Wet/Sono-Chemical Synthesis of Enzymatic Two-Dimensional MnO2 Nanosheets for Synergistic Catalysis-Enhanced Phototheranostics

Manganese oxide nanomaterials for bacterial infection detection and therapy

Bacterial infection has received substantial attention and poses a serious threat to human health. Although antibiotics can effectively fight against bacterial infection, the occurrence of antibiotic resistance has become increasingly serious in recent years, which tremendously hinders its clinical application. Consequently, it is urgent to explore novel strategies to achieve efficacious treatment of bacterial diagnosis and detection. Manganese dioxide (MnO₂) nanomaterial has been extensively reported in tumor therapy. Nevertheless, there are few antibacterial reviews of MnO₂. Herein, we will discuss the applications of MnO₂ in the detection and treatment of bacterial infection, including photodynamic therapy, immunotherapy, improvement of hypoxia, dual-modal combination therapy, reactive oxygen species scavenging, magnetic resonance imaging, optical application of acoustic imaging, and so forth. This review is expected to provide meaningful guidance on further research of MnO₂ nanomaterial for antibacterial applications.

Multifunctional inorganic nanomaterials for cancer photoimmunotherapy

Phototherapy and immunotherapy in combination is regarded as the ideal therapeutic modality to treat both primary and metastatic tumors. Immunotherapy uses different immunological approaches to stimulate the immune system to identify tumor cells for targeted elimination. Phototherapy destroys the primary tumors by light irradiation, which induces a series of immune responses through triggering immunogenic cancer cell death. Therefore, when integrating immunotherapy with phototherapy, a novel anti-cancer strategy called photoimmunotherapy (PIT) is emerging. This synergistic treatment modality can not only enhance the effectiveness of both therapies but also overcome their inherent limitations, opening a new era for the current anti-cancer therapy. Recently, the advancement of nanomaterials affords a platform for PIT. From all these nanomaterials, inorganic nanomaterials stand out as ideal mediators in PIT due to their unique physiochemical properties. Inorganic nanomaterials can not only serve as carriers to transport immunomodulatory agents in immunotherapy owing to their excellent drug-loading capacity but also function as photothermal agents or photosensitizers in phototherapy because of their great optical characteristics. In this review, the recent advances of multifunctional inorganic nanomaterial-mediated drug delivery and their contributions to cancer PIT will be highlighted.

Carrier-Free Delivery of Ultrasmall π-Conjugated Oligomer Nanoparticles with Photothermal Conversion over 80% for Cancer Theranostics

High-performance photothermal theranostics is urgently desired for cancer therapy because of their good controllability and noninvasive features. The relatively low photothermal conversion efficiency is still at the drawbacks because of the absence of efficient extraneous carriers. Herein, a carrier-free nanomedicine is developed to in vivo self-deliver organic photothermal agents for efficient cancer phototheranostics. By a facile self-assembly strategy, the near-infrared (NIR)-absorbing conjugated oligomer IDIC-4F is fabricated into a carrier-free nanoparticle (DCF-P), showing ultrasmall size of nearly 4.0 nm with a nearly 100% of drug loading capacity. Notably, DCF-P achieves a superhigh photothermal conversion efficiency of 80.5% that is far greater than that of IDIC-4F-loaded nanomicelle DCF-M (57.3%). With the guidance of NIR fluorescence and photoacoustic dual-imaging, it is verified that DCF-P could well achieve tumor-preferential accumulation and retention at 4 h postinjection, and meanwhile shows highly efficient in vivo tumor elimination with good biosafety. This study thus contributes a novel concept for designing ultrasmall nanoparticle characteristics of preferential accumulation in tumors, and also provides a strategy for creating high-performance carrier-free nanomedicine via highly ordered molecular stacking.

Boosting Chemodynamic Therapy via a Synergy of Hypothermal Ablation and Oxidation Resistance Reduction

Chemodynamic therapy (CDT), deemed as a cutting-edge antineoplastic therapeutic tactics, efficaciously suppresses tumors via catalytically yielding hydroxyl radicals (^•OH) in tumor regions. Nevertheless, its biomedical applications are often restricted by the limited hydrogen peroxide (H₂O₂) level and upregulated antioxidant defense. Herein, a versatile nanoreactor is elaborately designed via integrating Cu_2-xS and MnO₂ for T₁-weighted magnetic resonance (MR) imaging-guided CDT, synergistically enhanced through hypothermal ablation and oxidation resistance reduction, thereby displaying splendid antitumor efficiency as well as suppression on pulmonary metastasis. The as-synthesized Cu_2-xS@MnO₂ nanoreactors afford acid-dependent Cu-based and glutathione (GSH)-activated Mn-based catalytic properties for bimodal CDT. Owing to excellent absorbance at the second near-infrared (NIR-II) window, the Cu_2-xS furnishes hypo-photo-thermal therapy (PTT) against tumor growth and ameliorates the catalytic performance for thermal-enhanced CDT. Additionally, MnO₂ significantly downregulates GSH and glutathione peroxidase 4, which synergistically boosts CDT via promoting oxidative stress, simultaneously generating Mn²⁺ for MR contrast improvement and activatable tumor imaging. Therefore, this study proffers a new attempt centered on the collaborative strategy integrating NIR-II hypothermal PTT and synergistically enhanced CDT for tumor eradication.

An intelligent tumor microenvironment responsive nanotheranostic agent for T1/T2 dual-modal magnetic resonance imaging-guided and self-augmented photothermal therapy

Photothermal therapy (PTT), as a promising antineoplastic therapeutic strategy, has been harnessed to restrain tumor growth through near-infrared (NIR) irradiation mediated thermal ablation. Nevertheless, its biological applications are hampered by thermal diffusion and up-regulated heat shock proteins (HSPs). Herein, a versatile nanotheranostic agent is developed via integrating Zn_0.2Fe_2.8O₄ nanoparticles (NPs), polydopamine (PDA), and MnO₂ NPs for T1/T2 dual-modal magnetic resonance (MR) imaging-guided and self-augmented PTT. The as-designed Zn_0.2Fe_2.8O₄@PDA@MnO₂ NPs adequately serve as a PTT agent to realize effective photothermal conversion and obtain local hyperthermia. Additionally, the Zn_0.2Fe_2.8O₄@PDA@MnO₂ NPs can significantly consume overexpressed glutathione (GSH) and generate Mn²⁺ in the tumor microenvironment (TME), thus destroying redox homeostasis and catalytically generating hydroxyl radicals (˙OH) for HSP suppression and PTT enhancement. Meanwhile, Mn²⁺ and Zn_0.2Fe_2.8O₄ NPs significantly strengthen T1- and T2-weighted MR contrast for tumor imaging and PTT guidance. Hence, this study offers proof of concept for self-augmented PTT and T1/T2 dual-modal MR imaging for tumor elimination.

Recent Advances of Manganese-Based Hybrid Nanomaterials for Cancer Precision Medicine

Cancer precision medicine (CPM) could tailor the best treatment for individual cancer patients, while imaging techniques play important roles in its application. With the characteristics of noninvasion, nonionized, radiation-free, multidimensional imaging function, and real-time monitoring, magnetic resonance imaging (MRI) is an effective way for early tumor detection, and it has become a tower of strength in CPM imaging techniques. Due to linkage with nephrogenic systemic fibrosis (NSF), gadolinium (Gd)-based contrast agent (CA), which was long used in MRI, has been restricted by the Food and Drug Administration (FDA). In this review, we would like to introduce the manganese (Mn)-based CAs that could significantly increase the safety of MRI CAs by realizing more superior performance and functions simultaneously in the diagnosis and treatment of tumors. Also, recent advances in Mn-based hybrid nanomaterials for CPM are summarized and discussed.

Nanomedicine potentiates mild photothermal therapy for tumor ablation

The booming photothermal therapy (PTT) has achieved great progress in non-invasive oncotherapy, and paves a novel way for clinical oncotherapy. Of note, mild temperature PTT (mPTT) of 42–45 °C could avoid treatment bottleneck of the traditional PTT, including nonspecific injury to normal tissues, vasculature and host antitumor immunity. However, cancer cells can resist mPTT via heat shock response and autophagy, thus leading to insufficient mPTT monotherapy to ablate tumor. To overcome the deficient antitumor efficacy caused by thermo-resistance of cancer cells and mono mPTT, synergistic therapies towards cancer cells have been conducted with mPTT. This review summarizes the recent advances in nanomedicine-potentiated mPTT for cancer treatment, including strategies for enhanced single-mode mPTT and mPTT plus synergistic therapies. Moreover, challenges and prospects for clinical translation of nanomedicine-potentiated mPTT are discussed.

In Situ Coupling of Catalytic Centers into Artificial Substrate Mesochannels as Super-Active Metalloenzyme Mimics

Highly evolved substrate channels in natural enzymes facilitate the rapid capture of substrates and direct transfer of intermediates between cascaded catalytic units, thus rationalizing their efficient catalysis. In this study, a nanoscale ordered mesoporous Ce-based metal-organic framework (OMUiO-66(Ce)) is designed as an artificial substrate channel, where MnO₂ is coupled to Ce-O clusters as a super-active catalase (CAT). An in situ soft template reduction strategy is developed to deposit well-dispersed and exposed MnO₂ in the mesochannels of OMUiO-66(Ce). Several synthesis parameters are optimized to minimize the particle size to ≈150 nm for efficient intracellular endocytosis. The mesochannels provide interaction guidance that not only rapidly drove H₂ O₂ substrates to CAT-like catalytic centers, but also seamlessly transfer H₂ O₂ intermediates between superoxide dismutase-like and CAT-like biocatalytic cascades. As a result, the biomimetic system exhibits high efficiency, low dosage, and long-lasting intracellular antioxidant function. Under disease-related oxidative stress, the artificial substrate channels promote the rate of the reactions catalyzed by MnO₂ , which exceeds that of the reactions catalyzed by natural CAT. Based on this observation, a set of design rules for substrate channels are proposed to guide the rational design of super-active biomimetic systems.

Luminescent wearable biosensors based on gold nanocluster networks for "turn-on" detection of Uric acid, glucose and alcohol in sweat

From the difficulty of awareness of abnormal concentrations of biochemical indexes in people's daily life come wearable sensing technologies. Recently, luminescent wearable biosensors are emerging with simple fabrication, easy use, cost-effectivity and reliability. But several challenges should be taken up, such as availability of varied analytes, high sensitivity, stability of enzymes, photostability, low signal noises and recyclability of sensors. Here, the Luminescent Wearable Sweat Tape (LWST) biosensor is developed via embedding multi-component nanoprobes onto microwell-patterned paper substrates of hollowed-out double-side tapes. The nanoprobes consist of responsive luminophores, enzyme-loaded gold nanocluster (AuNCs) nano-networks, which are wrapped by the switch, MnO₂ nanosheets. The responsive luminophores are constructed by 3 substitutable components: enzymes (uricase, GOx and alcohol dehydrogenase) for molecular target recognition, glutathione-protected AuNCs (yellow, red and green) for luminescent signal output and polycations PAH for integration. MnO₂ NSs as the switch can quench the emission of the AuNCs but degraded by the reductive product of incorporated enzymes. Thus, targeting analysts (uric acid, glucose and alcohol) can be dose-dependently detected through "turn-on" luminescence approach. After incorporating the nanoprobes into hollow-out tapes, the formed LWST biosensors can detect uric acid, glucose and alcohol in sweat with the help of a smartphone. Subsequently, we primarily apply them into human daily life scenario, sampling from dine parties, and the positive relationships of analyte intakes and the increase of analytes in sweat are significant with individual difference.

A Review on Metal- and Metal Oxide-Based Nanozymes: Properties, Mechanisms, and Applications

Since the ferromagnetic (Fe3O4) nanoparticles were firstly reported to exert enzyme-like activity in 2007, extensive research progress in nanozymes has been made with deep investigation of diverse nanozymes and rapid development of related nanotechnologies. As promising alternatives for natural enzymes, nanozymes have broadened the way toward clinical medicine, food safety, environmental monitoring, and chemical production. The past decade has witnessed the rapid development of metal- and metal oxide-based nanozymes owing to their remarkable physicochemical properties in parallel with low cost, high stability, and easy storage. It is widely known that the deep study of catalytic activities and mechanism sheds significant influence on the applications of nanozymes. This review digs into the characteristics and intrinsic properties of metal- and metal oxide-based nanozymes, especially emphasizing their catalytic mechanism and recent applications in biological analysis, relieving inflammation, antibacterial, and cancer therapy. We also conclude the present challenges and provide insights into the future research of nanozymes constituted of metal and metal oxide nanomaterials.

Low dimensional materials for glucose sensing

Biosensors are essential components for effective healthcare management. Since biological processes occur on molecular scales, nanomaterials and nanosensors intrinsically provide the most appropriate landscapes for developing biosensors. Low-dimensional materials have the advantage of offering high surface areas, increased reactivity and unique physicochemical properties for efficient and selective biosensing. So far, nanomaterials and nanodevices have offered significant prospects for glucose sensing. Targeted glucose biosensing using such low-dimensional materials enables much more effective monitoring of blood glucose levels, thus providing significantly better predictive diabetes diagnostics and management. In this review, recent advances in using low dimensional materials for sensing glucose are summarized. Sensing fundamentals are discussed, as well as invasive, minimally-invasive and non-invasive sensing methods. The effects of morphological characteristics and size-dependent properties of low dimensional materials are explored for glucose sensing, and the key performance parameters such as selectivity, stability and sensitivity are also discussed. Finally, the challenges and future opportunities that low dimensional materials can offer for glucose sensing are outlined.

Glucose-oxidase like catalytic mechanism of noble metal nanozymes

Au nanoparticles (NPs) have been found to be excellent glucose oxidase mimics, while the catalytic processes have rarely been studied. Here, we reveal that the process of glucose oxidation catalyzed by Au NPs is as the same as that of natural glucose oxidase, namely, a two-step reaction including the dehydrogenation of glucose and the subsequent reduction of O₂ to H₂O₂ by two electrons. Pt, Pd, Ru, Rh, and Ir NPs can also catalyze the dehydrogenation of glucose, except that O₂ is preferably reduced to H₂O. By the electron transfer feature of noble metal NPs, we overcame the limitation that H₂O₂ must be produced in the traditional two-step glucose assay and realize the rapid colorimetric detections of glucose. Inspired by the electron transport pathway in the catalytic process of natural enzymes, noble metal NPs have also been found to mimic various enzymatic electron transfer reactions including cytochrome c, coenzymes as well as nitrobenzene reductions.

In vitro and in vivo osteogenesis up-regulated by two-dimensional nanosheets through a macrophage-mediated pathway

Two-dimensional (2D) nanomaterials are attracting more and more interest in regenerative medicine due to their unique properties; however 2D biomimetic calcium mineral has not yet been developed and demonstrated application for bone tissue engineering. Here we described a novel calcium phosphate material with a 2D nanostructure that was synthesized using collagen and sodium alginate as the template. In vitro performance of the nanocrystalline material was evaluated, and we found that 2D CaP nanoparticles (NPs) enhanced the in vitro osteogenic differentiation of rat mesenchymal stem cells (rMSCs) through a macrophage-mediated signal pathway, when co-cultured with RAW 264.7 cells, rather than direct NP/stem cell interaction. A 2D topology structured surface was constructed by encapsulating the CaP nanomaterials in a gelatin hydrogel, which was demonstrated to be able to mediate in vivo ossification through a macrophage polarization related pathway in a femur defect rat model, and allowed the optimal therapeutic outcome compared to normal CaP counterparts. Our current work may have enlightened a new mechanism regarding NP-induced stem cell differentiation through immunoregulation, and the 2D CaP encapsulated hydrogel scaffold may serve as a potential alternative to autograft bone for orthopedic applications.

Low-Temperature Photothermal Therapy: Strategies and Applications

Although photothermal therapy (PTT) with the assistance of nanotechnology has been considered as an indispensable strategy in the biomedical field, it still encounters some severe problems that need to be solved. Excessive heat can induce treated cells to develop thermal resistance, and thus, the efficacy of PTT may be dramatically decreased. In the meantime, the uncontrollable diffusion of heat can pose a threat to the surrounding healthy tissues. Recently, low-temperature PTT (also known as mild PTT or mild-temperature PTT) has demonstrated its remarkable capacity of conquering these obstacles and has shown excellent performance in bacterial elimination, wound healing, and cancer treatments. Herein, we summarize the recently proposed strategies for achieving low-temperature PTT based on nanomaterials and introduce the synthesis, characteristics, and applications of these nanoplatforms. Additionally, the combination of PTT and other therapeutic modalities for defeating cancers and the synergistic cancer therapeutic effect of the combined treatments are discussed. Finally, the current limitations and future directions are proposed for inspiring more researchers to make contributions to promoting low-temperature PTT toward more successful preclinical and clinical disease treatments.

Multifunctional MnO2 nanoparticles for tumor microenvironment modulation and cancer therapy

Tumor microenvironment (TME) is generally featured by low pH values, high glutathione (GSH) concentrations, overproduced hydrogen peroxide (H₂ O₂ ), and severe hypoxia. These characteristics could provide an interior environment for origination and residence of tumor cells and would lead to tumor progression, metastasis, and drug resistance. Therefore, the development of TME-responsive smart nanosystems has shown significant potential to enhance the efficacy of current cancer treatments. Manganese dioxide (MnO₂ )-based nanosystems have attracted growing attentions for applications in cancer treatment as an excellent TME-responsive theranostic platform, due to their tunable structures/morphologies, pH responsive degradation, and excellent catalytic activities. In this review, we mainly summarize the strategies of MnO₂ and its nanocomposites to modulate TME, such as tumor hypoxia relief, excessive GSH depletion, glucose consumption, and tumor immunosuppressive microenvironment moderation. Such MnO₂ -based TME modulation would be beneficial for a wide range of cancer therapies including photodynamic therapy, radiotherapy, sonodynamic therapy, chemodynamic therapy, starvation therapy, and immunotherapy. Next, some representative designs of MnO₂ -based nanoplatforms in other tumor therapies are highlighted. Moreover, we will discuss the challenges and future perspectives of these MnO₂ -based nanosystems for enhanced tumor treatment. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Inkjet printing based ultra-small MnO2 nanosheets synthesis for glutathione sensing

Manganese dioxide (MnO₂) with small size is competent in sensing applications, but its synthesis generally adopts templates or in complex ways. Inkjet printing technique with excellent performance offers a versatile tool due to its stability, flexibility, economy. Herein, an inkjet printing method was developed for rapid synthesis of ultra-small MnO₂ nanosheets. The findings validated the feasibility of inkjet printing method for MnO₂ nanosheets synthesis and achieved the demand of small size and facile mode. Additionally, the limit of detection (LOD) of ultra-small MnO₂ nanosheets in glutathione (GSH) sensing achieved 0.26 μM, which was about 40% more sensitive than that of the typical MnO₂ nanosheets, enabling the establishment of a rapid and efficient modality for sensitive and selective GSH sensing. By virtue of the inkjet printing approach, the ultra-small MnO₂ nanosheets was obtained in a short time without complicated fabricating process. It can be foreseen that the proposed inkjet printing approach would facilitate the application prospects of ultra-small MnO₂ nanosheets in diverse fields. Such a facile approach may open new avenues for synthesis of ultra-small or ultrafine nanomaterials.

Biomimetic two-dimensional nanozymes: synthesis, hybridization, functional tailoring, and biosensor applications

Biological enzymes play important roles in mediating the biological reactions in vitro and in vivo due to their high catalytic activity, strong bioactivity, and high specificity; however, they have also some disadvantages such as high cost, low environmental stability, weak reusability, and difficult production. To overcome these shortcomings, functional nanomaterials including metallic nanoparticles, single atoms, metal oxides, alloys, and others have been utilized as nanozymes to mimic the properties and functions of natural enzymes. Due to the development of the synthesis and applications of two-dimensional (2D) materials, 2D nanomaterials have shown high potential to be used as novel nanozymes in biosensing, bioimaging, therapy, logic gates, and environmental remediation due to their unique physical, chemical, biological, and electronic properties. In this work, we summarize recent advances in the preparation and functionalization, as well as biosensor and immunoassay applications of various 2D material-based nanozymes. To achieve this aim, first we demonstrate the preparation strategies of 2D nanozymes such as chemical reduction, templated synthesis, chemical exfoliation, calcination, electrochemical deposition, hydrothermal synthesis, and many others. Meanwhile, the structure and properties of the 2D nanozymes prepared by conjugating 2D materials with nanoparticles, metal oxides, biomolecules, polymers, ions, and 2D heteromaterials are introduced and discussed in detail. Then, the applications of the prepared 2D nanozymes in colorimetric, electrochemical, fluorescent, and electrochemiluminescent sensors are demonstrated.

Recent Trends in Photoacoustic Imaging Techniques for 2D Nanomaterial-Based Phototherapy

A variety of 2D materials have been developed for therapeutic biomedical studies. Because of their excellent physicochemical properties, 2D materials can be used as carriers for delivering therapeutic agents into a lesion, leading to phototherapy. Various optical imaging techniques have been used for the monitoring of the treatment process. Among these, photoacoustic imaging has unique advantages including relatively deep imaging depth and large field of view with high spatial resolution. In this review article, we summarize the types of photoacoustic imaging systems used for phototherapy monitoring, then we explore contrast-enhanced photoacoustic images using 2D materials. Finally, photoacoustic image-guided phototherapies are discussed. We conclude that 2D material-based phototherapy can be efficiently monitored by photoacoustic imaging techniques.

A novel "off-on-off" fluorescent-nanoprobe based on B, N co-doped carbon dots and MnO2 nanosheets for sensitive detection of GSH and Ag. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021;244:118831. [PMID: 32860994 DOI: 10.1016/j.saa.2020.118831]

In this study, a new "off-on-off" fluorescence strategy for detecting glutathione (GSH) and silver ions (Ag⁺) is presented. The constructed nanoprobe is composed of B, N co-doped carbon dots (B, N-CDs) and manganese dioxide nanosheets (MnO₂ nanosheets), where MnO₂ nanosheets serve as a kind of efficient fluorescence quencher. The sensing mechanism of the system is based on the inner filter effect (IFE) and destruction-protection strategy. The assay strategy includes three processes: fluorescence quenching of B, N-CDs by MnO₂ nanosheets, the deconstruction of MnO₂ nanosheets by GSH, the combination between GSH and Ag⁺. The MnO₂ nanosheets are reduced to Mn²⁺ because of the addition of GSH and restoring the fluorescence intensity of the system, while the formation of the complex between GSH and Ag⁺ inhibit the reduction of MnO₂ nanosheets on account of the addition of Ag⁺, leading to the decrease in fluorescence of the probe. This strategy allows the quantitative detection of GSH and Ag⁺ with detection limit of 0.32 μmol·L^-1 and 0.24 μmol·L^-1, respectively. Moreover, this approach displays good sensitivity, selectivity and broad linear range, which could be broadly applicable for practical applications.

Gellan hydrogel-template synthesis of Au/MnO2 with enhanced photothermal conversion performance for localized cancer therapy

A Au/MnO2@GG nanocomposite hydrogel is in situ synthesized in a gellan matrix showing NIR-triggered hyperthermia with high photothermal conversion efficiency for antitumor applications.

Chemodynamic/photothermal synergistic therapy based on Ce-doped Cu–Al layered double hydroxides

Ultrathin CuAlCe layered double hydroxide nanosheets loaded with indocyanine green (ICG) were designed, and showed excellent synergetic chemodynamic/photothermal therapy.

Recent Advances in the Design and Photocatalytic Enhanced Performance of Gold Plasmonic Nanostructures Decorated with Non-Titania Based Semiconductor Hetero-Nanoarchitectures

Plasmonic photocatalysts combining metallic nanoparticles and semiconductors have been aimed as versatile alternatives to drive light-assisted catalytic chemical reactions beyond the ultraviolet (UV) regions, and overcome one of the major drawbacks of the most exploited photocatalysts (TiO2 or ZnO). The strong size and morphology dependence of metallic nanostructures to tune their visible to near-infrared (vis-NIR) light harvesting capabilities has been combined with the design of a wide variety of architectures for the semiconductor supports to promote the selective activity of specific crystallographic facets. The search for efficient heterojunctions has been subjected to numerous studies, especially those involving gold nanostructures and titania semiconductors. In the present review, we paid special attention to the most recent advances in the design of gold-semiconductor hetero-nanostructures including emerging metal oxides such as cerium oxide or copper oxide (CeO2 or Cu2O) or metal chalcogenides such as copper sulfide or cadmium sulfides (CuS or CdS). These alternative hybrid materials were thoroughly built in past years to target research fields of strong impact, such as solar energy conversion, water splitting, environmental chemistry, or nanomedicine. Herein, we evaluate the influence of tuning the morphologies of the plasmonic gold nanostructures or the semiconductor interacting structures, and how these variations in geometry, either individual or combined, have a significant influence on the final photocatalytic performance.

A biomimetic nanoenzyme for starvation therapy enhanced photothermal and chemodynamic tumor therapy

Photothermal therapy (PTT) and chemodynamic therapy (CDT) are promising therapeutic modalities with high specificity, however, a single therapeutic modality cannot maximize therapeutic efficacy. In the present study, glucose oxidase (GOx) was decorated on N-doped carbon (NC) nanoparticles (NPs) as a biomimetic nanoenzyme (NC@GOx NPs), which could promote starvation therapy enhanced PTT and CDT against tumors. GOx could decompose to cut off the supply of energy and nutrients, inducing starvation therapy, which further lowered adenosine triphosphate (ATP) levels, inducing downregulated heat shock proteins and creating a more suitable microenvironment for improving PTT efficacy. Meanwhile, the generated endogenous hydrogen peroxide (H2O2) could be converted into hydroxyl radicals to attack cancer cells. In fact, in vitro and in vivo experiments demonstrated that NC@GOx NPs could effectively kill cancer cells and eliminate tumors. This design provides a strategy for synergistic cancer therapy by using biomimetic nanoenzymes.

Engineering of CoSe2 Nanosheets via Vacancy Manipulation for Efficient Cancer Therapy

CoSe₂ nanosheets with different vacancy associates (i.e., V_SeSe, V_CoCoSe, V_CoSeSe, and V_CoCoCoSe) were synthesized by selecting different templates and calcination temperatures. The nanosheets having higher theoretical adsorption toward cellular membrane phospholipids exerted more damage to both artificial liposomes and cell membranes (V_SeSe > V_CoCoSe > V_CoCoCoSe > V_CoSeSe) and exhibited higher efficiency to kill tumor cells (e.g., A549 lung cancer cells and HeLa cervical cancer cells). Moreover, V_CoCoCoSe CoSe₂ nanosheets can be easily coated with the tumor-targeting protein transferrin (Tf), and these Tf-coated nanosheets (Tf-V_CoCoCoSe) drastically decreased the viability of various types of cancer cells (81%) without significantly damaging normal cells. Importantly, this treatment was more efficient in eliminating tumor tissues than the common chemotherapeutic drug oxaliplatin. Thus, this study offers proof of concept that manipulating the surface vacancies of CoSe₂ nanosheets could provide an efficient route for cancer therapy in a manner that could circumvent or minimize drug resistance development.

Carbon nanocage-based nanozyme as an endogenous H2O2-activated oxygenerator for real-time bimodal imaging and enhanced phototherapy of esophageal cancer

Intelligent phototherapy by theranostic nanosystems that can be activated by a tumor microenvironment has high sensitivity and specificity. However, hypoxia and low drug accumulation in tumors greatly limit its clinical application. Herein, we have designed a cage-like carbon-manganese nanozyme, which effectively relieves tumor hypoxia and delivers numerous photosensitizers (PSs) to the tumor site, for real-time imaging and enhanced phototherapy of esophageal cancer. Specifically, bovine serum albumin (BSA) was used as a template and reducing agent for preparing a BSA-MnO2 nanozyme; then a BSA-MnO2/IR820@OCNC (BMIOC) nanosystem was successfully synthesized by crosslinking BSA-MnO2 on the surface of IR820-loaded carboxylated carbon nanocages (OCNCs). Abundant PSs were successfully delivered to tumor sites via hollow OCNCs, and the final loading rate of IR820 reached 42.8%. The intratumor BMIOC nanosystem can be initiated by a tumor microenvironment to switch on its magnetic resonance (MR) imaging signal, and photothermal therapy (PTT) and photodynamic therapy (PDT) functions. Notably, the BSA-MnO2 nanozyme, with intrinsic catalase (CAT)-like activity, catalyzed endogenous H2O2 for oxygen generation to overcome tumor hypoxia and enhance PDT, thereby leading to more efficient therapeutic effects in combination with OCNC-elevated PTT. In addition, the H2O2-activated and acid-enhanced properties enable our nanosystem to be specific to tumors, protecting normal tissues from damage. By integrating a high drug loading capacity, a hypoxia regulation function, an enlarged phototherapy effect, and bimodal imaging into a nanozyme-mediated nanoreactor, this work realizes a "one for all" system and represents promising clinical translation for efficient esophageal cancer theranostics.

Cascade Reactions Catalyzed by Planar Metal-Organic Framework Hybrid Architecture for Combined Cancer Therapy

Chemical transformation in cellular environment is critical for regulating biological processes and metabolic pathways. Harnessing biocatalytic cascades to produce chemicals of interest has become a research focus to benefit industrial and pharmaceutic areas. Nanoreactors, which can act as artificial cell-like devices to organize cascade reactions, have been recently proposed for potential therapeutic applications for life-threatening illnesses. Among various types of nanomaterials, there is a growing interest in 2D metal-organic frameworks (MOFs). By virtue of the ultralarge specific surface area, high porosity, and structural diversity, 2D MOF nanosheets hold great promise for a broad spectrum of biomedical use. Herein, a unique planar MOF-based hybrid architecture (GMOF-LA) is introduced by incorporating ultrasmall gold nanoparticles (Au NPs) as nanozyme and l-Arginine (l-Arg) as nitric oxide (NO) donor. The prepared Au NPs enable oxidation of glucose into hydrogen peroxide, which drives biocatalytic cascades to covert l-Arg into NO. Interestingly, the well-designed nanosheets not only possess excellent catalytical activity for NO generation, resulting in gas therapeutic effect, but also serve as a desired photosensitizer for photodynamic therapy. This study establishes a good example of exploring bioinspired nanoreactors for cooperative anticancer effect, which may pave the path for future "bench-to-bedside" design of nanomedicine.

Nanostructured manganese dioxide for anticancer applications: preparation, diagnosis, and therapy

Nanostructured manganese dioxide (MnO₂) has attracted extensive attention in the field of anticancer applications. As we all know, the tumor microenvironment is usually characterized by a high glutathione (GSH) concentration, overproduced hydrogen peroxide (H₂O₂), acidity, and hypoxia, which affect the efficacy of many traditional treatments such as chemotherapy, radiotherapy, and surgery. Fortunately, as one kind of redox-active nanomaterial, nanostructured MnO₂ has many excellent properties such as strong oxidation ability, excellent catalytic activity, and good biodegradability. It can be used effectively in diagnosis and treatment when it reacts with some harmful substances in the tumor site. It can not only enhance the therapeutic effect but also adjust the tumor microenvironment. Therefore, it is necessary to present the recent achievements and progression of nanostructured MnO₂ for anticancer applications, including preparation methods, diagnosis, and treatment. Special attention was paid to photodynamic therapy (PDT), bioimaging and cancer diagnosis (BCD), and drug delivery systems (DDS). This review is expected to provide helpful guidance on further research of nanostructured MnO₂ for anticancer applications.

Recent Advances in Crosslinked Nanogel for Multimodal Imaging and Cancer Therapy

Nanomaterials have been widely applied in the field of cancer imaging and therapy. However, conventional nanoparticles including micelles and liposomes may suffer the issue of dissociation in the circulation. In contrast, crosslinked nanogels the structures of which are covalently crosslinked have better physiological stability than micelles and liposomes, making them more suitable for cancer theranostics. In this review, we summarize recent advances in crosslinked nanogels for cancer imaging and therapy. The applications of nanogels in drug and gene delivery as well as development of novel cancer therapeutic methods are first introduced, followed by the introduction of applications in optical and multimodal imaging, and imaging-guided cancer therapy. The conclusion and future direction in this field are discussed at the end of this review.

Grafted semiconducting polymer amphiphiles for multimodal optical imaging and combination phototherapy

Semiconducting polymer nanoparticles (SPNs) have gained growing attention in biomedical applications. However, the preparation of SPNs is usually limited to nanoprecipitation in the presence of amphiphilic copolymers, which encounters the issue of dissociation. As an alternative to SPNs, grafted semiconducting polymer amphiphiles (SPAs) composed of a semiconducting polymer (SP) backbone and hydrophilic side chains show increased physiological stability and improved optical properties. This review summarizes recent advances in SPAs for cancer imaging and combination phototherapy. The applications of SPAs in optical imaging including fluorescence, photoacoustic, multimodal and activatable imaging are first described, followed by the discussion of applications in imaging-guided phototherapy and combination therapy, light-triggered drug delivery and gene regulation. At last, the conclusion and future prospects in this field are discussed.

MnOx Nanospikes as Nanoadjuvants and Immunogenic Cell Death Drugs with Enhanced Antitumor Immunity and Antimetastatic Effect

Despite the widespread applications of manganese oxide nanomaterials (MONs) in biomedicine, the intrinsic immunogenicity of MONs is still unclear. MnO_x nanospikes (NSs) as tumor microenvironment (TME)-responsive nanoadjuvants and immunogenic cell death (ICD) drugs are proposed for cancer nanovaccine-based immunotherapy. MnO_x NSs with large mesoporous structures show ultrahigh loading efficiencies for ovalbumin and tumor cell fragment. The combination of ICD via chemodynamic therapy and ferroptosis inductions, as well as antigen stimulations, presents a better synergistic immunopotentiation action. Furthermore, the obtained nanovaccines achieve TME-responsive magnetic resonance/photoacoustic dual-mode imaging contrasts, while effectively inhibiting primary/distal tumor growth and tumor metastasis.

Au2Pt-PEG-Ce6 nanoformulation with dual nanozyme activities for synergistic chemodynamic therapy / phototherapy

Although synergistic therapy for tumors has displayed significant promise for effective treatment of cancer, developing a simple and effective strategy to build a multi-functional nanoplatform is still a huge challenge. By virtue of the characteristics of tumor microenvironment, such as hypoxia, slight acidity and H₂O₂ overexpression, Au₂Pt-PEG-Ce6 nanoformulation is constructed for collaborative chemodynamic/phototherapy of tumors. Specifically, the Au₂Pt nanozymes with multiple functions are synthesized in one step at room temperature. The photosensitizer chlorin e6 (Ce6) is covalently linked to Au₂Pt nanozymes for photodynamic therapy (PDT). Interestingly, the Au₂Pt nanozymes possess catalase- and peroxidase-like activities simultaneously, which not only can generate O₂ for relaxation of tumor hypoxia and enhancement of PDT efficiency but also can produce ∙OH for chemodynamic therapy (CDT). In addition, the high photothermal conversion efficiency (η = 31.5%) of Au₂Pt-PEG-Ce6 nanoformulation provides the possibility for photoacoustic (PA) and photothermal (PT) imaging guided photothermal therapy (PTT). Moreover, the presence of high-Z elements (Au and Pt) in Au₂Pt-PEG-Ce6 nanoformulation endows it with the ability to act as an X-ray computed tomography (CT) imaging contrast agent. All in all, the Au₂Pt-PEG-Ce6 exhibits great potential in multimodal imaging-guided synergistic PTT/PDT/CDT with remarkably tumor specificity and enhanced therapy.

Bacterial Template Synthesis of Multifunctional Nanospindles for Glutathione Detection and Enhanced Cancer-Specific Chemo-Chemodynamic Therapy

Biological synthetic methods of nanoparticles have shown great advantages, such as environmental friendliness, low cost, mild reaction conditions, and enhanced biocompatibility and stability of products. Bacteria, as one of the most important living organisms, have been utilized as bioreducing nanofactories to biosynthesize many metal nanoparticles or compounds. Here, inspired by the disinfection process of KMnO₄, we for the first time introduce bacteria as both the template and the reducing agent to construct a novel tumor microenvironment-responsive MnO_x-based nanoplatform for biomedical applications in various aspects. It is found that the bacterium/MnO_x-based nanospindles (EM NSs) can efficiently encapsulate the chemotherapeutic agent doxorubicin (DOX), leading to the fluorescence quenching of the drug. The as-formed DOX-loaded EM NSs (EMD NSs) are proven to be decomposed by glutathione (GSH) and can simultaneously release DOX and Mn²⁺ ions. The former can be utilized for sensitive fluorescence-based GSH sensing with a limit of detection as low as 0.28 μM and selective cancer therapy, while the latter plays important roles in GSH-activated magnetic resonance imaging and chemodynamic therapy. We also demonstrate that these nanospindles can generate oxygen in the presence of endogenous hydrogen peroxide to inhibit P-glycoprotein expression under hypoxia and can achieve excellent tumor eradication and tumor metastasis inhibition performance. Taken together, this work designs a multifunctional bacterially synthesized nanomissile for imaging-guided tumor-specific chemo-chemodynamic combination therapy and will have implications for the design of microorganism-derived smart nanomedicines.

Manganese Oxide Nanomaterials: Synthesis, Properties, and Theranostic Applications

Despite the comprehensive applications in bioimaging, biosensing, drug/gene delivery, and tumor therapy of manganese oxide nanomaterials (MONs including MnO₂ , MnO, Mn₂ O₃ , Mn₃ O₄ , and MnO_x ) and their derivatives, a review article focusing on MON-based nanoplatforms has not been reported yet. Herein, the representative progresses of MONs on synthesis, heterogene, properties, surface modification, toxicity, imaging, biodetection, and therapy are mainly introduced. First, five kinds of primary synthetic methods of MONs are presented, including thermal decomposition method, exfoliation strategy, permanganates reduction method, adsorption-oxidation method, and hydro/solvothermal. Second, the preparations of hollow MONs and MON-based composite materials are summarized specially. Then, the chemical properties, surface modification, and toxicity of MONs are discussed. Next, the diagnostic applications including imaging and sensing are outlined. Finally, some representative rational designs of MONs in photodynamic therapy, photothermal therapy, chemodynamic therapy, sonodynamic therapy, radiotherapy, magnetic hyperthermia, chemotherapy, gene therapy, starvation therapy, ferroptosis, immunotherapy, and various combination therapy are highlighted.

Layered double hydroxide nanosheets: towards ultrasensitive tumor microenvironment responsive synergistic therapy

The tumor microenvironment (TME), which is characterised by high H₂O₂ and glutathione (GSH) levels, low pH value and hypoxia, imposes crucial influences on tumor therapeutic outcomes. Rational design and preparation of nanomaterial systems that are responsive to the intrinsic properties of the TME open a promising avenue towards tumor-specific treatment. Herein, CoMn-layered double hydroxide (CoMn-LDH) nanosheets were synthesized via a bottom-up method followed by surface modification with a photosensitizer, chlorin e6 (Ce6), which exhibited TME-responsive imaging as well as photodynamic and chemodynamic synergistic therapy (PDT/CDT). Due to their ultralow bond energy and large adsorption energy, CoMn-LDH nanosheets show fast self-degradability in a GSH (10 mM) microenvironment, giving an excellent CDT activity in mildly acidic conditions (pH = 6.5), superior GSH removal ability (99.82%) and O₂ production (35.37 μg L^-1 s^-1). Moreover, Ce6/CoMn-LDH nanosheets display satisfactory photoacoustic (PA) imaging and GSH-enhanced magnetic resonance imaging (MRI) with a 45.1-fold T₁-enhancement. In addition, both in vitro and in vivo therapeutic tests based on Ce6/CoMn-LDH demonstrate a satisfactory anticancer activity with complete cancer cell apoptosis and dramatic tumor elimination. This work provides a new perspective for the design of multifunctional 2D nanosheets towards a fully promoted TME-responsive synergistic therapy, which holds great promise for future clinical diagnosis and treatment.

Exonuclease III-Regulated Target Cyclic Amplification-Based Single Nucleotide Polymorphism Detection Using Ultrathin Ternary Chalcogenide Nanosheets

Herein, we report that the ternary chalcogenide nanosheet exhibits different affinity toward oligonucleotides with different lengths and efficiently quenches the fluorescence of dye-labeled DNA probes. Based on these findings, as a proof-of-concept application, the ternary chalcogenide nanosheet is used as a target cyclic amplification biosensor, showing high specificity in discriminating single-base mismatch. This simple strategy is fast and sensitive for the single nucleotide polymorphism detection. Ultralow detection limit of unlabeled target (250 fM) and high discrimination ratio (5%) in the mixture of perfect match (mutant-type) and single-base mismatch (wild-type) target are achieved. This sensing method is extensively compatible for the single nucleotide polymorphism detection in clinical samples, making it a promising tool for the mutation-based clinical diagnostic and genomic research.

MnO2-Based nanosystems for cancer therapy

Recent achievements of MnO₂-based nanosystems for various cancer therapies are comprehensively reviewed.

2D nanostructures beyond graphene: preparation, biocompatibility and biodegradation behaviors

The research advances of the preparation, biocompatibility and biodegradation of 2D nanomaterials are introduced. The prospects and challenges of the biomedical applications of 2D nanomaterials are summarized.

Dendritic silica with carbon dots and gold nanoclusters for dual nanozymes

dSCS-Au NPs were established for dual nanozymes with dendritic silica spheres containing C-dots and Au NCs.

Colorimetric biosensing of glucose in human serum based on the intrinsic oxidase activity of hollow MnO2 nanoparticles

Hollow MnO₂ nanoparticles with excellent oxidase-like activity for the sensitive and selective detection of glucose in human serum.

Optimization of Antibacterial Efficacy of Noble-Metal-Based Core-Shell Nanostructures and Effect of Natural Organic Matter

Noble-metal-based nanomaterials made of less toxic metals have been utilized as potential antibacterial agents due to their distinctive oxidase-like activity. In this study, we fabricated core-shell structured Pd@Ir bimetallic nanomaterials with an ultrathin shell. Pd@Ir nanostructures show morphology-dependent bactericidal activity, in which Pd@Ir octahedra possessing higher oxidase-like activity exert bactericidal activity stronger than that of Pd@Ir cubes. Furthermore, our results reveal that the presence of natural organic matter influences the antibacterial behaviors of nanomaterials. Upon interaction with humic acid (HA), the Pd@Ir nanostructures induce an elevated level of reactive oxygen species, resulting in significantly enhanced bactericidal activity of the nanostructures. Mechanism analysis shows that the presence of HA efficiently enhances the oxidase-like activity of nanomaterials and promotes the cellular internalization of nanomaterials. We believe that the present study will not only demonstrate an effective strategy for improving the bactericidal activity of noble-metal-based nanomaterials but also provide an understanding of the antibacterial behavior of nanomaterials in the natural environment.

Construction of CPs@MnO2-AgNPs as a multifunctional nanosensor for glutathione sensing and cancer theranostics

A multifunctional nanosensor of CPs@MnO₂-AgNPs was constructed for sensitive and selective sensing of GSH and cancer theranostics in this work. The CPs@MnO₂ nanocomposite was synthesized by capping MnO₂ onto carbon nanoparticles through an in situ redox reaction under ultrasonication. AgNPs with fluorescence were obtained through a silver-mirror-like reaction using BSA as both a template and reductant and further anchored onto the surface of CPs@MnO₂ through electrostatic interaction to construct the CPs@MnO₂-AgNP nanocomposite. The fluorescence of AgNPs was effectively quenched by MnO₂ through an inner filter effect and a static quenching effect and further recovered by GSH owing to the unique redox reaction between GSH and MnO₂. Therefore, a novel fluorescent turn-on nanosensor was established for GSH sensing in vitro and in vivo. For GSH sensing, a satisfactory linear range of 0.8-80 μM with a detection limit of 0.55 μM was obtained under optimal conditions. Moreover, by integrating the GSH-responsive fluorescence imaging capacity, the photothermal activity of carbon nanoparticles and the anticancer effect of AgNPs, the CPs@MnO₂-AgNP nanocomposite was successfully applied for cancer theranostics. The fluorescence recognition of cancer was achieved by overexpressing GSH in cancer, meanwhile the photothermal therapy from CPs and chemotherapy from AgNPs jointly produced an enhanced therapeutic effect. This redox-responsive nanocomposite of CPs@MnO₂-AgNPs improves the MnO₂ nanomaterial-based applications in GSH sensing and cancer theranostics.

Advances in nanomedicine for cancer starvation therapy

Abnormal cell metabolism with vigorous nutrition consumption is one of the major physiological characteristics of cancers. As such, the strategy of cancer starvation therapy through blocking the blood supply, depleting glucose/oxygen and other critical nutrients of tumors has been widely studied to be an attractive way for cancer treatment. However, several undesirable properties of these agents, such as low targeting efficacy, undesired systemic side effects, elevated tumor hypoxia, induced drug resistance, and increased tumor metastasis risk, limit their future applications. The recent development of starving-nanotherapeutics combined with other therapeutic methods displayed the promising potential for overcoming the above drawbacks. This review highlights the recent advances of nanotherapeutic-based cancer starvation therapy and discusses the challenges and future prospects of these anticancer strategies.