Development of Nanoscale Drug Delivery Systems of Dihydroartemisinin for Cancer Therapy: A Review

Dihydroartemisinin induces ferroptosis in T cell acute lymphoblastic leukemia cells by downregulating SLC7A11 and activating the ATF4‑CHOP signaling pathway

The present study aimed to investigate the anti-leukemic effects of dihydroartemisinin (DHA) on T-cell acute lymphoblastic leukemia (T-ALL) cell lines, Jurkat and Molt-4, and the underlying mechanisms. Cell Counting Kit-8 was performed to measure cell viability. Cell apoptosis and cell cycle distribution were assessed by flow cytometry. The expression levels of ATF4 and CHOP mRNA were assessed by reverse transcription-quantitative PCR, while the protein abundance of SLC7A11, GPX4, ATF4 and CHOP was determined by western blotting. Moreover, malondialdehyde, glutathione (GSH) and reactive oxygen species (ROS) assays were used to detect the levels of ferroptosis. The results showed that DHA suppressed T-ALL cell viability in vitro, and induced cell cycle arrest at S or G2/M phase. DHA also induced ROS burst, activated endoplasmic reticulum (ER) stress, disrupted the system Xc--GSH-GSH peroxidase 4 antioxidant system, and increased lipid peroxide accumulation, resulting in cell death. By contrast, the pharmacological inhibition of ferroptosis alleviated DHA-induced cell death, confirming that DHA induces T-ALL cell death via ferroptosis. Mechanistically, the effect of DHA on ferroptosis was partly mediated by downregulating SLC7A11 and upregulating the ATF4-CHOP signaling pathway, which is associated with ER stress. These results indicated that DHA may induce ferroptosis in T-ALL cell lines and could represent a promising therapeutic agent for treating T-ALL.

2-Monoacylglycerol Mimetic Liposomes to Promote Intestinal Lymphatic Transport for Improving Oral Bioavailability of Dihydroartemisinin

Purpose

Reducing the first-pass hepatic effect via intestinal lymphatic transport is an effective way to increase the oral absorption of drugs. 2-Monoacylglycerol (2-MAG) as a primary digestive product of dietary lipids triglyceride, can be assembled in chylomicrons and then transported from the intestine into the lymphatic system. Herein, we propose a biomimetic strategy and report a 2-MAG mimetic nanocarrier to target the intestinal lymphatic system via the lipid absorption pathway and improve oral bioavailability.

Methods

The 2-MAG mimetic liposomes were designed by covalently bonding serinol (SER) on the surface of liposomes named SER-LPs to simulate the structure of 2-MAG. Dihydroartemisinin (DHA) was chosen as the model drug because of its disadvantages such as poor solubility and high first-pass effect. The endocytosis and exocytosis mechanisms were investigated in Caco-2 cells and Caco-2 cell monolayers. The capacity of intestinal lymphatic transport was evaluated by ex vivo biodistribution and in vivo pharmacokinetic experiments.

Results

DHA loaded SER-LPs (SER-LPs-DHA) had a particle size of 70 nm and a desirable entrapment efficiency of 93%. SER-LPs showed sustained release for DHA in the simulated gastrointestinal environment. In vitro cell studies demonstrated that the cellular uptake of SER-LPs primarily relied on the caveolae- rather than clathrin-mediated endocytosis pathway and preferred to integrate into the chylomicron assembly process through the endoplasmic reticulum/Golgi apparatus route. After oral administration, SER-LPs efficiently promoted drug accumulation in mesenteric lymphatic nodes. The oral bioavailability of DHA from SER-LPs was 10.40-fold and 1.17-fold larger than that of free DHA and unmodified liposomes at the same dose, respectively.

Conclusion

SER-LPs improved oral bioavailability through efficient intestinal lymphatic transport. These findings of the current study provide a good alternative strategy for oral delivery of drugs with high first-pass hepatic metabolism.

A multifunctional biomimetic nanoplatform for image-guideded photothermal-ferroptotic synergistic osteosarcoma therapy

Much effort has been devoted to improving treatment efficiency for osteosarcoma (OS). However, most current approaches result in poor therapeutic responses, thus indicating the need for the development of other therapeutic options. This study developed a multifunctional nanoparticle, PDA-MOF-E-M, an aggregation of OS targeting, programmed death targeting, and near-infrared (NIR)-aided targeting. At the same time, a multifunctional nanoparticle that utilises Fe-MOFs to create a cellular iron-rich environment and erastin as a ferroptosis inducer while ensuring targeted delivery to OS cells through cell membrane encapsulation is presented. The combination of PDA-MOF-E-M and PTT increased intracellular ROS and LPO levels and induced ferroptosis-related protein expression. A PDA-based PTT combined with erastin showed significant synergistic therapeutic improvement in the anti-tumour efficiency of the nanoparticle in vitro and vivo. The multifunctional nanoparticle efficiently prevents the osteoclasia progression of OS xenograft bone tumors in vivo. Finally, this study provides guidance and a point of reference for clinical approaches to treating OS.

Ferroptosis: emerging roles in lung cancer and potential implications in biological compounds

Lung cancer has high metastasis and drug resistance. The prognosis of lung cancer patients is poor and the patients' survival chances are easily neglected. Ferroptosis is a programmed cell death proposed in 2012, which differs from apoptosis, necrosis and autophagy. Ferroptosis is a novel type of regulated cell death which is driven by iron-dependent lipid peroxidation and subsequent plasma membrane ruptures. It has broad prospects in the field of tumor disease treatment. At present, multiple studies have shown that biological compounds can induce ferroptosis in lung cancer cells, which exhibits significant anti-cancer effects, and they have the advantages in high safety, minimal side effects, and less possibility to drug resistance. In this review, we summarize the biological compounds used for the treatment of lung cancer by focusing on ferroptosis and its mechanism. In addition, we systematically review the current research status of combining nanotechnology with biological compounds for tumor treatment, shed new light for targeting ferroptosis pathways and applying biological compounds-based therapies.

A lava-inspired proteolytic enzyme therapy on cancer with a PEG-based hydrogel enhances tumor distribution and penetration of liposomes

The enhanced permeability and retention (EPR) effect has become the guiding principle for nanomedicine against cancer for a long time. However, several biological barriers severely resist therapeutic agents' penetration and retention into the deep tumor tissues, resulting in poor EPR effect and high tumor mortality. Inspired by lava, we proposed a proteolytic enzyme therapy to improve the tumor distribution and penetration of nanomedicine. A trypsin-crosslinked hydrogel (Trypsin@PSA Gel) was developed to maintain trypsin's activity. The hydrogel postponed trypsin's self-degradation and sustained the release. Trypsin promoted the cellular uptake of nanoformulations in breast cancer cells, enhanced the penetration through endothelial cells, and degraded total and membrane proteins. Proteomic analysis reveals that trypsin affected ECM components and down-regulated multiple pathways associated with cancer progression. Intratumoral injection of Trypsin@PSA Gel significantly increased the distribution of liposomes in tumors and reduced tumor vasculature. Combination treatment with intravenous injection of gambogic acid-loaded liposomes and intratumoral injection of Trypsin@PSA Gel inhibited tumor growth. The current study provides one of the first investigations into the enhanced tumor distribution of liposomes induced by a novel proteolytic enzyme therapy.

Dual pH/redox-responsive hyperbranched polymeric nanocarriers with TME-trigger size shrinkage and charge reversible ability for amplified chemotherapy of breast cancer

A novel pH/redox-responsive hyperbranched MeO-PEG-b-(NIPAAm-co-PBAE) nanoparticles (NPs) were designed with size shrinkage and charge-reversible potential for targeted delivery of docetaxel (DTX) to MDA-MB-231 cell lines. In the tumor microenvironment (TME), amine protonation induces charge reversal and disulfide bond cleavage under high TME GSH concentration causing size shrinkage, improved deep tumor penetration, and active targeting of the therapeutic agents. These nano drug delivery systems (NDDSs) significantly promoted cancer cell uptake (~ 100% at 0.5 h), facilitating site-specific delivery and deep tumor penetration. The MTT assay revealed significantly higher cytotoxicity (P value < 0.0001) for DTX-loaded NPs compared to free DTX. Cell cycle analysis revealed G2/M (58.3 ± 2.1%) and S (21.5 ± 1.3%) arrest for DTX-loaded NPs, while free DTX caused G2/M (67.9 ± 1.1%) and sub-G1 (10.3 ± 0.8%) arrest. DTX-loaded NPs induced higher apoptosis (P value < 0.001) in MDA-MB-231 cells (71.5 ± 2.8%) compared to free DTX (42.3 ± 3.1%). Western blotting and RT-PCR assays confirmed significant up-regulation of protein levels and apoptotic genes by DTX-loaded NPs compared to free DTX. In conclusion, TME-responsive charge reversal and size-shrinkable smart NDDSs designed based on low pH, and high glutathione (GSH), offer more effective site-specific delivery of therapeutic agents to tumors.

Self-assembled nanodrug delivery systems for anti-cancer drugs from traditional Chinese medicine

Traditional Chinese medicine (TCM) is a combination of raw herbs and herbal extracts with a plethora of documented beneficial bioactivities, which has unique advantages in anti-tumor therapy, and many of its major bioactive molecules have been identified in recent years due to advances in chemical separation and structural analysis. However, the major chemical classes of plant-derived bioactive compounds frequently possess chemical properties, including poor water solubility, stability, and bioavailability, that limit their therapeutic application. Alternatively, natural small molecules (NSMs) containing these components possess modifiable groups, multiple action sites, hydrophobic side chains, and a rigid skeleton with self-assembly properties that can be exploited to construct self-assembled nanoparticles with therapeutic effects superior to their individual constituents. For instance, the construction of a self-assembled nanodrug delivery system can effectively overcome the strong hydrophobicity and poor in vivo stability of NSMs, thereby greatly improving their bioavailability and enhancing their anti-tumor efficacy. This review summarizes the self-assembly methods, mechanisms, and applications of a variety of NSMs, including terpenoids, flavonoids, alkaloids, polyphenols, and saponins, providing a theoretical basis for the subsequent research on NSMs and the development of SANDDS.

Resibufogenin: An Emerging Therapeutic Compound with Multifaceted Pharmacological Effects - A Comprehensive Review

Resibufogenin (RBG), a significant bufadienolide compound found in the traditional Chinese medicine Chansu, has garnered increasing attention in recent years for its wide range of pharmacological effects. This compound has shown promising potential in various therapeutic areas, including oncology, cardiology, and respiratory medicine. Among its notable properties, the anticancer effects of RBG are particularly striking, positioning it as a potential candidate for innovative cancer treatments. The mechanism of action of RBG is diverse, impacting various cellular processes. Its anticancer efficacy has been observed in different types of cancer cells, where it induces apoptosis and inhibits cell proliferation. Beyond its oncological applications, RBG also demonstrates substantial anti-inflammatory and antiviral activities. These properties suggest its utility in managing chronic inflammatory disorders and viral infections, respectively. The compound's cardiotonic effects are also noteworthy, providing potential benefits in cardiovascular health, particularly in heart failure management. Additionally, RBG has shown effectiveness in blood pressure regulation and respiratory function improvement, making it a versatile agent in the treatment of hypertension and respiratory disorders. However, despite these promising aspects, systematic reviews focusing specifically on RBG are limited. This article aims to address this gap by comprehensively reviewing RBG's origin, physiological, and pharmacological effects. The review will serve as a crucial reference for clinicians and researchers interested in the therapeutic applications of RBG, highlighting its potential in various medical domains. By synthesizing current research findings, this review will facilitate a deeper understanding of RBG's role in medicine and encourage further investigation into its clinical uses.

Recent advances in zwitterionic nanoscale drug delivery systems to overcome biological barriers

Nanoscale drug delivery systems (nDDS) have been employed widely in enhancing the therapeutic efficacy of drugs against diseases with reduced side effects. Although several nDDS have been successfully approved for clinical use up to now, biological barriers between the administration site and the target site hinder the wider clinical adoption of nDDS in disease treatment. Polyethylene glycol (PEG)-modification (or PEGylation) has been regarded as the gold standard for stabilising nDDS in complex biological environment. However, the accelerated blood clearance (ABC) of PEGylated nDDS after repeated injections becomes great challenges for their clinical applications. Zwitterionic polymer, a novel family of anti-fouling materials, have evolved as an alternative to PEG due to their super-hydrophilicity and biocompatibility. Zwitterionic nDDS could avoid the generation of ABC phenomenon and exhibit longer blood circulation time than the PEGylated analogues. More impressively, zwitterionic nDDS have recently been shown to overcome multiple biological barriers such as nonspecific organ distribution, pressure gradients, impermeable cell membranes and lysosomal degradation without the need of any complex chemical modifications. The realization of overcoming multiple biological barriers by zwitterionic nDDS may simplify the current overly complex design of nDDS, which could facilitate their better clinical translation. Herein, we summarise the recent progress of zwitterionic nDDS at overcoming various biological barriers and analyse their underlying mechanisms. Finally, prospects and challenges are introduced to guide the rational design of zwitterionic nDDS for disease treatment.

Anticancer Effect of Dihydroartemisinin via Dual Control of ROS-induced Apoptosis and Protective Autophagy in Prostate Cancer 22Rv1 Cells

BACKGROUND

Dihydroartemisinin (DHA), a natural agent, exhibits potent anticancer activity. However, its biological activity on prostate cancer (PCa) 22Rv1 cells has not been previously investigated.

OBJECTIVES

In this study, we demonstrate that DHA induces anticancer effects through the induction of apoptosis and autophagy.

METHODS

Cell viability and proliferation rate were assessed using the CCK-8 assay and cell clone formation assay. The generation of reactive oxygen species (ROS) was detected by flow cytometry. The molecular mechanism of DHA-induced apoptosis and autophagy was examined using Western blot and RT-qPCR. The formation of autophagosomes and the changes in autophagy flux were observed using transmission electron microscopy (TEM) and confocal microscopy. The effect of DHA combined with Chloroquine (CQ) was assessed using the EdU assay and flow cytometry. The expressions of ROS/AMPK/mTOR-related proteins were detected using Western blot. The interaction between Beclin-1 and Bcl-2 was examined using Co-IP.

RESULTS

DHA inhibited 22Rv1 cell proliferation and induced apoptosis. DHA exerted its antiprostate cancer effects by increasing ROS levels. DHA promoted autophagy progression in 22Rv1 cells. Inhibition of autophagy enhanced the pro-apoptotic effect of DHA. DHA-induced autophagy initiation depended on the ROS/AMPK/mTOR pathway. After DHA treatment, the impact of Beclin- 1 on Bcl-2 was weakened, and its binding with Vps34 was enhanced.

CONCLUSION

DHA induces apoptosis and autophagy in 22Rv1 cells. The underlying mechanism may involve the regulation of ROS/AMPK/mTOR signaling pathways and the interaction between Beclin-1 and Bcl-2 proteins. Additionally, the combination of DHA and CQ may enhance the efficacy of DHA in inhibiting tumor cell activity.

Dihydroartemisinin inhibits melanoma migration and metastasis by affecting angiogenesis

Tumor angiogenesis is critical for tumor metastasis by providing oxygen, nutrients, and metastatic pathways. As a potential anti-angiogenic agent, Dihydroartemisinin (DHA) can effectively inhibit tumor metastasis. However, the mechanism how it regulates angiogenesis to affect tumor metastasis has not been fully clarified. To investigate the mechanisms of how DHA regulates melanoma progression. In this study, bioinformatics methods were used to analyze the correlation between angiogenesis and melanoma metastasis. Then, B16F10, A375, HUVECs and mouse metastasis models were adapted to clarify the inhibition of DHA in melanoma. GESA analysis revealed melanoma metastasis significantly positive correlated with angiogenesis. Meanwhile, DHA significantly decreased melanoma nodules and lung wet weight in metastatic tumor mice, and inhibited the expression of the angiogenic marker CD31 in vitro and in vivo. Similarly, DHA inhibited the expression of the angiogenic signal molecule VEGFR2 in A375 and B16F10 cells, and significantly suppressed the formation of their tubular structures. DHA-treated supernatants significantly inhibited the tubule-forming ability as well as lateral and longitudinal migration ability of HUVECs compared with untreated melanoma cell supernatants. Screening yielded the angiogenic pathways HIF-1α/VEGF, PI3K/ATK/mTOR associated with melanoma metastasis, and DHA may inhibit tumor metastasis by inhibiting these angiogenic pathways in melanoma cells to inhibit tumor metastasis. Further non-targeted metabolomics analysis revealed that DHA-treated model mice produced differential metabolites that were also associated with angiogenic pathways. DHA inhibits melanoma invasion and metastasis by mediating angiogenesis. These results have important implications for the potential use of DHA in treatment of melanoma.

Drug Repurposing-Based Brain-Targeting Self-Assembly Nanoplatform Using Enhanced Ferroptosis against Glioblastoma

Glioblastoma (GBM), the most aggressive and lethal form of malignant brain tumor, is a therapeutic challenge due to the drug filtration capabilities of the blood-brain barrier (BBB). Interestingly, glioblastoma tends to resist apoptosis during chemotherapy, but is susceptible to ferroptosis. Developing therapies that can effectively target glioblastoma by crossing the BBB and evoke ferroptosis are, therefore, crucial for improving treatment outcomes. Herein, a versatile biomimetic nanoplatform, L-D-I/NPs, is designed that self-assembled by loading the antimalarial drug dihydroartemisinin (DHA) and the photosensitizer indocyanine green (ICG) onto lactoferrin (LF). This nanoplatform can selectively target glioblastoma by binding to low-density lipoprotein receptor-related protein-1 (LRP1) and crossing the BBB, thus inducing glioblastoma cell ferroptosis by boosting intracellular reactive oxygen species (ROS) accumulation and iron overload. In addition, L-D-I/NPs have demonstrated the ability to effectively suppress the progression of orthotopic glioblastoma and significantly prolong survival in a mouse glioblastoma model. This nanoplatform has facilitated the application of non-chemotherapeutic drugs in tumor treatment with minimal adverse effects, paving the way for highly efficient ferroptosis-based therapies for glioblastoma.

A mitochondria-targeted far-red AIE fluorescent probe for distinguishing between mitophagy and ferroptosis in cancer cells

A mitochondria-targeted far-red fluorescent probe LY-1 with AIE character was formulated to track cell viscosity alterations with excellent sensitivity and selectivity, which was used to discriminate between mitophagy and ferroptosis in cancer cells. Probe LY-1 is expected to be an effective vehicle for the diagnosis of mitochondrial viscosity relevant diseases.

Metal-organic framework-encapsulated dihydroartemisinin nanoparticles induces apoptotic cell death in ovarian cancer by blocking ROMO1-mediated ROS production

Dihydroartemisinin (DHA), a natural product derived from the herbal medicine Artemisia annua, is recently used as a novel anti-cancer agent. However, some intrinsic disadvantages limit its potential for clinical management of cancer patients, such as poor water solubility and low bioavailability. Nowadays, the nanoscale drug delivery system emerges as a hopeful platform for improve the anti-cancer treatment. Accordingly, a metal-organic framework (MOF) based on zeolitic imidazolate framework-8 was designed and synthesized to carry DHA in the core (ZIF-DHA). Contrast with free DHA, these prepared ZIF-DHA nanoparticles (NPs) displayed preferable anti-tumor therapeutic activity in several ovarian cancer cells accompanied with suppressed production of cellular reactive oxygen species (ROS) and induced apoptotic cell death. 4D-FastDIA-based mass spectrometry technology indicated that down-regulated reactive oxygen species modulator 1 (ROMO1) might be regarded as potential therapeutic targets for ZIF-DHA NPs. Overexpression of ROMO1 in ovarian cancer cells significantly reversed the cellular ROS-generation induced by ZIF-DHA, as well as the pro-apoptosis effects. Taken together, our study elucidated and highlighted the potential of zeolitic imidazolate framework-8-based MOF to improve the activity of DHA to treat ovarian cancer. Our findings suggested that these prepared ZIF-DHA NPs could be an attractive therapeutic strategy for ovarian cancer.

Fe-MnO2 nanosheets loading dihydroartemisinin for ferroptosis and immunotherapy

Ferroptosis has emerged as a therapeutic tactic to trigger cancer cell death driven by abnormal accumulation of reactive oxygen species (ROS). However, a single ferroptosis treatment modality is often limited. In this work, a combination therapy of ferroptosis and immunotherapy for cancer was proposed. Specifically, a versatile nanodrug was designed for the multiple treatment of hepatocellular carcinoma (HCC) by loading dihydroartemisinin (DHA) on Fe³⁺-doped MnO₂ nanosheets (Fe-MnO₂/DHA). Firstly, Fe-MnO₂/DHA was degraded by glutathione (GSH) in the tumor microenvironment (TME) to release Fe²⁺, Mn²⁺ and DHA, leading to aberrant ROS accumulation due to Fenton/Fenton-like reaction. Secondly, breakage of endoperoxide bridge from DHA was caused by Fe²⁺ to further induce oxidative stress. Thirdly, the depleted GSH promoted the inactivation of glutathione peroxidase 4 (GPX4), resulting in lipid peroxide (LPO) accumulation. The resulting LPO and ROS could induce ferroptosis and apoptosis of liver cancer cells. Furthermore, Fe-MnO₂/DHA mediated three-pronged stimulation of oxidative stress, resulting in high levels of targeted immunogenic cell death (ICD). It could enhance the infiltration of CD4⁺ T and CD8⁺ T cells, and promote macrophage polarization. DHA also acted as an immunomodulator to inhibit regulatory T cells (Tregs) for systemic antitumor. Overall, Fe-MnO₂/DHA presents a multi-modal therapy for HCC driven by ferroptosis, apoptosis and immune activation, significantly advancing synergistic cancer treatment.

S-allylmercapto-N-acetylcysteine ameliorates pulmonary fibrosis in mice via Nrf2 pathway activation and NF-κB, TGF-β1/Smad2/3 pathway suppression

Pulmonary fibrosis (PF) is a chronic lung disease characterised by alveolar inflammatory injury, alveolar septal thickening, and eventually fibrosis. Patients with severe Coronavirus Disease 2019 (COVID-19) may have left a certain degree of pulmonary fibrosis. PF is commonly caused by oxidative imbalance and inflammatory damage. S-allylmercapto-N-acetylcysteine (ASSNAC) exhibits anti-oxidative and anti-inflammatory effects in other diseases. However, the pharmacodynamics of ASSNAC remain unclear for PF. This investigation aimed to evaluate the efficacy and mechanism of ASSNAC against PF. The PF model was established by TGF-β1 stimulating HFL-1 cells in vitro. ASSNAC exhibited the potential to inhibit fibroblast transformation into myofibroblasts. Also, in the PF mice model with bleomycin (BLM), the sodium salt of ASSNAC (ASSNAC-Na) inhalation was treated. ASSNAC remarkably improved mice's lung tissue structure and collagen deposition. The important indicator proteins of PF, collagen Ⅰ, collagen Ⅲ, and α-SMA significantly decreased in the ASSNAC treated groups. Besides, ASSNAC attenuated oxidative stress by reversing glutathione (GSH), superoxide dismutase (SOD) levels and interfering with Nrf2/NOX4 signaling pathways. ASSNAC showed an anti-inflammatory effect by reducing the number of inflammatory cells and inflammatory cytokines, such as TNF-α and IL-6, and blocking the NF-κB signaling pathway. ASSNAC inhibited fibroblast differentiation by blocking the TGF-β1/Smad2/3 signaling pathway. This study implicates that ASSNAC alleviates pulmonary fibrosis through fighting against oxidative stress, reducing inflammation and inhibiting fibroblast differentiation.

Ferroptosis-based drug delivery system as a new therapeutic opportunity for brain tumors

The brain tumor is a kind of malignant tumor with brutal treatment, high recurrence rate, and poor prognosis, and the incidence and death rate is increasing yearly. Surgery is often used to remove the primary tumor, supplemented by radiotherapy and chemotherapy, which have highly toxic side effects. Therefore, there is an urgent need to explore new strategies, methods, and technologies that can genuinely improve the treatment of brain tumors. Ferroptosis differs from traditional apoptosis's morphological and biochemical characteristics, and ferroptosis possesses its unique characteristics and mechanisms, opening up a new field of ferroptosis treatment for cancer. It has been found that there is a close relationship between ferroptosis and brain tumors, and a novel nano-drug delivery system based on ferroptosis has been used for the ferroptosis treatment of brain tumors with remarkable effects. This review firstly analyzes the characteristics of ferroptosis, summarizes the mechanism of its occurrence and some factors that can be involved in the regulation of ferroptosis, introduces the potential link between ferroptosis and brain tumors, and clarifies the feasibility of ferroptosis in the treatment of brain tumors. It then presents the ferroptosis nano drug delivery systems developed under different metabolic pathways for ferroptosis treatment of brain tumors. Finally, it summarizes the current problems and solutions of ferroptosis nano drugs for brain tumor treatment, aiming to provide a reference for developing ferroptosis nano drugs against brain tumors.