PFP NDs. BPD-loaded PFP NDs successfully delivered the photosensitizer into the spheroid core in a time-dependent manner. Furthermore, we evaluated the efficacy of oxygen-dependent treatment modality, namely, photodynamic therapy (PDT) with BPD and oxygen-loaded PFP NDs compared to free BPD. The NDs formulation exhibited superior PDT outcomes, which were attributed to improved oxygen availability during the treatment. This study provides comprehensive evidence for the potential of PFP NDs as a codelivery platform to overcome hypoxia-mediated treatment resistance and enhance PDT efficacy in HNC. Our findings pave the way for further investigation of this promising approach in more complex in vivo models, potentially leading to improved therapeutic strategies for hypoxic solid tumors.

Hybrid Nanoplatforms Based on Photosensitizers and Metal/Covalent Organic Frameworks for Improved Cancer Synergistic Treatment Nano-Delivery Systems

Researchers have extensively investigated photosensitizer (PS) derivatives for various applications due to their superior photophysical and electrochemical properties. However, inherent problems, such as instability and self-quenching under physiological conditions, limit their biological applications. Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) represent two relatively new material types. These materials have high surface areas and permanent porosity, and they show a tremendous deal of potential for applications like these. This review summarizes key synthesis processes and highlights recent advancements in integrating PS-based COF and MOF nanocarriers for biomedical applications while addressing potential obstacles and prospects.

Light-based technologies in immunotherapy: advances, mechanisms and applications

Light-based immunotherapy uses specific wavelengths of light to activate or modulate immune responses. It primarily employs two mechanisms: direct activation of immune cells and indirect modulation of the tumor microenvironment (TME). Several light-based technologies are under investigation or clinical use in immunotherapy, including photodynamic immunotherapy (PDIT) and photothermal therapy (PTT). Optogenetic tools have the potential to precisely control T-cell receptor activation, cytokine release, or the activity of other immune effector cells. Light-based technologies present innovative opportunities within the realm of immunotherapy. The ability to precisely regulate immune cell activation via optogenetics, alongside the improved targeting of cancer cells through photoimmunotherapy, signifies a transformative shift in our strategies for immune modulation. Although many of these technologies remain in the experimental stage for various applications, initial findings are encouraging, especially concerning cancer treatment and immune modulation. Continued research and clinical trials are essential to fully harness the capabilities of light technology in the context of immune cell therapy.

Copper-Based biomaterials for anti-tumor therapy: Recent advances and perspectives

Copper, an essential trace element, is integral to numerous metabolic pathways across biological systems. In recent years, copper-based biomaterials have garnered significant interest due to their superior biocompatibility and multifaceted functionalities, particularly in the treatment of malignancies such as sarcomas and cancers. On the one hand, these copper-based materials serve as efficient carriers for a range of therapeutic agents, including chemotherapeutic drugs, small molecule inhibitors, and antibodies, allowing them for precise delivery and controlled release triggered by specific modifications and stimuli. On the other hand, they can induce cell death through mechanisms such as ferroptosis, cuproptosis, apoptosis, and pyroptosis, or inhibit the proliferation and invasion of cancer cells via their outstanding properties. Furthermore, advanced design approaches enable these materials to support tumor imaging and immune activation. Despite this progress, the full scope of their functional capabilities remains to be fully elucidated. This review provides an overview of the anti-tumor functions, underlying mechanisms, and design strategies of copper-based biomaterials, along with their advantages and limitations. The aim is to provide insights into the design, study, and development of novel multifunctional biomaterials, with the ultimate goal of accelerating the clinical application of copper-based nanomaterials in cancer therapy. STATEMENT OF SIGNIFICANCE: This study explores the groundbreaking potential of copper-based biomaterials in cancer therapy, uniquely combining biocompatibility with diverse therapeutic mechanisms such as targeted drug delivery and inhibition of cancer cells through specific cell death pathways. By enhancing tumor imaging and immune activation, copper-based nanomaterials have opened new avenues for cancer treatment. This review examines these multifunctional biomaterials, highlighting their advantages and current limitations while addressing gaps in existing research. The findings aim to accelerate clinical applications of these materials in the field of oncology, providing valuable insights for the design of next-generation copper-based therapies. Therefore, this work is highly relevant to researchers and practitioners focused on innovative cancer treatments.

Blazing Carbon Dots: Unfolding its Luminescence Mechanism to Photoinduced Biomedical Applications

Carbon dots (CDs) are carbon-based nanomaterials that have garnered immense attention owing to their exceptional photophysical and optoelectronic properties. They have been employed extensively for biomedical imaging and phototherapy due to their superb water dispersibility, low toxicity, outstanding biocompatibility, and exceptional tissue permeability. This review summarizes the structural classification of CDs, the classification of CDs according to precursor sources, and the luminescence mechanism of CDs. The modification in CDs via various doping routes is comprehensively reviewed, and the effect of such alterations on their photophysical properties, such as absorbance, photoluminescence (PL), and reactive oxygen species generation ability, is also highlighted. This review strives to summarize the role of CDs in cellular imaging and fluorescence lifetime imaging for cellular metabolism. Subsequently, recent advancements and the future potential of CDs as nanotheranostic agents have been discussed. Herein, we have discussed the role of CDs in photothermal, photodynamic, and synergistic therapy of anticancer, antiviral, and antibacterial applications. The overall summary of the review highlights the prospects of CD-based research in bioimaging and biomedicine.

AQ4N nanocomposites for hypoxia-associated tumor combination therapy

Hypoxia in solid tumors increases their invasiveness and resistance to therapy, presenting a formidable obstacle in tumor therapy. The hypoxia prodrug banoxantrone (AQ4N) undergoes conversion into its topoisomerase II inhibitor form AQ4 under hypoxic conditions, which inhibits tumor cells while leaving normal cells unharmed. Numerous studies have found that AQ4N significantly enhances the tumor effect while minimizing toxicity to normal tissues when combined with other drugs or therapeutic approaches. Thus, to maximize AQ4N's effectiveness, co-delivery of AQ4N with other therapeutic agents to the tumor site is paramount, leading to the development of multifunctional multicomponent AQ4N nanocomposites thereby emerging as promising candidates for combination therapy in tumor treatment. However, currently there is a lack of systematic analysis and reviews focusing on AQ4N. Herein, this review provides a comprehensive retrospect and analysis of the recent advancements in AQ4N nanocomposites. Specifically, we discuss the synergistic effects observed when AQ4N is combined with chemotherapeutic drugs, radiotherapy, phototherapy, starvation, sonodynamic therapy and immunotherapy in preclinical models. Moreover, the advantages, limitations, and future perspectives of different AQ4N nanocomposites are highlighted, providing researchers from diverse fields with novel insights into tumor treatment.

Photodynamic Therapy Induced Mitochondrial Targeting Strategies for Cancer Treatment: Emerging Trends and Insights

The perpetuity of cancer prevalence at a global level calls for development of novel therapeutic approaches with improved targetability and reduced adverse effects. Conventional cancer treatments have a multitude of limitations such as nonselectivity, invasive nature, and severe adverse effects. Chemotherapy is also losing its efficacy because of the development of multidrug resistance in the majority of cancers. To address these issues, selective targeting-based approaches are being explored for an effective cancer treatment. Mitochondria, being the moderator of a majority of crucial cellular pathways like metabolism, apoptosis, and reactive oxygen species (ROS) homeostasis, are an effective targeting site. Mitochondria-targeted photodynamic therapy (PDT) has arisen as a potential approach in this endeavor. By designing photosensitizers (PSs) that preferentially accumulate in the mitochondria, PDT offers a localized technique to induce cytotoxicity in cancer cells. In this review, we intend to explore the crucial principles and challenges associated with mitochondria-targeted PDT, including variability in mitochondrial function, mitochondria-specific PSs, targeted nanocarrier-based monotherapy, and combination therapies. The hurdles faced by this emerging strategy with respect to safety, optimization, clinical translation, and scalability are also discussed. Nonetheless, mitochondria-targeted PDT exhibits a significant capacity in cancer treatment, especially in combination with other therapeutic modalities. With perpetual research and technological advancements, this treatment strategy is a great addition to the arsenal of cancer treatment options, providing better tumor targetability while reducing the damage to surrounding healthy tissues. This review emphasizes the current status of mitochondria-targeted PDT, limitations, and future prospects in its pursuit of safe and efficacious cancer therapy.

Photodynamic Therapy for Eye, Ear, Laryngeal Area, and Nasal and Oral Cavity Diseases: A Review

Photodynamic therapy (PDT) has emerged as a promising modality for the treatment of various diseases. This non-invasive approach utilizes photosensitizing agents and light to selectively target and destroy abnormal cells, providing a valuable alternative to traditional treatments. Research studies have explored the application of PDT in different areas of the head. Research is focusing on a growing number of new developments and treatments for cancer. One of these methods is PDT. Photodynamic therapy is now a revolutionary, progressive method of cancer therapy. A very important feature of PDT is that cells cannot become immune to singlet oxygen. With this therapy, patients can avoid lengthy and costly surgeries. PDT therapy is referred to as a safe and highly selective therapy. These studies collectively highlight the potential of PDT as a valuable therapeutic option in treating the head area. As research in this field progresses, PDT may become increasingly integrated into the clinical management of these conditions, offering a balance between effectiveness and minimal invasiveness.

Current Advances on Nanomaterials Interfering with Lactate Metabolism for Tumor Therapy

Increasing numbers of studies have shown that tumor cells prefer fermentative glycolysis over oxidative phosphorylation to provide a vast amount of energy for fast proliferation even under oxygen-sufficient conditions. This metabolic alteration not only favors tumor cell progression and metastasis but also increases lactate accumulation in solid tumors. In addition to serving as a byproduct of glycolytic tumor cells, lactate also plays a central role in the construction of acidic and immunosuppressive tumor microenvironment, resulting in therapeutic tolerance. Recently, targeted drug delivery and inherent therapeutic properties of nanomaterials have attracted great attention, and research on modulating lactate metabolism based on nanomaterials to enhance antitumor therapy has exploded. In this review, the advanced tumor therapy strategies based on nanomaterials that interfere with lactate metabolism are discussed, including inhibiting lactate anabolism, promoting lactate catabolism, and disrupting the "lactate shuttle". Furthermore, recent advances in combining lactate metabolism modulation with other therapies, including chemotherapy, immunotherapy, photothermal therapy, and reactive oxygen species-related therapies, etc., which have achieved cooperatively enhanced therapeutic outcomes, are summarized. Finally, foreseeable challenges and prospective developments are also reviewed for the future development of this field.

Bacterial outer membrane vesicles as drug delivery carrier for photodynamic anticancer therapy

Photodynamic Therapy (PDT) is an effective tumor treatment strategy that not only induces photocytotoxicity to kill tumor cells directly but also activates the immune system in the body to generate tumor-specific immunity, preventing cancer metastasis and recurrence. However, some limitations of PDT limit the therapeutic efficacy in deep tumors. Previous studies have used different types of nanoparticles (NPs) as drug carriers of photosensitizers (PSs) to overcome the shortcomings of PDT and improve therapeutic efficacy. Among them, bacterial outer membrane vesicles (OMVs) have natural advantages as carriers for PS delivery. In addition to the targeted delivery of PSs into tumor cells, their unique immunogenicity helps them to serve as immune adjuvants to enhance the PDT-induced immune effect, providing new ideas for photodynamic anticancer therapy. Therefore, in this review, we will introduce the biogenesis and anticancer functions of OMVs and the research on them as drug delivery carriers in PDT. Finally, we also discuss the challenges and prospects of OMVs as a versatile drug delivery carrier for photodynamic anticancer therapy.

Platinum based theranostics nanoplatforms for antitumor applications

Platinum (Pt) based nanoplatforms are biocompatible nanoagents with photothermal antitumor performance, while exhibiting excellent radiotherapy sensitization properties. Pt-nanoplatforms have extensive research prospects in the realm of cancer treatment due to their highly selective and minimally invasive treatment mode with low damage, and integrated diagnosis and treatment with image monitoring and collaborative drug delivery. Platinum based anticancer chemotherapeutic drugs can kill tumor cells by damaging DNA through chemotherapy. Meanwhile, Pt-nanoplatforms also have good electrocatalytic activity, which can mediate novel electrodynamic therapy. Simultaneously, Pt(II) based compounds also have potential as photosensitizers in photodynamic therapy for malignant tumors. Pt-nanoplatforms can also modulate the immunosuppressive environment and synergistically ablate tumor cells in combination with immune checkpoint inhibitors. This article reviews the research progress of platinum based nanoplatforms in new technologies for cancer therapy, starting from widely representative examples of platinum based nanoplatforms in chemotherapy, electrodynamic therapy, photodynamic therapy, photothermal therapy, and immunotherapy. Finally, multimodal imaging techniques of platinum based nanoplatforms for biomedical diagnosis are briefly discussed.

NIR diagnostic imaging of triple-negative breast cancer and its lymph node metastasis for high-efficiency hypoxia-activated multimodal therapy

BACKGROUND

Triple-negative breast cancer (TNBC) possesses special biological behavior and clinicopathological characteristics, which is highly invasive and propensity to metastasize to lymph nodes, leading to a worse prognosis than other types of breast cancer. Thus, the development of an effective therapeutic method is significant to improve the survival rate of TNBC patients.

RESULTS

In this work, a liposome-based theranostic nanosystem (ILA@Lip) was successfully prepared by simultaneously encapsulating IR 780 as the photosensitizer and lenvatinib as an anti-angiogenic agent, together with banoxantrone (AQ4N) molecule as the hypoxia-activated prodrug. The ILA@Lip can be applied for the near-infrared (NIR) fluorescence diagnostic imaging of TNBC and its lymph node metastasis for multimodal therapy. Lenvatinib in ILA@Lip can inhibit angiogenesis by cutting oxygen supply, thereby leading to enhanced hypoxia levels. Meanwhile, large amounts of reactive oxygen species (ROS) were produced while IR 780 was irradiated by an 808 nm laser, which also rapidly exhausted oxygen in tumor cells to worsen tumor hypoxia. Through creating an extremely hypoxic in TNBC, the conversion of non-toxic AQ4N to toxic AQ4 was much more efficiency for hypoxia-activated chemotherapy. Cytotoxicity assay of ILA@Lip indicated excellent biocompatibility with normal cells and tissues, but showed high toxicity in hypoxic breast cancer cells. Also, the in vivo tumors treated by the ILA@Lip with laser irradiation were admirably suppressed in both subcutaneous tumor model and orthotopic tumor models.

CONCLUSION

Utilizing ILA@Lip is a profound strategy to create an extremely hypoxic tumor microenvironment for higher therapeutic efficacy of hypoxia-activated chemotherapy, which realized collective suppression of tumor growth and has promising potential for clinical translation.

Are tumour-associated carbonic anhydrases genuine therapeutic targets for photodynamic therapy?

INTRODUCTION

Photodynamic therapy (PDT) is a reactive oxygen species (ROS)-dependent treatment modality which has emerged as an alternative cancer therapy strategy. However, in solid tumors, the therapeutic efficacy of PDT is strongly reduced by hypoxia, a typical feature of many such tumors. The tumor-associated carbonic anhydrases IX (hCA IX) and XII (hCA XII), which are overexpressed under hypoxia are attractive, validated anticancer drug targets in solid tumors. Current challenges in therapeutic design of effective PDT systems aim to overcome the limitation of hypoxia by developing synergistic CA-targeted therapies combining photosensitizers and hCA IX/XII inhibitors.

AREA COVERED

In this review, the current literature on the use of hCA IX/XII inhibitors (CAi) for targeting photosensitizing chemical systems useful for PDT against hypoxic solid tumors is summarized, along with recent progress, challenges, and future prospects.

EXPERT OPINION

hCA IX/XII-focused photosensitizers have recently provided new generation of compounds of considerable potential. Proof of concept of in vivo efficacy studies suggested enhanced efficacy for CAi-PDT hybrid systems. Further research is needed to deepen our understanding of how hCA IX/hCA XII inhibition can enhance PDT and for obtaining more effective such derivatives.

Biomedical applications of MnO2 nanomaterials as nanozyme-based theranostics

Manganese dioxide (MnO₂) nanoenzymes/nanozymes (MnO₂-NEs) are 1-100 nm nanomaterials that mimic catalytic, oxidative, peroxidase, and superoxide dismutase activities. The oxidative-like activity of MnO₂-NEs makes them suitable for developing effective and low-cost colorimetric detection assays of biomolecules. Interestingly, MnO₂-NEs also demonstrate scavenging properties against reactive oxygen species (ROS) in various pathological conditions. In addition, due to the decomposition of MnO₂-NEs in the tumor microenvironment (TME) and the production of Mn²⁺, they can act as a contrast agent for improving clinical imaging diagnostics. MnO₂-NEs also can use as an in situ oxygen production system in TME, thereby overcoming hypoxic conditions and their consequences in the progression of cancer. Furthermore, MnO₂-NEs as a shell and coating make the nanosystems smart and, therefore, in combination with other nanomaterials, the MnO₂-NEs can be used as an intelligent nanocarrier for delivering drugs, photosensitizers, and sonosensitizers in vivo. Moreover, these capabilities make MnO₂-NEs a promising candidate for the detection and treatment of different human diseases such as cancer, metabolic, infectious, and inflammatory pathological conditions. MnO₂-NEs also have ROS-scavenging and anti-bacterial properties against Gram-positive and Gram-negative bacterial strains, which make them suitable for wound healing applications. Given the importance of nanomaterials and their potential applications in biomedicine, this review aimed to discuss the biochemical properties and the theranostic roles of MnO₂-NEs and recent advances in their use in colorimetric detection assays of biomolecules, diagnostic imaging, drug delivery, and combinatorial therapy applications. Finally, the challenges of MnO₂-NEs applications in biomedicine will be discussed.

Organic disulfide-modified folate carbon dots for tumor-targeted synergistic chemodynamic/photodynamic therapy

Carbon dots (CDs) have great potential for cancer diagnosis and treatment. Photodynamic therapy and chemodynamic therapy are promising treatments mediated by reactive oxygen species (ROS), which have the advantages of being minimally invasive, having no multi-drug resistance, and having no systemic toxic side effects. However, the tumor microenvironment (TME) and poor targetability often reduce the therapeutic effect. In this work, we have successfully prepared folate-based carbon dots (FCP-CDs) from folic acid (FA), citric acid (CA), and polyethyleneimine (PEI) for tumor-targeting. The surface of FCP-CDs was modified using organic disulfide, 3,3'-dithiodipropionic acid (DTPA), and a photosensitizer (PS) pyropheophorbide-a (PPa) to form a tumor microenvironment-responsive nanoplatform, FCP-CDs@DTPA@PPa (named FCPPD), for synergistic cancer therapy. The results showed that FCPPD effectively preserved the tumor target specificity of folic acid and the photodynamic therapeutic (PDT) activity of PPa, and could provide additional chemodynamic therapeutic (CDT) function by reacting with hydrogen peroxide (H₂O₂) to generate ˙OH. The introduction of DTPA, which contains disulfide bonds, endows FCPPD with an excellent ability to deplete glutathione (GSH) in tumors via intracellular redox reactions, amplifying intracellular oxidative strain and enhancing ROS-based therapeutic effects. Systematic in vitro and in vivo studies under various conditions have shown that the obtained FCPPD nanoparticles have good biocompatibility and could be a promising therapeutic agent for imaging-guided PDT/CDT combination therapy.

Ratiometric singlet oxygen self-detecting and oxygen self-supplying nanosensor for real-time photodynamic therapy feedback and therapeutic effect enhancement

Integration of singlet oxygen (¹O₂) detection that provides necessary therapeutic feedback into nanotheranostics for hypoxic tumor photodynamic therapy (PDT) is desirable but still challenging. Herein, we report a nanosensor (denominated PAPD) by combining dual-channel ratiometric sensing and oxygen-augmenting strategies, which synergistically realizes real-time ¹O₂ self-detection, O₂ self-supply and enhanced phototherapy. PAPD nanosensor is constructed by encapsulating anthracene-based ¹O₂ sensitive fluorophore (DPA) into porphyrin metal-organic frameworks (PCN-224), decorating gold nanoparticles (AuNPs) as nanoenzymes, and coating polyethylene glycol thiol (PEG-SH) by the Au-S bond. PCN-224 serves as ¹O₂ reference fluorescence (FL) agent and photosensitizer. Once PCN-224-induced ¹O₂ is synthesized, the dual-channel ratiometric FL signal of PAPD actualizes sensitive, accurate and dynamic ¹O₂ visualization and gives real-time therapeutic information correlated with the therapeutic progression. Additionally, the catalase-like activity of PAPD possesses in situ O₂ production via intracellular H₂O₂ decomposition and accelerates ¹O₂ yields for amplifying the tumor cell killing efficiency. Moreover, the ratiometric ¹O₂ self-detection affords the capacity to evaluate the O₂ self-supplying effect in tumor 4T1 cells. Consequently, the rational-designed nanosensor PAPD provides a paradigm for real-time therapeutic evaluation and precise hypoxic tumor treatment clinically.