One-Pot Synthesis-Biocompatible Copper-Tripeptide Complex as a Nanocatalytic Medicine to Enhance Chemodynamic Therapy

Stimuli-responsive mesoporous silica nanoplatforms for smart antibacterial therapies: From single to combination strategies

The demand for new antibacterial therapies is urgent and crucial in the clinical setting because of the growing degree of antibiotic resistance and the limits of conventional antibacterial therapies. Stimuli- responsive nanoplatforms, are sensitive to endogenous or exogenous stimulus (pH, temperature, light, and magnetic fields, etc.) which activate cargo release locally and on-demand, hold great potential in developing next generation personalized precision medicine. For instance, pH-sensitive nanoplatforms can selectively release antibacterial agents in the acidic environment of infection sites. To achieve the stimuli-responsive delivery, mesoporous silica nanoplatforms (MSNs) have demonstrated as prospective candidates for efficient cargo loading and controlled release through strategies such as tunable pore engineering, versatile surface modification/coating, and tailored framework composition. Furthermore, aiming for more precise delivery of MSNs, current research interests are increasingly shifting from single-stimuli antibacterial strategy to integrated strategy that combine multiple-stimulus. In this review, we briefly discuss the microenvironment of bacterial infections and provide a comprehensive summary of current stimuli-responsive strategies, and associated materials design principles of stimuli-responsive mesoporous silica-based smart nanoplatforms (SRMSNs). Additionally, integrative antibacterial strategies with synergistic effects, combining chemodynamic, photodynamic, photothermal, sonodynamic and gas therapies, have also been elaborated. Present research advances and limitations of SRMSNs-based antibacterial therapies, such as limited biodegradability and potential cytotoxicity, have been overviewed with future outlooks presented. This review aims to inspire and guide future research in developing novel antibacterial strategies with integrative solutions.

Cuproptosis: molecular mechanisms, cancer prognosis, and therapeutic applications

Cuproptosis differs from other forms of cell death, such as apoptosis, necroptosis, and ferroptosis, in its unique molecular mechanisms and signaling pathways. In this review, we delve into the cellular metabolic pathways of copper, highlighting the role of copper in biomolecule synthesis, mitochondrial respiration, and antioxidant defense. Furthermore, we elucidate the relationship between cuproptosis-related genes (CRGs) and cancer prognosis, analyzing their expression patterns across various tumor types and their impact on patient outcomes. Our review also uncovers the potential therapeutic applications of copper chelators, copper ionophores, and copper-based nanomaterials in oncology. In addition, we discuss the emerging role of cuproptosis in remodeling the tumor microenvironment, enhancing immune cell infiltration, and converting "cold tumors" into "hot tumors" that respond better to immunotherapy. In short, this review underscores the pivotal importance of cuproptosis in cancer biology and highlights its translational potential as a novel therapeutic target.

Integrating Photothermal, Photodynamic, and Chemodynamic Therapies: The Innovative Design Based on Copper Sulfide Nanoparticles for Enhanced Tumor Therapy

A multifunctional nanoplatform integrating multiple therapeutic functions may be an effective strategy to realize satisfactory therapeutic efficacy in the treatment of tumors. However, there is still a certain challenge in integrating multiple therapeutic agents into a single formulation using a simple method due to variations in their properties. In this work, multifunctional CuS-ICG@PDA-FA nanoparticles (CIPF NPs) with excellent ability to produce reactive oxygen species and photothermal conversion performance are fabricated by a simple and gentle method. Hollow mesoporous copper sulfide nanoparticles (HMCuS NPs) not only have excellent loading and photothermal conversion performance but also can cause a highly efficient Fenton-like reaction for chemodynamic therapy (CDT). The loaded photosensitizer indocyanine green (ICG) imparts excellent photodynamic properties to the NPs, which in turn enhances the stability of ICG. The polydopamine (PDA) coating improves the stability and biocompatibility of the NPs and creates the conditions for surface modification of folic acid. The FA-coated NPs show precise targeting of tumor cells. The results of the cellular uptake assay demonstrate that CIPF NPs enter tumor cells through an endocytic pathway. Lysosome colocalization and escape experiments prove that CIPF NPs possess good lysosomal escape ability under irradiation of NIR. Both in vitro and in vivo antitumor studies of CIPF NPs reveal excellent efficacy in photothermal/photodynamic/chemodynamic therapy. The construction of high-performance CIPF NPs offers valuable insights into the design of a multifunctional copper sulfide-based nanoplatform for combined cancer treatment and precise theranostics.

Recent advances in chemotherapy for cancer therapy over Cu-based nanocatalysts

Recently, the emerging chemotherapy (CDT) has provided a new biocompatibility pathway for cancer therapy. Among them, Cu-based nanocatalysts with good biocompatibility and Fenton-like catalytic efficiency are considered to be a promising approach for enhancing CDT and CDT-involved multimodal synergies to improve the effectiveness of catalytic cancer therapy. Meanwhile, the emerging in situ therapy strategy promoted by Cu-based nanocatalysts has proven to exhibit attractive clinical application potential in replacing traditional chemotherapy and radiotherapy for cancer therapy with significant toxic side effects. In this work, the recent progress of various Cu-based nanocatalysts in cancer therapy was reviewed, especially the remarkable achievements in the catalytic treatment of cancer in the tumor microenvironment using CDT and CDT-involved multimodal synergies. In addition, the development expectations and challenges of Cu-based nanocatalysts in the field of cancer therapy were briefly summarized and discussed. We expect that this review will contribute to the development of Cu-based nanocatalysts for cancer therapy.

Recent advances in copper homeostasis-involved tumor theranostics

As the third essential trace element in the human body, copper plays a crucial role in various physiological processes, which lays the foundation for its broad applications in cancer treatments. The overview of copper, including pharmacokinetics, signaling pathways, and homeostasis dysregulation, is hereby discussed. Additionally, cuproptosis, as a newly proposed cell death mechanism associated with copper accumulation, is analyzed and further developed for efficient cancer treatment. Different forms of Cu-based nanoparticles and their advantages, as well as limiting factors, are introduced. Moreover, the unique characteristics of Cu-based nanoparticles give rise to their applications in various imaging modalities. In addition, Cu-based nanomaterials are featured by their excellent photothermal property and ROS-associated tumor-killing potential, which are widely explored in diverse cancer therapies and combined therapies. Reducing the concentration of Cu2+/Cu+ is another cancer-killing method, and chelators can meet this need. More importantly, challenges and future prospects are identified for further research.

Cu2+-Citrate-Chitosan Complex Nanoparticles for the Chemodynamic Therapy of Lung Cancer

Lung cancer poses a significant threat to human health. Surgical intervention is the preferred treatment modality for lung cancer, but a large number of patients are deprived of the opportunity for surgery for various reasons and are compelled to undergo radiotherapy and chemotherapy, which entail systemic adverse reactions. In recent years, with the advancement of nanomedicine, chemodynamic therapy (CDT) based on free radicals has been extensively investigated. In this study, we fabricated copper-citrate-chitosan composite nanoparticles (CuCC NPs) by encapsulating copper-citrate complexes with natural chitosan polymers, resulting in a substantial reduction in the biotoxicity of copper ions. The CuCC NPs selectively accumulated in tumor tissues through the enhanced permeability and retention effect (EPR) and gradually degraded within the acidic and glutathione (GSH)-rich microenvironment of the tumor, thereby releasing the loaded copper ions. Through CDT, the copper ions converted the overexpressed hydrogen peroxide (H2O2) in the tumor tissue into hydroxyl radicals (•OH), leading to the eradication of tumor cells. In animal experiments, CuCC NPs exhibited remarkable efficacy in CDT. Further histopathological and hematological analyses demonstrated that CuCC NPs could induce substantial apoptosis in tumor tissues while maintaining an extremely high level of safety.

Natural Enzyme-Inspired Design of the Single-Atom Cu Nanozyme as Dual-Enzyme Mimics for Distinguishing Total Antioxidant Capacity and the Ascorbic Acid Level

Although various oxidase mimetic or peroxidase (POD) mimetic nanozymes have been extensively studied, their poor substrate selectivity significantly inhibits their practical applications. Nanozymes with specific biomolecules as substrates, especially ascorbic acid oxidase (AAO) mimetic nanozymes with ascorbic acid (AA) as a substrate, have scarcely been studied. Herein, inspired by the multi-Cu atom sites and the redox electron transfer pathway of Cu2+/Cu+ in the natural AAO, atomically dispersed Cu sites immobilized on N-doped porous carbon (Cu-N/C) are artificially designed to simulate the function of natural AAO. Compared with their natural counterparts, the Cu-N/C catalysts exhibited higher catalytic efficiency and superior stability. Combined theoretical calculation and experimental characterizations reveal that the Cu-N/C nanozymes could catalyze the AA oxidation through a 2e- oxygen reduction pathway with H2O2 as the product. Moreover, the Cu-N/C nanozymes also possess high POD activity. As a proof-of-concept application, Cu-N/C can simultaneously realize AA detection in fluorescent mode based on its AAO activity and total antioxidant capacity detection in colorimetric mode utilizing its POD activity.

Recent advances in nanoscale metal-organic frameworks for cancer chemodynamic therapy

Chemodynamic therapy (CDT), a novel therapeutic approach based on Fenton (Fenton-like) reaction, has been widely employed for tumor therapy. This approach utilizes Fe, Cu, or other metal ions (Mn, Zn, Co, or Mo) to react with the excess hydrogen peroxide (H₂O₂) in tumor microenvironments (TME), and form highly cytotoxic hydroxyl radical (˙OH) to kill cancer cells. Recently, nanoscale metal-organic frameworks (nMOFs) have attracted considerable attention as promising CDT agents with the rapid development of cancer CDT. This review focuses on summarizing the latest advances (2020-2022) on the design of nMOFs as nanomedicine for CDT or combination therapy of CDT and other therapies. The future development and challenges of CDT are also proposed based on recent progress. Our group hopes that this review will enlighten the research and development of nMOFs for CDT.

Polydopamine-based nanozyme with dual-recognition strategy-driven fluorescence-colorimetric dual-mode platform for Listeria monocytogenes detection

Development of a simple and efficient dual-mode analytical technique with the built-in cross reference correction feature is benefit to achieve the highly accurate detection of the target pollutants and avoid the false-positive outputs in environmental media. Here, we synthesized a Fe-doped polydopamine (Fe@PDA)-based nanozyme with prominent peroxide-mimetic enzyme activity and high fluorescence emission ability. On this basis, we designed a dual-recognition strategy-driven fluorescence-colorimetric dual-mode detection platform, consisting of Listeria monocytogenes (L. monocytogenes) recognition aptamer-modified Fe@PDA (apt/Fe@PDA) and vancomycin-functionalized Fe₃O₄ (van/Fe₃O₄), for L. monocytogenes. Owing to van/Fe₃O₄-powered magnetic separation, there was a L. monocytogenes concentration-dependent fluorescence enhancement of apt/Fe@PDA for performing fluorescence assay in the precipitate. In this case, the prominent peroxide-mimetic enzyme activity of the residual apt/Fe@PDA in the precipitation could catalyze H₂O₂ to further oxidate colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue oxTMB, which displayed a L. monocytogenes concentration-dependent absorbance enhancement for carrying out colorimetric assay as well. As a result, a fluorescence-colorimetric dual-mode analytical platform was proposed to successfully detect the residual L. monocytogenes in real environmental media with acceptable results. This work showed the great prospects by integrating dual-recognition strategy into fluorescence nanozyme to develop efficient and reliable dual-mode analytical platforms for safeguarding environmental health.

Advancements in redox-sensitive micelles as nanotheranostics: A new horizon in cancer management

World Health Organisation (WHO) delineated cancer as one of the foremost reasons for mortality with 10 million deaths in the year 2020. Early diagnosis and effective drug delivery are of utmost importance in cancer management. The entrapment of both bio-imaging dyes and drugs will open novel avenues in the area of tumor theranostics. Elevated levels of reactive oxygen species (ROS) and glutathione (GSH) are the characteristic features of the tumor microenvironment (TME). Researchers have taken advantage of these specific TME features in recent years to develop micelle-based theranostic nanosystems. This review focuses on the advantages of redox-sensitive micelles (RSMs) and supramolecular self-assemblies for tumor theranostics. Key chemical linkers employed for the tumor-specific release of the cargo have been discussed. In vitro characterisation techniques used for the characterization of RSMs have been deliberated. Potential bottlenecks that may present themselves in the bench-to-bedside translation of this technology and the regulatory considerations have been deliberated.

Multifunctional nanosystems sequentially regulating intratumor Fenton chemistry by remodeling the tumor microenvironment to reinforce chemodynamic therapy

The particularity of the tumor microenvironment (TME) significantly limits the efficiency of chemodynamic therapy (CDT). Although various measures have been taken to improve the efficiency of CDT, how to organically integrate them into one nanosystem to achieve efficient synergy for CDT according to predetermined procedures is still an urgent problem to be solved. This work reported a multifunctional nanosystem, TP_I@PP_CAI, which comprised the inner triphenylphosphine modified D-α-Tocopheryl polyethylene glycol 1000 succinate (TPGS-PPh₃) micelles loading iron-oxide nanoparticles (IONs), and the outer poly (dopamine-co-protocatechuic acid) (PDA-PA, PP) coating modified with carbonic anhydrase IX inhibitor (CAI). TP_I@PP_CAI remodeled TME by sequential function adjustment to make it suitable for the efficient Fenton reactions: CAI first inhibited the overexpressed CA IX to result in intracellular acidification, which combined with near-infrared light (NIR) irradiation to accelerate the PP coating degradation, thereby promoting the exposure and disintegration of the inner micellar structure to release TPGS-PPh₃ and IONs. The TPGS-PPh₃ further elevated the intracellular ROS basal level by targeting and interfering with the mitochondrial function. Therefore, the TME was transformed into an acidic microenvironment with high ROS levels, which vigorously promoted the Fenton reaction mediated by IONs with the aid of photothermal effect induced by PP coating via NIR irradiation, ultimately earning high-efficiency CDT on xenograft MDA-MB-231 tumor-bearing mice. This study improved the efficiency of Fenton reaction in biological systems through the practical design of nanostructures and provided a novel thought for ROS-mediated therapy.

Reaction of N-Acetylcysteine with Cu2+: Appearance of Intermediates with High Free Radical Scavenging Activity: Implications for Anti-/Pro-Oxidant Properties of Thiols

We studied the kinetics of the reaction of N-acetyl-l-cysteine (NAC or RSH) with cupric ions at an equimolar ratio of the reactants in aqueous acid solution (pH 1.4−2) using UV/Vis absorption and circular dichroism (CD) spectroscopies. Cu2+ showed a strong catalytic effect on the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) radical (ABTSr) consumption and autoxidation of NAC. Difference spectra revealed the formation of intermediates with absorption maxima at 233 and 302 nm (ε302/Cu > 8 × 103 M−1 cm−1) and two positive Cotton effects centered at 284 and 302 nm. These intermediates accumulate during the first, O2-independent, phase of the NAC autoxidation. The autocatalytic production of another chiral intermediate, characterized by two positive Cotton effects at 280 and 333 nm and an intense negative one at 305 nm, was observed in the second reaction phase. The intermediates are rapidly oxidized by added ABTSr; otherwise, they are stable for hours in the reaction solution, undergoing a slow pH- and O2-dependent photosensitive decay. The kinetic and spectral data are consistent with proposed structures of the intermediates as disulfide-bridged dicopper(I) complexes of types cis-/trans-CuI2(RS)2(RSSR) and CuI2(RSSR)2. The electronic transitions observed in the UV/Vis and CD spectra are tentatively attributed to Cu(I) → disulfide charge transfer with an interaction of the transition dipole moments (exciton coupling). The catalytic activity of the intermediates as potential O2 activators via Cu(II) peroxo-complexes is discussed. A mechanism for autocatalytic oxidation of Cu(I)−thiolates promoted by a growing electronically coupled −[CuI2(RSSR)]n− polymer is suggested. The obtained results are in line with other reported observations regarding copper-catalyzed autoxidation of thiols and provide new insight into these complicated, not yet fully understood systems. The proposed hypotheses point to the importance of the Cu(I)−disulfide interaction, which may have a profound impact on biological systems.

Copper(II) Complexes of Halogenated Quinoline Schiff Base Derivatives Enabled Cancer Therapy through Glutathione-Assisted Chemodynamic Therapy and Inhibition of Autophagy Flux

Twelve new complexes Cu(L¹)₂-Cu(L¹²)₂ were designed and synthesized to improve their chemotherapeutic properties. They showed considerable antiproliferative activity against T24 cancer cells but lower cytotoxicity to human normal cells HL-7702 and WI-38. A mechanism study indicated that Cu(L⁴)₂ and Cu(L¹⁰)₂ were reduced to Fenton-like Cu⁺ by glutathione depletion, and the resulting Cu⁺ catalyzed the generation of highly toxic hydroxyl radicals from excess H₂O₂. Simultaneously, Cu(L⁴)₂ and Cu(L¹⁰)₂ could decrease the catalase activity to restrain H₂O₂ transfer to H₂O for enhanced chemodynamic therapy (CDT). These induced mitochondrial dysfunctions and endoplasmic reticulum stress to induce T24 cell apoptosis. In addition, Cu(L⁴)₂ and Cu(L¹⁰)₂ inhibited autophagy flux to promote cell apoptosis. Cu(L⁴)₂ and Cu(L¹⁰)₂ demonstrated strong tumor inhibition ability in the T24 xenograft model. Moreover, Cu(L¹⁰)₂ showed higher antitumor activity and a better safety profile than the CDT agent Cu1. Cu(L¹⁰)₂ exhibited excellent pharmacokinetic properties. Collectively, Cu(L⁴)₂ and Cu(L¹⁰)₂ could be developed as potential CDT candidates for cancer treatment.

Fe-Doped polydopamine nanoparticles with peroxidase-mimicking activity for the detection of hypoxanthine related to meat freshness

Rapid and accurate monitoring of food freshness to provide consumers with high-quality meat continues to be of tremendous importance to the food industry. In this report, an efficient Fe-doped polydopamine (Fe-PDA) nanozyme with peroxidase-mimicking activity was synthesized by a high-temperature hydrothermal method, and was applied to a spectrophotometric sensing system, which successfully reports the concentration of hypoxanthine (Hx) related to meat freshness. The Fe-PDA nanozyme showed excellent peroxidase simulation activity, which was primarily verified by steady-state kinetics experiments. In the presence of xanthine oxidase (XOD), Hx can react quantitatively with dissolved O₂ to generate H₂O₂, which can be further catalyzed and produce hydroxyl radicals (•OH) under acidic conditions via the Fe-PDA nanozyme and oxidize colorless TMB to blue oxTMB with absorbance at 653 nm. The absorbance at 653 nm expressed a clear linear relationship with hypoxanthine concentration in the range of 5.13-200 μM, and the detection limit was 1.54 μM. This method was further assessed by measuring the recovery of Hx added to meat samples, which showed promising accuracy. Overall, the developed Fe-PDA nanozyme with excellent peroxidase-mimicking activity is cost-effective, high-performance and easy to produce, offering an efficient and low-cost sensing system based on spectrophotometry for meat freshness determination as an alternative to conventional methods.

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.

Multifunctional carbon quantum dots as a theranostic nanomedicine for fluorescence imaging-guided glutathione depletion to improve chemodynamic therapy

To minimize unwanted reactions with high concentrations of reduced glutathione (GSH) in the tumor microenvironment (TME) during chemodynamic therapy (CDT), a simple and effective strategy was developed to fabricate a TME stimuli-responsive theranostic nanomedicine (Fe-CD) for fluorescence imaging-guided GSH depletion and cancer therapy by combining fluorescent imaging carbon dots (CD) and Fe(III). Introducing Fe(III) into Fe-CD not only quenched the fluorescence of CD while reacting with and consuming intracellular GSH for fluorescence imaging of the depletion of GSH but also provided a source of metal ions to generate more abundant hydroxyl radicals (•OH) with hydrogen peroxide (H₂O₂) through the Fenton reaction to improve CDT. Fe-CD showed promising •OH generation under H₂O₂ to effectively degrade methylene blue in vitro and obviously activate the green fluorescence of the reactive oxygen species (ROS) probe in cells. Benefiting from the fluorescence enhancement in response to TME stimulation, Fe-CD greatly enhanced CDT cytotoxicity while monitoring successful GSH depletion by fluorescence imaging. Fe-CD has the potential to act as a theranostic nanomedicine for fluorescence imaging-guided GSH depletion to amplify CDT.

Self-Assembly of Multifunctional DNA Nanohydrogels with Tumor Microenvironment-Responsive Cascade Reactions for Cooperative Cancer Therapy

A DNA structure-based nanoreactor has emerged as a promising biomaterial for antitumor therapy with its intrinsic biodegradability, biocompatibility, and tunable multifunctionality. Herein, the intelligent DNA nanohydrogel was reported to target cancer cells, control the size, be pH-responsive, and be loaded with glucose oxidase (GOx). Two kinds of X-shaped DNA monomers and DNA linkers were assembled to form a DNA nanohydrogel by hybridization. GOx was successfully encapsulated in the DNA nanohydrogel. The DNA linker was designed with i-motif sequences and modified with ferrocene (Fc). The i-motif-like quadruplex structures were formed in acidic tumor microenvironments, resulting in the disassembly of the DNA nanohydrogel to release GOx. The GOx could oxidize the intratumoral glucose to produce gluconic acid and H₂O₂. The generated H₂O₂ was catalyzed by Fc to induce toxic hydroxyl radicals (^•OH), which could effectively kill cancer cells. Both the in vitro and the in vivo results demonstrated that the multifunctional DNA nanohydrogel had high-efficiency tumor suppression through combined chemodynamic and starvation cancer therapies.