A Modular Ionophore Platform for Liver-Directed Copper Supplementation in Cells and Animals

Cuproplasia and cuproptosis, two sides of the coin

Copper is an essential micronutrient in the human body, mainly acting as a crucial cofactor required for a wide range of physiological processes across nearly all cell types. Recent advances revealed that tumor cells seize copper to fulfill their rapid proliferation, metastasis, immune evasion, and so on by reprogramming the copper regulatory network, defined as cuproplasia. Thus, targeting copper chelation to reduce copper levels has been considered a rational tumor therapy strategy. However, overloaded copper ions could be toxic, which leads to the aggregation of lipoylated mitochondrial proteins and the depletion of iron-sulfur clusters, ultimately resulting in cell death, termed cuproptosis. Upon its discovery, cuproptosis has attracted great interest from oncologists, and targeting cuproptosis by copper ionophores exhibits as a potential anti-tumor therapy. In this review, we present the underlying mechanisms involved in cuproplasia and cuproptosis. Additionally, we sum up the chemicals targeting either cuproplasia or cuproptosis for cancer therapy. Further attention should be paid to distinguishing cancer patients who are suitable for targeting cuproplasia or cuproptosis.

Pseudonatural Flavonols as Novel Copper Ionophores for NAFLD Intervention via Synergistic Copper Delivery and Flavonoid Activity

Copper plays crucial roles in fundamental life processes, including proliferation, metabolism, and survival. Copper deficiency is associated with multiple diseases, such as nonalcoholic fatty liver disease (NAFLD) and Wilson's disease. Therapeutic programs targeting copper supply are prospectively employed for disease intervention. Herein, we developed biofriendly copper ionophores (HQFs) by constructing pseudonatural flavonols, which possess flavonoid bioactivity and enhanced copper transport properties. In cell models and mice, we found that HQF-mediated copper delivery synergistically, safely, and efficiently intervened in the development of fatty liver. Mechanistically, NAFLD remission involves fatty acid metabolism, anti-inflammatory processes, and pentose phosphate pathway (PPP) enhancement. Our work is the first to propose the utilization of synergistic copper loading and flavonoid activity for NAFLD intervention, which may inform the clinical management of liver disease.

Functionalized Green Carbon dots for Specific Detection of Copper in Human Serum Samples and Living Cells

Intracellular copper ion (Cu2+) is irreplaceable and essential in regulation of physiological and biological processes, while excessive copper from bioaccumulation may cause potential hazards to human health. Hence, effective and sensitive recognition is urgently significant to prevent over-intake of copper. In this work, a novel highly sensitive and green carbon quantum dots (Green-CQDs) were synthesized by a low-cost and facile one-step microwave auxiliary method, which utilized gallic acid, carbamide and PEG400 as carbon source, nitrogen source and surface passivation agent, respectively. The decreased fluorescence illustrated excellent linear relationship with the increasing of Cu2+ concentration in a wide range. Substantial surface amino and hydroxyl group introduced by PEG400 significantly improved selectivity and sensitivity of Green-CQDs. The surface amino chelation mechanism and fluorescence internal filtration effect were demonstrated by the restored fluorescence after addition of EDTA. Crucially, the nanosensor illustrated good cell permeability, high biocompatibility and recovery rate, significantly practical application in fluorescent imaging and biosensing of intracellular Cu2+ in HepG-2 cells, which revealed a potential and promising biological applications in early diagnosis and treatment of copper ion related disease.

Role of copper homeostasis and cuproptosis in heart failure pathogenesis: implications for therapeutic strategies

Copper is an essential micronutrient involved in various physiological processes in various cell types. Consequently, dysregulation of copper homeostasis-either excessive or deficient-can lead to pathological changes, such as heart failure (HF). Recently, a new type of copper-dependent cell death known as cuproptosis has drawn increasing attention to the impact of copper dyshomeostasis on HF. Notably, copper dyshomeostasis was associated with the occurrence of HF. Hence, this review aimed to investigate the biological processes involved in copper uptake, transport, excretion, and storage at both the cellular and systemic levels in terms of cuproptosis and HF, along with the underlying mechanisms of action. Additionally, the role of cuproptosis and its related mitochondrial dysfunction in HF pathogenesis was analyzed. Finally, we reviewed the therapeutic potential of current drugs that target copper metabolism for treating HF. Overall, the conclusions of this review revealed the therapeutic potential of copper-based therapies that target cuproptosis for the development of strategies for the treatment of HF.

Glycosylated AIE-active Red Light-triggered Photocage with Precisely Tumor Targeting Capability for Synergistic Type I Photodynamic Therapy and CPT Chemotherapy

Photocaging is an emerging protocol for precisely manipulating spatial and temporal behaviors over biological activity. However, the red/near-infrared light-triggered photolysis process of current photocage is largely singlet oxygen (1O2)-dependent and lack of compatibility with other reactive oxygen species (ROS)-activated techniques, which has proven to be the major bottleneck in achieving efficient and precise treatment. Herein, we reported a lactosylated photocage BT-LRC by covalently incorporating camptothecin (CPT) into hybrid BODIPY-TPE fluorophore via the superoxide anion radical (O2 -⋅)-cleavable thioketal bond for type I photodynamic therapy (PDT) and anticancer drug release. Amphiphilic BT-LRC could be self-assembled into aggregation-induced emission (AIE)-active nanoparticles (BT-LRCs) owing to the regulation of carbohydrate-carbohydrate interactions (CCIs) among neighboring lactose units in the nanoaggregates. BT-LRCs could simultaneously generate abundant O2 -⋅ through the aggregation modulated by lactose interactions, and DNA-damaging agent CPT was subsequently and effectively released. Notably, the type I PDT and CPT chemotherapy collaboratively amplified the therapeutic efficacy in HepG2 cells and tumor-bearing mice. Furthermore, the inherent AIE property of BT-LRCs endowed the photocaged prodrug with superior bioimaging capability, which provided a powerful tool for real-time tracking and finely tuning the PDT and photoactivated drug release behavior in tumor therapy.

Recent Advances in Nanomaterial-Mediated Cell Death for Cancer Therapy

Nanomedicine has shown great anticancer potential by disrupting redox homeostasis and increasing the levels of oxidative stress, but the therapeutic effect is limited by factors including the intrinsic self-protection mechanism of tumors. Cancer cell death can be induced by the exploration of different cell death mechanisms, such as apoptosis, pyroptosis, necroptosis, cuproptosis, and ferroptosis. The merging of nanotechnology with biomedicine has provided tremendous opportunities to construct cell death-based nanomedicine for innovative cancer therapy. Nanocarriers are not only used for the targeted delivery of cell death inducers, but also as therapeutic components to induce cell death to achieve efficient tumor treatment. This review focuses on seven cell death modalities mediated by nanomaterials, such as apoptosis, pyroptosis, necroptosis, ferroptosis, cuprotosis, immunogenic cell death, and autophagy. The mechanisms of these seven cell death modalities are described in detail, as well as the preparation of nanomaterials that induce them and the mechanisms, they used to exert their effects. Finally, this work describes the potential future development based on the current knowledge related to cell death induced by nanomaterials.

A glycosylated AIE-active Fe(III) photosensitizer activated by the tumor microenvironment for synergistic type I photodynamic and chemodynamic therapy

Photodynamic therapy (PDT) and chemodynamic therapy (CDT) are both promising cancer treatments to inhibit tumor cells by generating highly cytotoxic reactive oxygen species (ROS). Herein, we report a novel tumor microenvironment (TME) stimulus-responsive water-soluble glycosylated photosensitizer (BT-TPE@Fe-Lac), which can serve as a high-efficiency antitumor agent by combining PDT and CDT, based on the coordination of Fe3+ with lactosyl bis(2-pyridylmethyl)amine and an AIE luminogen (benzothiazole-hydroxytetraphenylethene, BT-TPE). BT-TPE@Fe-Lac is stable under physiological conditions and selectively targets HepG2 cells via asialoglycoprotein receptor (ASGPR)-mediated endocytosis. It rapidly dissociates into AIE-active BT-TPE molecules and a lactosyl ferric(III) complex in the acidic lysosomes of cancer cells. Upon exposure to light, BT-TPE produces O2˙- radicals for type I PDT. The ferric(III) complex is reduced to an Fe(II) complex upon depletion of glutathione, which primes the breakdown of endogenous H2O2 within the tumor microenvironment, thus generating highly toxic ˙OH for enhanced CDT. Compared with the monotherapy of PDT or CDT, BT-TPE@Fe-Lac can significantly increase the intracellular ROS levels to induce more tumor cell death under low drug doses and hypoxia-dependent conditions. This strategy leverages the unique properties of the TME to optimize therapeutic outcomes, offering a promising approach for the TME-responsive nanoplatform in advanced cancer therapy.

Copper homeostasis and cuproptosis in central nervous system diseases

Copper (Cu), an indispensable micronutrient for the sustenance of living organisms, contributes significantly to a vast array of fundamental metabolic processes. The human body maintains a relatively low concentration of copper, which is mostly found in the bones, liver, and brain. Despite its low concentration, Cu plays a crucial role as an indispensable element in the progression and pathogenesis of central nervous system (CNS) diseases. Extensive studies have been conducted in recent years on copper homeostasis and copper-induced cell death in CNS disorders, including glioma, Alzheimer's disease, Amyotrophic lateral sclerosis, Huntington's disease, and stroke. Cuproptosis, a novel copper-induced cell death pathway distinct from apoptosis, necrosis, pyroptosis, and ferroptosis, has been identified as potentially intricately linked to the pathogenic mechanisms underlying various CNS diseases. Therefore, a systematic review of copper homeostasis and cuproptosis and their relationship with CNS disorders could deepen our understanding of the pathogenesis of these diseases. In addition, it may provide new insights and strategies for the treatment of CNS disorders.

Minimizing higher-order aggregation maximizes iron mobilization by small molecules

The natural product hinokitiol mobilizes iron across lipid bilayers at low concentrations and restores hemoglobinization in iron transporter protein-deficient systems. But hinokitiol fails to similarly mobilize iron at higher concentrations, limiting its uses in chemical biology and medicine. Here we show that at higher concentrations, hinokitiol3:Fe(III) complexes form large, higher-order aggregates, leading to loss of transmembrane iron mobilization. Guided by this understanding and systematic structure-function studies enabled by modular synthesis, we identified FeM-1269, which minimally aggregates and dose-dependently mobilizes iron across lipid bilayers even at very high concentrations. In contrast to hinokitiol, FeM-1269 is also well-tolerated in animals at high doses for extended periods of time. In a mouse model of anemia of inflammation, FeM-1269 increases serum iron, transferrin saturation, hemoglobin and hematocrit. This rationally developed iron-mobilizing small molecule has enhanced potential as a molecular prosthetic for understanding and potentially treating iron transporter deficiencies.

Metal-organic frameworks in oral drug delivery

Metal-organic frameworks (MOFs) offer innovative solutions to the limitations of traditional oral drug delivery systems through their unique combination of metal ions and organic ligands. This review systematically examines the structural properties and principles of MOFs, setting the stage for their application in drug delivery. It discusses various classes of MOFs, including those based on zirconium, iron, zinc, copper, titanium, aluminum, potassium, and magnesium, assessing their drug-loading capacities, biocompatibility, and controlled release mechanisms. The effectiveness of MOFs is illustrated through case studies that highlight their capabilities in enhancing drug solubility, providing protection against the harsh gastrointestinal environment, and enabling precise drug release. The review addresses potential challenges, particularly the toxicity concerns associated with MOFs, and calls for further research into their biocompatibility and interactions with biological systems. It concludes by emphasizing the potential of MOFs in revolutionizing oral drug delivery, highlighting the critical need for comprehensive research to harness their full potential in clinical applications.

Retinoic acid mitigates the NSC319726-induced spermatogenesis dysfunction through cuproptosis-independent mechanisms

Copper ionophore NSC319726 has attracted researchers' attention in treating diseases, particularly cancers. However, its potential effects on male reproduction during medication are unclear. This study aimed to determine whether NSC319726 exposure affected the male reproductive system. The reproductive toxicity of NSC319726 was evaluated in male mice following a continuous exposure period of 5 weeks. The result showed that NSC319726 exposure caused testis index reduction, spermatogenesis dysfunction, and architectural damage in the testis and epididymis. The exposure interfered with spermatogonia proliferation, meiosis initiation, sperm count, and sperm morphology. The exposure also disturbed androgen synthesis and blood testis barrier integrity. NSC319726 treatment could elevate the copper ions in the testis to induce cuproptosis in the testis. Copper chelator rescued the elevated copper ions in the testis and partly restored the spermatogenesis dysfunction caused by NSC319726. NSC319726 treatment also decreased the level of retinol dehydrogenase 10 (RDH10), thereby inhibiting the conversion of retinol to retinoic acid, causing the inability to initiate meiosis. Retinoic acid treatment could rescue the meiotic initiation and spermatogenesis while not affecting the intracellular copper ion levels. The study provided an insight into the bio-safety of NSC319726. Retinoic acid could be a potential therapy for spermatogenesis impairment in patients undergoing treatment with NSC319726.

Multifunctional nanomaterials via cell cuproptosis and oxidative stress for treating osteosarcoma and OS-induced bone destruction

Reactive Oxygen Species (ROS) refers to a highly reactive class of oxidizing species that have the potential to induce cellular apoptosis and necrosis. Cuproptosis, a type of cell death, is primarily associated with the effects of copper ions. However, the specific relationship between ROS, cuproptosis, and osteosarcoma (OS) remains relatively unexplored. Additionally, there is limited research on the use of cuproptosis in conjunction with oxidative stress for treating OS and inhibiting tumor-induced bone destruction. To address these gaps, a novel treatment approach has been developed for OS and neoplastic bone destruction. This approach involves the utilization of glutathione (GSH) and pH-responsive organic-inorganic mesoporous silica nanoparticles@Cu2S@oxidized Dextran (short for MCD). The MCD material demonstrates excellent cytocompatibility, osteogenesis, tumor suppression, and the ability to inhibit osteoclast formation. The specific mechanism of action involves the mitochondria of the MCD material inhibiting key proteins in the tricarboxylic acid (TCA) cycle. Simultaneously, the generation of ROS promotes this inhibition and leads to alterations in cellular energy metabolism. Moreover, the MCD biomaterial exhibits promising mild-temperature photothermal therapy in the second near-infrared (NIR-II) range, effectively mitigating tumor growth and OS-induced bone destruction in vivo.

Genotoxicity responses of single and mixed exposure to heavy metals (cadmium, silver, and copper) as environmental pollutants in Drosophila melanogaster

Heavy metals are now persistently present in living things' environments, in addition to their potential toxicity. Therefore, the aim of this study was to utilize D. melanogaster to determine the biological effects induced by different heavy metals including cadmium chloride (CdCl2), copper (II) sulfate pentahydrate (CuSO 4.5 H2O), and silver nitrate (AgNO3). In vivo experiments were conducted utilizing three low and environmentally relevant concentrations from 0.01 to 0.5 mM under single and combined exposure scenarios on D. melanogaster larvae. The endpoints measured included viability, reactive oxygen species (ROS) generation and genotoxic effects using Comet assay and the wing-spot test. Results indicated that tested heavy metals were not toxic in the egg-to adult viability. However, combined exposure (CdCl2+AgNO3 and CdCl2+AgNO3+CuSO 4.5 H2O) resulted in significant genotoxic and unfavorable consequences, as well as antagonistic and/or synergistic effects on oxidative damage and genetic damage.

Potential of lncRNAs to regulate cuproptosis in hepatocellular carcinoma: Establishment and validation of a novel risk model

Cuproptosis, a distinct form of programmed cell death, is an emerging field in oncology with promising implications. This novel mode of cell death has the potential to become a regulatory target for tumor therapy, thus expanding the currently limited treatment options available for patients with cancer. Our research team focused on investigating the role of functional long non-coding RNA (lncRNAs) in hepatocellular carcinoma (HCC). We were particularly intrigued by the potential implications of HCC-lncRNAs on cuproptosis. Through a comprehensive analysis, we identified three cuproptosis-related lncRNAs (CRLs): AC018690.1, AL050341.2, and LINC02038. These lncRNAs were found to influence the sensitivity of HCC to cuproptosis. Based on our results, we constructed a risk model represented by the equation: risk score = 0.82 * AC018690.1 + 0.65 * AL050341.2 + 0.61 * LINC02038. Notably, significant disparities were observed in clinical features, such as the response rate to immunotherapy and targeted therapy, as well as in cellular characteristics, including the composition of the tumor immune microenvironment (TIME), when comparing the high- and low-risk groups. Most importantly, knockdown of these CRLs was confirmed to significantly weaken the resistance to cuproptosis in HCC. This effect resulted from the accelerated accumulation of lipoacylated-DLAT and lipoacylated-DLST. In summary, we identified three CRLs in HCC and established a novel risk model with potential clinical applications. Additionally, we proposed a potential therapeutic method consisting of sorafenib-copper ionophores-immunotherapy.

Impact of human serum albumin on CuII and ZnII complexation by ATSM (diacetyl-bis(N4-methylthiosemicarbazone)) and a water soluble analogue

The chelator diacetyl-bis(N4-methylthiosemicarbazone) (ATSM) and its complexes with CuII and ZnII are becoming increasingly investigated for medical applications such as PET imaging for anti-tumour therapy and the treatment of amyotrophic lateral sclerosis. However, the solubility in water of both the ligand and the complexes presents certain limitations for in vitro studies. Moreover, the stability of the CuII and ZnII complexes and their metal exchange reaction against the potential biological competitor human serum albumin (HSA) has not been studied in depth. In this work it was observed that the ATSM with an added carboxylic group into the structure increases its solubility in aqueous solutions without altering the coordination mode and the conjugated system of the ligand. The poorly water-soluble CuII- and ZnII-ATSM complexes were prevented from precipitating due to the binding to HSA. Both HSA and ATSM show a similar thermodynamic affinity for ZnII. Finally, the CuII-competition experiments with EDTA and the water-soluble ATSM ligands yielded an apparent log Kd at pH 7.4 of about -19. When ATSM was added to CuII- and ZnII-loaded HSA, withdrawing of ZnII was kinetically favoured, but this metal is slowly substituted by the CuII afterwards taken from HSA so that this protein could be considered as a source of CuII for ATSM.

Copper homeostasis and cuproptosis in cardiovascular disease therapeutics

Copper (Cu) homeostasis is gaining increasing attention in human health as both Cu overload and deficiency evokes pathological changes including cardiovascular diseases (CVDs). Cu supplementation, nanocarriers, and chelators have all exhibited therapeutic promise in some human diseases, although how Cu dyshomeostasis and cuproptosis, a novel form of regulated cell death, contribute to CVD pathology remains elusive. Here, we discuss Cu dyshomeostasis and the potential role of cuproptosis in various CVDs. We evaluate underlying cellular mechanisms, aiming to provide some insights regarding the utility of targeting Cu dyshomeostasis and cuproptosis as a novel strategy in the management of CVDs.

Exploring cuproptosis as a mechanism and potential intervention target in cardiovascular diseases

Copper (Cu) is a vital trace element for maintaining human health. Current evidence suggests that genes responsible for regulating copper influx and detoxification help preserve its homeostasis. Adequate Cu levels sustain normal cardiac and blood vessel activity by maintaining mitochondrial function. Cuproptosis, unlike other forms of cell death, is characterized by alterations in mitochondrial enzymes. Therapeutics targeting cuproptosis in cardiovascular diseases (CVDs) mainly include copper chelators, inhibitors of copper chaperone proteins, and copper ionophores. In this review, we expound on the primary mechanisms, critical proteins, and signaling pathways involved in cuproptosis, along with its impact on CVDs and the role it plays in different types of cells. Additionally, we explored the influence of key regulatory proteins and signaling pathways associated with cuproptosis on CVDs and determined whether intervening in copper metabolism and cuproptosis can enhance the outcomes of CVDs. The insights from this review provide a fresh perspective on the pathogenesis of CVDs and new targets for intervention in these diseases.

Metalloallostery and Transition Metal Signaling: Bioinorganic Copper Chemistry Beyond Active Sites

Transition metal chemistry is essential to life, where metal binding to DNA, RNA, and proteins underpins all facets of the central dogma of biology. In this context, metals in proteins are typically studied as static active site cofactors. However, the emergence of transition metal signaling, where mobile metal pools can transiently bind to biological targets beyond active sites, is expanding this conventional view of bioinorganic chemistry. This Minireview focuses on the concept of metalloallostery, using copper as a canonical example of how metals can regulate protein function by binding to remote allosteric sites (e.g., exosites). We summarize advances in and prospects for the field, including imaging dynamic transition metal signaling pools, allosteric inhibition or activation of protein targets by metal binding, and metal-dependent signaling pathways that underlie nutrient vulnerabilities in diseases spanning obesity, fatty liver disease, cancer, and neurodegeneration.

Copper homeostasis and copper-induced cell death in the pathogenesis of cardiovascular disease and therapeutic strategies

Copper is a vital mineral, and an optimal amount of copper is required to support normal physiologic processes in various systems, including the cardiovascular system. Over the past few decades, copper-induced cell death, named cuproptosis, has become increasingly recognized as an important process mediating the pathogenesis and progression of cardiovascular disease (CVD), including atherosclerosis, stroke, ischemia-reperfusion injury, and heart failure. Therefore, an in-depth understanding of the regulatory mechanisms of cuproptosis in CVD may be useful for improving CVD management. Here, we review the relationship between copper homeostasis and cuproptosis-related pathways in CVD, as well as therapeutic strategies addressing copper-induced cell death in CVD.

Cuproptosis: p53-regulated metabolic cell death?

Cuproptosis is a novel type of copper-induced cell death that primarily occurs in cells that utilize oxidative phosphorylation as the main metabolic pathway to produce energy. Copper directly associates with the lipoylated proteins of the tricarboxylic acid cycle, leading to the disulfide-bond-dependent aggregation of these lipoylated proteins, destabilization of the iron-sulfur cluster proteins, and consequent proteotoxic stress. Cancer cells prefer glycolysis (Warburg effect) to oxidative phosphorylation for producing intermediate metabolites and energy, thereby achieving resistance to cuproptosis. Interestingly, the tumor suppressor p53 is a crucial metabolic regulator that inhibits glycolysis and drives a metabolic switch towards oxidative phosphorylation in cancer cells. Additionally, p53 regulates the biogenesis of iron-sulfur clusters and the copper chelator glutathione, which are two critical components of the cuproptotic pathway, suggesting that this tumor suppressor might play a role in cuproptosis. Furthermore, the possible roles of mutant p53 in regulating cuproptosis are discussed. In this essay, we review the recent progress in the understanding of the mechanism underlying cuproptosis, revisit the roles of p53 in metabolic regulation and iron-sulfur cluster and glutathione biosynthesis, and propose several potential mechanisms for wild-type and mutant p53-mediated cuproptosis regulation.

Application and trend of bioluminescence imaging in metabolic syndrome research

Bioluminescence imaging is a non-invasive technology used to visualize physiological processes in animals and is useful for studying the dynamics of metabolic syndrome. Metabolic syndrome is a broad spectrum of diseases which are rapidly increasing in prevalence, and is closely associated with obesity, type 2 diabetes, nonalcoholic fatty liver disease, and circadian rhythm disorder. To better serve metabolic syndrome research, researchers have established a variety of animal models expressing luciferase, while also committing to finding more suitable luciferase promoters and developing more efficient luciferase-luciferin systems. In this review, we systematically summarize the applications of different models for bioluminescence imaging in the study of metabolic syndrome.

Dithiol-Activated Bioorthogonal Chemistry for Endoplasmic Reticulum-Targeted Synergistic Chemophototherapy

The controlled intracellular release of nitrite is still an unmet challenge due to the lack of bio-friendly donors, and the antitumor effect of nitrite is limited by its physiologically inert activity. Herein, we designed benzothiadiazole-based organic nitrite donors that are stable against bio-relevant species but selectively respond to dithiol species through S_N Ar/intramolecular cyclization tandem reactions in the aqueous media. The bioorthogonal system was established to target the endoplasmic reticulum (ER) of liver cancer HepG2 cells. The nitrite and nonivamide were coupled to induce elevation of intracellular levels of calcium ions as well as reactive oxygen/nitrogen species, which resulted in ER stress and mitochondrial dysfunction. We demonstrated that a combination of photoactivation and "click to release" strategy could enhance antitumor effect in cellular level and show good potential for cancer precision therapy.

Copper-based metal-organic frameworks for biomedical applications

Metal-organic frameworks (MOFs) are a class of important porous, crystalline materials composed of metal ions (clusters) and organic ligands. Owing to the unique redox chemistry, photochemical and electrical property, and catalytic activity of Cu^2+/+, copper-based MOFs (Cu-MOFs) have been recently and extensively explored in various biomedical fields. In this review, we first make a brief introduction to the synthesis of Cu-MOFs and their composites, and highlight the recent synthetic strategies of two most studied representatives, three-dimensional HKUST-1 and two-dimensional Cu-TCPP. The recent advances of Cu-MOFs in the applications of cancer treatment, bacterial inhibition, biosensing, biocatalysis, and wound healing are summarized and discussed. Furthermore, we propose a prospect of the future development of Cu-MOFs in biomedical fields and beyond.

Rational Design of Silicon-Based Zinc Ionophores

Ionophores transport ions across biological membranes and have wide-ranging applications, but a platform for their rapid development does not exist. We report a platform for developing ionophores from metal-ion chelators, which are readily available with wide-ranging affinities and specificities, and structural data that can aid rational design. Specifically, we fine-tuned the binding affinity and lipophilicity of a Zn^II -chelating ligand by introducing silyl groups proximal to the Zn^II -binding pocket, which generated ionophores that performed better than most of the currently known Zn^II ionophores. Furthermore, these silicon-based ionophores were specific for Zn^II over other metals and exhibited better antibacterial activity and less toxicity to mammalian cells than several known Zn^II ionophores, including pyrithione. These studies establish rational design principles for the rapid development of potent and specific ionophores and a new class of antibacterial agents.

Selective Targeting of Cancer Cells by Copper Ionophores: An Overview

Conventional cancer therapies suffer from severe off-target effects because most of them target critical facets of cells that are generally shared by all rapidly proliferating cells. The development of new therapeutic agents should aim to increase selectivity and therefore reduce side effects. In addition, these agents should overcome cancer cell resistance and target cancer stem cells. Some copper ionophores have shown promise in this direction thanks to an intrinsic selectivity in preferentially inducing cuproptosis of cancer cells compared to normal cells. Here, Cu ionophores are discussed with a focus on selectivity towards cancer cells and on the mechanisms responsible for this selectivity. The proposed strategies, to further improve the targeting of cancer cells by copper ionophores, are also reported.

Connecting copper and cancer: from transition metal signalling to metalloplasia

Copper is an essential nutrient whose redox properties make it both beneficial and toxic to the cell. Recent progress in studying transition metal signalling has forged new links between researchers of different disciplines that can help translate basic research in the chemistry and biology of copper into clinical therapies and diagnostics to exploit copper-dependent disease vulnerabilities. This concept is particularly relevant in cancer, as tumour growth and metastasis have a heightened requirement for this metal nutrient. Indeed, the traditional view of copper as solely an active site metabolic cofactor has been challenged by emerging evidence that copper is also a dynamic signalling metal and metalloallosteric regulator, such as for copper-dependent phosphodiesterase 3B (PDE3B) in lipolysis, mitogen-activated protein kinase kinase 1 (MEK1) and MEK2 in cell growth and proliferation and the kinases ULK1 and ULK2 in autophagy. In this Perspective, we summarize our current understanding of the connection between copper and cancer and explore how challenges in the field could be addressed by using the framework of cuproplasia, which is defined as regulated copper-dependent cell proliferation and is a representative example of a broad range of metalloplasias. Cuproplasia is linked to a diverse array of cellular processes, including mitochondrial respiration, antioxidant defence, redox signalling, kinase signalling, autophagy and protein quality control. Identifying and characterizing new modes of copper-dependent signalling offers translational opportunities that leverage disease vulnerabilities to this metal nutrient.

Metal-Organic Frameworks Encapsulating Carbon Dots Enable Fast Speciation of Mono- and Divalent Copper

Copper is an essential element to play significant roles in human health associated to the strong redox properties of Cu(I) and Cu(II). The concurrent monitoring of copper species in biological matrixes is highly desired. Herein, a dual-channel fluorescence nanoprobe was designed for the speciation of mono- and divalent copper by conjugating carbon dots (CDs) with Eu-based metal-organic frameworks (Eu-MOFs). The obtained Eu-MOFs@CD nanoprobe exhibits fluorescence at λ_ex/λ_em = 380/454 nm from CDs and λ_ex/λ_em = 275/615 nm from Eu-MOFs. Bathocuproine disulfonate (BCS) specifically chelates Cu⁺ to produce a BCS-Cu⁺ adduct with absorption at 480 nm, which quenches the fluorescence of CDs at 454 nm due to the inner filter effect. On the other hand, Cu²⁺ quenches the fluorescence of Eu-MOFs due to the replacement of Eu³⁺ by Cu²⁺. Thus, Eu-MOFs@CDs enable extremely fast detection of Cu⁺ and Cu²⁺ within 1 min. Furthermore, the nanoprobe is demonstrated by monitoring the variation of Cu⁺ and Cu²⁺ in the degradation process of copper nanoparticles and Cu-based MOFs.

Recent research progress in galactose-based fluorescent probes for detection of biomarkers of liver diseases

This highlight illustrates the challenges and latest progress in galactose-based fluorescent probes for early diagnosis of liver diseases.

Leveraging disulfiram to treat cancer: Mechanisms of action, delivery strategies, and treatment regimens

Disulfiram (DSF) has been used as an alcoholism drug for 70 years. Recently, it has attracted increasing attention owing to the distinguished anticancer activity, which can be further potentiated by the supplementation of Cu²⁺. Although encouraging anticancer results are obtained in lab, the clinical outcomes of oral DSF are not satisfactory, which urges an in-depth understanding of the underlying mechanisms, bottlenecks, and proposal of potential methods to address the dilemma. In this review, a critical summarization of various molecular biological anticancer mechanisms of DSF/Cu²⁺ is provided and the predicament of orally delivering DSF in clinical oncotherapy is explained by the metabolic barriers. We highlight the recent advances in the DSF/Cu²⁺ delivery strategies and the emerging treatment regimens for cancer treatment. Last but not the least, we summarize the clinical trials regarding DSF and make a prospect of DSF/Cu-based cancer therapy.

Modulation of Intracellular Copper Levels as the Mechanism of Action of Anticancer Copper Complexes: Clinical Relevance

Copper (Cu) is a vital element required for cellular growth and development; however, even slight changes in its homeostasis might lead to severe toxicity and deleterious medical conditions. Cancer patients are typically associated with higher Cu content in serum and tumor tissues, indicating increased demand of cancer cells for this micronutrient. Cu is known to readily cycle between the +1 and +2 oxidation state in biological systems. The mechanism of action of Cu complexes is typically based on their redox activity and induction of reactive oxygen species (ROS), leading to deadly oxidative stress. However, there are a number of other biomolecular mechanisms beyond ROS generation that contribute to the activity of anticancer Cu drug candidates. In this review, we discuss how interfering with intracellular Cu balance via either diet modification or addition of inorganic Cu supplements or Cu-modulating compounds affects tumor development, progression, and sensitivity to treatment modalities. We aim to provide the rationale for the use of Cu-depleting and Cu-overloading conditions to generate the best possible patient outcome with minimal toxicity. We also discuss the advantages of the use of pre-formed Cu complexes, such as Cu-(bis)thiosemicarbazones or Cu-N-heterocyclic thiosemicarbazones, in comparison with the in situ formed Cu complexes with metal-binding ligands. In this review, we summarize available clinical and mechanistic data on clinically relevant anticancer drug candidates, including Cu supplements, Cu chelators, Cu ionophores, and Cu complexes.

Synthesis and Evaluation of New Trivalent Ligands for Hepatocyte Targeting via the Asialoglycoprotein Receptor

Since the asialoglycoprotein receptor (also known as the "Ashwell-Morell receptor" or ASGPR) was discovered as the first cellular mammalian lectin, numerous drug delivery systems have been developed and several gene delivery systems associated with multivalent ligands for liver disease targeting are undergoing clinical trials. The success of these systems has facilitated the further study of new ligands with comparable or higher affinity and less synthetic complexity. Herein, we designed two novel trivalent ligands based on the esterification of tris(hydroxymethyl) aminomethane (TRIS) followed by the azide-alkyne Huisgen cycloaddition with azido N-acetyl-d-galactosamine. The presented triazolyl glycoconjugates exhibited good binding to ASGPR, which was predicted using in silico molecular docking and assessed by a surface plasmon resonance (SPR) technique. Moreover, we demonstrated the low level of in vitro cytotoxicity, as well as the optimal spatial geometry and the required amphiphilic balance, for new, easily accessible ligands. The conjugate of a new ligand with Cy5 dye exhibited selective penetration into HepG2 cells in contrast to the ASGPR-negative PC3 cell line.

A CD44-targeted Cu(ii) delivery 2D nanoplatform for sensitized disulfiram chemotherapy to triple-negative breast cancer

Recent studies have suggested that the anticancer activity of disulfiram (DSF, an FDA-approved alcohol-abuse drug) is Cu-dependent. Low system toxicity and explicit pharmacokinetic characteristics of DSF necessitate safe and effective Cu supplementation in local lesion for further applications. Herein, we presented a new conceptual 'nanosized coordination transport' strategy of Cu(ii) that was realized in porphyrin-based metal-organic frameworks, Sm-TCPP, with strong binding ability to Cu(ii) due to their coordination interactions. Sm-TCPP(Cu) was coated by hyaluronic acid (HA) that termed by Sm-TCPP(Cu)@HA, acting as 'beneficial horse' to target the tumor-localized HA receptor (CD44), thus liberating Cu(ii) ions in cellular overexpressed reductants. The CD44-mediated Cu(ii) accumulation efficiency of Sm-TCPP(Cu)@HA was benchmarked in vitro and vivo against the free TCPP (Cu) via ICP-MS analysis. More importantly, the sensitization effects of Sm-TCPP(Cu)@HA on the anticancer activity of DSF were demonstrated in vivo and in vitro. This study offered a new class of targeted Cu supplements to sensitize DSF for the effective treatment of cancer and established a versatile methodology for constructing a safe and specific delivery of metal ions within living organisms.

A Dual-Targeting Functionalized Graphene Film for Rapid and Highly Sensitive Fluorescence Imaging Detection of Hepatocellular Carcinoma Circulating Tumor Cells

High recurrence and metastasis rates are the major causes of the high mortality of hepatocellular carcinoma (HCC). Circulating tumor cells (CTCs) disseminating into the bloodstream play an essential role in cancer metastasis. However, since HCC-CTCs are extremely rare, limitations of current detection methods impede accurate discerning of HCC-CTCs under complicated biological context. Here, a dual-targeting functionalized reduced graphene oxide film (DTFGF) for specifically identifying HCC-CTCs was created via coinstantaneous targeting epithelial cell adhesion molecule (EpCAM) and HCC cell-specific asialoglycoprotein receptor (ASGPR). Anti-EpCAM antibodies and galactose-rhodamine-polyacrylamide nanoparticles (Gal-Rh-PAA NPs) specifically recognizing ASGPR are modified on the surface of a graphene film that quenches the rhodamine fluorescence. HCC-CTCs can be captured by anti-EpCAM antibodies and endocytose Gal-Rh-PAA NPs, recovering the rhodamine fluorescence. Profiting from the accuracy of dual-targeting, less handling steps, and high resolution of fluorescence imaging, a simple, rapid, and low-cost HCC-CTC enumeration method is established with excellent sensitivity and selectivity than conventional methods. Using DTFGFs, as low as five HCC-CTCs were detected in a 1 mL blood sample. Further results revealed that larger HCC-CTC quantities indicate more advanced stages of HCC in patients. Overall, this work holds great promise for the early diagnosis, prognosis, and therapeutic evaluation of HCC.

Targeted photoswitchable imaging of intracellular glutathione by a photochromic glycosheet sensor

The development of photochromic fluorescence sensors with dynamic and multiple-signaling is beneficial to the improvement of biosensing/imaging precision. However, elaborate designs with complicated molecular structures are always required to integrate these functions into one molecule. By taking advantages of both redox-active/high loading features of two-dimensional (2D) manganese dioxide (MnO₂) and dynamic fluorescence photoswitching of photochromic sensors, we here design a hybrid photochromic MnO₂ glycosheet (Glyco-DTE@MnO₂) to achieve the photoswitchable imaging of intracellular glutathione (GSH). The photochromic glycosheet manifests significantly turn-on fluorescence and dynamic ON/OFF fluorescence signals in response to GSH, which makes it favorable for intracellular GSH double-check in targeted human hepatoma cell line (HepG2) through the recognition between β-D-galactoside and asialoglycoprotein receptor (ASGPr) on cell membranes. The dynamic fluorescence signals and excellent selectivity for detection and imaging of GSH ensure the precise determination of cell states, promoting its potential applications in future disease diagnosis and therapy.

The release and detection of copper ions from ultrasmall theranostic Cu2-xSe nanoparticles

Nanoscale copper chalcogenides have been widely used in nanomedicine, however, their pharmacokinetics, degradation, and biological effects of released copper ions are usually overlooked, which are crucial for their future clinical translation. Herein, we report the in vitro and in vivo release of copper ions from polyvinylpyrrolidone (PVP) functionalized ultrasmall copper selenide (Cu2-xSe) theranostic nanoparticles. We synthesized a Cu2+-specific fluorescent probe (NCM), which can quickly and specifically react with copper ions to exhibit very strong near infrared fluorescence. The in vitro study shows that copper ions can be slowly released from Cu2-xSe nanoparticles in aqueous solution with the progress of their oxidation. The release of copper ions from Cu2-xSe nanoparticles in RAW 264.7 murine macrophages is very fast, evidenced by the gradual increase of fluorescence intensity and the diffusion of fluorescence from cytoplasm into nuclei. We also demonstrate the distribution, degradation, and the metabolism of ultrasmall Cu2-xSe nanoparticles by the in vivo fluorescence imaging, the blood routine test, blood biochemistry and histology analysis, and the characterization of copper transport and binding proteins. The results show that ultrasmall Cu2-xSe nanoparticles were mainly eliminated through feces and urine from the body within 72 h after intravenous injection, and the released copper ions did not cause severe toxicity. Our research highlights the great potential of copper chalcogenide nanoparticles in nanomedicine.

Caged luciferins for bioluminescent activity-based sensing

Bioluminescence imaging is a powerful modality for in vivo imaging owing to its low background and high signal-to-noise ratio. Because bioluminescent emission occurs only upon the catalytic reaction between the luciferase enzyme and its luciferin substrate, caging luciferins with analyte-reactive triggers offers a general approach for activity-based sensing of specific biochemical processes in living systems across cell, tissue, and animal models. In this review, we summarize recent efforts in the development of synthetic caged luciferins for tracking enzyme, small molecule, and metal ion activity and their contributions to physiological and pathological processes.