Enhancing magnetic resonance/photoluminescence imaging-guided photodynamic therapy by multiple pathways

Visualizing mitochondrial ATP fluctuations in single cells during photodynamic therapy by In-Situ SERS three-dimensional imaging

An ultrasensitive strategy for in-situ visual monitoring of ATP in a single living tumor cell during mitochondria-targeted photodynamic therapy (PDT) process with high spatiotemporal resolution was proposed using surface-enhanced Raman scattering (SERS) 3D imaging technique. The nanostructures consisting of Au-Ag2S Janus nanoparticles functionalized with both Au nanoparticles linked by a DNA chain and a mitochondrial-targeting peptide (JMDA NPs) were deliberately employed to target mitochondria. The JMDA NPs exhibit excellent SERS activity and remarkable antitumor activity. The quantization of ATP relies on the intensity of the SERS probes bonded to the DNA, which shows a strong correlation with the generated hot spot between the Janus and the Au. Consequently, spatiotemporally controlled monitoring of ATP in the mitochondria of single living cells during the PDT process was achieved. Additionally, the JMDA NPs demonstrated remarkable capability for mitochondria-targeted PDT, providing significant antitumor effects and superior therapeutic safety both in vitro and in vivo. Our work presents an effective JMDA NPs-based SERS imaging strategy for in-situ and real-time 3D visualization of intracellular ATP in living tumor cells during the mitochondria-targeted PDT process, which enables significant information on the time point of PDT treatment and is beneficial to precious PDT applications in tumor therapy.

A "lysosomal bomb" constructed based on amorphous calcium carbonate to induce tumor apoptosis by amplified sonodynamic therapy

The acidic nature of malignant tumors leads to increased drug sequestration and the evasion of apoptotic damage, which is further exacerbated by abnormal lysosomes in tumor cells. In this study, a "lysosomal bomb" will be constructed using a type of acid-neutralized amorphous calcium carbonate (ACC) to encapsulate the sonosensitizer protoporphyrin IX (PpIX), and then coated with homologous tumor cell membranes to increase water solubility and homologous targeting. The PpIX-ACC@CMs designed in this paper are popcorn-like structures, which can not only neutralize the tumor's acidic microenvironment to balance the pH value and release excess Ca2+, but also cause lysosomal dysfunction and achieve drug lysosomal escape to increase drug accumulation. Additionally, the CO2 gas nucleus produced by the acid reaction of ACC can increase the ultrasonic cavitation effect to amplify the sonodynamic therapy (SDT) effect. In vitro and in vivo experiments demonstrated that PpIX-ACC@CMs, serving as a "lysosomal bomb," successfully localized to lysosomes of tumor cells and exhibited lysosomal escape ability through its acid reaction ability, achieving excellent SDT efficacy under ultrasound stimulation. Furthermore, exogenous Ca2+ overload also increased the likelihood of tumor calcification, which could contribute to in vivo tumor inhibition and facilitate CT medical imaging to monitor treatment efficacy.

Mitochondria-mediated self-cycling nanoreactor enabling uninterrupted oxidative damage for enhanced chemodynamic therapy

Chemodynamic therapy (CDT), which employs intracellular H2O2 to produce toxic hydroxyl radicals to kill cancer cells, has received great attention due to its specificity to tumors. However, the relatively insufficient endogenous H2O2 and the short-lifetime and limited diffusion distance of •OH compromise the therapeutic efficacy of CDT. Mitochondria, which play crucial roles in oncogenesis, are highly vulnerable to elevated oxidative stress. Herein, we constructed a mitochondria-mediated self-cycling system to achieve high dose of •OH production through continuous H2O2 supply. Cinnamaldehyde (CA), which can elevate H2O2 level in the mitochondria, was loaded in Cu(II)-containing metal organic framework (MOF), termed as HKUST-1. After actively targeting mitochondria, the intrinsic H2O2 in mitochondria of cancer cells could induce degradation of MOF, releasing the initial free CA. The released CA further triggered the upregulation of endogenous H2O2, resulting in the subsequent adequate release of CA and the final burst growth of H2O2. The cycle process greatly promoted the Fenton-like reaction between Cu2+ and H2O2 and induced long-term high oxidative stress, achieving enhanced chemodynamic therapy. In a word, we put forward an efficient strategy for enhanced chemodynamic therapy.

Macromolecular Nano-Assemblies for Enhancing the Effect of Oxygen-Dependent Photodynamic Therapy Against Hypoxic Tumors

In oxygen (O2)-dependent photodynamic therapy (PDT), photosensitizers absorb light energy, which is then transferred to ambient O2 and subsequently generates cytotoxic singlet oxygen (1O2). Therefore, the availability of O2 and the utilization efficiency of generated 1O2 are two significant factors that influence the effectiveness of PDT. However, tumor microenvironments (TMEs) characterized by hypoxia and limited utilization efficiency of 1O2 resulting from its short half-life and short diffusion distance significantly restrict the applicability of PDT for hypoxic tumors. To address these challenges, numerous macromolecular nano-assemblies (MNAs) have been designed to relieve hypoxia, utilize hypoxia or enhance the utilization efficiency of 1O2. Herein, we provide a comprehensive review on recent advancements achieved with MNAs in enhancing the effectiveness of O2-dependent PDT against hypoxic tumors.

Manganese Dioxide-Based Nanomaterials for Medical Applications

Manganese dioxide (MnO2) nanomaterials can react with trace hydrogen peroxide (H2O2) to produce paramagnetic manganese (Mn2+) and oxygen (O2), which can be used for magnetic resonance imaging and alleviate the hypoxic environment of tumors, respectively. MnO2 nanomaterials also can oxidize glutathione (GSH) to produce oxidized glutathione (GSSG) to break the balance of intracellular redox reactions. As a consequence of the sensitivity of the tumor microenvironment to MnO2-based nanomaterials, these materials can be used as multifunctional diagnostic and therapeutic platforms for tumor imaging and treatment. Importantly, when MnO2 nanomaterials are implanted along with other therapeutics, synergetic tumor therapy can be achieved. In addition to tumor treatment, MnO2-based nanomaterials display promising prospects for tissue repair, organ protection, and the treatment of other diseases. Herein, we provide a thorough review of recent progress in the use of MnO2-based nanomaterials for biomedical applications, which may be helpful for the design and clinical translation of next-generation MnO2 nanomaterials.

Design strategies for enhancing antitumor efficacy through tumor microenvironment exploitation using albumin-based nanosystems: A review

The tumor microenvironment (TME) is a complex and dynamic system that plays a crucial role in regulating cancer progression, treatment response, and the emergence of acquired resistance mechanisms. The TME is usually featured by severe hypoxia, low pH values, high hydrogen peroxide (H2O2) concentrations, and overproduction of glutathione (GSH). The current development of intelligent nanosystems that respond to TME has shown great potential to enhance the efficacy of cancer treatment. As one of the functional macromolecules explored in this field, albumin-based nanocarriers, known for their inherent biocompatibility, serves as a cornerstone for constructing diverse therapeutic platforms. In this paper, we present a comprehensive overview of the latest advancements in the design strategies of albumin nanosystems, aiming to enhance cancer therapy by harnessing various features of solid tumors, including tumor hypoxia, acidic pH, the condensed extracellular matrix (ECM) network, excessive GSH, high glucose levels, and tumor immune microenvironment. Furthermore, we highlight representative designs of albumin-based nanoplatforms by exploiting the TME that enhance a broad range of cancer therapies, such as chemotherapy, phototherapy, radiotherapy, immunotherapy, and other tumor therapies. Finally, we discuss the existing challenges and future prospects in direction of albumin-based nanosystems for the practical applications in advancing enhanced cancer treatments.

The ceRNA Mechanism of lncRNA MEG3/miR-21-5p/SPRY2 in Cell Proliferation and Apoptosis in Bladder Cancer

Bladder cancer (BC) is the second most common genitourinary malignancy. Long noncoding RNA (lncRNA) is implicated in BC progression. This study delved into the underlying mechanism of lncRNA MEG3 in BC. Bioinformatics analysis predicted the expression of lncRNA MEG3, its association with the survival of BC patients, its subcellular localization, and its binding sites with miR-21-5p. Differentially expressed genes (DEGs) in the GSE13507 chip were analyzed using GEOexplorer, downstream targets of miR-21-5p were predicted from databases, and the overlapping genes were analyzed by the website Venny2.1 (https://bioinfogp.cnb.csic.es/tools/venny/index.html); their impacts on patient survival were analyzed by the Starbase database. The expression of SPRY2 and TGFBI associated with patient survival was analyzed in TCGA. RT-qPCR and western blot were performed to detect levels of MEG3, miR-21-5p, and SPRY2 in BC/SV-HUC-1 cells. Malignant biological behaviors of BC cells were detected using CCK8, flow cytometry, and Transwell assays. RNA pull-down and dual-luciferase assays were employed to verify the binding relationship of miR-21-5p with MEG3 and SPRY2. MEG3 was found to be lowly expressed in BC cells and mainly distributed in the cytoplasm. Over-expression of MEG3 was found to inhibit BC cell activity, promote apoptosis, and reduce invasion and migration. miR-21-5p was found to be highly expressed in BC cells, and its down-regulation was found to inhibit the malignant behavior of BC cells. Over-expression of miR-21-5p was found to reverse the effect of pcDNA3.1-MEG3 on BC cells. MEG3 was found to competitively bind to miR-21-5p as a ceRNA to promote SPRY2 levels. LncRNA MEG3 promotes SPRY2 expression by competitively binding to miR-21-5p, thereby inhibiting proliferation and promoting apoptosis of BC cells.

Near-infrared photodynamic and photothermal co-therapy based on organic small molecular dyes

Near-infrared (NIR) organic small molecule dyes (OSMDs) are effective photothermal agents for photothermal therapy (PTT) due to their advantages of low cost and toxicity, good biodegradation, and strong NIR absorption over a wide wavelength range. Nevertheless, OSMDs have limited applicability in PTT due to their low photothermal conversion efficiency and inadequate destruction of tumor regions that are nonirradiated by NIR light. However, they can also act as photosensitizers (PSs) to produce reactive oxygen species (ROS), which can be further eradicated by using ROS-related therapies to address the above limitations of PTT. In this review, the synergistic mechanism, composition, and properties of photodynamic therapy (PDT)-PTT nanoplatforms were comprehensively discussed. In addition, some specific strategies for further improving the combined PTT and PDT based on OSMDs for cancer to completely eradicate cancer cells were outlined. These strategies include performing image-guided co-therapy, enhancing tumor infiltration, increasing H2O2 or O2 in the tumor microenvironment, and loading anticancer drugs onto nanoplatforms to enable combined therapy with phototherapy and chemotherapy. Meanwhile, the intriguing prospects and challenges of this treatment modality were also summarized with a focus on the future trends of its clinical application.

Regulating Photosensitizer Metabolism with DNAzyme-Loaded Nanoparticles for Amplified Mitochondria-Targeting Photodynamic Immunotherapy

Mitochondria-specific photosensitizer accumulation is highly recommended for photodynamic therapy and mitochondrial DNA (mtDNA) oxidative damage-based innate immunotherapy but remains challenging. 5-Aminolevulinic acid (ALA), precursor of photosensitizer protoporphyrin IX (PpIX), can induce the exclusive biosynthesis of PpIX in mitochondria. Nevertheless, its photodynamic effect is limited by the intracellular biotransformation of ALA in tumors. Here, we report a photosensitizer metabolism-regulating strategy using ALA/DNAzyme-co-loaded nanoparticles (ALA&Dz@ZIF-PEG) for mitochondria-targeting photodynamic immunotherapy. The zeolitic imidazolate framework (ZIF-8) nanoparticles can be disassembled and release large amounts of zinc ions (Zn2+) within tumor cells. Notably, Zn2+ can relieve tumor hypoxia for promoting the conversion of ALA to PpIX. Moreover, Zn2+ acts as a cofactor of rationally designed DNAzyme for silencing excessive ferrochelatase (FECH; which catalyzes PpIX into photoinactive Heme), cooperatively promoting the exclusive accumulation of PpIX in mitochondria via the "open source and reduced expenditure" manner. Subsequently, the photodynamic effects derived from PpIX lead to the damage and release of mtDNA and activate the innate immune response. In addition, the released Zn2+ further enhances the mtDNA/cGAS-STING pathway mediated innate immunity. The ALA&Dz@ZIF-PEG system induced 3 times more PpIX accumulation than ALA-loaded liposome, significantly enhancing tumor regression in xenograft tumor models.

Visualization of Phototherapy Evolution by Optical Imaging

Phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is a non-invasive and effective approach used for cancer treatment, in which phototherapeutic agents are irradiated with an appropriate light source to produce cytotoxic reactive oxygen species (ROS) or heat to ablate cancer cells. Unfortunately, traditional phototherapy lacks a facile imaging method to monitor the therapeutic process and efficiency in real time, usually leading to severe side effects due to high levels of ROS and hyperthermia. To realize precise cancer treatment methods, it is highly desired to develop phototherapeutic agents possessing an imaging ability to evaluate the therapeutic process and efficacy in real time during cancer phototherapy. Recently, a series of self-reporting phototherapeutic agents were reported to monitor PDT and PTT processes by combining optical imaging technologies with phototherapy. Due to the real-time feedback provided by optical imaging technology, therapeutic responses or dynamic changes in the tumor microenvironment could be evaluated in a timely manner, thereby achieving personalized precision treatment and minimizing toxic side effects. In this review, we focus on the advances in the development of self-reporting phototherapeutic agents for a cancer phototherapy evaluation based on optical imaging technology to realize precision cancer treatments. Additionally, we propose the current challenges and future directions of self-reporting agents for precision medicine.

BSA-coated β-FeOOH nanoparticles efficiently deliver the photosensitizer chlorin e6 for synergistic anticancer PDT/CDT

Photodynamic therapy (PDT) has many exceptional advantages in cancer treatment, such as minor trauma, low toxicity side effects, and strong adaptability, effectively overcoming some obstacles of traditional therapy and providing more revolutionary opportunities for curing cancer. Chlorin e6 (Ce6) exhibits excellent singlet oxygen generation and conversion efficiency under near-infrared laser irradiation and is a promising PDT photosensitizer. However, its hydrophobicity, short half-life and lack of tumor specificity limit its in vivo anticancer application. Therefore, this work has designed and prepared a multifunctional nanoplatform, Ce6/FeOOH@BSA, to efficiently deliver Ce6. Nanoparticles exhibit excellent dispersion and stability in deionized water, PBS and DMEM, and the blood half-life is 3.98 ± 0.31 h. The nanoplatform demonstrates effective tumor targeting and accumulation, overcoming the obstacles of the biological application of Ce6. Iron ions can exert a chemodynamic therapy (CDT) effect by reacting with overexpressed H₂O₂ in the tumor to generate toxic hydroxyl radicals (·OH). Moreover, FeOOH nanoparticles effectively promote glutathione (GSH) consumption in tumor cells, which is conducive to accumulating reactive oxygen species (ROS). In brief, Ce6/FeOOH@BSA nanoparticles realize the targeted delivery of Ce6 and mediate synergistic PDT/CDT against tumors, broadening the biomedical application of nanomaterials.

Use of stimulatory responsive soft nanoparticles for intracellular drug delivery

Drug delivery has made tremendous advances in the last decade. Targeted therapies are increasingly common, with intracellular delivery highly impactful and sought after. Intracellular drug delivery systems have limitations due to imprecise and non-targeted release profiles. One way this can be addressed is through using stimuli-responsive soft nanoparticles, which contain materials with an organic backbone such as lipids and polymers. The choice of biomaterial is essential for soft nanoparticles to be responsive to internal or external stimuli. The nanoparticle must retain its integrity and payload in non-targeted physiological conditions while responding to particular intracellular environments where payload release is desired. Multiple internal and external factors could stimulate the intracellular release of drugs from nanoparticles. Internal stimuli include pH, oxidation, and enzymes, while external stimuli include ultrasound, light, electricity, and magnetic fields. Stimulatory responsive soft nanoparticulate systems specifically utilized to modulate intracellular delivery of drugs are explored in this review.

Nanofibrillar peptide hydrogels for self-delivery of lonidamine and synergistic photodynamic therapy

The use of lonidamine (LND) in photodynamic therapy (PDT) provides a viable approach to develop low-dose PDT modules with high efficacy, for LND potentiates cytotoxicity of photosensitizers through dysregulation of mitochondrial function. Yet, the efficacy of LND is restricted by its low accumulation in cancer cells, especially in the mitochondrial compartments. To address the problem, we design an LND-derived self-assembling peptide molecule (LND-K) that dually targets integrin receptors and mitochondria of cancer cells. The targeted cellular delivery of LND-K gives higher efficacy in ablation of mitochondrial function in melanoma cells A375, as compared to free LND or the control molecule that lacks mitochondria-targeting moieties. To integrate LND-K in a typical PDT module, we develop a nanofibrillar hydrogel system through co-assembly of LND-K and TPPS₄, an anionic photosensitizer that forms tight electrostatic interactions with cationic residues of LND-K. Notably, hydrogel formulation of LND-K/TPPS₄ facilitates slow release of TPPS₄ over 14 days in vitro, and displays a longer retention time than aqueous solution of TPPS₄in vivo. By integrating a mitochondria-targeted molecule (LND-K) in a typical PDT module, we achieve synergistic killing of A375 cells with dual drugs, where LND-K not only serves as a chemotherapeutic drug, but also potentiates the cytotoxicities of TPPS₄ toward A375 cells in vitro and in vivo. The peptide-based drug self-delivery system promises the development of efficacious combination treatments against cancer, that integrate cell sensitization with existing anticancer modules (e.g., chemotherapy and PDT) for enhanced therapeutic efficacy. STATEMENT OF SIGNIFICANCE: This study reports the design and synthesis of a lonidamine (LND)-derived self-assembling peptide (LND-K) that dually targets integrin receptors and mitochondria of cancer cells. Under the precision guidance of a mitochondria-targeting sequence, LND-K-containing nanofibers target mitochondria and ablate mitochondrial functions. On one hand, the targeted delivery of LND-K reduces cell viabilities through a chemotherapy route; on the other hand, LND-K sensitizes cancer cells for subsequent PDT treatment with enhanced efficacy, which is mediated by induction of ROS, loss of mitochondrial membrane potential, and decrease of cellular ATP level. We believe that the design of mitochondria-targeted drug delivery systems with a self-assembling molecule provides a new approach to potentiate cytotoxicity of photosensitizers in a low-dose PDT module.

MOF(Fe)-derived composites as a unique nanoplatform for chemo-photodynamic tumor therapy

Fe-based metal-organic frameworks (MOFs) can be used for chemodynamic therapy (CDT) for tumors due to their unique Fenton-like effects and porous and biodegradable nature. The adsorption and transport of small molecule drugs by their structure has attracted much attention. Herein, MnO₂@NH₂-MIL101(Fe)@Ce6-F127 nanoparticles (MNMCF NPs) were synthesized using a facile solvothermal strategy. The small molecule photosensitizer Ce6 was adsorbed by MOFs to improve the biocompatibility of Ce6 and give it high bioavailability when injected intravenously. When the MNMCF NPs reached the tumor site, Fe-based MOFs exhibited Fenton-like properties, producing ˙OH and showing CDT effects. MnO₂ could specifically respond to produce O₂ in a tumor microenvironment, thereby improving the tumor hypoxia state and enhancing the efficacy of photodynamic therapy (PDT) by Ce6. Both the in vitro and in vivo experiments showed that the MNMCF-guided CDT/PDT combination therapy could effectively ablate tumors without the drawbacks of poor tolerability and potential long-term side effects. Therefore, the prepared MNMCF NPs can be used as promising candidates for synergistic CDT/PDT tumor therapy.

An Intracellular Self-Assembly-Driven Uninterrupted ROS Generator Augments 5-Aminolevulinic-Acid-Based Tumor Therapy

Free radical therapy based on 5-aminolevulinic acid (ALA, a precursor of the photosensitizer protoporphyrin IX (PpIX)) has been approved by the US Food and Drug Administration for clinical tumor treatment. However, PpIX can be quickly converted into photoinactive heme, leading to unexpectedly paused production of free radicals and severely hindering its therapeutic benefits. Here, inspired by the natural biotransformation of ALA (ALA-PpIX-heme), an uninterrupted reactive oxygen species generator (URG) that converts useless heme to peroxidase mimics via intracellular self-assembly is developed. The URG is prepared by enwrapping ALA-loaded polyamide-amine dendrimers in red blood cell membrane vesicles with a further surface modification of G-quadruplex-structured AS1411. The URGs realize "¹ O₂ -•OH" uninterrupted generation through "recycling waste" in two steps: i) PpIX generates ¹ O₂ under laser irradiation; and ii) the photoinactive metabolite heme self-assembled with AS1411 to catalyze H₂ O₂ conversion into •OH. Interestingly, the specific generation of ¹ O₂ in mitochondria and •OH in nuclei further augments the free-radical-induced damage. It is demonstrated that URG can continuously produce free radicals for 6 h postirradiation, and shows 3.3-times more than that of the nonassembly group, achieving nearly 80% regression of tumors in vivo.

A Nanoarchitectonic Approach Enables Triple Modal Synergistic Therapies To Enhance Antitumor Effects

Improvement of antitumor effects relies on the development of biocompatible nanomaterials and combination of various therapies to produce synergistic effects and avoid resistance. In this work, we developed GBD-Fe, a nanoformulation that effectively integrated chemotherapy (CT), chemodynamic therapy (CDT), and photothermal therapy (PTT). GBD-Fe used gold nanorods as photothermal agents and encapsulated doxorubicin to amplify Fe³⁺-guided CDT effects by producing H₂O₂ and reducing the intracellular glutathione levels. In vitro and in vivo experiments were conducted to demonstrate the enhanced accumulation and antitumor effects of this tripronged therapy under magnetic resonance imaging (MRI) guidance. This tripronged approach of CT/CDT/PTT effectively induced tumor cytotoxicity and inhibited tumor growth in tumor-bearing mice and therefore represents a promising strategy to effectively treat tumors.

GSH-Responsive Drug Delivery System for Active Therapy and Reducing the Side Effects of Bleomycin

The application of drug delivery system (DDS) has achieved breakthroughs in many aspects, especially in the field of tumor treatment. In this work, polyethylene glycol (PEG)-modified hollow mesoporous manganese dioxide (HMnO₂@PEG) nanoparticles were used to load the anti-tumor drug bleomycin (BLM). When the DDS reached the tumor site, HMnO₂@PEG was degraded and reduced to Mn²⁺ by the overexpression of glutathione in the tumor microenvironment, and the drug was released simultaneously. BLM coordinated with Mn²⁺ in situ, thereby greatly improving the therapeutic activity of BLM. The results of in vivo and in vitro treatment experiments showed that the DDS had excellent responsive therapeutic activation ability. In addition, Mn²⁺ exhibited strong paramagnetism and was used for T₁-weighted magnetic resonance imaging in vivo. Furthermore, this therapeutic mode of responsively releasing drugs and activating in situ effectively attenuated pulmonary fibrosis initiated by BLM. In short, this DDS could help in avoiding the side effects of drugs.

Multifunctional phototheranostic nanoplatform based on polydopamine-manganese dioxide-IR780 iodide for effective magnetic resonance imaging-guided synergistic photodynamic/photothermal therapy

Multifunctional phototheranostics combining diagnostic and therapeutic modalities may provide a revolutionary opportunity for cancer treatment. As a promising tumor phototheranostic molecule, IR780 iodide (IR780) shows excellent photodynamic and photothermal performance under near-infrared laser irradiation; however, its hydrophobicity and instability limit its further use in organisms. This work demonstrates the design and development of a multifunctional nanoplatform (PMIDA, referring to polydopamine (PDA)-manganese dioxide (MnO₂)-IR780) for imaging-guided phototherapy. The good biocompatibility of PDA greatly improves the water solubility and photostability of IR780, and its excellent photothermal properties make PMIDA a dual photothermal therapy (PTT). MnO₂-induced generation of oxygen in the tumor microenvironment improves the hypoxia effect and photodynamic therapy (PDT) of IR780. Moreover, Mn²⁺ serves as a decent T₁-weighted magnetic resonance imaging (MRI) probe to guide treatment. Notably, in relevant cellular assays, PMIDA shows high photodynamic and photothermal effects contributing to the final therapeutic effect. The MRI-guided PDT/PTT synergistic therapy effect in vivo is demonstrated by precise tumor diagnosis and complete tumor elimination outcomes. Based on these experiments, PMIDA nanoparticles display promising effects in facilitating intravenous injection of IR780 and achieving magnetic resonance imaging (MRI)-guided phototheranostic efficacy for tumor treatment.

Mitochondria-Targeted Nanomedicine for Enhanced Efficacy of Cancer Therapy

Nanomedicines have been designed and developed to deliver anticancer drugs or exert anticancer therapy more selectively to tumor sites. Recent investigations have gone beyond delivering drugs to tumor tissues or cells, but to intracellular compartments for amplifying therapy efficacy. Mitochondria are attractive targets for cancer treatment due to their important functions for cells and close relationships to tumor occurrence and metastasis. Accordingly, multifunctional nanoplatforms have been constructed for cancer therapy with the modification of a variety of mitochondriotropic ligands, to trigger the mitochondria-mediated apoptosis of tumor cells. On this basis, various cancer therapeutic modalities based on mitochondria-targeted nanomedicines are developed by strategies of damaging mitochondria DNA (mtDNA), increasing reactive oxygen species (ROS), disturbing respiratory chain and redox balance. Herein, in this review, we highlight mitochondria-targeted cancer therapies enabled by nanoplatforms including chemotherapy, photothermal therapy (PTT), photodynamic therapy (PDT), chemodynamic therapy (CDT), sonodynamic therapy (SDT), radiodynamic therapy (RDT) and combined immunotherapy, and discussed the ongoing challenges.

Construction of nanomaterials as contrast agents or probes for glioma imaging

Malignant glioma remains incurable largely due to the aggressive and infiltrative nature, as well as the existence of blood-brain-barrier (BBB). Precise diagnosis of glioma, which aims to accurately delineate the tumor boundary for guiding surgical resection and provide reliable feedback of the therapeutic outcomes, is the critical step for successful treatment. Numerous imaging modalities have been developed for the efficient diagnosis of tumors from structural or functional aspects. However, the presence of BBB largely hampers the entrance of contrast agents (Cas) or probes into the brain, rendering the imaging performance highly compromised. The development of nanomaterials provides promising strategies for constructing nano-sized Cas or probes for accurate imaging of glioma owing to the BBB crossing ability and other unique advantages of nanomaterials, such as high loading capacity and stimuli-responsive properties. In this review, the recent progress of nanomaterials applied in single modal imaging modality and multimodal imaging for a comprehensive diagnosis is thoroughly summarized. Finally, the prospects and challenges are offered with the hope for its better development.

Construction of Smart Nanotheranostic Platform Bi-Ag@PVP: Multimodal CT/PA Imaging-Guided PDT/PTT for Cancer Therapy

High-efficiency nanotheranostic agents with multimodal imaging guidance have attracted considerable interest in the field of cancer therapy. Herein, novel silver-decorated bismuth-based heterostructured polyvinyl pyrrolidone nanoparticles (NPs) with good biocompatibility (Bi-Ag@PVP NPs) were synthesized for accurate theranostic treatment, which can integrate computed tomography (CT)/photoacoustic (PA) imaging and photodynamic therapy/photothermal therapy (PDT/PTT) into one platform. The Bi-Ag@PVP NPs can enhance light absorption and achieve a better photothermal effect than bismuth NPs. Moreover, after irradiation under an 808 nm laser, the Bi-Ag@PVP NPs can efficiently induce the generation of reactive oxygen species (ROS), thereby synergizing PDT/PTT to exert an efficient tumor ablation effect both in vitro and in vivo. Furthermore, Bi-Ag@PVP NPs can also be employed to perform enhanced CT/PA imaging because of their high X-ray absorption attenuation and enhanced photothermal conversion. Thus, they can be utilized as a highly effective CT/PA imaging-guided nanotheranostic agent. In addition, an excellent antibacterial effect was achieved. After irradiation under an 808 nm laser, the Bi-Ag@PVP NPs can destroy the integrity of Escherichia coli, thereby inhibiting E. coli growth, which can minimize the risk of infection during cancer therapy. In conclusion, our study provides a novel nanotheranostic platform that can achieve CT/PA-guided PDT/PTT synergistic therapy and have potential antibacterial properties. Thus, this work provides an effective strategy for further broad clinical application prospects.

One-pot synthesis of a self-reinforcing cascade bioreactor for combined photodynamic/chemodynamic/starvation therapy

The combination of photodynamic therapy (PDT) and chemodynamic therapy (CDT) have attracted a great deal of interest, but tumor hypoxia and glutathione (GSH) overproduction still limit their further applications. Herein, an intelligent reactive oxygen species (ROS) nanogenerator Ce6/GOx@ZIF-8/PDA@MnO₂ (denoted as CGZPM; Ce6, GOx, ZIF-8, PDA, MnO₂ are chlorin e6, glucose oxidase, zeolitic imidazolate framework-8, polydopamine and manganese dioxide respectively) with O₂-generating and GSH-/glucose-depleting abilities was constructed by a facile and green one-pot method. After intake by tumor cells, the outer MnO₂ was rapidly degraded by the acidic pH, and the overexpression of hydrogen peroxide (H₂O₂) and GSH with abundant Mn²⁺ and O₂ produced would eventually achieve multifunctionality. The Mn²⁺ acted as an ideal Fenton-like agent and magnetic resonance (MR) imaging contrast agent, while the O₂ promoted the PDT via hypoxia relief and facilitated the intratumoral glucose oxidation by GOx for starvation therapy (ST). Benefiting from the GOx-based glycolysis process, sufficient H₂O₂ was generated to improve the CDT efficacy through Mn²⁺-mediated Fenton-like reaction. Notably, MnO₂ and PDA could decrease the tumor antioxidant activity by consuming GSH, resulting in remarkably enhanced PDT/CDT. Such a novel cascade bioreactor with tumor microenvironment (TME)-modulating capability opens new opportunities for ROS-based and combinational treatment paradigms.

Optical and magnetic resonance imaging approaches for investigating the tumour microenvironment: state-of-the-art review and future trends

The tumour microenvironment (TME) strongly influences tumorigenesis and metastasis. Two of the most characterized properties of the TME are acidosis and hypoxia, both of which are considered hallmarks of tumours as well as critical factors in response to anticancer treatments. Currently, various imaging approaches exist to measure acidosis and hypoxia in the TME, including magnetic resonance imaging (MRI), positron emission tomography and optical imaging. In this review, we will focus on the latest fluorescent-based methods for optical sensing of cell metabolism and MRI as diagnostic imaging tools applied both in vitro and in vivo. The primary emphasis will be on describing the current and future uses of systems that can measure intra- and extra-cellular pH and oxygen changes at high spatial and temporal resolution. In addition, the suitability of these approaches for mapping tumour heterogeneity, and assessing response or failure to therapeutics will also be covered.

Regulating glucose metabolism using nanomedicines for cancer therapy

The regulation of glucose metabolism is a research focus in cancer treatment. Glucose metabolism is essential for maintaining the growth and proliferation of tumor cells, thus offering us great opportunities for tumor treatment. Recently, much progress has been made in efficient cancer treatment by regulating the pathway of glucose metabolism with nanomedicines due to the rapid development of nanotechnology and promising drug targets. In this review, we first introduced the pathway of cell energy supply from the perspective of aerobic and anaerobic processes. Then, we discussed the recent research progress in regulating glucose metabolism for various tumor resistance strategies including heat resistance, multiple drug resistance, and hypoxia. Finally, we presented the prospects and challenges of developing multifunctional nanoagents for efficient chemotherapy, hyperthermia, dynamic therapy and so on by regulating glucose metabolism.

Glutathione-Responsive Multifunctional "Trojan Horse" Nanogel as a Nanotheranostic for Combined Chemotherapy and Photodynamic Anticancer Therapy

It remains a great challenge to design a multifunctional and robust nanoplatform for stimuli-responsive drug delivery toward a lesion, which tactfully integrates multiple molecules with therapeutic and diagnostic characteristics. Herein, we reported a facile and ingenious cross-linked nanogel (DSA) based on the chemical cross-link of drugs as a straightforward strategy to overcome the instability of the assembly. In DSA, doxorubicin (DOX) and 5-aminolevulinic acid (ALA) were cross-linked with a disulfide linker for realizing synergistic anticancer therapy. The stability of DSA was adjusted via balancing the hydrophobic/hydrophilic property with hydrophilic NH2-PEG1k. After regulating the coordination of the DOX part and ALA moiety, the drug-loaded nanogel exhibited superior chemotherapeutic efficacies. Additionally, the DSA could selectively biosynthesize fluorescent protoporphyrin IX (PpIX) in tumor cells, which could be applied for a real-time imaging probe of accurate cancer diagnosis. Besides, the in situ synthesized PpIX in mitochondria could serve as a photosensitizer to convert oxygen into toxic reactive oxygen species under a near infrared ray at 660 nm irradiation, leading to an excellent tumor-killing efficacy. This work proposed a unique strategy for designing a series of prodrug nanogels as a universal drug delivery platform for realizing precise disease therapy and diagnostics.

Nanostructured manganese dioxide for anticancer applications: preparation, diagnosis, and therapy

Nanostructured manganese dioxide (MnO₂) has attracted extensive attention in the field of anticancer applications. As we all know, the tumor microenvironment is usually characterized by a high glutathione (GSH) concentration, overproduced hydrogen peroxide (H₂O₂), acidity, and hypoxia, which affect the efficacy of many traditional treatments such as chemotherapy, radiotherapy, and surgery. Fortunately, as one kind of redox-active nanomaterial, nanostructured MnO₂ has many excellent properties such as strong oxidation ability, excellent catalytic activity, and good biodegradability. It can be used effectively in diagnosis and treatment when it reacts with some harmful substances in the tumor site. It can not only enhance the therapeutic effect but also adjust the tumor microenvironment. Therefore, it is necessary to present the recent achievements and progression of nanostructured MnO₂ for anticancer applications, including preparation methods, diagnosis, and treatment. Special attention was paid to photodynamic therapy (PDT), bioimaging and cancer diagnosis (BCD), and drug delivery systems (DDS). This review is expected to provide helpful guidance on further research of nanostructured MnO₂ for anticancer applications.

Broaden sources and reduce expenditure: Tumor-specific transformable oxidative stress nanoamplifier enabling economized photodynamic therapy for reinforced oxidation therapy

Cancer cells immersed in inherent oxidative stress are more vulnerable to exogenous oxidative damages than normal cells. Reactive oxygen species (ROS)-mediated oxidation therapy preferentially aggravating tumor oxidative stress to disrupt redox homeostasis, has emerged as an effective and specific anticancer treatment. Herein, following an ingenious strategy of “broaden sources and reduce expenditure”, we designed a versatile tumor-specific oxidative stress nanoamplifier enabling economized photodynamic therapy (PDT), to achieve synergistic oxidative stress explosion for superior oxidation therapy.

Methods: Cinnamaldehyde (CA) as a therapeutic ROS generator was first conjugated to hyaluronic acid (HA) through acid-labile hydrazone bond to synthesize tailored amphiphilic HA@CA conjugates, which could surprisingly self-assemble into uniform nanofibers in aqueous media. Photosensitizer protoporphyrin (PpIX) was efficiently encapsulated into HA@CA nanofibers and transformed HA@CA nanofibers to final spherical HA@CAP.

Results: With beneficial pH-responsiveness and morphology transformation, improved bioavailability and selective tumor accumulation, HA@CAP combining ROS-based dual chemo/photodynamic treatment modalities could induce cytotoxic ROS generation in a two-pronged approach to amplify tumor oxidative stress, termed “broaden sources”. Moreover, utilizing CA-induced H₂O₂ production and cascaded Fenton reaction in mitochondria to consume intracellular overloaded Fe(II), HA@CAP could skillfully block endogenic heme biosynthesis pathway on site to restrain undesired elimination of PpIX for economized PDT, termed “reduce expenditure”. Both in vitro and in vivo results demonstrated the superior antitumor performance of HA@CAP.

Conclusion: This study offered an inspiring strategy of “broaden sources and reduce expenditure” to specifically boost tumor oxidative stress for reinforced oxidation therapy.

Tumor Microenvironment-triggered Nanosystems as dual-relief Tumor Hypoxia Immunomodulators for enhanced Phototherapy

Photodynamic therapy (PDT) is a promising strategy in cancer treatment that utilizes photosensitizers (PSs) to produce reactive oxygen species (ROS) and eliminate cancer cells under specific wavelength light irradiation. However, special tumor environments, such as those with overexpression of glutathione (GSH), which will consume PDT-mediated ROS, as well as hypoxia in the tumor microenvironment (TME) could lead to ineffective treatment. Moreover, PDT is highly light-dependent and therefore can be hindered in deep tumor cells where light cannot easily penetrate. To solve these problems, we designed oxygen-dual-generating nanosystems MnO2@Chitosan-CyI (MCC) for enhanced phototherapy. Methods: The TME-sensitive nanosystems MCC were easily prepared through the self-assembly of iodinated indocyanine green (ICG) derivative CyI and chitosan, after which the MnO2 nanoparticles were formed as a shell by electrostatic interaction and Mn-N coordinate bonding. Results: When subjected to NIR irradiation, MCC offered enhanced ROS production and heat generation. Furthermore, once endocytosed, MnO2 could not only decrease the level of GSH but also serve as a highly efficient in situ oxygen generator. Meanwhile, heat generation-induced temperature increase accelerated in vivo blood flow, which effectively relieved the environmental tumor hypoxia. Furthermore, enhanced PDT triggered an acute immune response, leading to NIR-guided, synergistic PDT/photothermal/immunotherapy capable of eliminating tumors and reducing tumor metastasis. Conclusion: The proposed novel nanosystems represent an important advance in altering TME for improved clinical PDT efficacy, as well as their potential as effective theranostic agents in cancer treatment.

Versatile Nanoplatforms with enhanced Photodynamic Therapy: Designs and Applications

As an emerging antitumor strategy, photodynamic therapy (PDT) has attracted intensive attention for the treatment of various malignant tumors owing to its noninvasive nature and high spatial selectivity in recent years. However, the therapeutic effect is unsatisfactory on some occasions due to the presence of some unfavorable factors including nonspecific accumulation of PS towards malignant tissues, the lack of endogenous oxygen in tumors, as well as the limited light penetration depth, further hampering practical application. To circumvent these limitations and improve real utilization efficiency, various enhanced strategies have been developed and explored during the past years. In this review, we give an overview of the state-of-the-art advances progress on versatile nanoplatforms for enhanced PDT considering the enhancement from targeting or responsive, chemical and physical effect. Specifically, these effects mainly include organelle-targeting function, tumor microenvironment responsive release photosensitizers (PS), self-sufficient O2 (affinity oxygen and generating oxygen), photocatalytic water splitting, X-rays light stimulate, surface plasmon resonance enhancement, and the improvement by resonance energy transfer. When utilizing these strategies to improve the therapeutic effect, the advantages and limitations are addressed. Finally, the challenges and prospective will be discussed and demonstrated for the future development of advanced PDT with enhanced efficacy.

Roles of a TMPO-AS1/microRNA-200c/TMEFF2 ceRNA network in the malignant behaviors and 5-FU resistance of ovarian cancer cells

Competing endogenous RNA (ceRNA) networks consisted of long non-coding RNA (lncRNA), microRNA (miRNA) and mRNAs have aroused great interests recently. The current study aims to probe the mechanisms of lncRNA TMPO-AS1 in ovarian cancer (OC) development. A 5-fluorouracil (5-FU)-resistant subline of OC SKOV3 cells was developed, and differentially expressed lncRNAs in OC tissues and SKOV3 cells were analyzed. The miRNAs, genes and signaling pathways interacted with TMPO-AS1 were predicted and validated. TMPO-AS1 and the validated miRNA were inhibited to analyze their roles in malignant behaviors and 5-FU resistance of OC cells. In vivo studies were performed by inducing xenograft tumors in nude mice. Consequently, TMPO-AS1 was highly expressed in OC tissues and SKOV3 cells. TMPO-AS1 regulated transmembrane protein with epidermal growth factor and two follistatin motifs 2 (TMEFF2) through sponging miR-200c in OC cells, during which the PI3K/Akt signaling pathway was activated. Silenced TMPO-AS1 and over-expressed miR-200c inhibited epithelial-mesenchymal transition (EMT), invasion, migration and 5-FU resistance of OC cells. This study demonstrated that silencing of TMPO-AS1 might attenuate OC progression through inhibiting the invasion, metastasis and drug resistance of OC cells via the miR-200c/TMEFF2 network and the disruption of the PI3K/Akt signaling pathway.

A novel nanoparticle-based theranostic agent targeting LRP-1 enhances the efficacy of neoadjuvant radiotherapy in colorectal cancer

Neoadjuvant radiotherapy has become an important therapeutic option for colorectal cancer (CRC) patients, whereas complete tumor response is observed only in 20-30% patients. Therefore, the development of diagnostic probe for radio-resistance is important to decide an optimal treatment timing and strategy for radiotherapy-resistant CRC patients. In this study, using the patient-derived xenograft (PDX) mouse model established with a radio-resistant CRC tumor tissue, we found low-density lipoprotein receptor-related protein-1 (LRP-1) as a radio-resistant marker protein induced by initial-dose radiation in radio-resistant CRC tumors. Simultaneously, we discovered a LRP-1 targeting peptide in a radio-resistant CRC PDX through in vivo peptide screening. We next engineered the theranostic agent made of human serum albumin nanoparticles (HSA NPs) containing 5-FU for chemo-radiotherapy and decorating LRP-1-targeting peptide for tumor localization, Cy7 fluorophore for diagnostic imaging. The nanoparticle-based theranostic agent accurately targeted the tumor designated by LRP-1 responding radiation and showed dramatically improved therapeutic efficacy in the radio-resistant PDX model. In conclusion, we have identified LRP-1 as a signature protein of radio-resistant CRC and successfully developed LRP-1-targeting HSA-NP containing 5-FU that is a novel theranostic tool for both diagnostic imaging and neoadjuvant therapy of CRC patients. This approach is clinically applicable to improve the effectiveness of neo-adjuvant radiotherapy and increase the ratio of complete tumor response in radio-resistant CRC.

Prodrug-Based Versatile Nanomedicine for Enhancing Cancer Immunotherapy by Increasing Immunogenic Cell Death

Nanoparticle-based tumor immunotherapy has emerged to show great potential for simultaneously regulating the immunosuppressive tumor microenvironment, reducing the unpleasant side effects, and activating tumor immunity. Herein, an excipient-free glutathione/pH dual-responsive prodrug nanoplatform is reported for immunotherapy, simply by sequentially liberating 5-aminolevulinic acid and immunogenically inducing doxorubicin drug molecules, which can leverage the acidity and reverse tumor microenvironment. The obtained nanoplatform effectively boosts the immune system by promoting dendritic cell maturation and reducing the number of immune suppressive immune cells, which shows the enhanced adjunctive effect of anti-programmed cell death protein 1 therapy. Overall, the prodrug-based immunotherapy nanoplatform may offer a reliable strategy for improving synergistic antitumor efficacy.

Protein-based nanoplatforms for tumor imaging and therapy

Cancer is one of the leading causes of death all over the world. The development of nanoplatform provides a promising strategy for the diagnosis and treatment of cancer. As the foundation of the nanoplatform, the composition of nanocarrier decides the basic properties. Protein exists in all kinds of life and participates in any life activities, having great potentials to serve as a nanocarrier because of its excellent biocompatibility, abundance of functional groups, and inherent biological activity. As a result, protein-based nanoplatforms have evoked extensive interests for tumor imaging and therapy. This review presents the latest progresses on the advancement of protein-based nanoplatforms, introducing the most common protein nanocarriers (such as human/bovine serum albumin, ferritin, human transferrin) thoroughly including their physiochemical properties and specific applications. Also, other kinds of protein are briefly involved. Finally, the prospects and challenges of the development of protein-based nanoplatforms are summarized. This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

An optimized lanthanide-chlorophyll nanocomposite for dual-modal imaging-guided surgery navigation and anti-cancer theranostics

A lanthanide-chlorophyll nanocomposite with enhanced red emission under a near-infrared laser was designed for dual-modal imaging-guided surgery navigation and anti-cancer theranostics.

Metal-Organic Frameworks as a Theranostic Nanoplatform for Combinatorial Chemophotothermal Therapy Adapted to Different Administration

With the rapid development of nanotechnology, nanomaterial drug delivery systems have provided an alternative for designing controllable drug delivery systems due to their spatiotemporally controllable properties. As a new type of porous material, metal-organic frameworks (MOFs) have been widely used in biomedical applications, especially drug delivery systems, owing to their tunable pore size, high surface area and pore volume, and easy surface modification. Here, we demonstrate an MOF as a theranostic nanoplatform to combine drug therapy and phototherapy after labeling targeting peptide iRGD. The micropore Fe-MOF was used as MRI agents for locating tumors and as nanocarriers to upload chemotherapeutic drugs. Moreover, MOF showed excellent targeting performance under different administration including intravenous injection for breast cancer and local instillation for bladder cancer. Notably, when irradiated with an 808 nm laser, the agent demonstrates the high efficacy of photothermal therapy and heat release efficiency of the drug around the tumor site. This combination therapy provides an alternative drug administration method and can be adapted to a series of cancer cell types and molecular targets associated with disease progression.

Degradable magnetic-response photoacoustic/up-conversion luminescence imaging-guided photodynamic/photothermal antitumor therapy

In this research, a degradable uniform mesoporous platform was designed as an imaging-guided photothermal therapy (PTT)/photodynamic therapy (PDT) agent.