Piezoelectric Nanostructured Surface for Ultrasound-Driven Immunoregulation to Rescue Titanium Implant Infection

Treating bacterial biofilm infections on implanted materials remains challenging in clinical practice, as bacteria can be resistant by weakening the host defense from immune cells like macrophages. Herein, a metal-piezoelectric hetero-nanostructure with mechanical energy-driven antimicrobial property is in situ constructed on the Ti implant. Under ultrasonic irradiation, the formed piezotronic Ti (piezoTi) can promote the generation of reactive oxygen species (ROS) by facilitating local charge transfer at the surface, thus leading to piezodynamic killing of Staphylococcus aureus (S. aureus) while downregulating biofilm-forming genes. In addition, the stimulated macrophages on piezoTi display potent phagocytosis and anti-bacterial activity through the activation of PI3K-AKT and MAPK pathway. As a demonstration, one-time ultrasound irradiation of piezoTi pillar implanted in an osteomyelitis model efficiently eliminates the S. aureus biofilm infection and rescues the implant with enhanced osteointegration. By the synergistic effect of ultrasound-driven piezodynamic therapy and immuno-regulation, the proposed piezoelectric nanostructured surface can endow Ti implants with highly efficient antibacterial performance in an antibiotic-free, noninvasive, and on-demand manner.     

A Dual-Mode Electrochromic Platform Integrating Zinc Anode-Based and Rocking-Chair Electrochromic Devices

The complementary electrochromic device, where the optical transmittance changes upon the flow of cations back and forth between anodic and cathodic electrodes, operates in a rocking-chair fashion if it can inherently self-discharge. Herein, the first demonstration of a dual-mode electrochromic platform having self-coloring and self-bleaching characteristics is reported, which is realized by sandwiching zinc metal within a newly-designed Prussian blue (PB)-WO₃ rocking-chair type electrochromic device. It is demonstrated that the redox potential differences between the zinc metal and the WO₃/PB electrodes endow the self-color-switching of these electrodes. By employing a hybrid electrolyte of Zn²⁺/K⁺, it is further shown that the colored PB-WO₃ rocking-chair device is capable of spontaneously bleaching when the anodic and cathodic electrodes are coupled. This dual-mode light-control strategy enables the electrochromic devices to exhibit four distinct optical states with the highest optical contrast of 72.6% and fast switching times (<5 s for the bleaching/coloration processes). Furthermore, the built-in voltage of the dual-mode electrochromic devices not only promotes energy efficiency, but also augments the bistability of the devices. It is envisioned that the broad implication of the present platform is in the development of self-powered smart windows, colorful displays, optoelectronic switches, and optical sensors.     

High-Performing Quasi-2D Perovskite Photodetectors with Efficient Charge Transport Network Built from Vertically Orientated and Evenly Distributed 3D-Like Phases

Quasi-two-dimensional (Q-2D) perovskites are emerging as one of the most promising materials for photodetectors. However, a significant challenge to Q-2D perovskites for photodetection is their insufficient charge transport ability, which is mainly attributed to their hybrid low-dimensional n-phase structure. This study demonstrates that evenly-distributed 3D-like phases with vertical orientation throughout the film can greatly facilitate charge transport and suppress charge recombination, outperforming the prevalent phase structure with a vertical dimension gradient. Based on such a phase structure, a Q-2D Ruddlesden−Popper perovskite self-powered photodetector achieving a combination of exceptional figures-of-merit is realized, including a responsivity of 0.45 AW⁻¹, a peak specific detectivity of 2.3 × 10¹³ Jones, a 156 dB linear dynamic range, and a rise/fall time of 2.89 µs/1.93 µs. The desired phase structure is obtained by utilizing a double-hole transport layer (HTL), combining hydrophobic PTAA and hydrophilic PEDOT: PSS. Besides, the dependence of the hybrid low-dimensional phase structure is also identified on the surface energy of the buried HTL substrate. This study gives insight into the correlation between Q-2D perovskites’ phase structure and performance, providing a valuable design guide for Q-2D perovskite-based photodetectors.     

Magnetic Large-Mesoporous Nanoreactors Enable Enzymatically Regulated Background-Free and Persistently Signalling Diseases Diagnosis

Diverse diseases and increasing prevalence pose a serious threat to public health. Point-of-care testing (POCT) techniques have imposed superior requirements over sensitivity, selectivity, robustness, affordability, and high-throughput. However, transient signal, complex sample pretreatment, and low signal-to-noise ratio make POCT severely limited in detection accuracy, efficiency, and sensitivity. Here, an enzyme-assisted magnetic large-mesoporous nanoreactor (FS) is constructed for achieving persistent-chemiluminescence signal output and eliminating matrix interference in disease diagnosis. The core-shell structured FS synthesized via an interface coassembly method exhibits uniform size, large and open mesopores (≈22 nm), and intrinsic magnetic separability. Such unique FS acts as efficient nanoreactor for confined cascade reactions enable efficient persistent-chemiluminescence (pCL) signal transduction and high-SNR chromogenic analysis of diverse biomarkers. The developed pCL assays facilitate high-sensitive determination of chronic disease biomarkers glucose and uric acid with detection limits (DL) of 5.4 mg L⁻¹ and 151.2 ng L⁻¹, respectively. The proposed chromogenic immunoassay enables an ultrasensitive and visual determination of alpha-fetoprotein with a DL of 1.2 ng L⁻¹, which is superior to previously published immunoassays. The feasibility of the developed methods for real-world applications are demonstrated in 159 clinical serum samples, and the determination results agree well with the clinical data. The proposed technique is expected to promote highly sensitive disease diagnosis in primary medical institutions and resource-limited areas since not relying on expensive automatic sampling and testing instruments. The good flexibility of the customizable nanoreactor makes it a powerful tool for developing various POCT techniques for rapid, sensitive, and accurate diseases diagnosis.     

Kinetically Accelerating Elementary Steps via Bridged Ru-H State for the Hydrogen-Evolution in Anion-Exchange Membrane Electrolyzer

Designing hydrogen evolution reaction (HER) electrocatalysts for facilitating its sluggish adsorption kinetics is crucial in generating green hydrogen via sustainable water electrolysis. Herein, a high-performance ultra-low Ruthenium (Ru) catalyst is developed consisting of atomically-layered Ru nanoclusters with adjacent single Ru sites, which executs a bridging-Ru-H activation strategy to kinetically accelerate the HER elementary steps. Owing to its optimal electronic structure and unique adsorption configuration, the hybrid Ru catalyst simultaneously displayed a drastically reduced overpotential of 16 mV at 10 mA cm⁻² as well as a low Tafel slope of 35.2 mV dec⁻¹ in alkaline electrolyte. When further coupled with a commercial IrO₂ anode catalyst, the ensembled anion-exchange membrane water electrolyzer achievs a current density of 1.0 A cm⁻² at a voltage of only 1.70 V_cell. In situ spectroscopic analysis verified that Ru single atom and atomically-layered Ru nanoclusters in the hybrid materials play a critical role in facilitating water dissociation and weakening *H adsorption, respectively. Theoretical calculations further elucidate the underlaying mechanism, suggesting that the dissociated proton at the single atom Ru site orients itself adjacently with Ru nanoclusters in a bridged structure through targeted charge transfer, thus promoting Volmer-Heyrovsky dynamics and boosting the HER activity.     

Catalytically Induced Robust Inorganic-Rich Cathode Electrolyte Interphase for 4.5 V Li||NCM622 Batteries

Tailoring inorganic components of cathode electrolyte interphase (CEI) and solid electrolyte interphase (SEI) is critical to improving the cycling performance of lithium metal batteries. However, it is challenging due to complicated electrolyte reactions on cathode/anode surfaces. Herein, the species and inorganic component content of the CEI/SEI is enriched with an objectively gradient distribution through employing pentafluorophenyl 4-nitrobenzenesulfonate (PFBNBS) as electrolyte additive guided by engineering bond order with functional groups. In addition, a catalytic effect of LiNi_0.6Mn_0.2Co_0.2O₂ (NCM622) cathode is proposed on the decomposition of PFBNBS. PFBNBS with lower highest occupied molecular orbital can be preferentially oxidized on the NCM622 surface with the help of the catalytic effect to induce an inorganic-rich CEI for superior electrochemical performance at high voltage. Moreover, PFBNBS can be reduced on the Li surface due to its lower lowest unoccupied molecular orbital , increasing inorganic moieties in SEI for inhibiting Li dendrite generation. Thus, 4.5 V Li||NCM622 batteries with such electrolyte can retain 70.4% of initial capacity after 500 cycles at 0.2 C, which is attributed to the protective effect of the excellent CEI on NCM622 and the inhibitory effect of its derived CEI/SEI on continuous electrolyte decomposition.     

Self-Mineralizing Dnazyme Hydrogel as a Multifaceted Bone Microenvironment Amendment for Promoting Osteogenesis in Osteoporosis

The accumulation of reactive oxygen species (ROS) and minimal osteogenic raw material in the osteoporotic bone microenvironment greatly inhibits the activity of osteoblasts. Herein, it is originally proposed to construct a biomatrix multifaceted bone microenvironment amendment -Mineralized zippered G4-Hemin DNAzyme hydrogel (MDH)-to improve osteoporotic osteogenic capacity and promote high-quality bone defect repair. The programmed design of the rolling circle amplified DNA hydrogel synthesis system allows the introduction of massive amounts of zippered G4-Hemin DNAzyme in MDH. The zippered G4-Hemin DNAzyme highly mimics the tight catalytic configuration of horseradish peroxidase and exerts excellent enzyme-like activity with considerable ROS molecule scavenging ability. In addition, the DNA amplification by-product pyrophosphate is ingeniously employed as a sufficient phosphorus source, thus constituting an autonomous mineralization system for waste reuse through the introduction of pyrophosphate hydrolase and calcium ions, which deposits in MDH as an osteogenic raw material and addresses the challenge of DNA hydrogel bio-application stability. The remarkable in vitro and in vivo outcomes demonstrate that MDH can effectively improve the oxidative stress status of osteoblasts, restore the balance of mitochondrial membrane potential, and reduce apoptosis, ultimately demonstrating superior osteogenic capacity.     

Ultra-Thin Single-Particle-Layer Sodium Beta-Alumina-Based Composite Polymer Electrolyte Membrane for Sodium-Metal Batteries

Inorganic/organic composite polymer electrolytes (CPEs) with good flexibility and electrode contact have been pursued for solid−state sodium-metal batteries. However, the application of CPEs for high energy density solid−state sodium-metal batteries is still limited by the low Na⁺ conductivity, large thickness, and low ion transference number. Herein, an ultra-thin single-particle-layer (UTSPL) composite polymer electrolyte membrane with a thickness of ≈20 µm straddled by a sodium beta−alumina ceramic electrolyte (SBACE) is presented. A ceramic Na⁺-ion electrolyte that bridges or percolates across an ultra-thin and flexible polymer membrane provides: 1) the strength and flexibility from the polymer membrane, 2) excellent electrolyte/electrode interfacial contact, and 3) a percolation path for Na⁺-ion transfer. Owing to this novel design, the obtained UTSPL-35SBACE membrane exhibits a high Na⁺-ion conductivity of 0.19 mS cm⁻¹ and a transference number of 0.91 at room temperature, contributing to long−term cycling stability of symmetric sodium cells with a small overpotential. The assembled quasi-solid-state cell with the as−prepared UTSPL-35SBACE membrane displays superior cycling performance with a discharge capacity of 105 mAh g⁻¹ at 0.5 °C rate after 100 cycles and excellent rate performance (82 mAh g⁻¹ at 5 °C rate) at room temperature with the potassium manganese hexacyanoferrate (KMHCF)@CNTs/CNFs cathode, where KMHCF refers to potassium manganese hexacyanoferrate.     

Cell Development Enhanced Bionic Silk Hydrogel on Remodeling Immune Pathogenesis of Spinal Cord Injury via M2 Polarization of Microglial

Due to the complex spatial-temporal pathophysiology of spinal cord injury (SCI), effective modulation of SCI-specific inflammatory pathogenesis to achieve desirable therapeutic effects on functional recovery still remains challenging. Herein, cell-enhanced photocrosslinked silk fibroin hydrogels with extracellular matrix-mimicking cues of mechanical properties and RGD (Arg-Gly-Asp) signals are gelled in situ to fill the lesion site to modulate injury-induced neuroinflammation and promote neurite regrowth after SCI. The bionic hydrogel system provides biomimetic mechanical cues to promote neuronal differentiation of neural stem/progenitor cells (NPCs) and neurite growth by activating YAP nuclear expression. Importantly, favored by the strong capacity of silk fibroin hydrogels on macrophage/microglia recruitment, NPCs encapsulated hydrogel (NPCs@SFRGD0.1) effectively promotes recruited macrophages/microglia to M2 polarization in the lesion site by releasing S100A4 and thereby remodels the inflammatory microenvironment after SCI. Moreover, NPCs@SFRGD0.1 successfully reduces glial scar formation and accelerates corticospinal tract axon regrowth to improve locomotor recovery. Overall, this work contributes to illustrating the therapeutic mechanism of NPCs development based biomaterial therapies on modulating inflammatory microenvironment and this NPCs enhanced silk fibroin hydrogel provides a promising therapeutic strategy for SCI.     

A Stable Polymer-based Solid-State Lithium Metal Battery and its Interfacial Characteristics Revealed by Cryogenic Transmission Electron Microscopy

Solid-state lithium metal batteries (SSLMBs) are a promising candidate for next-generation energy storage systems due to their intrinsic safety and high energy density. However, they still suffer from poor interfacial stability, which can incur high interfacial resistance and insufficient cycle lifespan. Herein, a novel poly(vinylidene fluoride‑hexafuoropropylene)-based polymer electrolyte (PPE) with LiBF₄ and propylene carbonate plasticizer is developed, which has a high room-temperature ionic conductivity up to 1.15 × 10⁻³ S cm⁻¹ and excellent interfacial stability. Benefitting from the stable interphase, the PPE-based symmetric cell can operate for over 1000 h. By virtue of cryogenic transmission electron microscopy (Cryo-TEM) characterization, the high interfacial compatibility between Li metal anode and PPE is revealed. The solid electrolyte interphase is made up of an amorphous outer layer that can keep intimate contact with PPE and an inner Li₂O-dominated layer that can protect Li from continuous side reactions during battery cycling. A LiF-rich transition layer is also discovered in the region of PPE close to Li metal anode. The feasibility of investigating interphases in polymer-based solid-state batteries via Cryo-TEM techniques is demonstrated, which can be widely employed in future to rationalize the correlation between solid-state electrolytes and battery performance from ultrafine interfacial structures.