Targeting the Opening of Mitochondrial Permeability Transition Pores Potentiates Nanoparticle Drug Delivery and Mitigates Cancer Metastasis

2D nanomaterials-based delivery systems and their potentials in anticancer synergistic photo-immunotherapy

As the field of cancer therapeutics evolves, integrating two-dimensional (2D) nanomaterials with photo-immunotherapy has emerged as a promising approach with significant potential to augment cancer treatment efficacy. These 2D nanomaterials include graphene-based 2D nanomaterials, 2D MXenes, 2D layered double hydroxides, black phosphorus nanosheets, 2D metal-organic frameworks, and 2D transition metal dichalcogenides. They exhibit high load capacities, multiple functionalization pathways, optimal biocompatibility, and physiological stability. Predominantly, they function as anti-tumor delivery systems, amalgamating diverse therapeutic modalities, most notably phototherapy and immunotherapy, and the former is a recognized non-invasive treatment modality, and the latter represents the most promising anti-cancer strategy presently accessible. Thus, integrating phototherapy and immunotherapy founded on 2D nanomaterials unveils a novel paradigm in the war against cancer. This review delineates the latest developments in 2D nanomaterials as delivery systems for synergistic photo-immunotherapy in cancer treatment. We elaborate on the burgeoning realm of photo-immunotherapy, exploring the interplay between phototherapy and enhanced immune cells, immune response modulation, or immunosuppressive tumor microenvironments. Notably, the strategies to augment photo-immunotherapy have also been discussed. Finally, we discuss the challenges and future perspectives of these 2D nanomaterials in photo-immunotherapy.

Biodegradable copper-iodide clusters modulate mitochondrial function and suppress tumor growth under ultralow-dose X-ray irradiation

Both copper (Cu2+/+) and iodine (I-) are essential elements in all living organisms. Increasing the intracellular concentrations of Cu or I ions may efficiently inhibit tumor growth. However, efficient delivery of Cu and I ions into tumor cells is still a challenge, as Cu chelation and iodide salts are highly water-soluble and can release in untargeted tissue. Here we report mitochondria-targeted Cu-I cluster nanoparticles using the reaction of Cu+ and I- to form stable bovine serum albumin (BSA) radiation-induced phosphors (Cu-I@BSA). These solve the stability issues of Cu+ and I- ions. Cu-I@BSA exhibit bright radioluminescence, and easily conjugate with the emission-matched photosensitizer and targeting molecule using functional groups on the surface of BSA. Investigations in vitro and in vivo demonstrate that radioluminescence under low-dose X-ray irradiation excites the conjugated photosensitizer to generate singlet oxygen, and combines with the radiosensitization mechanism of the heavy atom of iodine, resulting in efficient tumor inhibition in female mice. Furthermore, our study reveals that BSA protection causes the biodegradable Cu-I clusters to release free Cu and I ions and induce cell death by modulating mitochondrial function, damaging DNA, disrupting the tricarboxylic acid cycle, decreasing ATP generation, amplifying oxidative stress, and boosting the Bcl-2 pathway.

Mitochondrial metabolism blockade nanoadjuvant reversed immune-resistance microenvironment to sensitize albumin-bound paclitaxel-based chemo-immunotherapy

Currently, the efficacy of albumin-bound paclitaxel (PTX@Alb) is still limited due to the impaired PTX@Alb accumulation in tumors partly mediated by the dense collagen distribution. Meanwhile, acquired immune resistance always occurs due to the enhanced programmed cell death-ligand 1 (PD-L1) expression after PTX@Alb treatment, which then leads to immune tolerance. To fill these gaps, we newly revealed that tamoxifen (TAM), a clinically widely used adjuvant therapy for breast cancer with mitochondrial metabolism blockade capacity, could also be used as a novel effective PD-L1 and TGF-β dual-inhibitor via inducing the phosphorylation of adenosine 5'-monophosphate-activated protein kinase (AMPK) protein. Following this, to obtain a more significant effect, TPP-TAM was prepared by conjugating mitochondria-targeted triphenylphosphine (TPP) with TAM, which then further self-assembled with albumin (Alb) to form TPP-TAM@Alb nanoparticles. By doing this, TPP-TAM@Alb nanoparticles effectively decreased the expression of collagen in vitro, which then led to the enhanced accumulation of PTX@Alb in 4T1 tumors. Besides, TPP-TAM@Alb also effectively decreased the expression of PD-L1 and TGF-β in tumors to better sensitize PTX@Alb-mediated chemo-immunotherapy by enhancing T cell infiltration. All in all, we newly put forward a novel mitochondrial metabolism blockade strategy to inhibit PTX@Alb-resistant tumors, further supporting its better clinical application.

A Less-is-More Strategy for Mitochondria-Targeted Photodynamic Therapy of Rheumatoid Arthritis

Conventional photodynamic therapy (PDT) of rheumatoid arthritis (RA) faces a dilemma: low-power is insufficient to kill pro-inflammatory cells while high-power exacerbates inflammation. Herein, mitochondrial targeting is introduced in PDT of RA to implement a "less-is-more" strategy, where higher apoptosis in pro-inflammatory cells are achieved with lower laser power. In arthritic rats, chlorine 6-loaded and mitochondria-targeting liposomes (Ce6@M-Lip) passively accumulated in inflamed joints, entered pro-inflammatory macrophages, and actively localized to mitochondria, leading to enhanced mitochondrial dysfunction under laser irradiation. By effectively disrupting mitochondria, pro-inflammatory macrophages are more susceptible to PDT, resulting in increased apoptosis initiation. Additionally, it identifies that high-power irradiation caused cell rupture and release of endogenous danger signals that recruited and activated additional macrophages. In contrast, under low-power irradiation, mitochondria-targeting Ce6@M-Lip not only prevented inflammation but also reduced pro-inflammatory macrophage infiltration and pro-inflammatory cytokine secretion. Overall, targeting mitochondria reconciled therapeutic efficacy and inflammation, thus enabling efficacious yet inflammation-sparing PDT for RA. This highlights the promise of mitochondrial targeting to resolve the dilemma between anti-inflammatory efficacy and inflammatory exacerbation in PDT by implementing a "less-is-more" strategy.

Nano-flow cytometry unveils mitochondrial permeability transition process and multi-pathway cell death induction for cancer therapy

Mitochondrial permeability transition (mPT)-mediated mitochondrial dysfunction plays a pivotal role in various human diseases. However, the intricate details of its mechanisms and the sequence of events remain elusive, primarily due to the interference caused by Bax/Bak-induced mitochondrial outer membrane permeabilization (MOMP). To address these, we have developed a methodology that utilizes nano-flow cytometry (nFCM) to quantitatively analyze the opening of mitochondrial permeability transition pore (mPTP), dissipation of mitochondrial membrane potential ( Δ Ψm), release of cytochrome c (Cyt c), and other molecular alternations of isolated mitochondria in response to mPT induction at the single-mitochondrion level. It was identified that betulinic acid (BetA) and antimycin A can directly induce mitochondrial dysfunction through mPT-mediated mechanisms, while cisplatin and staurosporine cannot. In addition, the nFCM analysis also revealed that BetA primarily induces mPTP opening through a reduction in Bcl-2 and Bcl-xL protein levels, along with an elevation in ROS content. Employing dose and time-dependent strategies of BetA, for the first time, we experimentally verified the sequential occurrence of mPTP opening and Δ Ψm depolarization prior to the release of Cyt c during mPT-mediated mitochondrial dysfunction. Notably, our study uncovers a simultaneous release of cell-death-associated factors, including Cyt c, AIF, PNPT1, and mtDNA during mPT, implying the initiation of multiple cell death pathways. Intriguingly, BetA induces caspase-independent cell death, even in the absence of Bax/Bak, thereby overcoming drug resistance. The presented findings offer new insights into mPT-mediated mitochondrial dysfunction using nFCM, emphasizing the potential for targeting such dysfunction in innovative cancer therapies and interventions.

Bioinspired cytomembrane coating besieges tumor for blocking metabolite transportation

The metabolite transport inhibition of tumor cells holds promise to achieve anti-tumor efficacy. Herein, we presented an innovative strategy to hinder the delivery of metabolites through the in-situ besieging tumor cells with polyphenolic polymers that strongly adhere to the cytomembrane of tumor cells. Simultaneously, these polymers underwent self-crosslinking under the induction of tumor oxidative stress microenvironment to form an adhesive coating on the surface of the tumor cells. This polyphenol coating effectively obstructed glucose uptake, reducing metabolic products such as lactic acid, glutathione, and adenosine triphosphate, while also causing reactive oxygen species to accumulate in the tumor cells. The investigation of various tumor models, including 2D cells, 3D multicellular tumor spheroids, and xenograft tumors, demonstrated that the polyphenolic polymers effectively inhibited the growth of tumor cells by blocking key metabolite transport processes. Moreover, this highly adhesive coating could bind tumor cells to suppress their metastasis and invasion. This work identified polyphenolic polymers as a promising anticancer candidate with a mechanism by impeding the mass transport of tumor cells.

Unlocking the Mitochondria for Nanomedicine-based Treatments: Overcoming Biological Barriers, Improving Designs, and Selecting Verification Techniques

Enhanced targeting approaches will support the treatment of diseases associated with dysfunctional mitochondria, which play critical roles in energy generation and cell survival. Obstacles to mitochondria-specific targeting include the presence of distinct biological barriers and the need to pass through (or avoid) various cell internalization mechanisms. A range of studies have reported the design of mitochondrially-targeted nanomedicines that navigate the complex routes required to influence mitochondrial function; nonetheless, a significant journey lies ahead before mitochondrially-targeted nanomedicines become suitable for clinical use. Moving swiftly forward will require safety studies, in vivo assays confirming effectiveness, and methodologies to validate mitochondria-targeted nanomedicines' subcellular location/activity. From a nanomedicine standpoint, we describe the biological routes involved (from administration to arrival within the mitochondria), the features influencing rational design, and the techniques used to identify/validate successful targeting. Overall, rationally-designed mitochondria-targeted-based nanomedicines hold great promise for precise subcellular therapeutic delivery.

Nanocarriers address intracellular barriers for efficient drug delivery, overcoming drug resistance, subcellular targeting and controlled release

The cellular barriers are major bottlenecks for bioactive compounds entering into cells to accomplish their biological functions, which limits their biomedical applications. Nanocarriers have demonstrated high potential and benefits for encapsulating bioactive compounds and efficiently delivering them into target cells by overcoming a cascade of intracellular barriers to achieve desirable therapeutic and diagnostic effects. In this review, we introduce the cellular barriers ahead of drug delivery and nanocarriers, as well as summarize recent advances and strategies of nanocarriers for increasing internalization with cells, promoting intracellular trafficking, overcoming drug resistance, targeting subcellular locations and controlled drug release. Lastly, the future perspectives of nanocarriers for intracellular drug delivery are discussed, which mainly focus on potential challenges and future directions. Our review presents an overview of intracellular drug delivery by nanocarriers, which may encourage the future development of nanocarriers for efficient and precision drug delivery into a wide range of cells and subcellular targets.

A nano-platform combats the "attack" and "defense" of cytoskeleton to block cascading tumor metastasis

The cytoskeleton facilitates tumor cells invasion into the bloodstream via vasculogenic mimicry (VM) for "attack", and protects cells against external threats through cytoskeletal remodeling and tunneling nanotubes (TNTs) for "defense". However, the existing strategies involving cytoskeleton are not sufficient to eliminate tumor metastasis due to mitochondrial energy supply, both within tumor cells and from outside microenvironment. Here, considering the close relationship between cytoskeleton and mitochondria both in location and function, we construct a nano-platform that combats the "attack" and "defense" of cytoskeleton in the cascading metastasis. The nano-platform is composed of KFCsk@LIP and KTMito@LIP for the cytoskeletal collapse and mitochondrial dysfunction. KFCsk@LIP prevents the initiation and circulation of cascading tumor metastasis, but arouses limited suppression in tumor cell proliferation. KTMito@LIP impairs mitochondria to trigger apoptosis and impede energy supply both from inside and outside, leading to an amplified effect for metastasis suppression. Further mechanisms studies reveal that the formation of VM and TNTs are seriously obstructed. Both in situ and circulating tumor cells are disabled. Subsequently, the broken metastasis cascade results in a remarkable anti-metastasis effect. Collectively, based on the nano-platform, the cytoskeletal collapse with synchronous mitochondrial dysfunction provides a potential therapeutic strategy for cascading tumor metastasis suppression.

The involvement of the mitochondrial membrane in drug delivery

Treatment effectiveness and biosafety are critical for disease therapy. Bio-membrane modification facilitates the homologous targeting of drugs in vivo by exploiting unique antibodies or antigens, thereby enhancing therapeutic efficacy while ensuring biosafety. To further enhance the precision of disease treatment, future research should shift focus from targeted cellular delivery to targeted subcellular delivery. As the cellular powerhouses, mitochondria play an indispensable role in cell growth and regulation and are closely involved in many diseases (e.g., cancer, cardiovascular, and neurodegenerative diseases). The double-layer membrane wrapped on the surface of mitochondria not only maintains the stability of their internal environment but also plays a crucial role in fundamental biological processes, such as energy generation, metabolite transport, and information communication. A growing body of evidence suggests that various diseases are tightly related to mitochondrial imbalance. Moreover, mitochondria-targeted strategies hold great potential to decrease therapeutic threshold dosage, minimize side effects, and promote the development of precision medicine. Herein, we introduce the structure and function of mitochondrial membranes, summarize and discuss the important role of mitochondrial membrane-targeting materials in disease diagnosis/treatment, and expound the advantages of mitochondrial membrane-assisted drug delivery for disease diagnosis, treatment, and biosafety. This review helps readers understand mitochondria-targeted therapies and promotes the application of mitochondrial membranes in drug delivery. STATEMENT OF SIGNIFICANCE: Bio-membrane modification facilitates the homologous targeting of drugs in vivo by exploiting unique antibodies or antigens, thereby enhancing therapeutic efficacy while ensuring biosafety. Compared to cell-targeted treatment, targeting of mitochondria for drug delivery offers higher efficiency and improved biosafety and will promote the development of precision medicine. As a natural material, the mitochondrial membrane exhibits excellent biocompatibility and can serve as a carrier for mitochondria-targeted delivery. This review provides an overview of the structure and function of mitochondrial membranes and explores the potential benefits of utilizing mitochondrial membrane-assisted drug delivery for disease treatment and biosafety. The aim of this review is to enhance readers' comprehension of mitochondrial targeted therapy and to advance the utilization of mitochondrial membrane in drug delivery.

A glycyrrhetinic acid-iridium(III) conjugate as a theranostic NIR probe for hepatocellular carcinoma with mitochondrial-targeting ability

Hepatocellular carcinoma (HCC) is a major contributor to global mortality rates, but current treatment options have limitations. Advanced theranostics are needed to effectively integrate diagnosis and therapeutic of HCC. Glycyrrhetinic acid (GA) has abundant binding sites with glycyrrhetinic acid receptors (GA-Rs) on the surface of HCC cells and has also been reported to possess ligands with mitochondrial-targeting capability but with limited efficacy. Herein, we report a near-infrared (NIR) luminescent theranostic complex 1 through conjugating an iridium(III) complex to GA, which exhibits the desired photophysical properties and promotes mitochondrial-targeting capability. Complex 1 was selectively taken up by HepG2 liver cancer cells and was imaged within mitochondria with NIR emission. Complex 1 targeted mitochondria and opened mitochondrial permeability transition pores (MPTPs), resulting in ROS accumulation, mitochondrial damage, disruption of Bax/Bcl-2 equilibrium, and tumor cell apoptosis, resulting in significantly improved anticancer activity compared to GA. This work offers a methodology for developing multifunctional theranostic probes with amplified specificity and efficacy.

Single-Atom Nanoenzyme-Based Autoluminescence System for Cancer Cell Imaging and Mitochondrial-Targeted Therapy

The autoluminescence nanoplatform based on a single-atom catalyst has the potential to achieve accurate tumor diagnosis and treatment. Taking advantage of this, glycyrrhetinic acid (GA) and chitosan-modified single Fe-N-C atom catalysts (SAF NPs) loaded with luminol-curcumin (Cur) were fabricated (SAF-LCCG). Once delivered to the tumor, this autoluminescence SAF-LCCG could target the mitochondria to restrain tumor metastasis and promote the production of hydrogen peroxide (H2O2). Then, SAF NPs with Fenton-like properties could actively utilize intracellular H2O2 to produce ·OH for chemodynamic therapy. After that, excess ·OH and H2O2 were transmitted to luminol to emit blue-violet chemiluminescence (CL) for cancer cell imaging. Synchronously, light was transferred to Cur to produce reactive oxygen species (ROS) which realized photodynamic therapy. Besides, Cur could be served as a chemotherapeutic drug to enhance intracellular ROS for penetrating therapy. More importantly, the massive accumulation of ROS in cancer cells can promote the CL intensity of luminol, which realized the cyclic ROS amplification. This autoluminescence nanoplatform was developed for accurate cancer cell imaging, effective inhibition of tumor metastasis, and synergistic and penetrated treatment of tumors.

The mechanisms of action of mitochondrial targeting agents in cancer: inhibiting oxidative phosphorylation and inducing apoptosis

The tumor microenvironment affects the structure and metabolic function of mitochondria in tumor cells. This process involves changes in metabolic activity, an increase in the amount of reactive oxygen species (ROS) in tumor cells compared to normal cells, the production of more intracellular free radicals, and the activation of oxidative pathways. From a practical perspective, it is advantageous to develop drugs that target mitochondria for the treatment of malignant tumors. Such drugs can enhance the selectivity of treatments for specific cell groups, minimize toxic effects on normal tissues, and improve combinational treatments. Mitochondrial targeting agents typically rely on small molecule medications (such as synthetic small molecules agents, active ingredients of plants, mitochondrial inhibitors or autophagy inhibitors, and others), modified mitochondrial delivery system agents (such as lipophilic cation modification or combining other molecules to form targeted mitochondrial agents), and a few mitochondrial complex inhibitors. This article will review these compounds in three main areas: oxidative phosphorylation (OXPHOS), changes in ROS levels, and endogenous oxidative and apoptotic processes.

Subcellular visualization: Organelle-specific targeted drug delivery and discovery

Organelles perform critical biological functions due to their distinct molecular composition and internal environment. Disorders in organelles or their interacting networks have been linked to the incidence of numerous diseases, and the research of pharmacological actions at the organelle level has sparked pharmacists' interest. Currently, cell imaging has evolved into a critical tool for drug delivery, drug discovery, and pharmacological research. The introduction of advanced imaging techniques in recent years has provided researchers with richer biological information for viewing and studying the ultrastructure of organelles, protein interactions, and gene transcription activities, leading to the design and delivery of precision-targeted drugs. Therefore, this reviews the research on organelles-targeted drugs based upon imaging technologies and development of fluorescent molecules for medicinal purposes. We also give a thorough analysis of a number of subcellular-level elements of drug development, including subcellular research instruments and methods, organelle biological event investigation, subcellular target and drug identification, and design of subcellular delivery systems. This review will make it possible to promote drug research from the individual/cellular level to the subcellular level, as well as give a new focus based on newly found organelle activities.

Enhance Mitochondrial Damage by Nuclear Export Inhibition to Suppress Tumor Growth and Metastasis with Increased Antitumor Properties of Macrophages

Mitochondria-targeting damage has become a popular therapeutic option for tumor metastasis; however, its efficacy is limited by the adaptive rescue capacity of nuclei. There is an urgent need for a dual mitochondrial and nuclear targeting strategy that can also increase the antitumor capacity of macrophages. In this study, XPO1 inhibitor KPT-330 nanoparticles were combined with mitochondria-targeting lonidamine (TPP-LND) nanoparticles. The combination of nanoparticles with a 1:4 ratio of KPT and TL demonstrated the best synergistic effect in restraining the proliferation and metastasis of 4T1 breast cancer cells. Investigating the mechanisms both in vitro and in vivo, it was found that KPT nanoparticles not only directly impede tumor growth and metastasis by controlling the expression of associated proteins but also indirectly facilitate mitochondrial damage. The two nanoparticles synergistically decreased the expression of cytoprotective factors, such as Mcl-1 and Survivin, causing mitochondrial dysfunction and thus inducing apoptosis. Additionally, it downregulated metastasis-related proteins like HIF-1α, vascular endothelial growth factor (VEGF), and matrix metalloproteinase 2 (MMP-2) and reduced endothelial-to-mesenchymal transition. Significantly, their combination increased the ratio of M1 tumor-associated macrophages (TAMs)/M2 TAMs both in vitro and in vivo and increased the phagocytosis of tumor cells by macrophages, thus suppressing tumor growth and metastasis. In summary, this research revealed that nuclear export inhibition can synergistically enhance the prevention of mitochondrial damage to tumor cells, heightening the antitumor properties of TAMs, thereby providing a viable and safe therapeutic approach for the treatment of tumor metastasis.

Quantitative Measurement of Drug Release Dynamics within Targeted Organelles Using Förster Resonance Energy Transfer

Measuring the release dynamics of drug molecules after their delivery to the target organelle is critical to improve therapeutic efficacy and reduce side effects. However, it remains challenging to quantitatively monitor subcellular drug release in real time. To address the knowledge gap, a novel gemini fluorescent surfactant capable of forming mitochondria-targeted and redox-responsive nanocarriers is designed. A quantitative Förster resonance energy transfer (FRET) platform is fabricated using this mitochondria-anchored fluorescent nanocarrier as a FRET donor and fluorescent drugs as a FRET acceptor. The FRET platform enables real-time measurement of drug release from organelle-targeted nanocarriers. Moreover, the obtained drug release dynamics can evaluate the duration of drug release at the subcellular level, which established a new quantitative method for organelle-targeted drug release. This quantitative FRET platform can compensate for the absent assessment of the targeted release performances of nanocarriers, offering in-depth understanding of the drug release behaviors at the subcellular targets.

Mitochondrial-Targeted Triphenylphosphonium-Hydroxycamptothecin Conjugate and Its Nano-Formulations for Breast Cancer Therapy: In Vitro and In Vivo Investigation

Mitochondria are involved in various stages of cancer cell diffusion and metastasis. Therefore, targeting tumor mitochondria with antineoplastic medicines to cause mitochondria to initiate apoptosis may be an effective strategy for cancer therapy. Here, in order to enhance the anti-tumor efficacy of the antineoplastic agent hydroxycamptothecin (HCPT), the mitochondrial targeting ligand 4-(carboxybutyl) triphenylphosphine bromide (TPP) was attached to HCPT by an ester linkage. The resultant TPP-HCPT (TH) conjugate could self-assemble into nano-aggregates, with a mean particle size of 203.2 nm and a polydispersity index (PDI) value of 0.312. The TH conjugate could also co-assembly with mPEG₃₀₀₀-PLGA₅₀₀₀ into nanoparticles (TH-NPs), with a mean diameter of 86.41 nm, a PDI value of 0.256 and a zeta potential of -0.125 mV. In contrast to HCPT injections, TH aggregates displayed enhanced cellular uptake, mitochondria-targetability and cytotoxicity against 4T1 cells, while TH-NPs showed even better improvement than TH aggregates. In the in vivo study, TH aggregates displayed higher anti-tumor efficacy in 4T1 tumor-bearing mice than HCPT injections (tumor inhibition rate, 55.71% vs. 69.17%), and TH-NPs displayed more superior anti-tumor effects (tumor inhibition rate, 80.02%). In conclusion, our research demonstrated that the TPP-HCPT conjugate and its nano-formulations, including TH aggregates and TH-NPs, may be a promising mitochondria-targeting anticancer medicine for cancer therapy. As far as we know, this is the first report in which TPP and HCPT have been conjugated directly for this aim.

Hydrogel co-loading SO2 prodrug and FeGA nanoparticles for enhancing chemodynamic therapy by photothermal-triggered SO2 gas therapy

Chemodynamic therapy (CDT) is an effective anti-tumor method, while CDT alone cannot achieve a good therapeutic effect. Moreover, the overexpression of glutathione (GSH) in tumor cells dramatically limits the efficiency of CDT. Here, we proposed a hydrogel co-loading SO2 prodrug and FeGA nanoparticles (NPs) for enhancing CDT by photothermal-triggered SO2 gas therapy (FBH) system by mixing benzothiazolyl sulfonates (BTS) and FeGA NPs in a certain ratio and encapsulating them in a heat-sensitive hydrogel. FeGA NPs could accelerate the release of Fe2+ under acidic conditions and light, and combine with excess H2O2 in the tumor for chemokinetic treatment. BTS, as a water-soluble prodrug of SO2, can accurately control the release of SO2 gas by virtue of the excellent photothermal conversion ability of FeGA NPs and the acidic pH value of tumor site. SO2 can not only induce cell apoptosis, but also consume excess GSH in cancer cells and increase the content of reactive oxygen species, which seriously destroyed the redox balance in cancer cells and further promotes the therapeutic effect of Fenton reaction. The intelligent FBH system provided a new approach for the synergistic treatment of CDT and SO2 gas, which demonstrated good anticancer effects both in vivo and in vitro.

Nanomedicines Targeting Metabolism in the Tumor Microenvironment

Cancer cells reprogram their metabolism to meet their growing demand for bioenergy and biosynthesis. The metabolic profile of cancer cells usually includes dysregulation of main nutritional metabolic pathways and the production of metabolites, which leads to a tumor microenvironment (TME) having the characteristics of acidity, hypoxic, and/or nutrient depletion. Therapies targeting metabolism have become an active and revolutionary research topic for anti-cancer drug development. The differential metabolic vulnerabilities between tumor cells and other cells within TME provide nanotechnology a therapeutic window of anti-cancer. In this review, we present the metabolic characteristics of intrinsic cancer cells and TME and summarize representative strategies of nanoparticles in metabolism-regulating anti-cancer therapy. Then, we put forward the challenges and opportunities of using nanoparticles in this emerging field.

Split bullets loaded nanoparticles for amplified immunotherapy

Dendritic cells (DCs) play central role in adaptive antitumor immunity, while their function is often hampered by low immunogenicity of tumor tissues and surrounding hostile microenvironment. Herein, a "split bullets" loaded nanoplatform that can bidirectionally injure mitochondria (MT) and endoplasmic reticulum (ER) of tumor cells is developed. After cellular uptake, the released "split bullets" separately target to different subcellular destinations and exert distinct effects on DCs: (1) MT-targeted "bullet" recruits peripheral DCs into tumor sites, due to its capability to trigger adenosine triphosphate release from tumor cells; (2) ER-targeted "bullet" activates tumor-infiltrating DCs, which is attributed to its ability to evoke calreticulin exposure on tumor cells. These effects collectively improve the tropism and reactivity of DCs to tumor-specific antigen in a two-pronged way. As a result of enhanced function of DCs in antigen capture, treatment of the "split bullets" loaded nanoplatform ignites robust immune response to suppress primary melanoma, and establishes systemic immune memory against post-surgical tumor recurrence. Overall, this nanoplatform offers a generalizable approach to boost DCs and augment immunotherapy.

Charge Conversion Polymer–Liposome Complexes to Overcome the Limitations of Cationic Liposomes in Mitochondrial-Targeting Drug Delivery

Mitochondrial-targeting therapy is considered an important strategy for cancer treatment. (3-Carboxypropyl) triphenyl phosphonium (CTPP) is one of the candidate molecules that can drive drugs or nanomedicines to target mitochondria via electrostatic interactions. However, the mitochondrial-targeting effectiveness of CTPP is low. Therefore, pH-sensitive polymer–liposome complexes with charge-conversion copolymers and CTPP-containing cationic liposomes were designed for efficiently delivering an anti-cancer agent, ceramide, into cancer cellular mitochondria. The charge-conversion copolymers, methoxypoly(ethylene glycol)-block-poly(methacrylic acid-g-histidine), were anionic and helped in absorbing and shielding the positive charges of cationic liposomes at pH 7.4. In contrast, charge-conversion copolymers became neutral in order to depart from cationic liposomes and induced endosomal escape for releasing cationic liposomes into cytosol at acidic endosomes. The experimental results reveal that these pH-sensitive polymer–liposome complexes could rapidly escape from MCF-7 cell endosomes and target MCF-7 mitochondria within 3 h, thereby leading to the generation of reactive oxygen species and cell apoptosis. These findings provide a promising solution for cationic liposomes in cancer mitochondrial-targeting drug delivery.

One-Step Microfluidic Fabrication of Multi-Responsive Liposomes for Targeted Delivery of Doxorubicin Synergism with Photothermal Effect

Introduction

Cancer of the bladder is one of the most common and life-threatening. Compared with traditional delivery methods, intravesical administration reduces the amount of drugs required, increases the amount of drugs reaching the lesion site, and minimizes systemic exposure to therapeutic agents. To overcome the limitations of urinary voiding, low urothelium permeability, and intermittent catheterization for large dilution and irrigation of drugs in the bladder, magnetic and photothermal-responsive folate receptor-targeted thermal liposomes (FA-TMLs) were designed for the targeted delivery of doxorubicin (DOX) to bladder cancer cells.

Methods

Through a microfluidic mixer chip, the magnetic nanoparticles (MNPs), gold nanorods (GNRs) and DOX were encapsulated in folate-modified thermosensitive liposomes to form FA-TMLs@MNPs-GNRs-DOX. DLS, TEM, DSC, and magnetic hysteresis loop were used to characterize the construction of FA-TMLs@MNPs-GNRs-DOX.

Results

FA-TMLs@MNPs-GNRs-DOX had a size of about 230 nm and exhibited superparamagnetic properties with the saturation magnetization of 20 emu/g. The DOX loading capacity was as high as 0.57 mg/mL. Additionally, drug release of the FA-TMLs@MNPs-GNRs-DOX could be controlled by temperature change through the photothermal effect. A 980 nm laser beam was selectively irradiated on the FA-TMLs@MNPs-GNRs-DOX to trigger the structural changes of the FA-TMLs, and an average of 95% of the drug was released after 3 hours. The results of cell uptake experiments reveal indicated that FA-TMLs@MNPs-GNRs-DOX were able to specifically bind folate-receptor-positive cells and exhibited toxicity to bladder tumor cells.

Conclusion

The present results suggest FA-TMLs@MNPs-GNRs-DOX have a promising multifunctional response and can act as an ideal multifunctional drug delivery system (DDS) for the treatment of bladder tumors.

Tunicate-Inspired Photoactivatable Proteinic Nanobombs for Tumor-Adhesive Multimodal Therapy

Near-IR (NIR) light-responsive multimodal nanotherapeutics have been proposed to achieve improved therapeutic efficacy and high specificity in cancer therapy. However, their clinical application is still elusive due to poor biometabolization and short retention at the target site. Here, innovative photoactivatable vanadium-doped adhesive proteinic nanoparticles (NPs) capable of allowing biological photoabsorption and NIR-responsive anticancer therapeutic effects to realize trimodal photothermal-gas-chemo-therapy treatments in a highly biocompatible, site-specific manner are proposed. The photoactivatable tumor-adhesive proteinic NPs can enable efficient photothermal conversion via tunicate-inspired catechol-vanadium complexes as well as prolonged tumor retention by virtue of mussel protein-driven distinctive adhesiveness. The incorporation of a thermo-sensitive nitric oxide donor and doxorubicin into the photoactivatable adhesive proteinic NPs leads to synergistic anticancer therapeutic effects as a result of photothermal-triggered "bomb-like" multimodal actions. Thus, this protein-based phototherapeutic tumor-adhesive NPs have great potential as a spatiotemporally controllable therapeutic system to accomplish effective therapeutic implications for the complete ablation of cancer.

Hypoxia-Mediated ROS Amplification Triggers Mitochondria-Mediated Apoptotic Cell Death via PD-L1/ROS-Responsive, Dual-Targeted, Drug-Laden Thioketal Nanoparticles

Amalgamation of the reactive oxygen species (ROS)-responsive stimulus with nanoparticles has gained considerable interest owing to their high tumor specificity. Hypoxia plays a pivotal role in the acceleration of intracellular ROS production. Herein, we report the construction of a cancer cell (PD-L1)- and ROS-responsive, dual-targeted, temozolomide (TMZ)-laden nanosystem which offers a better anticancer effect in a hypoxic tumor microenvironment. A dual-targeted system boosted permeation in the cancer cells. Hypoxic conditions elevating the high ROS level accelerated the in situ release of TMZ from anti-PD-L1-TKNPs. Hyperaccumulated ROS engendered from TMZ caused oxidative damage leading to mitochondria-mediated apoptosis. TMZ fabricated in the multifunctional nanosystem (anti-PD-L1-TMZ-TKNPs) provided excellent tumor accumulation and retarded tumor growth under in vivo conditions. The elevated apoptosis effect with the activation of an apoptotic marker, DNA double-strand breakage marker, and downregulation of the angiogenesis marker in the tumor tissue following treatment with anti-PD-L1-TMZ-TKNPs exerts robust anticancer effect. Collectively, the nanoconstruct offers deep tumor permeation and high drug release and broadens the application of the ROS-responsive nanosystem for a successful anticancer effect.