Cu-doped cerium oxide-based nanomedicine for tumor microenvironment-stimulative chemo-chemodynamic therapy with minimal side effects

Sol-gel synthesis and cytotoxicity evaluation of selenium-doped cerium oxide nanoparticles for biomedical applications

Over the past few years, ovarian cancer is the second most commonly diagnosed cancer among women. Despite the widespread knowledge of its prevalence, the curative measures and survival rates for ovarian cancer have not improved significantly, making it a challenging condition. Nanotechnology has become increasingly prominent in the field of cancer treatment. Previous studies showed both cerium oxide nanoparticles (CONPs) and selenium (Se) had anti-cancer. Therefore, doping selenium into CONPs may exhibit a more significant anti-cancer effect on ovarian cancer cells. Cerium nitrate hexahydrate, sodium selenite, and gelatin were employed for the production of CONPs and Se-doped CONPs. The EDX, XRD, and TEM/PSA imaging were employed to investigate the structural characteristics and morphology of the synthesized Se-doped CONPs. The reactive oxygen species (ROS) level and TNF, IL-6, and IL-1B gene expression were evaluated after inoculating A2780 human epithelial ovarian carcinoma (HEOC) with Se-doped CONP. Statistical analysis was conducted using ANOVA, followed by Bonferroni's t-test for multiple group comparisons. Se-doped CONPs had IC50 of 113 and 49 PPM after 24 and 48 h, respectively. In addition, Se-doped CONPs with concentrations of 50 and 100 PPM significantly reduced to ROS levels in the HEOC cell line. Also, 50 and 100 PPM Se-doped CONPs lead to significantly reduced TNF, IL-6, and IL-1B gene expression compared to the control group in the HEOC cell line. Our study showed the potential anti-cancer effects of Se-doped CONPs on ovarian cancer cell lines.

Atomic Engineering of Single-Atom Nanozymes for Biomedical Applications

Single-atom nanozymes (SAzymes) showcase not only uniformly dispersed active sites but also meticulously engineered coordination structures. These intricate architectures bestow upon them an exceptional catalytic prowess, thereby captivating numerous minds and heralding a new era of possibilities in the biomedical landscape. Tuning the microstructure of SAzymes on the atomic scale is a key factor in designing targeted SAzymes with desirable functions. This review first discusses and summarizes three strategies for designing SAzymes and their impact on reactivity in biocatalysis. The effects of choices of carrier, different synthesis methods, coordination modulation of first/second shell, and the type and number of metal active centers on the enzyme-like catalytic activity are unraveled. Next, a first attempt is made to summarize the biological applications of SAzymes in tumor therapy, biosensing, antimicrobial, anti-inflammatory, and other biological applications from different mechanisms. Finally, how SAzymes are designed and regulated for further realization of diverse biological applications is reviewed and prospected. It is envisaged that the comprehensive review presented within this exegesis will furnish novel perspectives and profound revelations regarding the biomedical applications of SAzymes.

Enhanced ·OH-Scavenging Activity of Cu-CeOx Nanozyme via Resurrecting Macrophage Nrf2 Transcriptional Activity Facilitates Diabetic Wound Healing

Diabetic wounds are a prevalent and devastating complication of diabetes, which may impede their healing and regeneration. In diabetic wounds, excess reactive oxygen species (ROS) activate the nuclear factor kappa-B pathway, leading to transcriptional silencing of nuclear factor erythroid 2-related factor 2 (Nrf2), resulting in a vicious cycle of oxidative stress and inflammation. Conventional nanozymes have limitations in preventing the continuous production of ROS, including the most oxidizing reactive hydroxyl radical (·OH), although they can remove pre-existing ROS. Herein, a novel antioxidant nanoplatform addresses this challenge by incorporating JSH-23 into the mesoporous of cupric-doped cerium oxide nanozymes. Additionally, for rapid wound adaptability and durable tissue adhesion, a nanozyme hydrogel spray consisting of oxidized sodium alginate and methacrylate gelatin is constructed, named OG@CCJs. This platform resurrects Nrf2 transcriptional activity of macrophages in vitro, curbing the production of ROS at its source, particularly ·OH, while enabling the nanozymes to scavenge previously generated ROS. OG@CCJs significantly alleviate oxidative stress in diabetic wounds in vivo, promoting wound healing. Overall, the proposed nanozyme-hydrogel spray with enhanced ·OH-scavenging activity uses a "two-track" antioxidant strategy to rebuild the antioxidant defense barrier of macrophages. This pioneering approach highlights the tremendous potential of OG@CCJs for facilitating diabetic wound healing.

Doxorubicin loaded cerium substituted hydroxyapatite nanoparticles: A promising new therapeutic approach for bone regeneration, doxorubicin delivery, and cancer treatment

The current study used the precipitation method to prepare pure calcium hydroxyapatite (HA) and cerium-substituted hydroxyapatite (Ce-HA) nanoparticles, where cerium ions were exchanged into the HA structure at different concentrations ranging from 3 to 7 wt%. X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), Fourier transform infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) surface area measurements, and zeta potential were used to examine the structural characteristics of the nanoparticles. Additionally, the antibacterial and antifungal effects of the produced materials on Gram-positive, Gram-negative, and fungal bacterial species were studied. Nanoparticles with cerium doping showed effective antibacterial and antifungal properties. All samples were tested for bioactivity in simulated body fluid (SBF), and the formation of an apatite layer on their surfaces was highlighted using SEM in conjunction with energy-dispersive X-rays (EDX).Doxorubicin (DOX) release from Ce-HA nanoparticles and pure HA was tested in phosphate-buffered saline (PBS) for up to 28 days. Both nanoparticles were able to release the drug while still being semi-fully loaded. Similarly, the cytotoxic effect of all produced samples on the MG-63 cell line was evaluated, and all samples showed good cytocompatibility. The cytotoxic effect of doxorubicin-loaded nanoparticles showed promising anticancer activity against bone cancer cells, especially samples with high cerium content. The resulting nanoparticles show excellent promising ability for the delivery of doxorubicin to bone cancer with the capacity for bone regeneration.

Advances in Nanodynamic Therapy for Cancer Treatment

Nanodynamic therapy (NDT) exerts its anti-tumor effect by activating nanosensitizers to generate large amounts of reactive oxygen species (ROS) in tumor cells. NDT enhances tumor-specific targeting and selectivity by leveraging the tumor microenvironment (TME) and mechanisms that boost anti-tumor immune responses. It also minimizes damage to surrounding healthy tissues and enhances cytotoxicity in tumor cells, showing promise in cancer treatment, with significant potential. This review covers the research progress in five major nanodynamic therapies: photodynamic therapy (PDT), electrodynamic therapy (EDT), sonodynamic therapy (SDT), radiodynamic therapy (RDT), and chemodynamic therapy (CDT), emphasizing the significant role of advanced nanotechnology in the development of NDT for anti-tumor purposes. The mechanisms, effects, and challenges faced by these NDTs are discussed, along with their respective solutions for enhancing anti-tumor efficacy, such as pH response, oxygen delivery, and combined immunotherapy. Finally, this review briefly addresses challenges in the clinical translation of NDT.

Osteosarcoma-targeted Cu and Ce based oxide nanoplatform for NIR II fluorescence/magnetic resonance dual-mode imaging and ros cascade amplification along with immunotherapy

BACKGROUND

As the lethal bone tumor, osteosarcoma often frequently occurs in children and adolescents with locally destructive and high metastasis. Distinctive kinds of nanoplatform with high therapeutical effect and precise diagnosis for osteosarcoma are urgently required. Multimodal optical imaging and programmed treatment, including synergistic photothermal-chemodynamic therapy (PTT-CDT) elicits immunogenetic cell death (ICD) is a promising strategy that possesses high bio-imaging sensitivity for accurate osteosarcoma delineating as well as appreciable therapeutic efficacy with ignorable side-effects.

METHODS AND RESULTS

In this study, mesoporous Cu and Ce based oxide nanoplatform with Arg-Gly-Asp (RGD) anchoring is designed and successfully constructed. After loading with indocyanine green, this nanoplatform can be utilized for precisely targeting and efficaciously ablating against osteosarcoma via PTT boosted CDT and the closely following ICD stimulation both in vitro and in vivo. Besides, it provides off-peak fluorescence bio-imaging in the second window of near-infrared region (NIR II, 1000-1700 nm) and Magnetic resonance signal, serves as the dual-mode contrast agents for osteosarcoma tissue discrimination.

CONCLUSION

Tumor targeted Cu&Ce based mesoporous nanoplatform permits efficient osteosarcoma suppression and dual-mode bio-imaging that opens new possibility for effectively diagnosing and inhibiting the clinical malignant osteosarcoma.

Tumor-Microenvironment-Responsive Cerium-Enriched Copper Nanozyme with O2 Supply and Oxidative Stress Amplification for In Situ Disulfiram Chemotherapy and Chemodynamic Therapy Intensification

Traditional chemotherapy has faced tough challenges of systemic toxicity, hypoxia resistance, and inadequacy of monotherapy. Developing the tumor-specific O2-supply-enhanced chemotherapy without toxic drugs while combing other precise treatments can substantially improve therapeutic efficacy. Herein, a CeO2-enriched CuO nanozyme with O2 supply and oxidative stress amplification for tumor-specific disulfiram (DSF) chemotherapy and intensified chemodynamic therapy by synergistic in situ "nontoxicity-toxicity" activation is developed. Notably, CeO2 can not only act as a morphological "regulator," but also serve as a cascaded enzyme-mimetic catalyst via tumor-microenvironment-responsive cascaded-logical programmable valence conversion. Once internalized inside tumor cells, the nanozyme can be degraded by lysosomal acidity to release nontoxic DSF and Cu2+, which can trigger in situ "Cu2+-DSF" chelation, generating a highly toxic Cu(DTC)2 for in situ chemotherapy. Moreover, the enriched CeO2 with catalase-mimetic activity can decompose the endogenous H2O2 into O2, which can relieve the hypoxia to enhance the chemotherapeutic efficacy. Furthermore, the simultaneously generated Ce3+ can exert peroxidase-mimetic activity to catalyze H2O2 into hydroxyl radicals (•OH) for chemodynamic therapy. This Fenton-like chemistry is accompanied by the regeneration of Ce4+, which can deplete the intracellular overproduced GSH to amplify the oxidative stress. Therefore, this nanozyme can provide an alternative to precise cancer treatment.

Nanozyme-based Clusterphene for Enhanced Electrically Catalytic Cancer Therapy

Nanozyme mediated catalytic therapy is an attractive strategy for cancer therapy. However, the nanozymes are tended to assemble into 3D architectures, resulting in poor catalytic efficiency for therapy. This study designs the assembly of nanozymes and natural enzymes into the layered structures featuring hexagonal pores as nanozyme clusterphene and investigates their catalytic therapy with the assistance of electric field. The nanozyme-based clusterphene consists of polyoxometalate (POM) and natural glucose oxidase (GOx), named POMG-based clusterphene, which facilitate multi-enzyme activities including peroxidase (POD), catalase (CAT), and glutathione oxidase (GPx). The highly ordered layers with hexagonal pores of POMG units significantly improve the peroxidase-like (POD-like) activity of the nanozyme and thus the sustained production of reactive oxygen species (ROS). At the same time, GOx can increase endogenous H2O2 and produce gluconic acid while consuming glucose, the nutrient of tumor cell growth. The results indicate that the POD-like activity of POMG-based clusterphene increase approximately sevenfold under electrical stimulation compared with Nd-substituted keggin type POM cluster (NdPW11). The experiments both in vitro and in vivo show that the proposed POMG-based clusterphene mediated cascade catalytic therapy is capable of efficient tumor inhibiting and preventing tumor proliferation in tumor-bearing mice model, promising as an excellent candidate for catalytic therapy.

Consuming intracellular glucose and regulating the levels of O2/H2O2 via the closed cascade catalysis system of Cu-CeO2 nanozyme and glucose oxidase

Imbalances in the intracellular environment caused by high levels of glucose, H2O2, and hypoxia can greatly impact cancer development and treatment. However, there is limited research on regulating the levels of these species simultaneously in tumor cells. Here, a pH-responsive nanozyme-enzyme hybrid system was developed to regulate intracellular glucose, H2O2 and O2. The system, named DMSN@Cu-CeO2@GOx, consists of Cu-CeO2 nanoparticles and glucose oxidase (GOx) immobilized in dendritic mesoporous silica (DMSN) spheres. GOx efficiently consumes glucose in tumor cells, causing a drop in pH and producing a significant amount of H2O2. Cu-CeO2 then catalyzes the conversion of H2O2 to O2 due to its high catalase-like (CAT) activity in weakly acidic conditions. The process was monitored by fluorescence probes, and the mechanism was investigated through fluorescence spectroscopy and confocal laser scanning microscopy. The cascade catalytic system with excellent biocompatibility continuously consumes glucose and elevates the level of O2 in cells. This hybrid nanomaterial offers a means to regulate the glucose/H2O2/O2 levels in cells and may provide insights into starvation therapy by modulating reactive species within cells.

CeO2@CuS@PDA-FA as targeted near-infrared PTT/CDT therapeutic agents for cancer cells

Single tumor treatment method usually has some defects, which makes it difficult to achieve good therapeutic effect. The ingenious combination of multiple tumor treatment methods on a single nanoplatform to achieve multifunctional treatment can effectively improve the efficiency of treatment. The targeted modification of nanomaterials can augment the precision of nanotherapeutic drugs in tumor treatment. Herein, a multifunctional nanoplatform (CeO2@CuS@PDA-FA) based on cerium dioxide nanoparticles engineered with copper sulfide (CeO2@CuS) has been constructed for synergistic photothermal therapy (PTT) and chemodynamic therapy (CDT). The CeO2@CuS were coated using polydopamine (PDA), and the modification of PDA surface by folic acid, in order to achieve the targeted effect for tumors. The localized hyperthermia induced by PTT can further improve the CDT efficiency of the nanoplatform, leading to a PTT/CDT synergistic effect. The nanoplatform possessed the capability of cancer cell-targeted and achieved better therapeutic efficacyin vitro. This work provided a new strategy for combined multifunctional theranostic platform and shows strong potential in practical applications.

Structural and functional insights in polysaccharides coated cerium oxide nanoparticles and their potential biomedical applications: A review

Cerium oxide nanoparticles have now significant presence in biomedical fields due to their wide applications; however, challenges regarding their safety and biocompatibility persist. Polysaccharides based biopolymers have inherent hydroxyl and carboxyl groups, enabling them to govern the surface functionalization of cerium oxide nanoparticles, hence their chemical and physical characteristics. Because of this, polysaccharides such as dextran, alginate, pullulan, chitosan, polylactic acid, starch, and pectin are practical substitutes for the conventional coatings used to synthesize cerium oxide nanoparticles. This review discusses the effect of biopolymer coatings on the properties of cerium oxide nanoparticles, such as size, stability, aggregation, and biocompatibility. Additionally, it also summarises various biomedical applications of polysaccharides coated cerium oxide nanoparticles, such as in bone tissue regeneration, liver inflammation, wound healing, and antibacterial and anticancer activities. Biocompatible cerium oxide nanoparticles will surely improve their applications in the biomedical field.

A self-cascade system based on Ag nanoparticle/single-walled carbon nanotube nanocomposites as an enzyme mimic for ultrasensitive detection of L-cysteine

L-Cysteine, widely used in medicine and the food industry, is of great essentiality to organisms and the food quality. Given that current detection approaches require exacting lab conditions and tedious sample treatment, there is a pressing demand for developing a method that possesses advantages of user friendliness, prominent performance, and cost-effectiveness. Herein, a self-cascade system was developed for the fluorescence detection of L-cysteine based on the ingenious performance of Ag nanoparticle/single-walled carbon nanotube nanocomposites (AgNP/SWCNTs) and DNA-templated Ag nanoclusters (DNA-AgNCs). The fluorescence of DNA-AgNCs could be quenched on account of the adsorption of DNA-AgNCs on AgNP/SWCNTs by π-π stacking. With the cooperation of Fe²⁺, AgNP/SWCNTs with oxidase and peroxidase-like activities could catalyze the oxidation of L-cysteine to produce cystine and hydrogen peroxide (H₂O₂) and then break the O-O bond of H₂O₂ to generate a hydroxyl radical (·OH), which could cleave the DNA strand into different sequence fragments which subsequently peeled off from the AgNP/SWCNTs, resulting in a "turn-on" fluorescence response. In this paper, AgNP/SWCNTs with multi-enzyme activities was synthesized enabling the reaction to proceed in just one step. The successful preliminary applications for the L-cysteine detection in pharmaceutical, juice beverage, and serum samples indicated that the developed method exhibited great potential in medical diagnosis, food monitoring, and the biochemical field, which also broadened the horizon for follow-up research.

Cerium oxide nanoparticles exert antitumor effects and enhance paclitaxel toxicity and activity against breast cancer cells

Cerium oxide nanoparticles (CeONPs) displayed cytotoxic properties against some cancer cells. However, there is very limited data about the possible antitumoral potential of them in breast cancer cells when used alone and/or together with a chemotherapeutic drug. We investigated the effects of CeONPs alone or in combination with paclitaxel (PAC) on healthy or carcinoma breast cells. After human breast cancer cells (MCF-7) treated with CeONPs alone or together with PAC for 24, 48, and 72 h, the effects of CeONPs on cell viability, apoptosis, migration, and adhesion were investigated. All cell viability and IC50 values of CeONPs and PAC treatments in healthy breast cells (HTERT-HME1) were higher than MCF-7 cells. They showed higher cytotoxicity against MCF-7 cells. CeONPs (10, 20, and 30 mM) and/or abraxane (AB) (2 μM) significantly decreased cell viability values in MCF-7 cells. All CeONPs concentrations increased the number of apoptotic MCF-7 cells. CeONPs (20 and 30 mM) alone or in combination with AB for 72 h treatment also significantly increased the apoptosis in compared to AB alone. CeONPs and/or AB can significantly inhibit the migratory ability of breast cancer cells. The migration rates in co-treated groups with CeONPs and AB were lower than CeONPs treatments. Higher concentrations of CeONPs alone or together with AB inhibited cell adhesion. Our results showed CeONPs can increase cytotoxicity and apoptosis and decrease cell migration and cell adhesion when used alone or together with AB. Therefore, combination of chemotherapeutics with CeONPs may provide a good strategy against cancer.

Nanoceria: an innovative strategy for cancer treatment

Nanoceria or cerium oxide nanoparticles characterised by the co-existing of Ce³⁺ and Ce⁴⁺ that allows self-regenerative, redox-responsive dual-catalytic activities, have attracted interest as an innovative approach to treating cancer. Depending on surface characteristics and immediate environment, nanoceria exerts either anti- or pro-oxidative effects which regulate reactive oxygen species (ROS) levels in biological systems. Nanoceria mimics ROS-related enzymes that protect normal cells at physiological pH from oxidative stress and induce ROS production in the slightly acidic tumour microenvironment to trigger cancer cell death. Nanoceria as nanozymes also generates molecular oxygen that relieves tumour hypoxia, leading to tumour cell sensitisation to improve therapeutic outcomes of photodynamic (PDT), photothermal (PTT) and radiation (RT), targeted and chemotherapies. Nanoceria has been engineered as a nanocarrier to improve drug delivery or in combination with other drugs to produce synergistic anti-cancer effects. Despite reported preclinical successes, there are still knowledge gaps arising from the inadequate number of studies reporting findings based on physiologically relevant disease models that accurately represent the complexities of cancer. This review discusses the dual-catalytic activities of nanoceria responding to pH and oxygen tension gradient in tumour microenvironment, highlights the recent nanoceria-based platforms reported to be feasible direct and indirect anti-cancer agents with protective effects on healthy tissues, and finally addresses the challenges in clinical translation of nanoceria based therapeutics.

Ceria Nanoenzyme-Based Hydrogel with Antiglycative and Antioxidative Performance for Infected Diabetic Wound Healing

Diabetic wound healing still faces a dilemma because of the hostile hyperglycemic, oxidative, and easily-infected wound microenvironment. In addition, advanced glycation end products (AGEs) further impede wound repair by altering the immunological balance. Herein, ceria nanorods with distinctive antiglycative and excellent antioxidative capacities are innovatively introduced into a self-healing and erasable hydrogel, which could reshape the wound microenvironment by expediting hemostasis, inhibiting infection, reducing AGEs, and continuously depleting reactive oxygen species. The remitted oxidative stress and glycosylation synergistically regulate inflammatory responses, and promote revascularization and extracellular matrix deposition, resulting in accelerated diabetic wound repair. This study provides a highly efficient strategy for constructing nanoenzyme-reinforced antiglycative hydrogel that regulates every wound healing stage for diabetic wound management.

A synergistic chemodynamic-photodynamic-photothermal therapy platform based on biodegradable Ce-doped MoOx nanoparticles

Near-infrared light-induced catalysts are considered to be potential nanoagents for tumor therapy. Cerium (Ce) is a non-biotoxic lanthanide element and exhibits variable valence states for catalytic reactions. In this work, we report a one-step hydrothermal synthesis for Ce-doped MoO_x (CMO) nanomaterials. The obtained CMO nanomaterials show high absorption in the NIR II regime and a high photothermal conversion efficiency of 67.7% (1064 nm). Moreover, due to the doping of Ce element, the consumption of hydrogen peroxide (H₂O₂) and glutathione (GSH) is boosted which enhances the chemodynamic and photodynamic therapy simultaneously. Under NIR II laser irradiation, the designed CMO nanocatalysts induce metabolism disruption and mitochondrial damage in the tumor cells. As-prepared CMO nanomaterials also show good biocompatibility and pH-responsive degradation behavior, which can be degraded rapidly under alkaline conditions (pH = 7.4) and remain stable in acidic solution (pH = 5.6). These properties make CMO nanomaterials ideal biodegradable nanotheranostic agents for synergistic chemodynamic-photodynamic-photothermal antitumor therapy.

Chemodynamic Therapy via Fenton and Fenton-Like Nanomaterials: Strategies and Recent Advances

Chemodynamic therapy (CDT), a novel cancer therapeutic strategy defined as the treatment using Fenton or Fenton-like reaction to produce •OH in the tumor region, was first proposed by Bu, Shi, and co-workers in 2016. Recently, with the rapid development of Fenton and Fenton-like nanomaterials, CDT has attracted tremendous attention because of its unique advantages: 1) It is tumor-selective with low side effects; 2) the CDT process does not depend on external field stimulation; 3) it can modulate the hypoxic and immunosuppressive tumor microenvironment; 4) the treatment cost of CDT is low. In addition to the Fe-involved CDT strategies, the Fenton-like reaction-mediated CDT strategies have also been proposed, which are based on many other metal elements including copper, manganese, cobalt, titanium, vanadium, palladium, silver, molybdenum, ruthenium, tungsten, cerium, and zinc. Moreover, CDT has been combined with other therapies like chemotherapy, radiotherapy, phototherapy, sonodynamic therapy, and immunotherapy for achieving enhanced anticancer effects. Besides, there have also been studies that extend the application of CDT to the antibacterial field. This review introduces the latest advancements in the nanomaterials-involved CDT from 2018 to the present and proposes the current limitations as well as future research directions in the related field.

Insights on catalytic mechanism of CeO2 as multiple nanozymes

CeO₂ with the reversible Ce³⁺/Ce⁴⁺ redox pair exhibits multiple enzyme-like catalytic performance, which has been recognized as a promising nanozyme with potentials for disease diagnosis and treatments. Tailorable surface physicochemical properties of various CeO₂ catalysts with controllable sizes, morphologies, and surface states enable a rich surface chemistry for their interactions with various molecules and species, thus delivering a wide variety of catalytic behaviors under different conditions. Despite the significant progress made in developing CeO₂-based nanozymes and their explorations for practical applications, their catalytic activity and specificity are still uncompetitive to their counterparts of natural enzymes under physiological environments. With the attempt to provide the insights on the rational design of highly performed CeO₂ nanozymes, this review focuses on the recent explorations on the catalytic mechanisms of CeO₂ with multiple enzyme-like performance. Given the detailed discussion and proposed perspectives, we hope this review can raise more interest and stimulate more efforts on this multi-disciplinary field.

Targeting Killing of Tumor Cells Based on Isoelectric Point Suitable Nanoceria-rod with High Oxygen Vacancies

Nanozymes have great potential application in tumor treatment because of their good stability, high biocompatibility, easy preparation and versatility. However, it remains a challenge to design of highly active nanozyme...

Anticancer Therapeutic Effects of Cerium Oxide Nanoparticles: Known and Unknown Molecular Mechanisms

Cerium-based nanoparticles (CeNPs), particularly cerium oxide (CeO2), have been studied extensively for their antioxidant and prooxidant properties. However, their complete redox and enzyme-mimetic mechanisms of therapeutic action at the molecular...