Tumor microenvironment-responsive and oxygen self-sufficient oil droplet nanoparticles for enhanced photothermal/photodynamic combination therapy against hypoxic tumors

PEGylated chitosan-coated nanophotosensitizers for effective cancer treatment by photothermal-photodynamic therapy combined with glutathione depletion

The combination of photothermal therapy (PTT) and photodynamic therapy (PDT) has emerged as a promising strategy for cancer treatment. However, the poor photostability and photothermal conversion efficiency (PCE) of organic small-molecule photosensitizers, and the intracellular glutathione (GSH)-mediated singlet oxygen scavenging largely decline the antitumor efficacy of PTT and PDT. Herein, a versatile nanophotosensitizer (NPS) system is developed by ingenious incorporation of indocyanine green (ICG) into the PEGylated chitosan (PEG-CS)-coated polydopamine (PDA) nanoparticles via multiple π-π stacking, hydrophobic and electrostatic interactions. The PEG-CS-covered NPS showed prominent colloidal and photothermal stability as well as high PCE (ca 62.8 %). Meanwhile, the Michael addition between NPS and GSH can consume GSH, thus reducing the GSH-induced singlet oxygen scavenging. After being internalized by CT26 cells, the NPS under near-infrared laser irradiation produced massive singlet oxygen with the aid of thermo-enhanced intracellular GSH depletion to elicit mitochondrial damage and lipid peroxide formation, thus leading to ferroptosis and apoptosis. Importantly, the combined PTT and PDT delivered by NPS effectively inhibited CT26 tumor growth in vivo by light-activated intense hyperthermia and redox homeostasis disturbance. Overall, this work presents a new tactic of boosting antitumor potency of ICG-mediated phototherapy by PEG-CS-covered NPS.

Photosensitizer-singlet oxygen sensor conjugated silica nanoparticles for photodynamic therapy and bioimaging

Intracellular singlet oxygen (1O2) generation and detection help optimize the outcome of photodynamic therapy (PDT). Theranostics programmed for on-demand phototriggered 1O2 release and bioimaging have great potential to transform PDT. We demonstrate an ultrasensitive fluorescence turn-on sensor-sensitizer-RGD peptide-silica nanoarchitecture and its 1O2 generation-releasing-storing-sensing properties at the single-particle level or in living cells. The sensor and sensitizer in the nanoarchitecture are an aminomethyl anthracene (AMA)-coumarin dyad and a porphyrin or CdSe/ZnS quantum dots (QDs), respectively. The AMA in the dyad quantitatively quenches the fluorescence of coumarin by intramolecular electron transfer, the porphyrin or QD moiety generates 1O2, and the RGD peptide facilitates intracellular delivery. The small size, below 200 nm, as verified by scanning electron microscopy and differential light scattering measurements, of the architecture within the 1O2 diffusion length enables fast and efficient intracellular fluorescence switching by the tandem ultraviolet (UV)-visible or visible-near-infrared (NIR) photo-triggering. While the red emission and 1O2 generation by the porphyrin are continually turned on, the blue emission of coumarin is uncaged into 230-fold intensity enhancement by on-demand photo-triggering. The 1O2 production and release by the nanoarchitecture enable spectro-temporally controlled cell imaging and apoptotic cell death; the latter is verified from cytotoxic data under dark and phototriggering conditions. Furthermore, the bioimaging potential of the TCPP-based nanoarchitecture is examined in vivo in B6 mice.

Nanoparticles-based phototherapy systems for cancer treatment: Current status and clinical potential

Remarkable progress in phototherapy has been made in recent decades, due to its non-invasiveness and instant therapeutic efficacy. In addition, with the rapid development of nanoscience and nanotechnology, phototherapy systems based on nanoparticles or nanocomposites also evolved as an emerging hotspot in nanomedicine research, especially in cancer. In this review, first we briefly introduce the history of phototherapy, and the mechanisms of phototherapy in cancer treatment. Then, we summarize the representative development over the past three to five years in nanoparticle-based phototherapy and highlight the design of the innovative nanoparticles thereof. Finally, we discuss the feasibility and the potential of the nanoparticle-based phototherapy systems in clinical anticancer therapeutic applications, aiming to predict future research directions in this field. Our review is a tutorial work, aiming at providing useful insights to researchers in the field of nanotechnology, nanoscience and cancer.

Photo-controllable burst generation of peroxynitrite based on synergistic interactions of polymeric nitric oxide donors and IR780 for enhancing broad-spectrum antibacterial therapy

The newly attractive peroxynitrite (ONOO^-) therapy can prominently enhance antibacterial therapeutic efficacy. However, it is a great challenge but urgently needed to generate ONOO^- with adjustable release rate and dosage in order to satisfy personalized treatments for different disease types and severities. Herein, PSNO@IR780 nanoparticles are fabricated via co-assembly of an amphiphilic PEG-b-PAASNO block copolymer grafted with abundant nitric oxide (NO) donor units and IR780 as a photothermal and photodynamic agent. Photo-controllable burst generation of ONOO^- from PSNO@IR780 nanoparticles could be realized based on synergistic reactions of rapid NO release induced by increased local temperature and efficiently produced superoxide anion radical (O₂^•-) from IR780. The maximum ONOO^- release dosage is up to 6.73 ± 0.07 µM and release rate is up to 98.1 ± 1.38 nM/s. Furthermore, the ONOO^- release behavior can be precisely manipulated by varying sample concentrations, irradiated durations, output power densities, and laser switches, respectively. Ultra-efficiently generated ONOO^- from biocompatible PSNO@IR780 nanoparticles significantly elevated broad spectrum antibacterial efficiency through damaging bacterial membranes. Thus, PSNO@IR780 nanoparticles may present a new insight into preparation of burst and controllable generating ONOO^- materials, and provide new opportunities for antibacterial therapy. STATEMENT OF SIGNIFICANCE: 1. Polymeric NO donor (PEG-b-PAASNO) grafted with abundant NO donor units was synthesized. 2. PSNO@IR780 nanoparticles were prepared by co-assembly of IR780 and amphiphilic PEG-b-PAASNOpolymer. 3. The maximum ONOO^- release dosage from PSNO@IR780 nanoparticles was 6.73 ± 0.08 µM. 4. The fastest ONOO^- release rate from PSNO@IR780 nanoparticles was 98.1 ± 1.4 nM/s. 5. Ultra-efficiently generated ONOO^- significantly elevated antibacterial efficiency via damaging bac-terial membranes.

Research progress of potential factors influencing photodynamic therapy for gastrointestinal cancer

Gastrointestinal cancer is a malignant tumor of the gastrointestinal tract and its associated digestive organs, including esophageal cancer, gastric cancer, carcinoma of the ampulla, pancreas, bile duct, intestines and rectal cancer. They account for about 30% of global cancer-related incidence and about 40% of mortality. Photodynamic therapy (PDT), as a treatment mode, has been applied to the treatment of gastrointestinal cancer due to potential advantages targeting and potentially lower toxic side effects. However, In the course of clinical treatment, we have found that different patients have various responsiveness to PDT, and even the same patients may have different clinical effects after receiving treatment in different time periods. For influencing factors, traditionally, we only focus on adjusting the dose of photosensitizer and the intensity and time of irradiation,while minimizing other potential factors.Therefore, this paper looks for factors that affect PDT from the patient's own conditions, tumor characteristics and tumor microenvironment(including:tumor acidic microenvironment,tumor hypoxic microenvironment, multi-drug resistance, different tumor characteristics and the immune status of patients) and summarizes how to potentially improve the curative effect of PDT.

The Role of Imaging Biomarkers to Guide Pharmacological Interventions Targeting Tumor Hypoxia

Hypoxia is a common feature of solid tumors that contributes to angiogenesis, invasiveness, metastasis, altered metabolism and genomic instability. As hypoxia is a major actor in tumor progression and resistance to radiotherapy, chemotherapy and immunotherapy, multiple approaches have emerged to target tumor hypoxia. It includes among others pharmacological interventions designed to alleviate tumor hypoxia at the time of radiation therapy, prodrugs that are selectively activated in hypoxic cells or inhibitors of molecular targets involved in hypoxic cell survival (i.e., hypoxia inducible factors HIFs, PI3K/AKT/mTOR pathway, unfolded protein response). While numerous strategies were successful in pre-clinical models, their translation in the clinical practice has been disappointing so far. This therapeutic failure often results from the absence of appropriate stratification of patients that could benefit from targeted interventions. Companion diagnostics may help at different levels of the research and development, and in matching a patient to a specific intervention targeting hypoxia. In this review, we discuss the relative merits of the existing hypoxia biomarkers, their current status and the challenges for their future validation as companion diagnostics adapted to the nature of the intervention.

Nanotechnology-based combinatorial phototherapy for enhanced cancer treatment

Nanotechnology-based phototherapy has attracted enormous attention to cancer treatment owning to its non-invasiveness, high controllability and accuracy. Given the fast development of anti-tumor strategies, we summarize various examples of multifunctional nanosystems to highlight the recent advances in nanotechnology-based combinatorial phototherapy towards improving cancer treatment. The limitations of the monotherapeutic approach and the superiority of the photo-involved combinatorial strategies are discussed in each part. The future breakthroughs and clinical perspectives of combinatorial phototherapy are also outlooked. Our perspectives may inspire researchers to develop more effective phototherapy-based cancer-treating approaches.

A dual-responsive nanoplatform with feedback amplification improves antitumor efficacy of photodynamic therapy

A good photosensitizer (PS) delivery system could enhance the efficiency and reduce the side effects of anti-tumor photodynamic therapy (PDT) by improving accumulation in the tumor, uptake by tumor cells, and intracellular release of the PS. Thus, we rationally developed a multi-stimulus-responsive PS nanocarrier with a double-layered core-shell structure: mPEG-azo-hyaluronic acid-sulfide-Ce6 (PaHAsC). In PaHAsC, the mPEG coat provides protection before entering the hypoxic tumor microenvironment, where mPEG leaves to expose the HA layer. HA then targets overexpressed CD44 on tumor cells for enhanced internalization. Finally, GSH-mediated intracellular release of Ce6 augments ROS generation and O₂ consumption under light stimulation. This also aggravates hypoxia in tumor sites to accelerate mPEG removal, forming a positive feedback loop. Data show that PaHAsC dramatically improved the PDT efficacy of Ce6, eliminating most tumors and 80% of tumor-bearing mice survived. With a safe profile, PaHAsC has potential for further development and is a useful example of a PS delivery system.

Glycol chitosan/iron oxide/polypyrrole nanoclusters for precise chemodynamic/photothermal synergistic therapy

Noninvasive photothermal therapy (PTT) represents a promising direction for more modern and precise medical applications. However, PTT efficacy is still not satisfactory due to the existence of heat shock proteins (HSPs) and poorly targeted delivery. Herein, the design of a nanosystem with improved delivery efficacy for anticancer treatment employing the synergetic effects of reactive oxygen species (ROS)-driven chemodynamic therapy (CDT) to inactivated HSPs with photothermal-hyperthermia was therefore achieved through the development of pH-targeting glycol chitosan/iron oxide enclosed core polypyrrole nanoclusters (GCPI NCs). The designed NCs effectively accumulated toward cancer cells due to their acidic microenvironment, initiating ROS generation via Fenton reaction at the outset and performing site-specific near infrared (NIR)-photothermal effect. A comprehensive analysis of both surface and bulk material properties of the CDT/PTT NCs as well as biointerface properties were ascertained via numerous surface specific analytical techniques by bringing together heightened accumulation of CDT/PTT NCs, which can significantly eradicate cancer cells thus minimizing the side effects of conventional chemotherapies. All of these attributes act in synergy over the cancer cells succeeding in fashioning NC's able to act as competent agents in the MRI-monitored enhanced CDT/PTT synergistic therapy. Findings in this study evoke attention in future oncological therapeutic strategies.

Recent Advances in Strategies for Addressing Hypoxia in Tumor Photodynamic Therapy

Photodynamic therapy (PDT) is a treatment modality that uses light to target tumors and minimize damage to normal tissues. It offers advantages including high spatiotemporal selectivity, low side effects, and maximal preservation of tissue functions. However, the PDT efficiency is severely impeded by the hypoxic feature of tumors. Moreover, hypoxia may promote tumor metastasis and tumor resistance to multiple therapies. Therefore, addressing tumor hypoxia to improve PDT efficacy has been the focus of antitumor treatment, and research on this theme is continuously emerging. In this review, we summarize state-of-the-art advances in strategies for overcoming hypoxia in tumor PDTs, categorizing them into oxygen-independent phototherapy, oxygen-economizing PDT, and oxygen-supplementing PDT. Moreover, we highlight strategies possessing intriguing advantages such as exceedingly high PDT efficiency and high novelty, analyze the strengths and shortcomings of different methods, and envision the opportunities and challenges for future research.

Recent advances in in situ oxygen-generating and oxygen-replenishing strategies for hypoxic-enhanced photodynamic therapy

Cancer is a leading cause of death worldwide, accounting for an estimated 10 million deaths by 2020. Over the decades, various strategies for tumor therapy have been developed and evaluated. Photodynamic therapy (PDT) has attracted increasing attention due to its unique characteristics, including low systemic toxicity and minimally invasive nature. Despite the excellent clinical promise of PDT, hypoxia is still the Achilles' heel associated with its oxygen-dependent nature related to increased tumor proliferation, angiogenesis, and distant metastases. Moreover, PDT-mediated oxygen consumption further exacerbates the hypoxia condition, which will eventually lead to the poor effect of drug treatment and resistance and irreversible tumor metastasis, even limiting its effective application in the treatment of hypoxic tumors. Hypoxia, with increased oxygen consumption, may occur in acute and chronic hypoxia conditions in developing tumors. Tumor cells farther away from the capillaries have much lower oxygen levels than cells in adjacent areas. However, it is difficult to change the tumor's deep hypoxia state through different ways to reduce the tumor tissue's oxygen consumption. Therefore, it will become more difficult to cure malignant tumors completely. In recent years, numerous investigations have focused on improving PDT therapy's efficacy by providing molecular oxygen directly or indirectly to tumor tissues. In this review, different molecular oxygen supplementation methods are summarized to alleviate tumor hypoxia from the innovative perspective of using supplemental oxygen. Besides, the existing problems, future prospects and potential challenges of this strategy are also discussed.

Dual-Depletion of Intratumoral Lactate and ATP with Radicals Generation for Cascade Metabolic-Chemodynamic Therapy

Increasing evidence has demonstrated that lactate and adenosine triphosphate (ATP) both play important roles in regulating abnormal metabolism in the tumor microenvironment. Herein, an O2 self-supplying catalytic nanoagent, based on tannic acid (TA)-Fe(III) coordination complexes-coated perfluorooctyl bromide (PFOB) nanodroplets with lactate oxidases (LOX) loading (PFOB@TA-Fe(III)-LOX, PTFL), is designed for cascade metabolic-chemodynamic therapy (CDT) by dual-depletion of lactate and ATP with hydroxyl • OH radicals generation. Benefiting from the catalytic property of loaded LOX and O2 self-supplying of PFOB nanodroplets, PTFL nanoparticles (NPs) efficiently deplete tumoral lactate for down-regulation of vascular endothelial growth factor expression and supplement the insufficient endogenous H2 O2 . Simultaneously, TA-Fe(III) complexes release Fe(III) ions and TA in response to intracellular up-regulated ATP in tumor cells followed by TA-mediated Fe(III)/Fe(II) conversion, leading to the depletion of energy source ATP and the generation of cytotoxic • OH radicals from H2 O2 . Moreover, TA-Fe(III) complexes provide photoacoustic contrast as imaging guidance to enhance therapeutic accuracy. As a result, PTFL NPs efficiently accumulate in tumors for suppression of tumor growth and show evidence of anti-angiogenesis and anti-metastasis effects. This multifunctional nanoagent may provide new insight for targeting abnormal tumor metabolism with the combination of CDT to achieve a synergistic therapeutic effect.

Keratin-Based Nanoparticles with Tumor-Targeting and Cascade Catalytic Capabilities for the Combinational Oxidation Phototherapy of Breast Cancer

Photodynamic therapy (PDT) holds tantalizing prospects of a prominent cancer treatment strategy. However, its efficacy remains limited by virtue of the hypoxic tumor microenvironment and the inadequate tumor-targeted delivery of photosensitizers, and these can be further exacerbated by the lack of development of a well-controlled nitric oxide (NO) release system at the target site. Inspired by Chinese medicine, we propose a revealing new keratin application. Keratin has garnered attention as an NO generator; however, its oncological use has rarely been investigated. We hypothesized that the incorporation of a phenylboronic acid (PBA) targeting ligand/methylene blue (MB) photosensitizer with a keratin NO donor would facilitate precise tumor delivery, enhancing PDT. Herein, we demonstrated that MB@keratin/PBA/d-α-tocopherol polyethylene glycol 1000 succinate (TPGS) nanoparticles (MB@KPTNPs) specifically targeted breast cancer cells and effectively suppressed their growth. Through MB-mediated biometabolism, the endocytic MB@KPTNPs produced a sufficient amount of intracellular NO that reduced the glutathione level while boosting the efficiency of PDT. A therapeutic combination of NO/PDT was therefore achieved, resulting in significant inhibition of both in vivo tumor growth and lung metastasis. These findings underscore the importance of utilizing keratin-based nanoparticles that simultaneously combine targeting of the tumor and self-generating NO with a cascading catalytic ability as a novel oxidation therapeutic strategy for enhancing PDT.

Advances in chlorin-based photodynamic therapy with nanoparticle delivery system for cancer treatment

Introduction: The treatment of tumors is one of the most difficult problems in the medical field at present. Patients often use a comprehensive therapy that combines surgery, radiotherapy, and chemotherapy. Photodynamic therapy (PDT) has prominent potential for eradicating various cancers. Chlorin-based photosensitizers (PSs), as one of the most utilized photosensitizers, have many advantages over conventional photosensitizers; however, a successful chlorin-based PDT needs multi-functional nano-carriers for selective photosensitizer delivery. The number of researches about nanoparticles designed for improved chlorin-based PSs is increasing in the current era. In this article, we give a brief review focused on the recent research progress in design of chlorin-based nanoparticles for the treatment of malignant tumors with photodynamic therapy.Areas covered: This review focuses on the current nanoparticle platforms for PDT, and describes different strategies to achieve controllable PDT by chlorin-nano-delivery systems. The challenges and prospects of PDT in clinical applications are also discussed.Expert opinions: The requirement for PDT to eradicate cancers has increased exponentially in recent years. The major clinically used photosensitizers are hydrophobic. The main obstacles in effective delivery of PSs are associated with this intrinsic nature. The design of nano-delivery systems to load PSs is pivotal for PSs' widespread use.

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

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

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

Genetically modified bacteria for targeted phototherapy of tumor

Live attenuated bacteria have been used as target vehicles for genetic therapy of malignant carcinoma because they can be reprogrammed by following simple genetic rules and have the ability to target tumor hypoxic region. In this research, noninvasive Escherichia coli (E. Coli) is genetically modified through the plasmid transfection to afford E. Coli(p) with overexpressed human catalase for catalyzing H₂O₂ into O₂ in the tumor site. The produced O₂ is consequently converted to cytotoxic ¹O₂ under near-infrared (NIR) light irradiation for photodynamic therapy. Chlorin e6 (Ce6) is chosen as the photosensitizer for its excellent photodynamic ability, and polydopamine (pDA) is employed to encapsulate Ce6 for its good biosafety, photothermal ability, and adhesion capacity with bacteria. Dopamine polymerizes in the presence of Ce6 to form pDA/Ce6, and then E. Coli(p) is coated with pDA/Ce6 to afford the final E. Coli(p)/pDA/Ce6. The obtained system is intravenously administrated for selective accumulation and replication in the hypoxic tumor. NIR light irradiation is introduced to enable photothermal and O₂-enhanced photodynamic therapy. On account of complementary combination, the system exhibits efficient antitumor effect in vitro and in vivo. Thus, the integration of genetically modified bacteria with pDA/Ce6 presents a promising application potential for precise tumor inhibition.

Dual Targeting EGFR and STAT3 With Erlotinib and Alantolactone Co-Loaded PLGA Nanoparticles for Pancreatic Cancer Treatment

Pancreatic cancer (PC) is one of the most common malignancies and also a leading cause of cancer-related mortality worldwide. Many studies have shown that epidermal growth factor receptor (EGFR) is highly expressed in PC, which provides a potential target for PC treatment. However, EGFR inhibitors use alone was proven ineffective in clinical trials, due to the persistence of cellular feedback mechanisms which foster therapeutic resistance to single targeting of EGFR. Specifically, the signal transducer and activator of transcription 3 (STAT3) is over-activated when receiving an EGFR inhibitor and is believed to be highly involved in the failure and resistance of EGFR inhibitor treatment. Therein, we hypothesized that dual inhibition of EGFR and STAT3 strategy could address the STAT3 induced resistance during EGFR inhibitor treatment. To this end, we tried to develop poly (lactic-co-glycolic acid) (PLGA) nanoparticles to co-load Alantolactone (ALA, a novel STAT3 inhibitor) and Erlotinib (ERL, an EGFR inhibitor) for pancreatic cancer to test our guess. The loading ratio of ALA and ERL was firstly optimized in vitro to achieve a combined cancer-killing effect. Then, the ALA- and ERL-co-loaded nanoparticles (AE@NPs) were successfully prepared and characterized, and the related anticancer effects and cellular uptake of AE@NPs were studied. We also further detailly explored the underlying mechanisms. The results suggested that AE@NPs with uniform particle size and high drug load could induce significant pancreatic cancer cell apoptosis and display an ideal anticancer effect. Mechanism studies showed that AE@NPs inhibited the phosphorylation of both EGFR and STAT3, indicating the dual suppression of these two signaling pathways. Additionally, AE@NPs could also activate the ROS-p38 axis, which is not observed in the single drug treatments. Collectively, the AE@NPs prepared in this study possess great potential for pancreatic cancer treatment by dual suppressing of EGFR and STAT3 pathways and activating ROS-responsive p38 MAPK pathway.

Combined cancer therapeutics-Tackling the complexity of the tumor microenvironment

Cancer treatment has yet to find a "silver bullet" capable of selectively and effectively kill tumor cells without damaging healthy cells. Nanomedicine is a promising field that can combine several moieties in one system to produce a multifaceted nanoplatform. The tumor microenvironment (TME) is considered responsible for the ineffectiveness of cancer therapeutics and the difficulty in the translation from the bench to bed side of novel nanomedicines. A promising approach is the use of combinatorial therapies targeting the TME with the use of stimuli-responsive nanomaterials which would increase tumor targeting. Contemporary combined strategies for TME-targeting nanoformulations are based on the application of external stimuli therapies, such as photothermy, hyperthermia or ultrasounds, in combination with stimuli-responsive nanoparticles containing a core, usually composed by metal oxides or graphene, and a biocompatible stimuli-responsive coating layer that could also contain tumor targeting moieties and a chemotherapeutic agent to enhance the therapeutic efficacy. The obstacles that nanotherapeutics must overcome in the TME to accomplish an effective therapeutic cargo delivery and the proposed strategies for improved nanotherapeutics will be reviewed. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies.