Autophagy-Inducing MoO3-x Nanowires Boost Photothermal-Triggered Cancer Immunotherapy.

Autophagy could play suppressing role in cancer therapy by facilitating release of tumor antigens from dying cells and inducing immunogenic cell death (ICD). Therefore, discovery and rational design of more effective inducers of cytotoxic autophagy is expected to develop new strategies for finding innovative drugs for precise and successful cancer treatment. Herein, we develop MoO3-x nanowires (MoO3-x NWs) with high oxygen vacancy and strong photothermal responsivity to ablate tumors through hyperthermia, thus promote the induction of cytotoxic autophagy and severe ICD. As expected, the combination of MoO3-x NWs and photothermal therapy (PTT) effectively induces autophagy to promote the release of tumor antigens from the ablated cells, and induces the maturation and antigen presentation of dendritic cells (DCs), subsequently activates cytotoxic T lymphocytes (CTLs)-mediated adaptive immunity. Furthermore, the combination treatment of MoO3-x NWs with immune checkpoint blockade of PD-1 could promote the tumor-associated macrophages (TAMs) polarization into tumor-killing M1 macrophages, inhibit infiltration of Treg cells at tumor sites, and alleviate immunosuppression in the tumor microenvironment, finally intensify the anti-tumor activity in vivo. This study provides a strategy and preliminary elucidation of the mechanism of using MoO3-x nanowires with high oxygen vacancy to induce autophagy and thus enhance photothermal immunotherapy.

Single-Crystal Inorganic Helical Architectures Induced by Asymmetrical Defects in Sub-Nanometric Wires.

Constructing single-crystal inorganic helical structures is a fascinating subject for a large variety of research fields. However, the driving force of self-coiling, particularly in helical architectures, still remains a major challenge. Here, using MoO3-x sub-nanometric wires (SNWs) as an example, we identified that spontaneous helical architecture with different dimensional features is closely related with their surface asymmetrical defects. Specifically, the surface defects of SNWs are critical to produce the self-coiling process, thereby achieving the ordered helical conformations. Theoretical calculations further suggest that the formation of in-plane and out-of-plane coiling structures is determined by the asymmetrical distribution of the surface defects, and the inhomogeneous charge separation with strong Coulomb attraction dominates the different structural configurations. The resulting MoO3-x SNW exhibits excellent photothermal behaviors in both aqueous solutions and hydrogel matrixes. Our study provides a novel protocol to achieve helical structure design for their future applications.

Atomic-Level Nanorings (A-NRs) Therapeutic Agent for Photoacoustic Imaging and Photothermal/Photodynamic Therapy of Cancer.

Photothermal therapy (PTT) and photodynamic therapy (PDT) have emerged as effective approaches for cancer treatment. Herein, we present atomic-level scale (0.5 nm thickness) ultrathin sulfur-doped molybdenum oxide nanorings (S-MoOx A-NRs) and with surface coating of polyethylene glycol (PEG) (PEG@S-MoOx A-NRs). This nanomaterial shows high absorbance in the near-infrared (NIR) range and can be used as a sensitive photoacoustic imaging (PAI) contrast agent. Upon NIR irradiation, the particles show high photothermal conversion and reactive oxygen species (ROS) generation, which effectively kills cancer cells both in vitro and in vivo. The PEG@S-MoOx A-NRs allow PAI and synergistic PTT/PDT therapy, which is demonstrated as a promising theranostic strategy for future cancer therapy.

A monolayer crystalline covalent network of polyoxometalate clusters.

Monolayer two-dimensional (2D) materials are of great interest because of their unique electronic structures, noticeable in-plane confinement effect, and exceptional catalytic properties. Here, we prepared 2D covalent networks of polyoxometalate clusters (CN-POM) featuring monolayer crystalline molecular sheets, formed by the covalent connection between tetragonally arranged POM clusters. The CN-POM shows a superior catalytic efficiency in the oxidation of benzyl alcohol, and the conversion rate is five times higher than that of the POM cluster units. Theoretical calculations show that in-plane electron delocalization of CN-POM contributes to easier electron transfer and increases catalytic efficiency. Moreover, the conductivity of the covalently interconnected molecular sheets was 46 times greater than that of individual POM clusters. The preparation of monolayer covalent network of POM clusters provides a strategy to synthesize advanced cluster-based 2D materials and a precise molecular model to investigate the electronic structure of crystalline covalent networks.

Trimethoxyflavanone relieves Paclitaxel-induced neuropathic pain via inhibiting expression and activation of P2X7 and production of CGRP in mice.

Paclitaxel (PTX) is an anticancer drug used to treat solid tumors, but one of its common adverse effects is chemotherapy-induced peripheral neuropathy (CIPN). Currently, there is limited understanding of neuropathic pain associated with CIPN and effective treatment strategies are inadequate. Previous studies report the analgesic actions of Naringenin, a dihydroflavonoid compound, in pain. Here we observed that the anti-nociceptive action of a Naringenin derivative, Trimethoxyflavanone (Y3), was superior to Naringenin in PTX-induced pain (PIP). An intrathecal injection of Y3 (1 µg) reversed the mechanical and thermal thresholds of PIP and suppressed the PTX-induced hyper-excitability of dorsal root ganglion (DRG) neurons. PTX enhanced the expression of ionotropic purinergic receptor P2X7 (P2X7) in satellite glial cells (SGCs) and neurons in DRGs. The molecular docking simulation predicts possible interactions between Y3 and P2X7. Y3 reduced the PTX-enhanced P2X7 expression in DRGs. Electrophysiological recordings revealed that Y3 directly inhibited P2X7-mediated currents in DRG neurons of PTX-treated mice, suggesting that Y3 suppressed both expression and function of P2X7 in DRGs post-PTX administration. Y3 also reduced the production of calcitonin gene-related peptide (CGRP) in DRGs and at the spinal dorsal horn. Additionally, Y3 suppressed the PTX-enhanced infiltration of Iba1-positive macrophage-like cells in DRGs and overactivation of spinal astrocytes and microglia. Therefore, our results indicate that Y3 attenuates PIP via inhibiting P2X7 function, CGRP production, DRG neuron sensitization, and abnormal spinal glial activation. Our study implies that Y3 could be a promising drug candidate against CIPN-associated pain and neurotoxicity.

Recent Progress of Sub-Nanometric Materials in Photothermal Energy Conversion.

Sub-nanometric materials (SNMs) are an attractive scope in recent years due to their atomic-level size and unique properties. Among various performances of SNMs, photothermal energy conversion is one of the most important ones because it can efficiently utilize the light energy. Herein, the SNMs with photothermal energy conversion behaviors and their applications are reviewed. First, a hydrothermal/solvothermal method for the synthesis of SNMs is systematically discussed, including the LaMer pathway and the cluster-nuclei coassembly pathway. Based on this synthetic strategy, many kinds of SNMs with different morphologies are successfully prepared, such as nanorings, nanowires, nanosheets, and nanobelts. These SNMs exhibit excellent photothermal performance under the laser or solar irradiation according to their different light absorption ranges. These enhanced absorption performances of SNMs are induced by the mechanism of plasmonic localized heating or nonradiative relaxation. Finally, the applications of the photothermal SNMs are illustrated. The SNMs with photothermal behaviors can be widely applied in the fields of solar vapor generation, biomedicine, and light-responsive composites construction. It is hoped that this review can provide new viewpoints and profound understanding to the SNMs in photothermal energy conversion.

Tailoring Layer Number of 2D Porphyrin-Based MOFs Towards Photocoupled Electroreduction of CO2.

Inspired by the success of graphene, a series of single- or few-layer 2D materials have been developed and applied in the past decade. Here, the successful preparation of monolayer and bilayer 2D porphyrin-based metal-organic frameworks (MOFs) by a facile solvothermal method is reported. The structure transition from monolayer to bilayer drives distinct electronic properties and restructuring behaviors, which finally results in distinct catalytic pathways towards CO2 electrocatalysis. The monolayer favors CO2 -to-C2 pathway due to the restructuring of CuO4 sites, while CO and HCOO- are the major products over the bilayer. In photocoupled electrocatalysis, the Faradaic efficiency (FE) of the C2 compounds shows a nearly fourfold increase on the monolayer than that under dark conditions (FEC2 increases from 11.9% to 41.1% at -1.4 V). For comparison, the light field plays a negligible effect on the bilayer. The light-induced selectivity optimization is investigated by experimental characterization and density functional theory (DFT) calculations. This work opens up a novel possibility to tune the selectivity of carbon products just by tailoring the layer number of the 2D material.

Sub-Nanometer Nanobelts Based on Titanium Dioxide/Zirconium Dioxide-Polyoxometalate Heterostructures.

In addition to offering conformational flexibility, sub-nanometer nanobelts (SNBs) also outperform many larger nanobelts with large size owing to their ultrathin morphologies. However, to date, only a few monocomponent SNBs have been synthesized. This study presents a facile method for synthesizing ZrO2 -PMoO (PMZ) SNBs and TiO2 -PMoO (PMT) SNBs with heterostructures. The SNBs comprise ZrO2 /TiO2 and polyoxometalate (POM) nanoclusters, which are formed via the aggregation and subsequent transformation of nanoclusters. Significantly, these SNBs demonstrate high catalytic activity and stability in oxidative desulfurization reactions at room temperature. The impressive catalytic performance of the SNBs is aided by the POM nanoclusters, which not only coassemble with ZrO2 /TiO2 nuclei to form building blocks of PMZ SNBs/PMT SNBs but also serve as catalytic centers. The catalytic performance is further enhanced by the ZrO2 /TiO2 in the SNBs. Moreover, the proposed synthesis method can be utilized to produce other SNBs. Thus, this method provides valuable insights into the strong performance properties of SNBs created by combining metal oxides and POM nanoclusters into SNBs, which have great potential as redox catalysts.

Enhancing CO2 Electrocatalysis on 2D Porphyrin-Based Metal-Organic Framework Nanosheets Coupled with Visible-Light.

2D catalysts combined with single atom sites are promising candidates to promote CO2 reduction performance, but the ability to target stable materials with distinct structure still remains challenging. Herein, a series of single metal atoms anchored 2D metal-organic framework nanosheets (MOF-NS-M) with visualized and well-ordered mesoporous structures are fabricated and exhibit enhanced CO2 reduction activity and selectivity with the assistance of visible-light. Encouragingly, the CO Faradaic efficiency of MOF-NS-Co exceeds 90% in a wide potential window of -0.5 to -1.0 V versus RHE and reaches 98.7% with 100 mV positive shift compared with the result measured under dark. The catalytic kinetics studies show a fast initial electron transfer to CO2 to form *COO- , thanks to the sufficient exposed active sites resulting from the nanosheet nature and adjusted electron transfer pathway caused by the porphyrin photoswitch.

Nanoconfined Water-Molecule Channels for High-Yield Solar Vapor Generation under Weaker Sunlight.

Solar vapor generation is a promising method to efficiently produce fresh water. However, the insufficient vapor yields under natural daylight restrict its practical applications, and the basic evaporation mechanisms are deficient for reasonable design of evaporator structure. Here, hydrophobic nano-confined water molecule channels (NCWMCs) are demonstrated, which can reduce the vaporization enthalpy for water evaporation and achieve a record vapor generation rate of 1.25 kg m-2 h-1 under 0.5 sun irradiation. Molecular dynamics simulations reveal the cluster-evaporation process in the NCWMC system. As a result, the evaporator with NCWMC system can effectively purify seawater and wastewater samples using this environmentally friendly strategy.

Bio-inspired synthesis of mesoporous HfO2 nanoframes as reactors for piezotronic polymerization and Suzuki coupling reactions.

Complex nanostructures with high compositional and structural tailorability are highly desired in order to meet the material needs in the rapid development of nanoscience and nanotechnology. Therefore, the synthetic technique is of essential importance but currently still suffers from many challenges. Herein, we elaborately explore and demonstrate the flexibility of the anisotropic metallo-organic compound (dihafnium dichloride, Cp2HfCl2) for the fabrication of inorganic architectures by mimicking the assembly behaviors in biomolecules. The open and discrete architectures of mesoporous HfO2 nanoframes were constructed via the self-assembly of precursor with acetone as solvent and ammonia as the basic source, but without any addition of auxiliary organic molecules, like surfactants, DAN or peptides. In addition, the nanostructures (hollow spheres, solid spheres, yolk-shells, aggregations and defect-rich nanoparticles) of HfO2 assemblies can be well manipulated by simply modulating the synthesis parameters. The marked difference in the chemical bonds by the different ligands resulted in discrepant hydrolysis and then specific directional bonds for the diversity of the resultant HfO2 assemblies. Interestingly, the HfO2 nanoframe exhibits enhanced piezoelectricity, and can be used as a microelectrode reactor to trigger the pseudo-electrochemical aniline polymerization reaction by introducing ultrasonic excitation to renew the surface charges. Moreover, as compared with nanoparticle catalysts, the palladium (Pd) loaded nanoframe reactor exhibits obvious enhanced catalytic performance for classical Suzuki coupling, benefiting from the structural advantages of the HfO2 frame. Our findings here can be expected to offer new perspectives to find suitable materials by understanding the analogy between materials chemistry and biomolecule chemistry.

Atomic-level molybdenum oxide nanorings with full-spectrum absorption and photoresponsive properties.

Superthin nanostructures, particularly with atomic-level thicknesses, typically display unique optical properties because of their exceptional light-matter interactions. Here, we report a facile strategy for the synthesis of sulfur-doped molybdenum oxide nanorings with an atomic-level size (thickness of 0.5 nm) and a tunable ring-in-ring architecture. These atomic-level nanorings displayed strong photo-absorption in both the visible and infrared-light ranges and acted as a photothermal agent. Under irradiation with an 808 nm laser with an intensity of 1 W/cm2, a composite of the nanorings embedded in polydimethylsiloxane showed an ultrafast photothermal effect, delivering a local temperature of up to 400 °C within 20 s, which to the best of our knowledge is the highest temperature by light irradiation reported to date. Meanwhile, the resulting nanorings were also employed as a photoinitiator to remotely induce a visible-light shape memory response, self-healing, reshaping performance and reversible actuation of dynamic three-dimensional structures. This study demonstrates an advancement towards controlling atomic-level-sized nanostructures and achieving greatly enhanced optical performances for optoelectronics.