Singlet oxygen-responsive micelles for enhanced photodynamic therapy

Energy-storing DNA-based hydrogel remodels tumor microenvironments for laser-free photodynamic immunotherapy

Photodynamic therapy (PDT) is a promising modality for cancer treatment. However, limited tissue penetration of external radiation and complicated tumor microenvironments (TMEs) restrict the antitumor efficiency of PDT. Herein, we report an energy-storing DNA-based hydrogel, which enables tumor-selective PDT without external radiation and regulates TMEs to achieve boosted PDT-mediated tumor immunotherapy. The system is constructed with two ultralong single-stranded DNA chains, which programmed partial complementary sequences and repeated G-quadruplex forming AS1411 aptamer for photosensitizer loading via hydrophobic interactions and π-π stacking. Then, energy-storing persistent luminescent nanoparticles are incorporated to sensitize PDT selectively at tumor site without external irradiation, generating tumor antigen to agitate antitumor immune response. The system catalytically generates O2 to alleviate hypoxia and releases inhibitors to reverse the IDO-related immunosuppression, synergistically remodeling the TMEs. In the mouse model of breast cancer, this hydrogel shows a remarkable tumor suppression rate of 78.3 %. Our study represents a new paradigm of photodynamic immunotherapy against cancer by combining laser-free fashion and TMEs remodeling.

Recent progress in stimuli-responsive polymeric micelles for targeted delivery of functional nanoparticles

Stimuli-responsive polymeric micelles have emerged as a revolutionary approach for enhancing the in vivo stability, biocompatibility, and targeted delivery of functional nanoparticles (FNPs) in biomedicine. This article comprehensively reviews the preparation methods of these polymer micelles, detailing the innovative strategies employed to introduce stimulus responsiveness and surface modifications essential for precise targeting. We delve into the breakthroughs in utilizing these micelles to selectively deliver various FNPs including magnetic nanoparticles, upconversion nanoparticles, gold nanoparticles, and quantum dots, highlighting their transformative impact in the biomedical realm. Concluding, we present an insight into the current research landscape, addressing the challenges at hand, and envisioning the future trajectory in this burgeoning domain. Join us as we navigate the exciting confluence of polymer science and nanotechnology in reshaping biomedical solutions.

Effective Combination of Targeted Therapies with Sonodynamic Treatment for Use in Exploring Differences in Therapeutic Efficacy across Organelle Targets

Acoustic kinetic therapy systems that target specific organelles can improve the precision of a sonosensitizer, which is a perfect combination of targeted therapy and sonodynamic therapy (SDT) and plays an important role in current acoustic kinetic therapy. In this study, we loaded PpIX, a sonosensitizer, on targeted-functional carbon dots (CDs) via an amide reaction and then generated the mitochondria-targeted system (Mit-CDs-PpIX) and nucleus-targeted system (Nuc-CDs-PpIX), respectively, to deliver the sonosensitizer. Both systems exhibited minimal cytotoxicity in the absence of ultrasound stimulation. The efficacy of the targeted SDT systems was investigated using methylthiazol tetrazolium (MTT) assays, live/dead staining, flow cytometry, etc. Compared with the free PpIX and mitochondria-targeted system, the nucleus-targeted system is more potent in killing effect under ultrasound stimulation and induces apoptosis with higher intensity. To achieve the equal killing effect, the effective concentration of Nuc-CDs-PpIX is just one third of that of Mit-CDs-PpIX.

Hypoxia and Singlet Oxygen Dual-Responsive Micelles for Photodynamic and Chemotherapy Therapy Featured with Enhanced Cellular Uptake and Triggered Cargo Delivery

Introduction

Combination therapy provides better outcomes than a single therapy and becomes an efficient strategy for cancer treatment. In this study, we designed a hypoxia- and singlet oxygen-responsive polymeric micelles which contain azo and nitroimidazole groups for enhanced cellular uptake, repaid cargo release, and codelivery of photosensitizer Ce6 and hypoxia-activated prodrug tirapazamine TPZ (DHM-Ce6@TPZ), which could be used for combining Ce6-mediated photodynamic therapy (PDT) and PDT-activated chemotherapy to enhance the therapy effect of cancer.

Methods

The hypoxia- and singlet oxygen-responsive polymeric micelles DHM-Ce6@TPZ were prepared by film hydration method. The morphology, physicochemical properties, stimuli responsiveness, in vitro singlet oxygen production, cellular uptake, and cell viability were evaluated. In addition, the in vivo therapeutic effects of the micelles were verified using a tumor xenograft mice model.

Results

The resulting dual-responsive micelles not only increased the concentration of intracellular photosensitizer and TPZ, but also facilitated photosensitizer and TPZ release for enhanced integration of photodynamic and chemotherapy therapy. As a photosensitizer, Ce6 induced PDT by generating toxic singlet reactive oxygen species (ROS), resulting in a hypoxic tumor environment to activate the prodrug TPZ to achieve efficient chemotherapy, thereby evoking a synergistic photodynamic and chemotherapy therapeutic effect. The cascade synergistic therapeutic effect of DHM-Ce6@TPZ was effectively evaluated both in vitro and in vivo to inhibit tumor growth in a breast cancer mice model.

Conclusion

The designed multifunctional micellar nano platform could be a convenient and powerful vehicle for the efficient co-delivery of photosensitizers and chemical drugs for enhanced synergistic photodynamic and chemotherapy therapeutic effect of cancer.

Metal-Organic Framework for Hypoxia/ROS/pH Triple-Responsive Cargo Release

Nanoparticulate antitumor photodynamic therapy (PDT) is suffering from a very short lifetime, limited diffusion distance of reactive oxygen species (ROS). Herein, a hypoxia/ROS/pH triple-responsive metal-organic framework (MOF) is designed to facilitate the on-demand release of photosensitizers and hence enhanced PDT efficacy. Tailored azo-containing imidazole ligand is coordinated with zinc to form MOF where photosensitizer (Chlorin e6/Ce6) is encapsulated. Azo can be reduced by overexpressed azoreductase in hypoxic tumor cells, resulting in depletion of glutathione (GSH) and thioredoxin (Trx) which are major antioxidants against ROS oxidative damage in PDT, resulting in rapid cargo release and additional efficacy amplification. The imidazole ionization causes a proton sponge effect to ensure the disintegration of the nanocarriers in acidic organelles, allowing the rapid release of Ce6 through lysosome escape. Under light irradiation, ROS produced by Ce6 may oxidize imidazole to urea, resulting in rapid cargo release. All of the triggers are expected to show interactive synergism. The pH- and hypoxia-responsiveness can improve the release rate of Ce6 for enhanced PDT therapy, whereas the consumption of oxygen by PDT may induce elevated hypoxia and hence in turn enhanced cargo release. This work highlights the role of triple-responsive nanocarriers for triggered photosensitizer release and improved antitumor PDT efficacy.

Multifunctional biocompatible Ni/Ni-P nanospheres for anti-tumor "neoadjuvant phototherapy" combining photothermal therapy and photodynamic therapy

Gastric cancer, a gastrointestinal tumor with high morbidity and lethality, is often treated using strategies that are not as effective as they could be due to the locally advanced stage. Although pre-operative neoadjuvant chemotherapy can degrade the tumor stage to afford the possibility of surgery, it still possesses the problems of high systemic toxicity and low selectivity. In this work, we constructed an intelligent multi-functional nanoplatform (NNPIP NPs) with synergistic effects of photothermal therapy (PTT) and photodynamic therapy (PDT), which consisted of the nickel/nickel phosphide (Ni/Ni-P) nanosphere as the core, polyethyleneimine (PEI) as the shell, and the loaded indocyanine green (ICG). The mutual reinforcement of heat generated by the core and photosensitizer under 808 nm NIR laser irradiation is highly effective in the synergistic action of PTT. And co-delivery of ICG with nanoparticles into the cell enhances the PDT effect by reducing the consumption of singlet oxygen (1O2). Ultimately, this therapeutic strategy in vivo not only shrunk tumors but even eliminated tumors completely in a quarter of samples, which may be considered as a potential alternative to neoadjuvant chemotherapy and called "neoadjuvant phototherapy". In addition, as a nanoplatform based on transition metal nickel, NNPIP NPs could also be considered as a potential contrast agent for T1-weighted magnetic resonance imaging (MRI). Herein, we can diagnose and achieve pre-surgical downstaging of tumors and hope to improve R0 resection rates with lower toxicity and higher selectivity.

Strategies to prolong drug retention in solid tumors by aggregating Endo-CMC nanoparticles

Developing a highly effective nano-drug delivery system with sufficient drug permeability and retention in tumors is still a major challenge for oncotherapy. Herein, a tumor microenvironment responsive, aggregable nanocarriers embedded hydrogel (Endo-CMC@hydrogel) was developed to inhibit the tumoral angiogenesis and hypoxia for enhanced radiotherapy. The antiangiogenic drug (recombinant human endostatin, Endo) loaded carboxymethyl chitosan nanoparticles (Endo-CMC NPs) was wrapped by 3D hydrogel to comprise the Endo-CMC@hydrogel. After peritumoral injection, the Endo-CMC NPs were released, invaded deeply into the solid tumor, and cross-linked with intratumoral calcium ions. The cross-linking process enabled these Endo-CMC NPs to form larger particles, leading to long retention in tumor tissue to minimize premature clearance. This Endo-CMC@hydrogel, integrating the abilities of good tumoral penetration, long retention of anti-drug, and alleviation of hypoxia in tumor tissue, greatly improved the therapeutic effect of radiotherapy. This work provides a proof-of-concept of tumor microenvironment-responding and an aggregable nano-drug delivery system as promising antitumor drug carriers for effective tumor therapy.

Coenzyme-depleting nanocarriers for enhanced redox cancer therapy under hypoxia

Cancer cells show unique redox homeostasis. Glutathione (GSH) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) play essential roles as coenzymes of multiple key antioxidant enzymes. Coenzyme depletion offers a unique opportunity for cancer treatment by inducing oxidative stress. Here, we report an innovative hybrid nanocarrier for cancer redox therapy via selective depletion of GSH and NADPH. The nanocarrier core is a sorafenib-loaded porous zeolitic imidazole framework (ZIF-65), and the shell is epigallocatechin gallate (EGCG)-Fe³⁺ complex (EF). The nitroimidazole ligand in ZIF-65 could selectively deplete NADPH under hypoxia. Sorafenib diminished GSH by inhibiting cystine import and GSH biosynthesis. EGCG can reduce Fe³⁺ to Fe²⁺, which aids the generation of hydroxyl radicals via the Fenton reaction. The reversible coordination between nitroimidazole and Zn²⁺, EGCG, and Fe³⁺ enables triggered cargo release in acidic lysosomes. Tailored nanocarriers induced the depletion of both coenzymes (GSH and NADPH) and boosted reactive oxygen species in a 4T1 murine cancer cell line. The altered redox balance eventually resulted in efficient apoptotic cell death. The current work offers a novel means of redox cancer therapy via the selective depletion of key antioxidant enzymes in hypoxic cells.

Monoclonal Antibody-Guided Tumor-Targeted Hollow Virus-Like Cerium Oxide with Oxygen Self-Supply for Intensifying Photodynamic Therapy

The hypoxic character of tumors and the poor targeting ability of photosensitizers often limit the efficacy of photodynamic therapy (PDT). In recent years, the discovery of metal nanoenzymes and nanocarriers has improved PDT. Thereby, to improve the effective utilization of photosensitizers and oxygen (O₂ ) in tumors, herein, a nanosystem (LS-HB@HvCeO₂ -NRP1 mAb, LHCN1) is reported, in which a hollow virus-like cerium oxide (HvCeO₂ ) is surface-decorated with tumor-targeting neuropilin-1 monoclonal antibody (NRP1 mAb), and loaded with a photosensitizer (chlorin e6-C-15-ethyl ester, LS-HB). In vitro and in vivo experiments demonstrate that LHCN1 can efficiently accumulate within the tumor sites via the targeting guidance of NRP1 mAb and is then rapidly endocytosed into cells. Furthermore, HvCeO₂ with catalase-mimetic activity can decompose the endogenous hydrogen peroxide (H₂ O₂ ) to promote O₂ via the valence transformation between Ce⁴⁺ and Ce³⁺ , relieving tumor hypoxia and improving the PDT efficacy. Upon near-infrared laser irradiation, LS-HB produces large amounts of cytotoxic reactive oxygen species. Moreover, LHCN1 is used in fluorescence/photoacoustic multimodal imaging for in vivo drug localization, and its use in PDT evidently helps inhibit tumor growth with no apparent toxicity to normal tissues. Thus, LHCN1 may provide a promising strategy for precise tumor-specific diagnosis and treatment.

Reactive oxygen species-upregulating nanomedicines towards enhanced cancer therapy

Reactive oxygen species (ROS) play a crucial role in physiological and pathological processes, emerging as a therapeutic target in cancer. Owing to the high concentration of ROS in solid tumor tissues, ROS-based treatments, such as photodynamic therapy and chemodynamic therapy, and ROS-responsive drug delivery systems have been widely explored to powerfully and specifically suppress tumors. However, their anticancer efficacy is still hampered by the heterogeneous ROS levels, and thus comprehensively upregulating the ROS levels in tumor tissues can ensure an enhanced therapeutic effect, which can further sensitize and/or synergize with other therapies to inhibit tumor growth and metastasis. Herein, we review the recently emerging drug delivery strategies and technologies for increasing the H₂O₂, ˙OH, ¹O₂, and ˙O₂^- concentrations in cancer cells, including the efficient delivery of natural enzymes, nanozymes, small molecular biological molecules, and nanoscale Fenton-reagents and semiconductors and neutralization of intracellular antioxidant substances and localized input of mechanical and electromagnetic waves (such as ultrasound, near infrared light, microwaves, and X-rays). The applications of these ROS-upregulating nanosystems in enhancing and synergizing cancer therapies including chemotherapy, chemodynamic therapy, phototherapy, and immunotherapy are surveyed. In addition, we discuss the challenges of ROS-upregulating systems and the prospects for future studies.

Current Challenges and Opportunities of Photodynamic Therapy against Cancer

BACKGROUND

Photodynamic therapy (PDT) is an established, minimally invasive treatment for specific types of cancer. During PDT, reactive oxygen species (ROS) are generated that ultimately induce cell death and disruption of the tumor area. Moreover, PDT can result in damage to the tumor vasculature and induce the release and/or exposure of damage-associated molecular patterns (DAMPs) that may initiate an antitumor immune response. However, there are currently several challenges of PDT that limit its widespread application for certain indications in the clinic.

METHODS

A literature study was conducted to comprehensively discuss these challenges and to identify opportunities for improvement.

RESULTS

The most notable challenges of PDT and opportunities to improve them have been identified and discussed.

CONCLUSIONS

The recent efforts to improve the current challenges of PDT are promising, most notably those that focus on enhancing immune responses initiated by the treatment. The application of these improvements has the potential to enhance the antitumor efficacy of PDT, thereby broadening its potential application in the clinic.

Endoperoxides Compounds for Highly Efficient Cancer Treatment under Hypoxia

Photodynamic therapy (PDT) for cancer treatment has garnered tremendous attention with its promising non-invasiveness, low side effects, and spatiotemporal selectivity. However, the hypoxic microenvironment in solid tumours remains a serious resistant factor to reducing the effects of PDT. Endoperoxides are successfully utilized as the chemical storage or supplier of singlet oxygen (¹ O₂ ), the active substance for PDT in materials and other domains. Recent reports indicated that this type of compound could remarkably enhance the therapeutic effects of PDT under hypoxia. This concept mainly introduces a few representative endoperoxides and the outlook of their potent application for treating hypoxic cancer cells.

"NIR-triggered ROS storage" photodynamic intraocular implant for high-efficient and safe posterior capsular opacification prevention

Posterior capsular opacification (PCO) is the leading cause of vision loss after cataract, mainly caused by the adhesion, proliferation and trans-differentiation of post-operative residual lens epithelial cells (LECs). Effective PCO prevention remains a huge challenge to ophthalmologists and researches for decades. Herein, we developed a "NIR-triggered ROS storage" intraocular implant (CTR-Py-PpIX) based on capsular tension ring (CTR), which is concurrently linked with photosensitizer protophorphyrin IX (PpIX) and energy storage 2-pyridone derivative (Py), to guarantee instantaneous and sustainable ROS generation for LECs killing, aiming to achieve more efficient and safer photodynamic therapy (PDT) to effectively prevent PCO. The silylated PpIX-Si and Py-Si were covalently conjugated to the plasma activated CTR surface to obtain CTR-Py-PpIX. Results demonstrated that CTR-Py-PpIX had dual functions of PDT and battery, in which PpIX could generate ROS extracellularly under irradiation, with one part directly inhibiting LECs by lipid peroxidation (LPO) induction of cell membranes. Meanwhile, the excess ROS stored in Py could be continuously released to amplify LPO levels after the irradiation was removed. Ultimately, the proliferation of LECs in capsular bag was completely inhibited under mild irradiation conditions, achieving a sustainable and controlled PDT effect for effective PCO prevention with good biocompatibility. This NIR-triggered ROS storage intraocular implant would provide a more efficient and safer approach for long-term PCO prevention.

Exploration of Site-Specific Drug Targeting—A Review on EPR-, Stimuli-, Chemical-, and Receptor-Based Approaches as Potential Drug Targeting Methods in Cancer Treatment

Cancer has been one of the most dominant causes of mortality globally over the last few decades. In cancer treatment, the selective targeting of tumor cells is indispensable, making it a better replacement for conventional chemotherapies by diminishing their adverse side effects. While designing a drug to be delivered selectively in the target organ, the drug development scientists should focus on various factors such as the type of cancer they are dealing with according to which drug, targeting moieties, and pharmaceutical carriers should be targeted. All published articles have been collected regarding cancer and drug-targeting approaches from well reputed databases including MEDLINE, Embase, Cochrane Library, CENTRAL and ClinicalTrials.gov, Science Direct, PubMed, Scopus, Wiley, and Springer. The articles published between January 2010 and December 2020 were considered. Due to the existence of various mechanisms, it is challenging to choose which one is appropriate for a specific case. Moreover, a combination of more than one approach is often utilized to achieve optimal drug effects. In this review, we have summarized and highlighted central mechanisms of how the targeted drug delivery system works in the specific diseased microenvironment, along with the strategies to make an approach more effective. We have also included some pictorial illustrations to have a precise idea about different types of drug targeting. The core contribution of this work includes providing a cancer drug development scientist with a broad preliminary idea to choose the appropriate approach among the various targeted drug delivery mechanisms. Also, the study will contribute to improving anticancer treatment approaches by providing a pathway for lesser side effects observed in conventional chemotherapeutic techniques.

Molecularly Self-Engineered Nanoamplifier for Boosting Photodynamic Therapy via Cascade Oxygen Elevation and Lipid ROS Accumulation

Photodynamic therapy (PDT) has been extensively explored as a noninvasive cancer treatment modality. However, the dilemma of tumor hypoxia and short half-life of singlet oxygen (¹O₂) severely restrict the therapeutic efficacy of PDT. Herein, we develop a facile three-in-one PDT nanoamplifier (AA@PPa/Hemin NPs) assembled by pyropheophorbide a (PPa), hemin, and arachidonic acid (AA). Interestingly, AA not only acts as an enabler to facilitate the assembly of PPa and hemin in the construction of ternary hybrid nanoassemblies but also acts as a lipid reactive oxygen species (ROS) amplifier for robust PDT. In tumor cells, hemin plays the role of a catalase-like catalyst that accelerates the production of oxygen (O₂) from hydrogen peroxide (H₂O₂), significantly alleviating tumor hypoxia. Under laser irradiation, vast amounts of ¹O₂ generated by PPa trigger the peroxidation of AA to produce large amounts of cytotoxic lipid ROS, immensely amplifying the efficiency of PDT by promptly eliciting cellular oxidative stress. As expected, AA@PPa/Hemin NPs exert potent antitumor activity in a 4T1 breast-tumor-bearing BALB/c mice xenograft model. Such a cascade nanohybrid amplifier provides a novel codelivery platform for accurate and effective PDT of cancer.

Light-triggered photodynamic nanomedicines for overcoming localized therapeutic efficacy in cancer treatment

Photodynamic nanomedicines have significantly enhanced the therapeutic efficacy of photosensitizers (PSs) by overcoming critical limitations of PSs such as poor water solubility and low tumor accumulation. Furthermore, functional photodynamic nanomedicines have enabled overcoming oxygen depletion during photodynamic therapy (PDT) and tissue light penetration limitation by supplying oxygen or upconverting light in targeted tumor tissues, resulting in providing the potential to overcome biological therapeutic barriers of PDT. Nevertheless, their localized therapeutic effects still remain a huddle for the effective treatment of metastatic- or recurrent tumors. Recently, newly designed photodynamic nanomedicines and their combination chemo- or immune checkpoint inhibitor therapy enable the systemic treatment of various metastatic tumors by eliciting antitumor immune responses via immunogenic cell death (ICD). This review introduces recent advances in photodynamic nanomedicines and their applications, focusing on overcoming current limitations. Finally, the challenges and future perspectives of the clinical translation of photodynamic nanomedicines in cancer PDT are discussed.

When imaging meets size-transformable nanosystems

Imaging techniques, including magnetic, optical, acoustic and nuclear imaging, are gaining popularity as a research tool and clinical diagnostics. The advent of imaging agents-incorporated nanosystems (NSs), with sufficient contrast and high resolution, facilitates better monitoring of disease progression, targeted delivery and therapeutic process. Of note, the size of NSs remarkably affects imaging performance, while both large and small NSs enjoy respective features and superiority for imaging aspect, including penetration depth, signal-to-background ratio and spatiotemporal resolution. In this review, after a systematic summary of the basic knowledge of imaging techniques and its relation with size-tunable strategies, we further provide insights into the opportunities and challenges facing size-transformable NSs of the future for bio-imaging application and clinical translation.

An Energy-Storing DNA-Based Nanocomplex for Laser-Free Photodynamic Therapy

Photodynamic therapy (PDT) is a therapeutic strategy that is dependent on external light irradiation that faces a major challenge in cancer treatment due to the poor tissue-penetration depths of light irradiation. Herein, a DNA nanocomplex that integrates persistent-luminescence nanoparticles (PLNPs) is developed, which realizes tumor-site glutathione-activated PDT for breast cancer without exogenous laser excitation. The scaffold of the nanocomplex is AS1411-aptamer-encoded ultralong single-stranded DNA chain with two functions: i) providing sufficient intercalation sites for the photosensitizer, and ii) recognizing nucleolin that specifically overexpresses on the surface of cancer cells. The PLNPs in the nanocomplex are energy-charged to act as a self-illuminant and coated with a shell of MnO₂ for blocking energy degradation. In response to the overexpressed glutathione in cancer cells, the MnO₂ shell decomposes to provide Mn²⁺ to catalytically produce O₂ , which is essential to PDT. Meanwhile, PLNPs are released and act as a self-illuminant to activate the photosensitizer to convert O₂ into cytotoxic ¹ O₂ . Significant tumor inhibition effects are demonstrated in breast tumor xenograft models without exogenous laser excitation. It is envisioned that a laser-excitation-free PDT strategy enabled by the PLNP-DNA nanocomplex promotes the development of PDT and provides a new local therapeutic approach.

Mitochondria-Targeted Mesoporous Titanium Dioxide Nanoplatform for Synergistic Nitric Oxide Gas-Sonodynamic Therapy of Breast Cancer

Background

Sonodynamic therapy (SDT) has rapidly advanced as a promising alternative to conventional photodynamic therapy owing to its preferable therapeutic depth. However, single-modal SDT exhibits limited efficacy due to the long-term hypoxia in tumors.

Method and Results

To address these issues, we proposed a synergistic SDT strategy that integrates mitochondrial targeting with nitric oxide (NO) gas therapy by using multifunctional nanoplatforms. The nanoplatform, which was named as T-mTNPs@L-Arg, was composed of mesoporous titanium dioxide loaded with the NO donor precursor L-arginine (L-Arg) and modified with triphenyl phosphonium (TPP), a mitochondria-targeting ligand. Therefore, T-mTNPs@L-Arg could efficiently concentrate into mitochondria and release NO gas as well as generate reactive oxygen species (ROS) with ultrasound stimulus. Importantly, the released NO gas exerted multiple synergies with SDT, including inducing NO poisoning, generating more lethal reactive nitrogen species (RNS) by reaction with ROS, and alleviating hypoxia through NO-mediated mitochondrial respiration inhibition. On account of the synergistic effects, T-mTNPs@L-Arg showed an outstanding SDT efficacy and a reduced side effect.

Conclusion

This work designed a nanoplatform to integrate mitochondria targeting, SDT and NO gas therapy, providing a new strategy for highly efficient breast cancer therapy.

Tailored Trojan horse nanocarriers for enhanced redox-responsive drug delivery

Redox-responsive anti-tumor nanomedicine is appealing in improving the therapeutic efficacy and patient compliance. However, the thiol-disulfide exchange reaction is reversible and kinetically very slow, resulting in poor drug release and delayed onset of drug action. To address this issue, a tailored Trojan horse nanocarrier is designed with pH-labile zeolitic imidazolate framework-8 (ZIF-8) as the core and disulfide-linked amphiphilic polymer-drug conjugate as the steric shell. A potent reductant, tris(3-hydroxypropyl)phosphine (THPP) is loaded in ZIF-8 and capped by myristyl alcohol. At low pH (e.g. endosome and lysosome), the collapse of ZIF-8 can induce the liberation of THPP that further cleaves the disulfide bond and release the drug post self-immolation. As the reaction between THPP and disulfide is both thermodynamically and kinetically favored, the drug release rate can be boosted. The proof-of-concept is demonstrated both in 4T1 murine mammary carcinoma cells and 4T1 tumor-bearing mice with curcumin as the model drug. Compared to the control nanosystem without THPP, the tailored nanocarrier can significantly enhance the drug release and hence therapeutic efficacy, which is demonstrated by the assays of cell viability, tumor growth inhibition, and histological staining. Such strategy can extend to a plethora of thiol-free cargos for controlled intracellular delivery.

Atom transfer radical-polymerized cationic shells on gold nanoparticles for near infrared-triggered photodynamic therapy of tumor-bearing animals

Gold nanoparticles (AuNPs) were surface-engineered with a cationic corona to enhance the incorporation of photosensitizers for photodynamic therapy (PDT). The cationic corona composed of poly(2-(dimethylamino)ethyl methacrylate) was atom transfer radical-polymerized on the surface of the AuNPs. The cationic corona of the engineered surface was characterized by dynamic light scattering, electron microscopy, Raman spectroscopy, and mass spectroscopy. Chlorin-e6 (Ce6) incorporated onto the surface-engineered AuNPs exhibited higher cell incorporation efficiency than bare AuNPs. Ce6-incorporated AuNPs were confirmed to release singlet oxygen upon NIR irradiation. Compared to Ce6, Ce6-incorporated AuNPs exhibited higher cellular uptake and cytotoxicity against cancer cells in an irradiation time-dependent manner. Near-infrared-irradiated animals administered Ce6-incorporated AuNPs exhibited higher levels of tumor suppression without noticeable body weight loss. This result was attributed to the higher localization of Ce6 at the tumor sites to induce cancer cell apoptosis. Thus, we envision that engineered AuNPs with cationic corona can be tailored to effectively deliver photosensitizers to tumor sites for photodynamic therapy.

Amphiphilic Fullerene-BODIPY Photosensitizers for Targeted Photodynamic Therapy

Nanotheranostic tailor-made carriers are potent platforms for the treatment of cancer that propound a number of advantages over conventional agents for photodynamic therapy (PDT). Herein, four new heavy atom free amphiphilic glucose-BODIPY-fullerene dyads (14-17) endowed with carbohydrate units in the styryl units, which can also form nanomicelles (14-17NM) with Tween 80 for PDT are reported. Glucose-BODIPY-fullerene systems (14-17) and related nanomicelles (14-17NM) have been prepared to emcee efficient singlet oxygen generation upon light irradiation. In vitro anti-tumor effects of the compounds 14-17 and 14-17NM in the presence of light and in darkness have been investigated with K562 human chronic myelogenous leukemia suspension cells. Anti-tumor toxicity upon light irradiation was due to the formation of singlet oxygen and reactive oxygen species (ROS). This study may provide an accomplished example of efficient PDT applications based on nanovehicles fabricated with universal spin converter, fullerene, light harvesting unit, BODIPY dyes conjugated with targeting units to fight against cancer.

Mito-Bomb: Targeting Mitochondria for Cancer Therapy

Cancer has been one of the most common life-threatening diseases for a long time. Traditional cancer therapies such as surgery, chemotherapy (CT), and radiotherapy (RT) have limited effects due to drug resistance, unsatisfactory treatment efficiency, and side effects. In recent years, photodynamic therapy (PDT), photothermal therapy (PTT), and chemodynamic therapy (CDT) have been utilized for cancer treatment owing to their high selectivity, minor resistance, and minimal toxicity. Accumulating evidence has demonstrated that selective delivery of drugs to specific subcellular organelles can significantly enhance the efficiency of cancer therapy. Mitochondria-targeting therapeutic strategies are promising for cancer therapy, which is attributed to the essential role of mitochondria in the regulation of cancer cell apoptosis, metabolism, and more vulnerable to hyperthermia and oxidative damage. Herein, the rational design, functionalization, and applications of diverse mitochondria-targeting units, involving organic phosphine/sulfur salts, quaternary ammonium (QA) salts, peptides, transition-metal complexes, guanidinium or bisguanidinium, as well as mitochondria-targeting cancer therapies including PDT, PTT, CDT, and others are summarized. This review aims to furnish researchers with deep insights and hints in the design and applications of novel mitochondria-targeting agents for cancer therapy.

Dual-step irradiation strategy to sequentially destroy singlet oxygen-responsive polymeric micelles and boost photodynamic cancer therapy

Nanotechnology provides a powerful tool to overcome many disadvantages of small-molecule photosensitizers for photodynamic cancer therapy, such as hydrophobicity, rapid blood clearance, low accumulation in tumor tissue and low cell penetration, etc. The occurrence of quench in photosensitizer-loaded nanoparticle greatly downregulates the ability to generate singlet oxygen with light irradiation. Stimuli-responsive nanocarriers can improve the efficacy of PDT to a certain extent. However, insufficient release of photosensitizer from either endogenous or exogenous stimuli responsive nanocarriers in the short period of light irradiation restricts full usage of the photosensitizer delivered into cancer cells. We here report a dual-step light irradiation strategy to enhance the efficacy of cancer PDT. Ce6 as a photosensitizer is loaded in singlet oxygen-sensitive micelles (Ce6-M) via self-assembly of amphiphilic polymer mPEG₂₀₀₀-TK-C₁₆. After co-incubation of Ce6-M with cancer cells or i.v. injection of Ce6-M, cancer cells or tumor tissues are irradiated with light for a short time to trigger Ce6 release, and 2 h later, re-irradiated for relatively long time. The sufficient release of Ce6 in the period between twice light irradiation significantly improves the generation of singlet oxygen, leading to more efficient cancer therapeutic effects of dual-step irradiation than that of single-step irradiation for the same total irradiation time.

Combination of Chemotherapy and Photodynamic Therapy with Oxygen Self-Supply in the Form of Mutual Assistance for Cancer Therapy

INTRODUCTION

Photodynamic therapy (PDT) has been widely researched by cancer therapists in recent years. This study aims to establish a drug delivery system combining PDT and chemotherapy to show that chemotherapeutic drugs provide oxygen to PDT, while PDT promotes the release of chemotherapeutic drug.

METHODS

Firstly, poly(ethylene glycol)-lysine(Ce6)-block-poly(L-glutamate)-imidazole (mPEG-lys(Ce6)-PGA-AIM) was synthesized and self-assembled into micelles that exhibited pH- and ROS-responsiveness and buffering capacity. Perfluorohexanoate-modified cisplatin (FCP), as oxygen carriers, was encapsulated into mPEG-lys(Ce6)-PGA-AIM micelles. Then, the properties of micelles and their biological functions in vivo and in vitro were investigated.

RESULTS

The micelles exhibited remarkabe stability, pH regulated drug release, good biocompatibility and effective tumor penetration. Cellular uptake demonstrated the efficient endosome/lysosome escape of CFMs, which facilitates the intracellular drug release. Both in vitro and in vivo experiments reflected that CFMs with laser irradiation showed significantly improved therapeutic activity compared with single PDT or chemotherapy.

CONCLUSION

Chemotherapy and PDT were combined in the form of mutual assistance to provide a promising strategy for clinical treatment.

Transmucosal Delivery of Self-Assembling Photosensitizer-Nitazoxanide Nanocomplexes with Fluorinated Chitosan for Instillation-Based Photodynamic Therapy of Orthotopic Bladder Tumors

Theoretically, on account of improved local bioavailability of photosensitizers and attenuated systemic phototoxicity, intravesical instillation-based photodynamic therapy (PDT) for bladder cancer (BCa) would demonstrate significant advantages in comparison with the intravenous route. Actually, the low transmucosal efficiency, hypoxia regulation deficiency, as well as the biosafety risks of intravesical drug agents all have greatly limited the clinical development of instillation-based PDT for BCa. Herein, based on our recent findings on bladder intravesical vectors and photodynamic treatment, we explore and find that the conventional antiparasitic agent nitazoxanide (NTZ) by mixing with chlorine e6 (Ce6) conjugated human serum albumin (HSA), HSA-Ce6, is capable of forming self-assembled HSA-Ce6/NTZ nanoparticles (NPs). Then, the HSA-Ce6/NTZ complexes further fabricate with fluorinated chitosan (FCS), the synthesized transmucosal carrier, to form a biocompatible nanoscale system HSA-Ce6/NTZ/FCS NPs, which exhibit remarkably improved transmucosal delivery and uptake capacities compared with HSA-Ce6/NTZ alone or non-fluorinated HSA-Ce6/NTZ/CS NPs. Meanwhile, due to the metabolic regulation of tumor cells by NTZ, the tumor hypoxia could be efficaciously ameliorated to further favor PDT. This work represents a new photosensitizer nanomedicine formulation for the perfection of PDT performance through the modulation of tumor hypoxia by clinically approved agents. Thus, intravesical instillation of HSA-Ce6/NTZ/FCS NPs with favorable biocompatibility, followed by cystoscope-mediated PDT, could achieve a dramatically improved therapeutic effect to ablate orthotopic bladder tumors.

CD44-targeted pH-responsive micelles for enhanced cellular internalization and intracellular on-demand release of doxorubicin

Poor cellular uptake and slow intracellular drug release remain the main barriers for the efficient application of micellar delivery system. Taking advantage of the overexpressed CD44 receptor and mild acidic microenvironment of tumour cells, CD44-targeted pH-responsive micelles based on the self-assembly of histidine-hyaluronic acid-dodecylamine (His-HA-DA) were prepared for the delivery of doxorubicin (DOX). These micelles exhibited pH-responsive behaviour with increased particle size, decreased encapsulation efficiency (EE%) of DOX and rapid release of DOX triggered by low pH. Compared with free DOX, DOX/HHD exhibited relatively high cellular uptake mainly via the CD44-mediated endocytosis. The on-demand intracellular release of DOX from DOX/HHD led to improved cytotoxicity. DOX/HHD also showed great penetration efficiency in 3D tumour spheres in vitro. Moreover, these micelles with suitable particle size gained excellent tumour-targeting effects, as well as improved anti-tumour effects and reduced side effects in vivo. In conclusion, these micelles with CD44 targeted and pH-responsive behaviours provide a promising strategy for the efficient delivery of anti-tumour drugs in vivo.

Polymeric micelles in cancer therapy: State of the art

In recent years, polymeric micelles have been extensively utilized in pre-clinical studies for delivering poorly soluble chemotherapeutic agents in cancer. Polymeric micelles are formed via self-assembly of amphiphilic polymers in facile manners. The wide availability of hydrophobic and, to some extent, hydrophilic polymeric blocks allow researchers to explore various polymeric combinations for optimum loading, stability, systemic circulation, and delivery to the target cancer tissues. Moreover, polymeric micelles could easily be tailor-made by increasing and decreasing the number of monomers in each polymeric chain. Some of the widely accepted hydrophobic polymers are poly(lactide) (PLA), poly(caprolactone) (PCL), poly(lactide-co-glycolide) (PLGA), polyesters, poly(amino acids), lipids. The hydrophilic polymers used to wrap the hydrophobic core are poly(ethylene glycol), poly(oxazolines), chitosan, dextran, and hyaluronic acids. Drugs could be conjugated to polymers at the distal ends to prepare pharmacologically active polymeric systems that impart enhanced solubility and stability of the conjugates and provide an opportunity for combination drug delivery. Their nano-size enables them to accumulate to the tumor microenvironment via the Enhanced Permeability and Retention (EPR) effect. Moreover, the stimuli-sensitive breakdown provides the micelles an effective means to deliver the therapeutic cargo effectively. The tumor micro-environmental stimuli are pH, hypoxia, and upregulated enzymes. Externally applied stimuli to destroy micellar disassembly to release the payload include light, ultrasound, and temperature. This article delineates the current trend in developing polymeric micelles combining various block polymeric scaffolds. The development of stimuli-sensitive micelles to achieve enhanced therapeutic activity are also discussed.

An update in clinical utilization of photodynamic therapy for lung cancer

Lung cancer is one of the leading causes of cancer-related death worldwide, with nearly 1.8 million-diagnosis and 1.59 million deaths. Surgery, radiotherapy, and chemotherapy in individual or combination are commonly used to treat lung cancers. Photodynamic therapy (PDT) is a highly selective method for the destruction of cancer cells by exerting cytotoxic activity on malignant cells. PDT has been the subject of numerous clinical studies and has proven to be an effective strategy for cancer therapy. Clinical studies revealed that PDT could prolong survival in patients with inoperable cancers and significantly improve quality of life. For inoperable lung cancer cases, PDT could be an effective therapy. Despite the clinical success reported, PDT is still currently underutilized to treat lung cancer and other tumors. PTD is still a new treatment approach for lung cancer mainly due to the lack of enough clinical research evaluating its' effectiveness and side effects. In this review, we discuss the current prospects and future potentials of PDT in lung cancer treatment.

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photoactivatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.

Electron-Accepting Micelles Deplete Reduced Nicotinamide Adenine Dinucleotide Phosphate and Impair Two Antioxidant Cascades for Ferroptosis-Induced Tumor Eradication

Ferroptotic antitumor therapy has been compromised by various intracellular antioxidants, particularly glutathione and thioredoxin. Both are cofactors of glutathione peroxide 4 (GPX4) that act against oxidative stress via catalyzing the reduction of lipid peroxides. It was postulated that tailored polymer micelles could enhance ferroptotic antitumor efficacy via diminishing glutathione and thioredoxin under hypoxia. The aim was to engineer hypoxia-responsive micelles for selective enhancement of ferroptotic cell death in solid tumor. The polymer contains hydrophilic poly(ethylene glycol) (PEG) that is linked by azobenzene linker with nitroimidazole-conjugated polypeptide. The tailored polymer could self-assemble into nanoscale micelles to encapsulate RAS-selective lethal small molecule 3, a covalent GPX4 inhibitor. Under hypoxia, the azobenzene moiety enabled PEG shedding and enhanced micelles uptake in 4T1 cells. Likewise, the nitroimidazole moiety was reduced by the overexpressed nitroreductase with reduced nicotinamide adenine dinucleotide phosphate (NADPH) as the cofactor, resulting in transient depletion of NADPH. This impaired both the glutathione and thioredoxin redox cycle, leading to diminished intracellular glutathione and thioredoxin. The selective potency of ferroptotic micelles in depleting NADPH, glutathione and thioredoxin was further verified in vivo in the 4T1 tumor xenograft mice model. This work highlights the role of hypoxia-responsive polymers in enhancing the potency of ferroptotic inducers against solid tumors without additional side effects to healthy organs.

Redox-Responsive Self-Assembled Nanoparticles for Cancer Therapy

Chemotherapy, combined with other treatments, is widely applied in the clinical treatment of cancer. However, deficiencies inherited from the traditional route of administration limit its successful application. With the development of nanotechnology, a series of smart nanodelivery systems have been developed to utilize the unique tumor environment (pH changes, different enzymes, and redox potential gradients) and exogenous stimuli (thermal changes, magnetic fields, and light) to improve the curative effect of anticancer drugs. In this review, endogenous and exogenous stimuli are briefly introduced. Among these stimuli, various redox-sensitive linkages are primarily described in detail, and their application with self-assembled nanoparticles is recounted. Finally, the application of redox-responsive self-assembled nanoparticles in cancer therapy is summarized.

Biomedical Application of Reactive Oxygen Species-Responsive Nanocarriers in Cancer, Inflammation, and Neurodegenerative Diseases

Numerous pathological conditions, including cancer, inflammatory diseases, and neurodegenerative diseases, are accompanied by overproduction of reactive oxygen species (ROS). This makes ROS vital flagging molecules in disease pathology. ROS-responsive drug delivery platforms have been developed. Nanotechnology has been broadly applied in the field of biomedicine leading to the progress of ROS-responsive nanoparticles. In this review, we focused on the production and physiological/pathophysiological impact of ROS. Particular emphasis is put on the mechanisms and effects of abnormal ROS levels on oxidative stress diseases, including cancer, inflammatory disease, and neurodegenerative diseases. Finally, we summarized the potential biomedical applications of ROS-responsive nanocarriers in these oxidative stress diseases. We provide insights that will help in the designing of new ROS-responsive nanocarriers for various applications.

Development of red-light cleavable PEG-PLA nanoparticles as delivery systems for cancer therapy

The development of targeted delivery systems can improve the selectivity of cancer drugs. Additionally, a system that promotes the controlled delivery of the drug triggered by an external stimulus in the exact target tissue is highly desirable. Regarding the light stimulus, the NIR window (650-950 nm) is the most suitable due to its higher capacity of penetration in human tissues and less harmful effects on normal cells. In this work, new red-light-responsive nanoparticles for doxorubicin delivery were developed. The nanoparticles were based on cleavable di-block copolymers of poly(ethylene glycol) (PEG) and poly(lactic acid) (PLA) linked by a red-light sensitive segment (1,2-bis(2-hydroxyethylthio)ethylene, BHETE). The PEG-BHETE-PLA copolymers were synthesized under mild conditions and exhibited a narrow polydispersity. The nanoparticles presented a size between 53 and 133 nm, with a doxorubicin loading capacity between 1.2 and 4.4 wt%. Release study of the encapsulated doxorubicin confirms the light-triggered nanoparticle disassembly process. In vitro cytotoxicity tests in MCF7 cell line, for the light-triggered nanoparticles, showed a decrease in cancer cells' viability higher than 25% compared to non-irradiated cells. Due to the promising results obtained with the light-sensitive PEG-BHETE-PLA nanoparticles, these materials have great potential to be used in drug delivery systems for cancer therapy.

Fluorescein-Metal Hybrid Surfactant Conjugates as a Smart Material for Antimicrobial Photodynamic Therapy against Staphylococcus aureus

Photodynamic therapy (PDT) has been extensively used as an effective alternative for the treatment of bacterial infection using photosensitizers (PSs) in the presence of appropriate light. However, the limitation in the effectiveness of PDT is because of the low yield of singlet oxygen from existing PSs because of their low solubility. Thus, we have developed a platform to enhance the solubility and the photodynamic activity of PSs against bacterial cells using metallosurfactants. Herein, we have used manganese metal-containing single- (MnC I) and double-chain metallosurfactants (MnC II) which show an interplay of electrostatic/hydrophobic interactions with fluorescein (FL) dye (as a PS) and when used in the presence of light enhances the PDT. These interactions play a significant role in enhancing the singlet oxygen generation efficiency of FL. MnC I and MnC II have shown good antimicrobial activity against Gram-positive Staphylococcus aureus (S. aureus) bacteria. More interestingly, these metallosurfactants when combined with FL significantly enhanced the affectivity against S. aureus, wherein 100% killing was achieved. As compared to experiments performed in the dark, the metallosurfactant, by enhancing the solubility of FL, increases the formation of singlet oxygen upon light irradiation and thus increases cell death. Therefore, the synergistic effect of FL (light toxicity) and metallosurfactants (dark toxicity) defined excellent reduction in the colony formation of bacteria. These results were corroborated through field-emission scanning electron microscopy and optical microscopy, where the rupturing of the cell wall of bacterial cells was observed during this therapy. Moreover, the binding of metallosurfactants to the genomic DNA of S. aureus was also evaluated by gel retardation analysis and UV-visible spectroscopy. The outcomes from this study will deliver formulations for PDT which can be used in clinical medical applications and cancer therapy in the future.

PH and redox dual-responsive polymeric micelles with charge conversion for paclitaxel delivery

Here we demonstrate a type of pH and redox dual-responsive micelles, which were self-assembled in aqueous solution by an amphiphilic polymer, methoxypoly(ethylene glycol)-cystamine-poly(L-glutamic acid)-imidazole (mPEG-SS-PGA-IM). Considering tumor cells or tissues exhibiting low pH values and high glutathione (GSH) concentration, mPEG-SS-PGA-IM micelles possessed the charge conversion at pH of tumor tissues, which can facilitate cellular uptake of tumor cells. Furthermore, mPEG-SS-PGA-IM micelles can escape from endo/lysosomes based on the proton sponge effect, following degraded by higher concentration of GSH in cytoplasm. CLSM images of HCT116 cells indicated that mPEG-SS-PGA-IM micelles can escape from endo/lysosomes and enter cytoplasm. MTT assay showed that (paclitaxel) PTX-loaded mPEG-SS-PGA-IM micelles had higher cytotoxicity against HCT116 cells compared with PTX-loaded mPEG-PBLG and mPEG-SS-PBLG micelles. These results indicated that these mPEG-SS-PGA-IM micelles, as novel and effective pH- and redox-responsive nanocarriers, have great potential to both improve drug targeting efficiency while also enhancing the antitumor efficacy of PTX.

Stimuli-responsive nanocarriers for drug delivery, tumor imaging, therapy and theranostics

In recent years, much progress has been motivated in stimuli-responsive nanocarriers, which could response to the intrinsic physicochemical and pathological factors in diseased regions to increase the specificity of drug delivery. Currently, numerous nanocarriers have been engineered with physicochemical changes in responding to external stimuli, such as ultrasound, thermal, light and magnetic field, as well as internal stimuli, including pH, redox potential, hypoxia and enzyme, etc. Nanocarriers could respond to stimuli in tumor microenvironments or inside cancer cells for on-demanded drug delivery and accumulation, controlled drug release, activation of bioactive compounds, probes and targeting ligands, as well as size, charge and conformation conversion, etc., leading to sensing and signaling, overcoming multidrug resistance, accurate diagnosis and precision therapy. This review has summarized the general strategies of developing stimuli-responsive nanocarriers and recent advances, presented their applications in drug delivery, tumor imaging, therapy and theranostics, illustrated the progress of clinical translation and made prospects.

Rational design of block copolymer self-assemblies in photodynamic therapy

Photodynamic therapy is a technique already used in ophthalmology or oncology. It is based on the local production of reactive oxygen species through an energy transfer from an excited photosensitizer to oxygen present in the biological tissue. This review first presents an update, mainly covering the last five years, regarding the block copolymers used as nanovectors for the delivery of the photosensitizer. In particular, we describe the chemical nature and structure of the block copolymers showing a very large range of existing systems, spanning from natural polymers such as proteins or polysaccharides to synthetic ones such as polyesters or polyacrylates. A second part focuses on important parameters for their design and the improvement of their efficiency. Finally, particular attention has been paid to the question of nanocarrier internalization and interaction with membranes (both biomimetic and cellular), and the importance of intracellular targeting has been addressed.

Triggered All-Active Metal Organic Framework: Ferroptosis Machinery Contributes to the Apoptotic Photodynamic Antitumor Therapy

Nanoscale photodynamic therapy (PDT) is an appealing antitumor modality for which apoptosis is the major mechanism of toxicity induction. It was postulated that the highly reactive singlet oxygen in PDT could deplete glutathione (GSH) and activate ferroptosis, the extent to which could be further manipulated by a redox-responsive nanocarrier. To validate this, a disulfide-bearing imidazole ligand coordinated with zinc to form an all-active metal organic framework (MOF) nanocarrier where a photosensitizer (chlorin e6/Ce6) was encapsulated. Regardless of light irradiation, the Ce6-loaded nanocarrier caused the depletion of intracellular GSH via the disulfide-thiol exchange reaction in a murine mammary carcinoma cell line (4T1). The GSH depletion further caused the inactivation of glutathione peroxide 4 (GPX4) and the enhancement of cytotoxicity that was alleviated by ferroptosis inhibitors. The superior in vivo antitumor efficacy of the all-active nanocarrier was corroborated in a 4T1 tumor-bearing mice model regarding tumor growth suppression and animal survival rate. The coadministration of an iron chelator weakened the antitumor potency of the nanocarrier due to ferroptosis inhibition, which was supported by the fact of tumor growth upsurge and the recovered GPX4 activity. The current work highlights the contribution of ferroptotic machinery to antitumor PDT via an activatable, adaptable, all-active MOF nanocarrier.

Curved corannulene dually targets mitochondria and endoplasmic reticulum, and initiates apoptosis via localized ROS induction upon light triggering

Organelle-targeting agents are promising in both fundamental and applied biomedicine research, but such materials are very limited. As a curved 2D carbon material, corannulene (Cor) displays an uneven intramolecular electron distribution, producing a large dipole moment that can favor the electrostatic interaction. Based on the large negative mitochondrial membrane potential and the presence of a connection structure between mitochondria and endoplasmic reticulum (ER), we hypothesized that Cor could simultaneously target both mitochondria and ER. Such hypothesis was well validated by using the fluorescence tag-labelled Cor. The co-localization analysis in a model cell line (PC3) revealed a preferred accumulation of Cor in both organelles, as evidenced by a large Pearson correlation coefficient. The large dipole also empowered Cor the ability of controlled production of reactive oxygen species (ROS) upon light irradiation. This feature plus mitochondria targeting of Cor induced depletion of adenosine triphosphate (ATP) and caspase 9/3 activation. The triggered ROS generation in ER caused the calcium dumping in the cytosol, as revealed by a calcium-specific fluorescence probe. A significant degree of apoptosis was induced by Cor as a result of the interplay of dual mitochondria/ER targeting and triggered organelle-specific ROS delivery. This study demonstrated the subcellular targeting ability of Cor for potential ROS-based therapy, and implied that the dipole could be a valuable parameter for efficient design and tailored screening of organelle-targeting materials for various biomedical applications.

The Dark Side: Photosensitizer Prodrugs

Photodynamic therapy (PDT) and photodiagnosis (PD) are essential approaches in the field of biophotonics. Ideally, both modalities require the selective sensitization of the targeted disease in order to avoid undesired phenomena such as the destruction of healthy tissue, skin photosensitization, or mistaken diagnosis. To a large extent, the occurrence of these incidents can be attributed to “background” accumulation in non-target tissue. Therefore, an ideal photoactive compound should be optically silent in the absence of disease, but bright in its presence. Such requirements can be fulfilled using innovative prodrug strategies targeting disease-associated alterations. Here we will summarize the elaboration, characterization, and evaluation of approaches using polymeric photosensitizer prodrugs, nanoparticles, micelles, and porphysomes. Finally, we will discuss the use of 5-aminolevulinc acid and its derivatives that are selectively transformed in neoplastic cells into photoactive protoporphyrin IX.

Protoporphyrin IX-loaded laminarin nanoparticles for anticancer treatment, their cellular behavior, ROS detection, and animal studies

Laminarin conjugate-based nano-scaled particles were in this study proposed as a delivery system for protoporphyrin IX (Pp IX) in photodynamic therapy (PDT) of human breast cancer cells (MCF-7). Hematin-Laminarin-Dithiodipropionic Acid-MGK, named as HLDM, was an amphiphilic carrier material with dual pH/redox sensitive that could be used to load hydrophobic drug to improve their solubility and enhance biocompatibility. Therefore, we combined photosensitizer (Pp IX) with HLDM to fabricate a novel nano-micelles, herein called Pp IX-loaded HLDM micelles. The Pp IX-loaded HLDM micelles were 149.3 ± 35 nm sized in neutral water. Phototoxicity, in vitro PDT effect, and dual sensibility to pH and redox microenvironment of Pp IX-loaded HLDM micelles were examined at different concentrations by using MCF-7 human breast cancer cells. The experiments on phototoxicity and reactive oxygen species (ROS) production proved that the micelles could produce PDT to kill the cancer cells with a certain wavelength light. The apoptosis experiment indicated that the micelles could cause nuclear damage. In vivo PDT effect of the micelles was studied by constructing the tumor-bearing nude mouse model of MCF-7 cells. In vivo studies showed that the Pp IX-loaded HLDM micelles could induce remarkable anti-tumor effect. A promising laminarin-based nanomedicine platform acts as a new drug delivery system to enhance the uptake, accumulation, and PDT efficacy of Pp IX in vitro and in vivo.

Energy-Free, Singlet Oxygen-Based Chemodynamic Therapy for Selective Tumor Treatment without Dark Toxicity

Traditional singlet oxygen-based antitumor therapies have been burdened with the necessity of external energy (e.g., light and ultrasound) and harmful dark toxicity. Ascorbate at the pharmacological concentration could accumulate hydrogen peroxide only in the tumor site. It is postulated that the concurrent delivery of ascorbate and nanoparticulate hypochlorous ion (ClO^- ) could produce singlet oxygen at the tumor site as an energy-free, tumor-specific therapy. The ClO^- is loaded in a hybrid core-shell nanocarrier consisting of a zeolitic imidazolate framework and amphiphilic poloxamer 188. Intracellular singlet oxygen production is verified in 4T1 cells by the cooperation between hybrid nanocarriers and ascorbate, which induces significant apoptotic cell death. Upon intravenous nanocarriers delivery plus intraperitoneal ascorbate administration to xenograft mice, the in vivo antitumor efficacy of this cooperative nanomedicine is demonstrated without noticeable side-effects. This work demonstrates a proof-of-concept of singlet oxygen-based chemodynamic therapy for selective tumor eradication, which produces a novel trigger-free, singlet oxygen-based cancer therapy without the side effects of traditional photodynamic and sonodynamic therapy.