A photoelectrochemical aptasensor for omethoate determination based on a photocatalysis of CeO2@MnO2 heterojunction for glucose oxidation.

In the present work, we developed a photoelectrochemical aptasensor to determine omethoate (OMT) based on the dual signal amplification of CeO2@MnO2 photocatalysis for glucose oxidation and exonuclease I-assisted cyclic catalytic hydrolysis. CeO2@MnO2 heterojunction material prepared by hydrothermal method was linked with captured DNA (cDNA) and then assembled on the ITO conductive glass to form ITO/CeO2@MnO2-cDNA, which exhibited significant photocurrent response and good photocatalytic performance for glucose oxidation under visible light irradiation, providing the feasibility for sensitive determining OMT. After binding with the aptamer of OMT (apt), the formation of rigid double stranded cDNA/apt kept CeO2@MnO2 away from ITO surface, which ensured a low photocurrent background for the constructed ITO/CeO2@MnO2-cDNA/apt aptasensor. In the presence of target OMT, the restoration of the cDNA hairpin structure and the exonuclease I-assisted cyclic catalytic hydrolysis led to the generation and amplification of measurement photocurrent signals, and allowed the aptasensor to have an ideal quantitative range of 0.01-10.0 nM and low detection limit of 0.0027 nM. Moreover, the aptasensor has been applied for selective determination of OMT in real samples with good precision of the relative standard deviation less than 6.2 % and good accuracy of the recoveries from 93 % to 108 %. What's more, the aptasensor can be used for other target determination only by replacing the captured DNA and corresponding aptamer.

Tumor microenvironment responsive nano-platform for overcoming sorafenib resistance of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a malignant tumor, which seriously jeopardizes human health. The 5-year relative survival rate of HCC is only about 18%. Sorafenib, a small molecule multi-targeted tyrosine kinase inhibitor (MTKI), has been classified as the first-line treatment scheme for HCC and has significantly extended the median survival time for patients with advanced HCC. Nevertheless, the emergence of sorafenib resistance has substantially hampered its further clinical application. Herein, the nano-platform based on phototherapy and small molecular targeted therapy (SMTT) was devised to overcome the sorafenib resistance and reduce the adverse effects. Hollow mesoporous manganese dioxide (H-MnO2) was prepared by hard template method, and the prepared H-MnO2 was used to load sorafenib and Chlorin e6 (Ce6). Subsequently, the nanoparticle (NPs) were modified with dopamine to optimize biocompatibility. The final prepared NPs (MCS NPs) exhibit regular spherical shape with a hydrated particle size of approximately 97.02 nm. MCS NPs can not only possess tumor microenvironment (TME) stimuli-responsive drug release performance but also can enhance the efficacy of photodynamic therapy and reverse sorafenib resistance by alleviating tumor hypoxia. Under the action of phototherapy (Ce6) combined with molecular targeted therapy (sorafenib), MCS NPs manifest a satisfactory antitumor effect for sorafenib-sensitive or sorafenib-resistant HCC cells, and retain the antiangiogenic properties of sorafenib. In the nude mouse subcutaneous tumor model constructed with sorafenib-resistant cells, MCS NPs demonstrated superior tumor imaging ability and excellent biocompatibility. The tumor inhibition rate of the MCS NPs group without laser irradiation was 53.4 %, while the MCS NPs group with laser irradiation was as high as 100 %. The novel smart TME-responsive nano-platform shows great potential for overcoming sorafenib resistance and realizes multimodality imaging and therapy of HCC.

Green synthesis of MnO2 nanoparticles from Psidium guajava leaf extract: Morphological characterization, photocatalytic and DNA/BSA interaction studies.

In this work, a simple, efficient and eco-friendly green synthesis of manganese dioxide nanoparticles (MnO2NPs) by Psidium guajava leaf extract was described. Fourier-Transform infrared spectra results revealed that involvement of the plant extract functional groups in the formation of MnO2NPs. The UV-vis absorption spectra of the synthesized MnO2NPs exhibited absorption peaks at 374 nm, which were attributed to the band gap of the MnO2NPs. Crystal phase identification of the MnO2NPs were characterized by X-ray diffraction analysis and the formation of crystalline MnO2NPs have been confirmed. Furthermore, scanning electron microscopy analysis showed that the synthesized MnO2NPs have a spherical in shape. Interestingly, the prepared green synthesized MnO2NPs showed catalytic degradation activity for malachite green dye. Malachite green's photocatalytic degradation was detected spectrophotometrically in the wavelength range of 250-900 nm, and it was discovered to have a photodegradation efficiency of 75.5 % within 90 min when exposed to solar radiation. Green synthesized MnO2NPs are responsible for this higher activity. An interaction between synthesized NPs and biomolecules, including CT-DNA and BSA was also evaluated. The spectrophotometric and Fluoro spectroscopic analyses indicate a gradual reduction in peak intensities and shifts in wavelengths, indicating binding and affinity between the NPs and the biomolecules.

Gold Nanocage-Based Multifunctional Nanosensitizers for Programmed Photothermal /Radiation/Chemical Coordinated Therapy Guided by FL/MR/PA Multimodal Imaging.

Background: Radiotherapy is one of the main clinical methods for the treatment of malignant tumors at present. However, its application is limited by the radiation resistance of some tumor cells and the irradiation damage to the surrounding normal tissues, and the limitation of radiotherapy dose also affects the therapeutic effect. Therefore, developing diagnostic and therapeutic agents with imaging and radiosensitizing functions is urgently needed to improve the accuracy and efficacy of radiotherapy. Materials and Strategy: Herein, we synthesized multifunctional nanotheranostic FRNPs nanoparticles based on gold nanocages (GNCs) and MnO2 for magnetic resonance (MR)/photoacoustic (PA) imaging and combined photothermal, radiosensitive and chemical therapy. A programmed therapy strategy based on FRNPs is proposed. First, photothermal therapy is applied to ablate large tumors and increase the sensitivity of the tumor tissue to radiotherapy, then X-ray radiation is performed to further reduce the tumor size, and finally chemotherapeutic agents are used to eliminate smaller residual tumors and distant metastases. Results: As revealed by fluorescence, MR and PA imaging, FRNPs achieved efficient aggregation and retention at tumor sites of mice after intravenous injection. In vivo studies have shown that the programmed treatment of FRNPs-injected nude mice which were exposed to X-ray after 808 laser irradiation achieved the greatest inhibition of tumor growth compared with other treatment groups. Moreover, no obvious systemic toxicity was observed in all groups of mice, indicating the good biocompatibility of FRNPs and the safety of the treatment scheme. Conclusion: To sum up, our work not only showed a new radiosensitizer, but also provided a promising theranostic strategy for cancer treatment.

Synthesis and fabrication of segregative and durable MnO2@chitosan composite aerogel beads for uranium(VI) removal from wastewater.

To address the imperative need for efficient removal of uranium-containing wastewater and mitigate radioactive contamination risks associated with nuclear energy, the development of materials with high removal efficiency and facile separation is crucial. This study designed and synthesised MnO2@chitosan (CTS) composite aerogel beads by in-situ growing δ-MnO2 on porous CTS aerogel beads. This approach not only mitigates the agglomeration of MnO2 nanospheres but also significantly enhances the porous structure and surface area of MnO2@CTS. These cost-effective and eco-friendly millimeter-scale spherical aerogels exhibited convenient separation properties after adsorption. These characteristics help mitigate the risk of equipment seam blockage and secondary pollution that are often associated with powdered adsorbents. Additionally, MnO2@CTS exhibited remarkable mechanical strength (stress approximately 0.55 MPa at 60 % strain), enabling rapid separation and easy regeneration while maintaining high adsorption performance even after five cycles. Significantly, MnO2@CTS exhibited a maximum adsorption capacity of 410.7 mg/g at pH 6 and 298 K, surpassing reported values for most CTS/MnO2-based adsorbents. The chemisorption process of U(VI) on MnO2@CTS followed the pseudo-second-order kinetic and Dubinin-Radushkevish models. X-ray photoelectron spectroscopy analysis further confirmed the reduction of U(VI) to U(V/IV). These findings highlight the substantial potential of MnO2@CTS aerogel beads for U(VI) removal from aqueous solutions, positioning them as a promising solution for addressing U(VI) contamination in wastewater.

Enhancing oxidation reaction over Pt-MnO2 catalyst by activation of surface oxygen.

Formaldehyde (HCHO) and carbon monoxide (CO) are both common air pollutants and hazardous to human body. It is imperative to develop the catalyst that is able to efficiently remove these pollutants. In this work, we activated Pt-MnO2 under different conditions for highly active oxidation of HCHO and CO, and the catalyst activated under CO displayed superior performance. A suite of complementary characterizations revealed that the catalyst activated with CO created the highly dispersed Pt nanoparticles to maintain a more positively charged state of Pt, which appropriately weakens the Mn-O bonding strength in the adjacent region of Pt for efficient supply of active oxygen during the reaction. Compared with other catalysts activated under different conditions, the CO-activated Pt-MnO2 displays much higher activity for oxidation of HCHO and CO. This research contributes to elucidating the mechanism for regulating the oxidation activity of Pt-based catalyst.

Catechol-Modified and MnO2-Nanozyme-Reinforced Hydrogel with Improved Antioxidant and Antibacterial Capacity for Periodontitis Treatment.

Periodontitis is an inflammatory disease characterized by tooth loss and alveolar bone resorption. Bacteria are the original cause of periodontitis, and excess reactive oxygen species (ROS) encourage and intensify inflammation. In this study, a mussel-inspired and MnO2 NPs-reinforced adhesive hydrogel capable of alleviating periodontitis with improved antibacterial and antioxidant abilities was developed. The hydrogel was created by combining polyvinyl alcohol (PVA), 3,4-dihydroxy-d-phenylalanine (DOPA), and MnO2 nanoparticles (NPs) (named PDMO hydrogel). The hydrogel was demonstrated to be able to scavenge various free radicals (including total ROS─O2•- and OH•) and relieve the hypoxia in an inflammatory microenvironment by scavenging excess ROS and generating O2 due to its superoxide dismutase (SOD)/catalase (CAT)-like activity. Besides, under 808 nm near-infrared (NIR) light, the photothermal performance of the PDMO hydrogel displayed favorable antibacterial and antibiofilm effects toward Escherichia coli, Staphylococcus aureus, and Porphyromonas gingivalis (up to nearly 100% antibacterial rate). Furthermore, the PDMO hydrogel exhibited favorable therapeutic efficacy in alleviating gingivitis in Sprague-Dawley rats, even comparable to or better than the commercial PERIO. In addition, in the periodontitis models, the PDMO2 group showed the height of the residual alveolar bone and the smallest shadow area of low density among other groups, indicating the positive role of the PDMO2 hydrogel in bone regeneration. Finally, the biosafety of the PDMO hydrogel was comprehensively investigated, and the hydrogel was demonstrated to have good biocompatibility. Therefore, the developed PDMO hydrogel provided an effective solution to resolve biofilm recolonization and oxidative stress in periodontitis and could be a superior candidate for local drug delivery system in the clinical management of periodontitis with great potential for future clinical translation.

Efficacy and mechanisms of δ-MnO2 modified biochar with enhanced porous structure for uranium(VI) separation from wastewater.

Even though uranium (U) is considered to be an essential strategic resource with vital significance to nuclear power development and climate change mitigation, U exposure to human and ecological environment has received growing concerns due to its both highly chemically toxic and radioactively hazardous property. In this study, a composite (M-BC) based on Ficus macrocarpa (banyan tree) aerial roots biochar (BC) modified by δ-MnO2 was designed to separate U(VI) from synthetic wastewater. The results showed that the separation capacity of M-BC was 61.53 mg/g under the solid - liquid ratio of 1 g/L, which was significantly higher than that of BC (12.39 mg/g). The separation behavior of U(VI) both by BC and M-BC fitted well with Freundlich isothermal models, indicating multilayer adsorption occurring on heterogeneous surfaces. The reaction process was consistent with the pseudo-second-order kinetic model and the main rate-limiting step was particle diffusion process. It is worthy to note that the removal of U(VI) by M-BC was maintained at 94.56% even after five cycles, indicating excellent reusability and promising application potential. Multiple characterization techniques (e.g. Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) and X-ray Photoelectron Spectroscopy (XPS)) uncovered that U(VI) complexation with oxygen-containing functional groups (e.g. O-CO and Mn-O) and cation exchange with protonated ≡MnOH were the dominant mechanisms for U(VI) removal. Application in real uranium wastewater treatment showed that 96% removal of U was achieved by M-BC and more than 92% of co-existing (potentially) toxic metals such as Tl, Co, Pb, Cu and Zn were simultaneously removed. The work verified a feasible candidate of banyan tree aerial roots biowaste based δ-MnO2-modified porous BC composites for efficient separation of U(VI) from uranium wastewater, which are beneficial to help address the dilemma between sustainability of nuclear power and subsequent hazard elimination.

A MnAl double adjuvant nanovaccine to induce strong humoral and cellular immune responses.

At present, the most widely used aluminum adjuvants have poor ability to induce effective Th1 type immune responses. Existing evidence suggests that manganese is a potential metal adjuvant by activating cyclic guanosine phospho-adenosine synthase (cGAS)-interferon gene stimulator protein (STING) signaling pathway to enhance humoral and cellular immune response. Hence, the effective modulation of metal components is expected to be a new strategy to improve the efficiency of vaccine immunization. Here, we constructed a manganese and aluminum dual-adjuvant antigen co-delivery system (MnO2-Al-OVA) to enhance the immune responses of subunit vaccines. Namely, the aluminum hydroxide was first fused on the surface of the pre-prepared MnO2 nanoparticles, which were synthesized by a simple redox reaction with potassium permanganate (KMnO4) and oleic acid (OA). The engineered MnO2-Al-OVA could remarkably promote cellular internalization and maturation of dendritic cells. After subcutaneous vaccination, MnO2-Al-OVA rapidly migrated into the lymph nodes (LNs) and efficiently activate the cGAS-STING pathway, greatly induced humoral and cellular immune responses. Of note, our findings underscore the importance of coordination manganese adjuvants in vaccine design by promoting the activation of the cGAS-STING-IFN-I pathway. With a good safety profile and facile preparation process, this dual-adjuvant antigen co-delivery nanovaccine has great potential for clinical translation prospects.

Supplementation of Polymeric Reservoirs with Redox-Responsive Metallic Nanoparticles as a New Concept for the Smart Delivery of Insulin in Diabetes.

Type 1 diabetes is caused by the inability of the pancreatic beta cells to produce sufficient amounts of insulin, an anabolic hormone promoting the absorption of the blood glucose by various cells in the body, primarily hepatocytes and skeletal muscle cells. This form of impaired metabolism has been traditionally treated with subcutaneous insulin injections. However, because one such method of administration does not directly correspond to the glucose concentrations in the blood and may fail to reduce hyperglycemia or cause hypoglycemia, the delivery of insulin in a glucose-dependent manner has been researched intensely in the present and past. This study tested the novel idea that the supplementation of polymeric reservoirs containing insulin with metallic nanoparticle precursors responsive to the redox effect of glucose could be used to create triggers for the release of insulin in direct response to the concentration of glucose in the tissue. For that purpose, manganese oxide nanoparticles were dispersed inside a poly(ε-caprolactone) matrix loaded with an insulin proxy and the resulting composite was exposed to different concentrations of glucose. The release of the insulin proxy occurred in direct proportion to the concentration of glucose in the medium. Mechanistically, as per the central hypothesis of the study, glucose reduced the manganese cations contained within the metal oxide phase, forming finer and more dissipative zero-valent metallic nanoparticles, thus disrupting the polymeric network, opening up pores in the matrix and facilitating the release of the captured drug. The choice of manganese for this study over other metals was justified by its use as a supplement for protection against diabetes. Numerical analysis of the release mechanism revealed an increasingly nonlinear and anomalous release accompanied by a higher diffusion rate at the expense of chain rigidity as the glucose concentration increased. Future studies should focus on rendering the glucose-controlled release (i) feasible within the physiological pH range and (ii) sensitive to physiologically relevant glucose concentrations. These technical improvements of the fundamental new concept proven here may bring it closer to a real-life application for the mitigation of symptoms of hyperglycemia in patients with diabetes.

Label-free ultra-sensitive colorimetric detection of hepatitis E virus based on oxidase-like activity of MnO2 nanosheets.

Hepatitis E virus (HEV) is an evolving infectious entity that causes viral hepatitis infections worldwide. Current routine methods of identifying and diagnosing HEV are someway laborious and costly. Based on the biomimicking oxidase-like activity of MnO2 nanosheets, we designed a label-free, highly sensitive colorimetric sensing technique for HEV detection. The prepared MnO2 catalyst displays intrinsic biomimicking oxidase-like catalytic activity and efficiently oxidizes the 3,3',5,5'-tetramethylbenzidine (TMB) substrate from colorless to blue colored oxidized TMB (oxTMB) product which can be measured at 652 nm by UV-visible spectrum. When the HEV-DNA was added, DNA adsorbed easily on MnO2 surface through physical adsorption and electrostatic interaction which hinders the oxidase-like catalytic activity of MnO2. Upon the introduction of target, the HEV target DNA binds with its complementary ssDNA on the surface of MnO2, the hybridized DNA releases from the surface of MnO2, which leads to recovery of oxidase-like catalytic activity of MnO2. This strategy was applied to construct a colorimetric technique for HEV detection. The approach works in the linear range of 1 fM-100 nM DNA concentration with the limit of detection (LOD) of 3.26 fM (S/N = 3) and quantitative limit (LOQ) of 36.08 fM. The TMB-MnO2 platform was highly selective for HEV target DNA detection when compared with potential interferences. Result of serum sample analysis demonstrates that this sensing system can be used for clinical diagnostic applications.

Multifunctional Hollow MnO2 @Porphyrin@Bromelain Nanoplatform for Enhanced Photodynamic Therapy.

Photodynamic therapy (PDT) has been showing great potential in cancer treatment. However, the efficacy of PDT is always limited by the intrinsic hypoxic tumor microenvironment (TME) and the low accumulation efficiency of photosensitizers in tumors. To address the issue, a multifunctional hollow multilayer nanoplatform (H-MnO2 @TPyP@Bro) comprising manganese dioxide, porphyrin (TPyP) and bromelain (Bro), is developed for enhanced photodynamic therapy. MnO2 catalyzes the intracellular hydrogen peroxide (H2 O2 ) to produce oxygen (O2 ), reversing the hypoxic TME in vivo. The generated O2 is converted into singlet oxygen (1 O2 ) by the TPyP shell under near-infrared light, which can inhibit tumor proliferation. Meanwhile, the Bro can digest collagen in the extracellular matrix around the tumor, and can promote the accumulation of H-MnO2 @TPyP@Bro in the deeper tumor tissue, further improving the therapeutic effect of PDT. In addition, MnO2 can react with the overexpressed glutathione in TME to release Mn2+ . Consequently, Mn2+ not only induces chemo-dynamic therapy based on Fenton reaction by converting H2 O2 into hydroxyl radicals, but also activates the Mn2+ -based magnetic resonance imaging. Therefore, the developed H-MnO2 @TPyP@Bro nanoplatform can effectively modulate the unfavorable TME and overcome the limitations of conventional PDT for cancer diagnostic and therapeutic.

Comparative investigation of the catalytic application of α/ß/γ-MnO2 nanoparticles synthesized by green and chemical approaches.

Three phases (α, ß, and γ) of manganese dioxide (MnO2) are successfully stabilized in a single entity for the first time. For this purpose, Citrullus colocynthis (bitter apple) extract is used as a natural surfactant in green synthesis. MnO2 nanoparticles were synthesized in the presence and absence of plant extracts under the same conditions. The morphology of both products is analysed by SEM and STEM to understand the role of plant extract in controlling the morphology of particles. The crystallinity and composition are analysed by XRD and confirmed that the product is composed of multiple phases α, ß, and γ. The reduction of dyes and nitroarenes is studied using MnO2 nanoparticles (green and chemical products) as catalysts. The apparent rate constant, a percentage reduction, time reduction and reduced concentration compare the activities of both catalysts. After comparative data analysis, the catalytic reduction of picric acid is found fastest among all the substrates. All the results are analysed based on structure, functional group and affinity towards catalysts.

Polyethyleneimine incorporated chitosan/α-MnO2 nanorod honeycomb-like composite foams with remarkable elasticity and ultralight property for the effective removal of U(VI) from aqueous solution.

The development of new adsorbents is needed to address the environmental challenges of radioactive wastewater treatment. Herein we reported a novel polyethyleneimine incorporated chitosan/α-MnO2 nanorod honeycomb-like composite (PCM) foam with remarkable elasticity and ultralight property for U(VI) removal. Among different PCM sorbents, PCM-40 possessed the highest sorption capacity for U(VI) due to its highly developed macroporous structure and high content of amine/imine groups. The kinetics were well-simulated by the pseudo-second-order model, indicating chemisorption as the rate-controlling step. The isotherms could be described by the Langmuir model, suggesting mono-layer homogeneous sorption of U(VI). The maximum sorption U(VI) capacity for PCM-40 reaches up to 301.9 mg/g at pH 4.5 and 298 K. The thermodynamic parameters revealed the spontaneous and endothermic nature of the adsorption process. The main sorption mechanism is related to the complexation of uranyl ions with the amine/imine and hydroxyl groups. The high sorption capacity, fast kinetic rate and relatively good selectivity of PCM-40 highlights its promising application in radioactive pollution cleanup.

Acid-Sensitive Nanoparticles Based on Molybdenum Disulfide for Photothermal-Chemo Therapy.

The combination of multiple treatments has recently been investigated for tumor treatment. In this study, molybdenum disulfide (MoS2) with excellent photothermal conversion performance was used as the core, and manganese dioxide (MnO2), which responds to the tumor microenvironment, was loaded on its surface by liquid deposition to form a mesoporous core-shell structure. Then, the chemotherapeutic drug Adriamycin (DOX) was loaded into the hole. To further enhance its water solubility and stability, the surface of MnO2 was modified with mPEG-NH2 to prepare the combined antitumor nanocomposite MoS2@DOX/MnO2-PEG (MDMP). The results showed that MDMP had a diameter of about 236 nm, its photothermal conversion efficiency was 33.7%, and the loading and release rates of DOX were 13 and 65%, respectively. During in vivo and in vitro studies, MDMP showed excellent antitumor activity. Under the combined treatment, the tumor cell viability rate was only 11.8%. This nanocomposite exhibits considerable potential for chemo-photothermal combined antitumor therapy.

Eco-Friendly Synthesis of MnO2 Nanorods Using Gmelina arborea Fruit Extract and Its Anticancer Potency Against MCF-7 Breast Cancer Cell Line.

INTRODUCTION: Cancer disease is known due to its unregulated proliferation of cells that have evolved from the body's regular cells. The disease develops as a result of epigenetic and genetic modifications, tumor suppressor gene inactivation, and oncogene activation. The present work describes an environmentally benign approach for the synthesis of manganese oxide nanoparticles (MnO2 NPs) using Gmelina arborea fruit extract (GAE) in an aqueous medium. METHODS: The study evaluated the formation of MnO2 NPs and their anticancer efficacy against MCF-7 breast cancer cell line. RESULTS: The formation of MnO2 NPs was confirmed through powder X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HR-TEM). The crystalline nature of as-prepared MnO2 NPs was evident from XRD pattern. The morphology of the material was studied using SEM analysis, which suggested a rod-like nature with an average diameter of 50 nm. Further, the TEM and HR-TEM images confirmed the rod shape of the as-prepared MnO2 NPs with an interplanar distance of 0.271 nm. In addition, the concentric rings from selected area electron diffraction (SAED) analysis show the crystalline nature of the as-prepared material, which further supports the obtained XRD pattern. The anticancer efficacy of MnO2 NPs was evaluated against MCF-7 breast cancer cell line, which showed up to 96% inhibition of the cells at 400 µg/mL concentration. CONCLUSION: Bio-conjugation of MnO2 NPs can provide enough scope for the therapeutic use of Gmelina arborea, assuming appropriate mechanistic evaluations are conducted.

Photothermal MnO2 nanoparticles boost chemo-photothermal therapy-induced immunogenic cell death in tumor immunotherapy.

The induction of immunogenic cell death (ICD) is an attractive strategy for generating in situ autologous tumor cell-based vaccines and thus has great potential in cancer prevention and personalized immunotherapy. However, the effectiveness of ICD in tumor immunotherapy has been greatly limited, mainly by low induction efficiency and the immunosuppressive tumor microenvironment (TME). Herein, we report a new strategy for chemo-photothermal therapy-induced ICD by employing photothermal MnO2 nanoparticles loaded with doxorubicin (DOX) in tumor immunotherapy to overcome the low efficiency of traditional ICD inducers and the immunosuppressive TME. Specifically, we prepared photothermal bovine serum albumin (BSA)-templated MnO2 NPs (BSA/MnO2 NPs) with good aqueous dispersibility and high biocompatibility through the direct reduction of KMnO4 with BSA, and we then efficiently loaded DOX, an ICD inducer, onto the MnO2 NPs through coordination (DOX-BSA/MnO2 NPs). The DOX-BSA/MnO2 NPs achieved high photothermal conversion efficiency, highly efficient tumor targeting, TME-responsive DOX release and modulation of the hypoxic TME. Notably, a marked in vivo synergistic therapeutic effect was achieved in a triple-negative breast carcinoma-bearing mouse model by combining chemo-photothermal therapy-induced ICD with amelioration of the immunosuppressive TME. Our research highlights the great promise of modulating the TME with photothermal MnO2 nanosystems to enhance ICD-induced antitumor immunotherapy.

Multifunctional MnO2/Ag3SbS3 Nanotheranostic Agent for Single-Laser-Triggered Tumor Synergistic Therapy in the NIR-II Biowindow.

Regulating the level of reactive oxygen species (ROS) in a tumor is an efficient and innovative anticancer strategy. However, the therapeutic efficacy of ROS-based therapies, such as chemodynamic therapy (CDT) and photodynamic therapy (PDT), offers finite outcomes due to the oxygen dependence and limited concentration of hydrogen peroxide (H2O2) and overexpression of glutathione (GSH) within the tumor microenvironment (TME), so a single therapeutic strategy is insufficient to completely eliminate tumors. Therefore, we demonstrated an omnipotent nanoplatform MnO2/Ag3SbS3 (abbreviated as MA) with strong optical absorbance in the NIR-II biowindow and oxygen self-sufficient ROS-mediated ability, which not only relieves tumor hypoxia significantly but also enhances the photothermal therapy (PTT)/PDT/CDT efficacy. By 1064 nm laser irradiation, MnO2/Ag3SbS3 nanoparticles (NPs) reveal a favorable photothermal conversion efficiency of 23.15% and achieve a single-laser-triggered NIR-II PTT/PDT effect, resulting in effective tumor elimination. Once internalized into the tumor, MnO2/Ag3SbS3 NPs will be degraded to Mn2+ and Ag3SbS3. The released Ag3SbS3 NPs as a NIR-II phototherapy agent could be utilized for photoacoustic imaging-guided NIR-II PDT/PTT. Mn2+ could be used as a Fenton-like catalyst to continuously catalyze endogenous H2O2 for generating highly virulent hydroxyl radicals (•OH) for CDT and O2 for PDT, enhancing the efficiency of PDT and CDT, respectively. Meanwhile, Mn2+ realizes magnetic resonance imaging-guided accurate tumor therapy. Moreover, the MnO2/Ag3SbS3 NPs could deplete intracellular GSH in TME to promote oxidative stress of the tumor, further strengthening ROS-mediated antitumor treatment efficacy. Overall, this work presents a distinctive paradigm of TME-responsive PDT/CDT/PTT in the second near-infrared biowindow by depleting GSH and decomposing H2O2 for efficient and precise cancer treatment.

Hollow urchin-shaped manganese dioxide microspheres immobilized acetylcholinesterase for rapid screening inhibitors from traditional herbal medicines.

Acetylcholinesterase (AChE) is generally considered to be a valuable therapeutic target for Alzheimer's disease (AD). To rapidly screen novel AChE inhibitors from Traditional Chinese medicines (TCMs), polydopamine (PDA) coated hollow urchin-shaped manganese dioxide microspheres (h-MnO2@PDA) were fabricated in this work. AChE was immobilized onto the surface of h-MnO2@PDA for the first time, and the prepared h-MnO2@PDA immobilized AChE coupled with capillary electrophoresis (CE) was applied to AChE inhibitor screening. The enzyme catalytic activity and kinetic performances of the immobilized AChE were determined by measuring the peak areas of 5-thio-2-nitrobenzoic acid (TNB), which was produced by the reaction of thiocholine (TCh) with 5,5-dithiobis-(2-nitrobenzoic acid) (DTNB). Inhibition kinetics for the immobilized AChE was performed by employing huperzine A as model inhibitor, and its inhibition constant and IC50 were determined. The constructed AChE immobilized h-MnO2@PDA presented outstanding pH, thermal and storage stability. Ultimately, the constructed strategy was applied to screen AChE inhibitors from 7 TCMs and Schisandrae Chinensis Fructus was screened out for its superior AChE inhibitory activity. Therefore, our work not only established a platform for efficiently screening novel AChE inhibitors from TCMs, but also provided inspiration for further exploration of Schisandrae Chinensis Fructus as a potential drug for AD.

Discharging Behavior of Hollandite α-MnO2 in a Hydrated Zinc-Ion Battery.

Hollandite, α-MnO2, is of interest as a prospective cathode material for hydrated zinc-ion batteries (ZIBs); however, the mechanistic understanding of the discharge process remains limited. Herein, a systematic study on the initial discharge of an α-MnO2 cathode under a hydrated environment was reported using density functional theory (DFT) in combination with complementary experiments, where the DFT predictions well described the experimental measurements on discharge voltages and manganese oxidation states. According to the DFT calculations, both protons (H+) and zinc ions (Zn2+) contribute to the discharging potentials of α-MnO2 observed experimentally, where the presence of water plays an essential role during the process. This study provides valuable insights into the mechanistic understanding of the discharge of α-MnO2 in hydrated ZIBs, emphasizing the crucial interplay among the H2O molecules, the intercalated Zn2+ or H+ ions, and the Mn4+ ions on the tunnel wall to enhance the stability of discharged states and, thus, the electrochemical performances in hydrated ZIBs.