Exploiting Co Defects in CoFe-Layered Double Hydroxide (CoFe-LDH) Derivatives for Highly Efficient Photothermal Cancer Therapy

Comparative study of cerium-manganese ratios in the design of Ce-Mn-binuclear LDH-based Cu complex: a potent nanocatalyst for the green synthesis of spiro[acridine-9,3'-indole]triones

The Ce-Mn binuclear LDH was prepared at four different molar ratios of Ce to Mn (1:1, 1:2, 1:3, and 1:4), modified with both 3-chloropropyltrimethoxysilane (CPTMS) and N-amino-phthalimide (NAP), complexed with Cu(II), and characterized by the FT-IR, ICP, XPS, XRD, BET, UV/Vis, EDX, SEM, SEM-mapping, TEM, and TGA-DTA techniques. The ICP, XPS, BET, and UV-vis techniques showed that the 1:4 molar ratio of Ce to Mn is the best, therefore it was used as a heterogeneous nanocatalyst for the green synthesis of fourteen spiro[acridine-indole]triones from the three-component condensation reaction of isatin, aniline, and 1,3-diketone in mild reaction conditions. The advantages of this method include the absence of harmful organic solvents, easy separation of the catalyst and products, and rapid achievement of excellent yields. Furthermore, the activity of the catalyst was maintained even after four consecutive runs without a significant loss of activity.

Revealing the Synergistic Effect of Cation and Anion Vacancies on Enhanced Fenton-Like Reaction: The Electron Density Modulation of O 2p-Co 3d Bands

Defect engineering is considered as a flexible and effective mean to improve the performance of Fenton-like reactions. Herein, a simple method is employed to synthesize Co3O4 catalysts with Co-O vacancy pairs (VP) for peroxymonosulfate (PMS) activation. Multi-scaled characterization, experimental, and simulation results jointly revealed that the cation vacancies-VCo contributed to enhanced conductivity and anion vacancies-VO provided a new active center for the 1O2 generation. Co3O4-VP can optimize the O 2p and Co 3d bands with the strong assistance of synergistic double vacancies to reduce the reaction energy barrier of the "PMS → Co(IV) = O → 1O2" pathway, ultimately triggering the stable transition of mechanism. Co3O4-VP catalysts with radical-nonradical collaborative mechanism achieve the synchronous improvement of activity and stability, and have good environmental robustness to favor water decontamination applications. This result highlights the possibility of utilizing anion and cation vacancy engineering strategies to rational design Co3O4-based materials widely used in catalytic reactions.

Gelatin-Based Hydrogel Functionalized with Dopamine and Layered Double Hydroxide for Wound Healing

Hydrogels with adhesion properties and a wetted structure are promising alternatives to traditional wound dressing materials. The insufficiency of gelatin hydrogels in terms of their adhesive and mechanical strength limits their application in wound dressings. This work presents the design and preparation of a gelatin-based hydrogel functionalized with dopamine (DA) and layered double hydroxide (LDH). The combination of DA and LDH improves the hydrogel's adhesion properties in terms of interfacial adhesion and inner cohesion. Hydrogels with 8% DA and 4% LDH attained the highest adhesion strength of 266.5 kPa, which increased to 295.5 and 343.3 kPa after hydrophobically modifying the gelatin with octanoyl and decanoyl aldehydes, respectively. The gelatin-based hydrogels also demonstrated a macroporous structure, excellent biocompatibility, and a good anti-inflammatory effect. The developed hydrogels accelerated wound healing in Sprague Dawley rat skin full-thickness wound models.

Layered Double Hydroxides: Recent Progress and Promising Perspectives Toward Biomedical Applications

Layered double hydroxides (LDHs) have been widely studied for biomedical applications due to their excellent properties, such as good biocompatibility, degradability, interlayer ion exchangeability, high loading capacity, pH-responsive release, and large specific surface area. Furthermore, the flexibility in the structural composition and ease of surface modification of LDHs makes it possible to develop specifically functionalized LDHs to meet the needs of different applications. In this review, the recent advances of LDHs for biomedical applications, which include LDH-based drug delivery systems, LDHs for cancer diagnosis and therapy, tissue engineering, coatings, functional membranes, and biosensors, are comprehensively discussed. From these various biomedical research fields, it can be seen that there is great potential and possibility for the use of LDHs in biomedical applications. However, at the same time, it must be recognized that the actual clinical translation of LDHs is still very limited. Therefore, the current limitations of related research on LDHs are discussed by combining limited examples of actual clinical translation with requirements for clinical translation of biomaterials. Finally, an outlook on future research related to LDHs is provided.

Advances of Layered Double Hydroxide-Based Materials for Tumor Imaging and Therapy

Layered double hydroxides (LDH) are a class of functional anionic clays that typically consist of orthorhombic arrays of metal hydroxides with anions sandwiched between the layers. Due to their unique properties, including high chemical stability, good biocompatibility, controlled drug loading, and enhanced drug bioavailability, LDHs have many potential applications in the medical field. Especially in the fields of bioimaging and tumor therapy. This paper reviews the research progress of LDHs and their nanocomposites in the field of tumor imaging and therapy. First, the structure and advantages of LDH are discussed. Then, several commonly used methods for the preparation of LDH are presented, including co-precipitation, hydrothermal and ion exchange methods. Subsequently, recent advances in layered hydroxides and their nanocomposites for cancer imaging and therapy are highlighted. Finally, based on current research, we summaries the prospects and challenges of layered hydroxides and nanocomposites for cancer diagnosis and therapy.

Construction of an Injectable Composite Double-Network Hydrogel as a Liquid Embolic Agent

Conventional embolists disreputably tend to recanalization arising from the low filling ratio due to their rigidity or instability. As a result, intelligent hydrogels with a tunable modulus may meaningfully improve the therapeutic efficacy. Herein, an injectable composite double-network (CDN) hydrogel with high shear responsibility was prepared as a liquid embolic agent by cross-linking poly(vinyl alcohol) (PVA) and carboxymethyl chitosan (CMC) via dynamic covalent bonding of borate ester and benzoic-imine. A two-dimensional nanosheet, i.e., layered double hydroxide (LDH), was incorporated into the network through physical interactions which led to serious reduction of yield stress for the injection of the hydrogel and the capacity for loading therapeutic agents like indocyanine green (ICG) and doxorubicin (DOX) for the functions of photothermal therapy (PTT) and chemotherapy. The CDN hydrogel could thus be transported through a thin catheter and further in situ strengthened under physiological conditions, like in blood, by secondarily cross-linking with phosphate ions for longer degradation duration and better mechanical property. These characteristics met the requirements of arterial interventional embolization, which was demonstrated by renal embolism operation on rabbits, and meanwhile favored the inhibition of subcutaneous tumor growth on an animal model. Therefore, this work makes a breakthrough in the case of largely reducing the embolism risks, thus affording a novel generation for interventional embolization.

Electron-rich palladium regulated by cationic vacancies in CoFe layered double hydroxide boosts electrocatalytic hydrodechlorination

Palladium (Pd) is regarded as a promising electrocatalytic hydrodechlorination (EHDC) catalyst for the detoxification of halogenated phenols. Nevertheless, its intrinsic EHDC activity is seriously restricted by the hydrogen evolution reaction (HER), consuming the active hydrogen (H*) for EHDC. Here, we report a defect regulation strategy using cationic vacancies rich CoFeV-LDH with coupling ultrafine Pd nanoparticles that induces optimized electron distribution of Pd to promote EHDC. The experimental and theoretical results reveal that superior EHDC performance of Pd@CoFeV-LDH is attributed to the electron-rich Pd regulated by cationic vacancies in CoFeV-LDH support, driving facile adsorption of halogenated phenols, high water activation ability and H* selectivity for EHDC. Our findings provide a versatile defect-regulating strategy to overcome the challenge in efficiency and selectivity of EHDC process.

CuFe Layered Double Hydroxide as Self-Cascade Nanoreactor for Efficient Antibacterial Therapy

Nanozyme-induced reactive oxygen species (ROS)-dependent catalytic therapy has been developed into a powerful strategy against bacterial wound infections. However, the limited endogenous supply or instability of H2O2, the reliance on external stimuli for the generation of ROS, and the highly expressed glutathione (GSH) level make it a challenge to achieve high-performance therapeutic efficiency. In this work, a facile therapeutic strategy against bacterial infections with pristine CuFe layered double hydroxide (LDH) as the self-cascade nanoreactor is proposed without modification or additional energy input. CuFe LDH with an oxidase-like feature can catalyze the generation of multiple ROS, such as 1O2, ·O2-, and H2O2. And the self-generated H2O2 in the cascade nanoreactor could be further in situ transformed to ·OH owing to the peroxidase-like activity. As a result, the cell membrane of bacteria is destroyed, leading to death. Furthermore, its ultrahigh enzyme-like activity of CuFe LDH could effectively promote the breakdown of the biofilm structure. Additionally, the Cu2+-mediated GSH exhaustion of CuFe LDH further avoids the consumption of oxidized ROS and thereby significantly improves the sterilization effect. Finally, the as-prepared CuFe LDH with negligible side effects on normal tissues can be successfully used to eliminate the methicillin-resistant Staphylococcus aureus-infected wounds and accelerate their healing in the mouse model, which paves a new avenue as an antibacterial agent for clinical anti-infective treatment.

Sulfur-Doped NiFe Hydroxide Nanobowls with Wrinkling Patterns for Photothermal Cancer Therapy

Hierarchical multiscale wrinkling nanostructures have shown great promise for many biomedical applications, such as cancer diagnosis and therapy. However, synthesizing these materials with precise control remains challenging. Here, we report a sulfur doping strategy to synthesize sub-1 nm NiFe hydroxide ultrathin nanosheets (S-NiFe HUNs). The introduction of sulfur affects the reduction of the band gap and the adjustment of the electronic structure, thereby improving the light absorption ability of the S-NiFe HUNs. Additionally, S-NiFe HUNs show a multilayered nanobowl-like structure that enables multiple reflections of incident light inside the nanostructure, which improved the utilization of incident light and achieved high photothermal conversion. As a result, the as-prepared product with hydrophilic modification (dS-NiFe HUNs) demonstrated enhanced tumor-killing ability in vitro. In a mouse model of breast cancer, dS-NiFe HUNs combined with near-infrared light irradiation greatly inhibited tumor growth and prolonged the mice survival. Altogether, our study demonstrates the great potential of dS-NiFe HUNs for cancer photothermal therapy applications.

Advances in the two-dimensional layer materials for cancer diagnosis and treatment: unique advantages beyond the microsphere

In recent years, two-dimensional (2D) layer materials have shown great potential in the field of cancer diagnosis and treatment due to their unique structural, electronic, and chemical properties. These non-spherical materials have attracted increasing attention around the world because of its widely used biological characteristics. The application of 2D layer materials like lamellar graphene, transition metal dichalcogenides (TMDs), and black phosphorus (BPs) and so on have been developed for CT/MRI imaging, serum biosensing, drug targeting delivery, photothermal therapy, and photodynamic therapy. These unique applications for tumor are due to the multi-variable synthesis of 2D materials and the structural characteristics of good ductility different from microsphere. Based on the above considerations, the application of 2D materials in cancer is mainly carried out in the following three aspects: 1) In terms of accurate and rapid screening of tumor patients, we will focus on the enrichment of serum markers and sensitive signal transformation of 2D materials; 2) The progress of 2D nanomaterials in tumor MRI and CT imaging was described by comparing the performance of traditional contrast agents; 3) In the most important aspect, we will focus on the progress of 2D materials in the field of precision drug delivery and collaborative therapy, such as photothermal ablation, sonodynamic therapy, chemokinetic therapy, etc. In summary, this review provides a comprehensive overview of the advances in the application of 2D layer materials for tumor diagnosis and treatment, and emphasizes the performance difference between 2D materials and other types of nanoparticles (mainly spherical). With further research and development, these multifunctional layer materials hold great promise in the prospects, and challenges of 2D materials development are discussed.

Integration of CoAl-Layered Double Hydroxides on Commensal Bacteria to Enable Targeted Tumor Inhibition and Immunotherapy

Combining targeted therapy and immunotherapy brings hope for a complete cancer cure. Due to their selective colonization and immune activation capacity, some bacteria have the potential to realize targeted immunotherapy. Herein, a biohybrid system was designed and synthesized by cladding NO3--intercalated cobalt aluminum layered double hydroxides (LDH) on anaerobic Propionibacterium acnes (PA) (PA@LDH). In this system, the covering of LDH reduces the pathogenicity of PA to normal tissues and alters its surface charge for prolonged in vivo circulation. Once the tumor site is reached, the acid-responsive degradation of LDH enables PA exposure. PA can colonize and convert nitrate ions to nitric oxide (NO) through denitrification. Then, NO reacts with intracellular O2·- to produce toxic reactive nitrogen species ONOO- and induce tumor cell apoptosis. In addition, cobalt ions released from LDH can inhibit the activity of superoxide dismutase (SOD), thus increasing the level of O2·- and further enhancing the antitumor effect. Moreover, PA exposure activates M2-to-M1 macrophage polarization and a range of immune responses, thereby achieving a sustained antitumor activity. In vitro and in vivo results reveal that the biohybrid system eliminates solid tumors and inhibits tumor metastasis effectively. Overall, the biohybrid strategy provides a new avenue for realizing simultaneous immunotherapy and targeted therapy.

CoFe-Layered Double Hydroxide Coupled with Pd Particles for Electrocatalytic Ethanol Oxidation

Electrocatalytic efficiency and stability have emerged as critical issues in the ethanol oxidation reaction (EOR) of direct ethanol fuel cells. In this paper, Pd/Co₁Fe₃-LDH/NF as an electrocatalyst for EOR was prepared by a two-step synthetic strategy. Metal-oxygen bonds formed between Pd nanoparticles and Co₁Fe₃-LDH/NF guaranteed structural stability and adequate surface-active site exposure. More importantly, the charge transfer of the formed Pd-O-Co(Fe) bridge could effectively modulate the electrical structure of hybrids, improving the facilitated absorption of OH^- radicals and oxidation of CO_ads. Benefiting from the interfacial interaction, exposed active sites, and structural stability, the observed specific activity for Pd/Co₁Fe₃-LDH/NF (17.46 mA cm^-2) was 97 and 73 times higher than those of commercial Pd/C (20%) (0.18 mA cm^-2) and Pt/C (20%) (0.24 mA cm^-2), respectively. Besides, the j_f/j_r ratio representing the resistance to catalyst poisoning was 1.92 in the Pd/Co₁Fe₃-LDH/NF catalytic system. These results provide insights into optimizing the electronic interaction between metals and the support of electrocatalysts for EOR.

Promoting the electrocatalytic oxygen evolution reaction on NiCo2O4 with infrared-thermal effect: A strategy to utilize the infrared solar energy to reduce activation energy during water splitting

Utilization of the infrared (IR) solar energy remains a challenging task for traditional photo(electro)catalysis. Taking advantage of the IR-thermal effect to facilitate sluggish electrocatalytic reactions emerges as a promising way to utilize the IR band of the solar spectrum. In this work, nickel foam (NF) supported NiCo₂O₄ nanoneedles (NF/NiCo₂O₄ NNs) were prepared to promote the oxygen evolution reaction (OER) via the IR-thermal effect, with the NF/NiCo₂O₄ NNs acting as both the IR absorbing antennae and the OER active anode. The potential required to deliver a current density of 200 mA cm^-2 is negatively shifted from 1.618 V in the dark to 1.578 V under IR irradiation, and the Tafel slope is also decreased from 106 to 89 mV dec^-1. We demonstrate that the enhancement of OER activity is due to the localized temperature rise under IR irradiation. We measured the electrochemical activation energy of OER on NF/NiCo₂O₄ with and without IR irradiation, and the results reveal that IR irradiation reduces the kinetic energy barrier of the OER by IR-thermal effect and then facilitates OER kinetics. This work highlights a new approach to utilizing the IR portion of the sunlight to produce renewable hydrogen energy via water splitting.

Starvation-assisted and photothermal-thriving combined chemo/chemodynamic cancer therapy with PT/MR bimodal imaging

Chemodynamic therapy (CDT) reflects a novel reactive oxygen species (ROS)-related cancer therapeutic approach. However, CDT monotherapy is often limited by weak efficacy and insufficient endogenous H₂O₂. Herein, a multifunctional combined bioreactor (MnFe-LDH/MTX@GOx@Ta, MMGT) relying on MnFe-layered double hydroxide (MnFe-LDH) loaded with methotrexate (MTX) and coated with glucose oxidase (GOx)/tannin acid (Ta) is established for applications in H₂O₂ self-supply and photothermal enhanced chemo/chemodynamic combined therapy along with photothermal (PT) /magnetic resonance (MR) dual-modality imaging ability for cancer treatment. Once internalized into tumor cells, MMGT achieves starvation therapy by catalyzing the oxidation of glucose with GOx, accompanied by the regeneration of H₂O₂, enabling a Fenton-like reaction to accomplish GOx catalytic amplified CDT. Moreover, MMGT manifests significant tumor-killing ability through improved CDT performance with outstanding photothermal conversion efficiency (η = 52.2%) under 808 nm laser irradiation. In addition, the release of Mn²⁺ from MnFe-LDH in a solid tumor can significantly enhance T₁-contrast MR imaging signals. Combined with MnFe-LDH-induced PT imaging under 808 nm laser irradiation, a dual-modality imaging directed theranostic nanoplatform has been developed. The present study provides a new strategy to design H₂O₂ self-supply and ROS evolving NIR light-absorption theranostic nanoagent for highly efficient and combined chemo/chemodynamic cancer treatment.

Unveiling the Mechanism of Alleviating Ischemia Reperfusion Injury via a Layered Double Hydroxide-Based Nanozyme

Oxidative stress after ischemia reperfusion can cause irreversible brain damage. Thus, it is vital to timely consume excessive reactive oxygen species (ROS) and conduct molecular imaging monitoring on the brain injury site. However, previous studies have focused on how to scavenge ROS while ignoring the mechanism of relieving the reperfusion injury. Herein, we reported a layered double hydroxide (LDH)-based nanozyme (denoted as ALDzyme), which was fabricated by the confinement of astaxanthin (AST) with LDH. This ALDzyme can mimic natural enzymes, which include superoxide dismutase (SOD) and catalase (CAT). Furthermore, the SOD-like activity of ALDzyme is 16.3 times higher than that of CeO₂ (a typical ROS scavenger). Based on these enzyme-mimicking properties, this one-of-a-kind ALDzyme offers strong anti-oxidative properties as well as high biocompatibility. Importantly, this unique ALDzyme can establish an efficient magnetic resonance imaging platform, thus guiding the in vivo details. As a result, the infarct area can be reduced by 77% after reperfusion therapy, and the neurological impairment score can be lowered from 3-4 to 0-1. Density functional theory computations can reveal more about the mechanism of this ALDzyme's significant ROS consumption. These findings provide a method for unraveling the neuroprotection application process in ischemia reperfusion injury using an LDH-based nanozyme as a remedial nanoplatform.

State-of-the-art advancement of surface functionalized layered double hydroxides for cell-specific targeting of therapeutics

Over the years, layered double hydroxides (LDHs) hold a specific position in biomedicine due to their tunable chemical composition and appropriate structural properties. However, LDHs lack adequate sensitivity for active targeting because of less active surface area and low mechanical strength in physiological conditions. The exploitation of eco-friendly materials, such as chitosan (CS), for surface engineering of LDHs, whose payloads are transferred only under certain conditions, can help develop stimuli-responsive materials owing to high biosafety and unique mechanical strength. We aim to render a well-oriented scenario toward the latest achievements of a bottom-up technology relying on the surface functionalization of LDHs to fabricate functional formulations with promoted bio-functionality and high encapsulation efficiency for various bioactives. Many efforts have been devoted to critical aspects of LDHs, including systemic biosafety and the suitability for developing multicomponent systems via integration with therapeutic modalities, which are thoroughly discussed herein. In addition, a comprehensive discussion was provided for the recent progress in the emergence of CS-coated LDHs. Finally, the challenges and future perspectives in the fabrication of efficient CS-LDHs in biomedicine are considered, with a special focus on cancer treatment.

Eutectic solvent mediated synthesis of carbonated CoFe-LDH nanorods: The effect of interlayer anion (Cl-, SO42-, CO32-) variants for comparing the bifunctional electrochemical sensing application

The unabated usage of priority anthropogenic stressors is a serious concern in the global environmental context. Pharmaceutical drugs such as furazolidone (FL) and nilutamide (NL) have far-reaching repercussions due to the presence of the reactive nitroaromatic moiety. Despite the widespread awareness regarding the dangers posed by nitroaromatic drugs, the promises to alleviate the environmental consequences of drug pollution are often unmet. Accordingly, implementing practices to monitor their presence in various media is a highly desirable, but challenging undertaking. With the advent of deep eutectic solvent-assisted synthesis, it has become possible to fabricate LDH-based sensor materials with minimal energy inputs in a sustainable and scalable manner. In this work, we have framed a series of CoFe-LDH electrocatalysts utilizing deep eutectic solvent-assisted hydrothermal strategies for the simultaneous detection of FL and NL. The CoFe-LDHs intercalated with three distinct anions, namely, (i) Cl^-, (ii) SO₄^2-, and (iii) CO₃^2- are compared so as to establish a relationship between anion intercalation and electrochemical activity. Amongst the prepared electrodes, the CF-LDH-ii/SPCE displays highly appreciable selectivity, linear response range (0.09-237.9 μM), low detetion limits (FL = 1.2 nM and NL = 3.8 nM), high sensitivity (FL = 29.71 μA μM⁻¹ cm⁻² and NL = 19.29 μA μM⁻¹ cm⁻²), good reproducibility and repeatability towards FL and NL in water and urine samples. Thus, with tailored gallery anions, the proposed electrocatalyst establishes enhanced electrocatalytic performance for the real-time analysis of pharmaceutical contaminants.

The adjacent effect between Gd(III) and Cu(II) in layered double hydroxide nanoparticles synergistically enhances T1-weighted magnetic resonance imaging contrast

Magnetic resonance imaging (MRI) is one key technology in modern diagnostic medicine. However, the development of high-relaxivity contrast agents with favorable properties for imaging applications remains a challenging task. In this work, dual Gd(III) and Cu(II) doped-layered double hydroxide (GdCu-LDH) nanoparticles show significantly higher longitudinal relaxivity compared with sole-metal-based LDH (Gd-LDH and Cu-LDH) nanoparticles. This relaxation enhancement in GdCu-LDH is also much greater than the simple addition of the relaxivity rate of the two paramagnetic ions in Gd-LDH and Cu-LDH, presumably attributed to synergistic T₁ shortening between adjacent Gd(III) and Cu(II) in the LDH host layers (adjacent effect). Moreover, our GdCu-LDH nanoparticles exhibit a pH-ultrasensitive property in MRI performance and show much clearer MR imaging for tumor tissues in mice than Gd-LDH and Cu-LDH at the equivalent doses. Thus, these novel Gd/Cu-co-doped LDH nanoparticles provide higher potential for accurate cancer diagnosis in clinic application. To the best of our knowledge, this is the first report that two paramagnetic metal ions in one nanoparticle synergistically improve the T₁-MRI contrast.

Vacancy defect-promoted nanomaterials for efficient phototherapy and phototherapy-based multimodal Synergistic Therapy

Phototherapy and multimodal synergistic phototherapy (including synergistic photothermal and photodynamic therapy as well as combined phototherapy and other therapies) are promising to achieve accurate diagnosis and efficient treatment for tumor, providing a novel opportunity to overcome cancer. Notably, various nanomaterials have made significant contributions to phototherapy through both improving therapeutic efficiency and reducing side effects. The most key factor affecting the performance of phototherapeutic nanomaterials is their microstructure which in principle determines their physicochemical properties and the resulting phototherapeutic efficiency. Vacancy defects ubiquitously existing in phototherapeutic nanomaterials have a great influence on their microstructure, and constructing and regulating vacancy defect in phototherapeutic nanomaterials is an essential and effective strategy for modulating their microstructure and improving their phototherapeutic efficacy. Thus, this inspires growing research interest in vacancy engineering strategies and vacancy-engineered nanomaterials for phototherapy. In this review, we summarize the understanding, construction, and application of vacancy defects in phototherapeutic nanomaterials. Starting from the perspective of defect chemistry and engineering, we also review the types, structural features, and properties of vacancy defects in phototherapeutic nanomaterials. Finally, we focus on the representative vacancy defective nanomaterials recently developed through vacancy engineering for phototherapy, and discuss the significant influence and role of vacancy defects on phototherapy and multimodal synergistic phototherapy. Therefore, we sincerely hope that this review can provide a profound understanding and inspiration for the design of advanced phototherapeutic nanomaterials, and significantly promote the development of the efficient therapies against tumor.

Layered double hydroxide-based nanomaterials for biomedical applications

Against the backdrop of increased public health awareness, inorganic nanomaterials have been widely explored as promising nanoagents for various kinds of biomedical applications. Layered double hydroxides (LDHs), with versatile physicochemical advantages including excellent biocompatibility, pH-sensitive biodegradability, highly tunable chemical composition and structure, and ease of composite formation with other materials, have shown great promise in biomedical applications. In this review, we comprehensively summarize the recent advances in LDH-based nanomaterials for biomedical applications. Firstly, the material categories and advantages of LDH-based nanomaterials are discussed. The preparation and surface modification of LDH-based nanomaterials, including pristine LDHs, LDH-based nanocomposites and LDH-derived nanomaterials, are then described. Thereafter, we systematically describe the great potential of LDHs in biomedical applications including drug/gene delivery, bioimaging diagnosis, cancer therapy, biosensing, tissue engineering, and anti-bacteria. Finally, on the basis of the current state of the art, we conclude with insights on the remaining challenges and future prospects in this rapidly emerging field.

Ultrathin Nanosheet-Supported Ag@Ag2O Core-Shell Nanoparticles with Vastly Enhanced Photothermal Conversion Efficiency for NIR-II-Triggered Photothermal Therapy

Photothermal therapy (PTT) working in the second near-infrared (NIR-II) region has aroused a huge interest due to its potential application in terms of clinical cancer treatment. However, owing to the lack of photothermal nanoagents with high photothermal conversion efficiency, NIR-II-driven PTT still suffers from poor efficiency and subsequent cancer recurrence. In this work, we show a new and highly efficient preparation approach for NIR-II photothermal nanoagents and tailor ultrathin layered double hydroxide (LDH)-supported Ag@Ag₂O core-shell nanoparticles (Ag@Ag₂O/LDHs-U), vastly improving NIR-II photothermal performance. A combination study (high-resolution transmission electron microscopy (HRTEM), extended X-ray absorption fine structure spectroscopy (EXAFS), and X-ray photoelectron spectroscopy (XPS)) verifies that ultrafine Ag@Ag₂O core-shell nanoparticles (∼3.8 nm) are highly dispersed and firmly immobilized within ultrathin LDH nanosheets, and their Ag₂O shell possesses abundant vacancy-type defects. These unique Ag@Ag₂O/LDHs-U display an impressive photothermal conversion efficiency as high as 76.9% at 1064 nm. Such an excellent photothermal performance is likely attributed to the enhanced localized surface plasmon resonance (LSPR) coupling effect between Ag and Ag₂O and the reduced band gap caused by vacancy-type defects in the Ag₂O shell. Meanwhile, Ag@Ag₂O/LDHs-U also show prominent photothermal stability, due to the unique supported core-shell nanostructure. Moreover, both in vitro and in vivo studies further confirm that Ag@Ag₂O/LDHs-U possess good biocompatible properties and outstanding PTT therapeutic efficacy in the NIR-II region. This research shows a new strategy in the rational design and preparation of an efficient photothermal agent, which is helpful to achieve more accurate and effective cancer theranostics.

Migration inhibition and selective cytotoxicity of cobalt hydroxide nanosheets on different cancer cell lines

5 nm-thick cobalt hydroxide nanosheets exhibited concentration-dependent selective antitumor activity and cell migration inhibition against a variety of cancer cells.

Dynamic nano-assemblies based on two-dimensional inorganic nanoparticles: Construction and preclinical demonstration

Dynamic drug delivery systems (DDSs) have the ability of transforming their morphology and functionality in response to the biological microenvironments at the disease site and/or external stimuli, show spatio-temporally controllable drug delivery, and enhance the treatment efficacy. Due to the large surface area and modification flexibility, two-dimensional (2D) inorganic nanomaterials are being increasingly exploited for developing intelligent DDSs for biomedical applications. In this review, we summarize the engineering methodologies used to construct transformable 2D DDSs, including changing compositions, creating defects, and surface dot-coating with polymers, biomolecules, or nanodots. Then we present and discuss dynamic inorganic 2D DDSs whose transformation is driven by the diseased characteristics, such as pH gradient, redox, hypoxia, and enzyme in the tumor microenvironment as well as the external stimuli including light, magnetism, and ultrasound. Finally, the limitations and challenges of current transformable inorganic DDSs for clinical translation and their in vivo safety assessment are discussed.

Electrodeposition of Defect-Rich Ternary NiCoFe Layered Double Hydroxides: Fine Modulation of Co3+ for Highly Efficient Oxygen Evolution Reaction

The low-cost, high-abundance and durable layered double hydroxides (LDHs) have been considered as promising electrocatalysts for oxygen evolution reaction (OER). However, the easy agglomeration of lamellar LDHs in the aqueous phase limits their practical applications. Herein, a series of ternary NiCoFe LDHs were successfully fabricated on nickel foam (NF) via a simple electrodeposition method. The as-prepared Ni(Co_0.5 Fe_0.5 )/NF displayed an unique nanoarray structural feature. It showed an OER overpotential of 209 mV at a current density of 10 mA cm^-2 in alkaline solution, which was superior to most systems reported so far. As evidenced by the XPS and XAFS results, such excellent performance of Ni(Co_0.5 Fe_0.5 )/NF was attributed to the higher Co³⁺ /Co²⁺ ratio and more defects exposed, comparing with Ni(Co_0.5 Fe_0.5 )-bulk and Ni(Co_0.5 Fe_0.5 )-mono LDHs prepared by conventional coprecipitation method. Furthermore, the ratio of Co to Fe could significantly tune the Co electronic structure of Ni(Co_x Fe_1-x )/NF composites (x=0.25, 0.50 and 0.75) and affect the electrocatalytic activity for OER, in which Ni(Co_0.5 Fe_0.5 )/NF showed the lowest energy barrier for OER rate-determining step (from O* to OOH*). This work proposes a facile method to develop high-efficiency OER electrocatalysts.

Bi-Functional Fe3 O4 /Au/CoFe-LDH Sandwich-Structured Electrocatalyst for Asymmetrical Electrolyzer with Low Operation Voltage

The reduction of the overall electrolysis potential to produce hydrogen is a critical target for fabricating applicable hydrogen evolution cells. Sandwich-structured Fe₃ O₄ /Au/CoFe-LDH is synthesized via a spontaneous galvanic displacement reaction. A series of structural characterizations indicate the successful synthesis of sandwich-structured Fe₃ O₄ /Au/CoFe-LDH electrocatalyst. The trace amount of Au laying between Fe₃ O₄ and CoFe-LDH significantly improves the intrinsic conductivity and catalytic activity of the composite catalyst. In-depth investigations indicate that Fe₃ O₄ and CoFe-LDH are responsible for the electrocatalytic hydrogen evolution reaction (HER) whereas Au is responsible for the electrocatalytic glucose oxidation (GOR). The electrocatalytic tests indicate Fe₃ O₄ /Au/CoFe-LDH offers excellent electrocatalytic activity and stability for both HER and GOR, even at high current density (i.e., 1000 mA cm^-2 ). Further electrochemistry examinations in a two-compartment cell with a two-electrode configuration show that Fe₃ O₄ /Au/CoFe-LDH can significantly reduce the overall potential for this asymmetrical cell, with only 0.48 and 0.89 V required to achieve 10 mA cm^-2 current density with and without iR-compensation, which is the lowest overall potential requirement ever reported. The design and synthesis of Fe₃ O₄ /Au/CoFe-LDH pave a new way to electrochemically produce hydrogen and gluconate under extremely low cell voltage, which can readily match with a variety of solar cells.

Near-infrared inorganic nanomaterial-based nanosystems for photothermal therapy

The development of robust materials for treating diseases through non-invasive photothermal therapy (PTT) has attracted increasing attention in recent years. Among various types of nanomaterials, inorganic nanomaterials with strong absorption in the near-infrared (NIR) window can be employed as high-efficiency photothermal agents to treat cancer and bacterial infections. In addition, inorganic nanomaterials can be easily combined with other drugs or chemical reagents to construct multifunctional nanomaterials to cascade stimulation responses, enhance therapeutic effects, and perform precise medical treatments. In this review, focusing on the latest developments of inorganic nanomaterials in photothermal therapy, we firstly introduced the light-to-heat conversion mechanism of inorganic nanomaterials. Secondly, we summarized the application of common inorganic nanomaterials, such as metallic nanoparticles, transition metal oxide nanoparticles and two dimensional (2D) nanosheets. In addition, the strategy of developing multifunctional nano-platforms with excellent biocompatibility as well as good targeted capability was also expounded. Finally, challenges and new perspectives for designing effective inorganic nanomaterial-based nanosystems for photothermal assisted therapy were also discussed.

Tailoring the synergistic dual-decoration of (Cu–Co) transition metal auxiliaries in Fe-oxide/zeolite composite catalyst for the direct conversion of syngas to aromatics

Tailoring the crystal lattice and multiple phase interfaces via the feasible accommodation of Cu–Co into the host (Fe) structure, expedited the surface oxygen vacancies that modulated the reduction/chemisorption behavior of active Fe species.