Assembly-Induced Thermogenesis of Gold Nanoparticles in the Presence of Alternating Magnetic Field for Controllable Drug Release of Hydrogel

A wearable non-enzymatic sensor for continuous monitoring of glucose in human sweat

To enhance personalized diabetes management, there is a critical need for non-invasive wearable electrochemical sensors made from flexible materials to enable continuous monitoring of sweat glucose levels. The main challenge lies in developing glucose sensors with superior electrochemical characteristics and high adaptability. Herein, we present a wearable sensor for non-enzymatic electrochemical glucose analysis. The sensor was synthesized using hydrothermal and one-pot preparation methods, incorporating gold nanoparticles (AuNPs) functionalized onto aminated multi-walled carbon nanotubes (AMWCNTs) as an efficient catalyst, and crosslinked with carboxylated styrene butadiene rubber (XSBR) and PEDOT:PSS. The sensors were then integrated onto screen-printed electrodes (SPEs) to create flexible glucose sensors (XSBR-PEDOT:PSS-AMWCNTs/AuNPs/SPE). Operating under neutral conditions, the sensor exhibits a linear range of 50 μmol/L to 600 μmol/L, with a limit of detection limit of 3.2 μmol/L (S/N = 3), enabling the detection of minute glucose concentrations. The flexible glucose sensor maintains functionality after 500 repetitions of bending at a 180° angle, without significant degradation in performance. Furthermore, the sensor exhibits exceptional stability, repeatability, and resistance to interference. Importantly, we successfully monitored changes in sweat glucose levels by applying screen-printed electrodes to human skin, with results consistent with normal physiological blood glucose fluctuations. This study details the fabrication of a wearable sensor characterized by ease of manufacture, remarkable flexibility, high sensitivity, and adaptability for non-invasive blood glucose monitoring through non-enzymatic electrochemical analysis. Thus, this streamlined fabrication process presents a novel approach for non-invasive, real-time blood glucose level monitoring.

Stimuli-responsive polymer-based nanosystems for cardiovascular disease theranostics

Stimulus-responsive polymers have found widespread use in biomedicine due to their ability to alter their own structure in response to various stimuli, including internal factors such as pH, reactive oxygen species (ROS), and enzymes, as well as external factors like light. In the context of atherosclerotic cardiovascular diseases (CVDs), stimulus-response polymers have been extensively employed for the preparation of smart nanocarriers that can deliver therapeutic and diagnostic drugs specifically to inflammatory lesions. Compared with traditional drug delivery systems, stimulus-responsive nanosystems offer higher sensitivity, greater versatility, wider applicability, and enhanced biosafety. Recent research has made significant contributions towards designing stimulus-responsive polymer nanosystems for CVDs diagnosis and treatment. This review summarizes recent advances in this field by classifying stimulus-responsive polymer nanocarriers according to different responsiveness types and describing numerous stimuli relevant to these materials. Additionally, we discuss various applications of stimulus-responsive polymer nanomaterials in CVDs theranostics. We hope that this review will provide valuable insights into optimizing the design of stimulus-response polymers for accelerating their clinical application in diagnosing and treating CVDs.

Thermosensitive gel-nano system against esophageal cancer via restoring p53 activity and boosting T-cell immunity

In esophageal cancer (EC), clinical specimen testing has uncovered a significant increase in BTB and CNC homolog 1 (BACH1) expression and a shift towards an immunosuppressive environment, alongside a notable decrease in p53 protein expression. Therefore, therapeutic strategies focusing on BACH1 inhibition and p53 upregulation appear promising. Traditional oral treatments for EC lack precision and efficacy. Here, we propose a novel approach employing tumor-targeted nanoparticles (NPs) for drug delivery. However, the formation of a drug reservoir at the esophageal site, crucial for the sustained release of therapeutics, presents significant challenges in nano-delivery systems for EC treatment. To address this, we developed a thermosensitive hydrogel composed of F127 and tannic acid, serving as a vehicle for NP loading. These NPs, synthesized through the emulsion/volatization methods of mPEG-PLGA-PLL-cRGD, facilitate in situ drug delivery. Upon contacting esophageal tissue, the hydrogel transitions to a gel, adhering to the lining and enabling sustained release of encapsulated therapeutics. The formulation encompasses NPs laden with small interfering RNA targeting BACH1 (siBACH1) and the p53 activator PRIMA-1, creating a cohesive gel-nano system. Preliminary biological assessments demonstrate that this injectable, thermosensitive gel-nano system adheres effectively to esophageal tissue and targets EC cells. For better modeling clinical outcomes, a patient-derived organoid xenograft (PDOX) model was innovated, involving transplantation of EC-derived organoids into humanized mice, reconstructed with peripheral blood mononuclear cells (PBMCs). Post-treatment analysis showed substantial EC growth inhibition (89.51% tumor inhibition rate), significant BACH1 level reduction, restored anti-tumor immune responses, and pronounced tumor apoptosis. In summary, our study introduces a thermosensitive gel-nano system for EC treatment via restoring p53 activity and boosting T-cell immunity, with potential for clinical application.

Modeling of Magnetic Scaffolds as Drug Delivery Platforms for Tissue Engineering and Cancer Therapy

Magnetic scaffolds (MagSs) are magneto-responsive devices obtained by the combination of traditional biomaterials (e.g., polymers, bioceramics, and bioglasses) and magnetic nanoparticles. This work analyzes the literature about MagSs used as drug delivery systems for tissue repair and cancer treatment. These devices can be used as innovative drugs and/or biomolecules delivery systems. Through the application of a static or dynamic stimulus, MagSs can trigger drug release in a controlled and remote way. However, most of MagSs used as drug delivery systems are not optimized and properly modeled, causing a local inhomogeneous distribution of the drug's concentration and burst release. Few physical-mathematical models have been presented to study and analyze different MagSs, with the lack of a systematic vision. In this work, we propose a modeling framework. We modeled the experimental data of drug release from different MagSs, under various magnetic field types, taken from the literature. The data were fitted to a modified Gompertz equation and to the Korsmeyer-Peppas model (KPM). The correlation coefficient (R2) and the root mean square error (RMSE) were the figures of merit used to evaluate the fitting quality. It has been found that the Gompertz model can fit most of the drug delivery cases, with an average RMSE below 0.01 and R2>0.9. This quantitative interpretation of existing experimental data can foster the design and use of MagSs for drug delivery applications.

Strong, tough and anisotropic bioinspired hydrogels

Soft materials are widely used in tissue engineering, soft robots, wearable electronics, etc. However, it remains a challenge to fabricate soft materials, such as hydrogels, with both high strength and toughness that are comparable to biological tissues. Inspired by the anisotropic structure of biological tissues, a novel solvent-exchange-assisted wet-stretching strategy is proposed to prepare anisotropic polyvinyl alcohol (PVA) hydrogels by tuning the macromolecular chain movement and optimizing the polymer network. The reinforcing and toughening mechanisms are found to be "macromolecule crystallization and nanofibril formation". These hydrogels exhibit excellent mechanical properties, such as extremely high fracture stress (12.8 ± 0.7 MPa) and fracture strain (1719 ± 77%), excellent modulus (4.51 ± 0.76 MPa), high work of fracture (134.47 ± 9.29 MJ m-3), and fracture toughness (305.04 kJ m-2) compared with other strong hydrogels and even natural tendons. In addition, excellent conductivity, strain sensing capability, water retention, freezing resistance, swelling resistance, and biocompatibility can also be achieved. This work provides a new and effective method to fabricate multifunctional anisotropic hydrogels with high tunable strength and toughness with potential applications in the fields of regenerative medicine, flexible sensors, and soft robotics.

One-Minute Preparation of Iron Foam-Drug Implant for Ultralow-Power Magnetic Hyperthermia-Based Combination Therapy of Tumors in Vivo

The magnetic hyperthermia-based combination therapy (MHCT) is a powerful tumor treatment approach due to its unlimited tissue penetration depth and synergistic therapeutic effect. However, strong magnetic hyperthermia and facile drug loading are incompatible with current MHCT platforms. Herein, an iron foam (IF)-drug implant is established in an ultra-facile and universal way for ultralow-power MHCT of tumors in vivo for the first time. The IF-drug implant is fabricated by simply immersing IF in a drug solution at an adjustable concentration for 1 min. Continuous metal structure of IF enables ultra-high efficient magnetic hyperthermia based on eddy current thermal effect, and its porous feature provides great space for loading various hydrophilic and hydrophobic drugs via "capillary action". In addition, the IF has the merits of low cost, customizable size and shape, and good biocompatibility and biodegradability, benefiting reproducible and large-scale preparation of IF-drug implants for biological application. As a proof of concept, IF-doxorubicin (IF-DOX) is used for combined tumor treatment in vivo and achieves excellent therapeutic efficacy at a magnetic field intensity an order of magnitude lower than the threshold for biosafety application. The proposed IF-drug implant provides a handy and universal method for the fabrication of MHCT platforms for ultralow-power combination therapy.

Immune homeostasis modulation by hydrogel-guided delivery systems: a tool for accelerated bone regeneration

Immune homeostasis is delicately mediated by the dynamic balance between effector immune cells and regulatory immune cells. Local deviations from immune homeostasis in the microenvironment of bone fractures, caused by an increased ratio of effector to regulatory cues, can lead to excessive inflammatory conditions and hinder bone regeneration. Therefore, achieving effective and localized immunomodulation of bone fractures is crucial for successful bone regeneration. Recent research has focused on developing localized and specific immunomodulatory strategies using local hydrogel-based delivery systems. In this review, we aim to emphasize the significant role of immune homeostasis in bone regeneration, explore local hydrogel-based delivery systems, discuss emerging trends in immunomodulation for enhancing bone regeneration, and address the limitations of current delivery strategies along with the challenges of clinical translation.

Liquid metal microspheres with an eddy-thermal effect for magnetic hyperthermia-enhanced cancer embolization-immunotherapy

Patients with hepatocellular carcinoma (HCC) display poor prognosis because HCC involves a high rate of metastasis and regrowth. Herein, we present an effective strategy to treat HCC using magnetic hyperthermia therapy (MHT)-enhanced cancer immunotherapy combined with transcatheter arterial embolization (TAE). Uniform liquid metal microspheres (LM MSs) obtained by microfluidic technology with powerful eddy-thermal effects could be used as both MHT and TAE agents for effective cancer therapy. The eddy-thermal effect of LM MSs demonstrated effective MHT, whereas LM MS-induced MHT boosted the immune system, promoted immune cell infiltration, and further stimulated powerful immune responses to suppress the growth of distant tumors, together with immune checkpoint blockade therapy. Furthermore, LM MS-lipiodol dispersion displayed excellent efficacy of the combined MHT-TAE in the orthotopic rabbit liver cancer model. Our work not only highlighted that LM MSs could act as effective MHT agents to achieve MHT-enhanced immunotherapy but also presented the significant promise of combining MHT with TAE for the efficient treatment of large orthotopic liver tumors.

Antibacterial intraosseous implant surface coating that responds to changes in the bacterial microenvironment

Bone implant-associated infection is one of the most challenging problems encountered by orthopedic surgeons. There is considerable interest in the development of drug-loaded antibacterial coatings for the surfaces of metal implants. However, it is difficult to achieve the stable local release of an effective drug dose for many antibacterial coatings. In the present study, analyses of the thickness and water contact angle of multiple layers confirmed the successful assembly of multilamellar membrane structures. Measurement of the zone of bacterial inhibition indicated gradual degradation of the (montmorillonite [MMT]/hyaluronic acid [HA])₁₀ multilamellar film structure with concentration-dependent degradation during incubation with hyaluronidase solution and Staphylococcus aureus. In vivo results resembled the in vitro results. Overall, the findings confirm that the (MMT/HA-rifampicin)₁₀ multilamellar film structure exhibits good antibacterial properties and excellent biocompatibility. Further studies of the clinical potential of the antibacterial coating prepared in this experiment are warranted.

Plasmonic/magnetic nanoarchitectures: From controllable design to biosensing and bioelectronic interfaces

Controllable design of the nanocrystal-assembled plasmonic/magnetic nanoarchitectures (P/MNAs) inspires abundant methodologies to enhance light-matter interactions and control magnetic-induced effects by means of fine-tuning the morphology and ordered packing of noble metallic or magnetic building blocks. The burgeoning development of multifunctional nanoarchitectures has opened up broad range of interdisciplinary applications including biosensing, in vitro diagnostic devices, point-of-care (POC) platforms, and soft bioelectronics. By taking advantage of their customizability and efficient conjugation with capping biomolecules, various nanoarchitectures have been integrated into high-performance biosensors with remarkable sensitivity and versatility, enabling key features that combined multiplexed detection, ease-of-use and miniaturization. In this review, we provide an overview of the representative developments of nanoarchitectures that being built by plasmonic and magnetic nanoparticles over recent decades. The design principles and key mechanisms for signal amplification and quantitative sensitivity have been explored. We highlight the structure-function programmability and prospects of addressing the main limitations for conventional biosensing strategies in terms of accurate selectivity, sensitivity, throughput, and optoelectronic integration. State-of-the-art strategies to achieve affordable and field-deployable POC devices for early multiplexed detection of infectious diseases such as COVID-19 has been covered in this review. Finally, we discuss the urgent yet challenging issues in nanoarchitectures design and related biosensing application, such as large-scale fabrication and integration with portable devices, and provide perspectives and suggestions on developing smart biosensors that connecting the materials science and biomedical engineering for personal health monitoring.

Multichannel power electronics and magnetic nanoparticles for selective thermal magnetogenetics

OBJECTIVE

We present a combination of a power electronics system and magnetic nanoparticles that enable frequency-multiplexed magnetothermal-neurostimulation with rapid channel switching between three independent channels spanning a wide frequency range.

APPROACH

The electronics system generates alternating magnetic field spanning 50 kHz to 5 MHz in the same coil by combining silicon (Si) and gallium-nitride (GaN) transistors to resolve the high spread of coil impedance and current required throughout the wide bandwidth. The system drives a liquid-cooled field coil via capacitor banks, forming three series resonance channels which are multiplexed using high-voltage contactors. We characterized the system by the output channels' frequencies, field strength, and switching time, as well as the system's overall operation stability. Using different frequency-amplitude combinations of the magnetic field to target specific magnetic nanoparticles with different coercivity, we demonstrate actuation of iron oxide nanoparticles in all three channels, including a novel nanoparticle composition responding to magnetic fields in the megahertz range.

MAIN RESULTS

The system achieved the desired target field strengths for three frequency channels, with switching speed between channels on the order of milliseconds. Specific absorption rate measurements and infrared thermal imaging performed with three types of magnetic nanoparticles demonstrated selective heating and validated the system's intended use.

SIGNIFICANCE

The system uses a hybrid of Si and GaN transistors in bridge configuration instead of conventional amplifier circuit concepts to drive the magnetic field coil and contactors for fast switching between different capacitor banks. Series-resonance circuits ensure a high output quality while keeping the system efficient. This approach could significantly improve the speed and flexibility of frequency-multiplexed nanoparticle actuation, such as magnetogenetic neurostimulation, and thus provide the technical means for selective stimulation below the magnetic field's fundamental spatial focality limits.

Transparent photothermal hydrogels for wound visualization and accelerated healing

Utilizing photothermal hydrogels as a wound dressing is a promising strategy to accelerate wound healing. Usually, a photothermal hydrogel has a strong light-absorbing capability, and hence its transparency can be largely sacrificed, which is unbeneficial for the visual monitoring of wound states. It remains challenging to balance the trade-off between the photothermal conversion and wound visualization for the photothermal hydrogel dressing. Herein, a composite photothermal hydrogel film with high transparency is presented for the visual monitor of the wound, which is constructed by incorporating CsxWO3 nanorods into the networks of polyacrylamide hydrogels. The composite photothermal hydrogel film exhibits high light absorption in the near-infrared region and high transmittance in the visible light region. Under 980 nm laser irradiation, the composite hydrogel can be heated up to 45 °C. In vivo animal experiment on mouse skin wound model shows that the composite hydrogel film can locally heat the skin wound to accelerate healing while maintaining more than 70% transparency to realize real-time observation of the wound. This study provides the first attempt to solve the problem of opacity in photothermal hydrogel dressings, promoting the possibility of its clinical applications.

Versatile and Simple Strategy for Preparing Bilayer Hydrogels with Janus Characteristics

Bilayer hydrogels are attracting tremendous attention for their capability to integrate several different functions on the two sides of the gel, that is, imparting the gel with Janus characteristics, which is highly desired in many engineering and biomedical applications including soft actuators, hydrogel patches, and wearable electronics. However, the preparation process of the bilayer materials usually involves several complicated steps and is time-consuming, while the interfacial bonding is another main concern. Here, a simple and versatile method is proposed to obtain bilayer hydrogels within just one step based on the method of introducing viscosity contrast of the precursors for different layers. The bilayer structure can be well maintained during the whole preparation process with a constrained interfacial molecular exchange to ensure the strong bonding strength. The key requirements for forming distinct bilayer structures in situ are studied and discussed in detail. Bilayer hydrogels with different chemical designs are prepared via this strategy to tailor the good distribution of desired functions for soft actuators, wound healing patches, and wearable electronics. We believe that the strategy illustrated here will provide new insights into the preparation and application of bilayer materials.

DNA-mediated assembly of gold-nanoparticle film with controllable sonic behaviors detected by novel electric-induced ultrasound

Two-dimensional gold assembled nanomaterials have garnered considerable interests in biomedical application such as wearable sensors and flexible devices. The assembly can be accomplished via attractive interactions between gold nanoparticles (GNPs)...

Liquid Crystalline Hydrogel with Thermally Induced Reversible Shape Change and Water-Triggered Shape Memory

Liquid crystalline hydrogel (LCH) is synthesized through simultaneous polymerization of hydrophobic and hydrophilic monomers in an oil-in-water emulsion, resulting in phase-separated liquid crystalline network (LCN) embedded in a hydrogel matrix. This material features some properties and functions of both LCN and hydrogel, displaying stable LC phase over repeated hydration and dehydration cycles of the hydrogel matrix. Using mechanically stretched and photocrosslinked LCH, the thermally induced LC-isotropic phase transition in LCN domains can be translated into reversible macroscopic deformation of the LCH. Moreover, the LCH exhibits water absorption-controlled shape memory effect.

Magneto-Electrically Enhanced Intracellular Catalysis of FePt-FeC Heterostructures for Chemodynamic Therapy

Intracellular catalytic reactions can tailor tumor cell plasticity toward high-efficiency treatments, but the application is hindered by the low efficiency of intracellular catalysis. Here, a magneto-electronic approach is developed for efficient intracellular catalysis by inducing eddy currents of FePt-FeC heterostructures in mild alternating magnetic fields (frequency of f = 96 kHz and amplitude of B ≤ 70 mT). Finite element simulation shows a high density of induced charges gathering at the interface of FePt-FeC heterostructure in the alternating magnetic field. As a result, the concentration of an essential coenzyme-β-nicotinamide adenine dinucleotide-in cancer cells is significantly reduced by the enhanced catalytic hydrogenation reaction of FePt-FeC heterostructures under alternating magnetic stimulation, leading to over 80% of senescent cancer cells-a vulnerable phenotype that facilitates further treatment. It is further demonstrated that senescent cancer cells can be efficiently killed by the chemodynamic therapy based on the enhanced Fenton-like reaction. By promoting intracellular catalytic reactions in tumors, this approach may enable precise catalytic tumor treatment.

From prevention to diagnosis and treatment: Biomedical applications of metal nanoparticle-hydrogel composites

Recent advances in biomaterials integrate metal nanoparticles with hydrogels to generate composite materials that exhibit new or improved properties. By precisely controlling the composition, arrangement and interactions of their constituents, these hybrid materials facilitate biomedical applications through myriad approaches. In this work we seek to highlight three popular frameworks for designing metal nanoparticle-hydrogel hybrid materials for biomedical applications. In the first approach, the properties of metal nanoparticles are incorporated into a hydrogel matrix such that the composite is selectively responsive to stimuli such as light and magnetic flux, enabling precisely activated therapeutics and self-healing biomaterials. The second approach mediates the dynamic reorganization of metal nanoparticles based on environment-directed changes in hydrogel structure, leading to chemosensing, microbial and viral detection, and drug-delivery capabilities. In the third approach, the hydrogel matrix spatially arranges metal nanoparticles to produce metamaterials or passively enhance nanoparticle properties to generate improved substrates for biomedical applications including tissue engineering and wound healing. This article reviews the construction, properties and biomedical applications of metal nanoparticle-hydrogel composites, with a focus on how they help to prevent, diagnose and treat diseases. Discussion includes how the composites lead to new or improved properties, how current biomedical research leverages these properties and the emerging directions in this growing field.

Stimuli-Responsive Plasmonic Assemblies and Their Biomedical Applications

Among the diverse development of stimuli-responsive assemblies, plasmonic nanoparticle (NP) assemblies functionalized with responsive molecules are of a major interest. In this review, we outline a comprehensive and up-to-date overview of recently reported studies on in vitro and in vivo assembly/disassembly and biomedical applications of plasmonic NPs, wherein stimuli such as enzymes, light, pH, redox potential, temperature, metal ions, magnetic or electric field, and/or multi-stimuli were involved. Stimuli-responsive assemblies have been applied in various biomedical fields including biosensors, surfaced-enhanced Raman scattering (SERS), photoacoustic (PA) imaging, multimodal imaging, photo-activated therapy, enhanced X-ray therapy, drug release, stimuli-responsive aggregation-induced cancer therapy, and so on. The perspectives on the use of stimuli-responsive plasmonic assemblies are discussed by addressing future scientific challenges involving assembly/disassembly strategies and applications.

Near-Infrared-Controlled Nanoplatform Exploiting Photothermal Promotion of Peroxidase-like and OXD-like Activities for Potent Antibacterial and Anti-biofilm Therapies

Nanozymes that mimic peroxidase (POD) activity can convert H₂O₂ into bactericidal free radicals, which is referred to as chemodynamic therapy (CDT). High glutathione (GSH) levels in the infectious tissue severely limit the performance of CDT. Herein, we report a near-infrared-controlled antibacterial nanoplatform that is based on encapsulating tungsten sulfide quantum dots (WS₂QDs) and the antibiotic vancomycin in a thermal-sensitive liposome. The system exploits the photothermal sensitivity of the WS₂QDs to achieve selective liposome rupture for the targeted drug delivery. We determined that WS₂QDs show a strong POD-like activity under physiological conditions and the oxidase-like activity, which can oxidate GSH to further improve the CDT efficacy. Moreover, we found that increased temperature promotes multiple enzyme-mimicking activities of WS₂QDs. This platform exerts antibacterial effects against Gram-positive Mu50 (a vancomycin-intermediate Staphylococcus aureus reference strain) and Gram-negative Escherichia coli and disrupts biofilms for improved penetration of therapeutic agents inside biofilms. In vivo studies with mice bearing Mu50-caused skin abscess revealed that this platform confers potent antibacterial activity without obvious toxicity. Accordingly, our work illustrates that the photothermal and nanozyme properties of WS₂QDs can be deployed alongside a conventional therapeutic to achieve synergistic chemodynamic/photothermal/pharmaco therapy for powerful antibacterial effects.

Bioinspired Anisotropic Chitosan Hybrid Hydrogel

Natural soft tissues such as cartilage, tendon, and ligament have well-ordered hierarchical structures, which are crucial for their mechanical and biological functions. Inspired by the aligned fibrous structure, an anisotropic chitosan hybrid hydrogel (ACHH) is developed by combining the oriented chitosan nanofibers with the ductile polyacrylamide network. The resulting ACHH demonstrates outstanding mechanical properties: tensile strength and elastic modulus up to 25.6 and 218.2 MPa, which are comparable to those of natural cartilage and ligament. In addition, the ACHH also exhibits excellent biocompatibility and can promote the adhesion and proliferation of myoblasts. This work offers a facile method to fabricate an anisotropic, strong, and biocompatible chitosan-based hydrogel for potential biomaterials and tissue-engineering applications.

Supramolecular Biocomposite Hydrogels Formed by Cellulose and Host-Guest Polymers Assisted by Calcium Ion Complexes

Hydrogels are biocompatible polymer networks; however, they have the disadvantage of having poor mechanical properties. Herein, the mechanical properties of host-guest hydrogels were increased by adding a filler and incorporating other noncovalent interactions. Cellulose was added as a filler to the hydrogels to afford a composite. Citric acid-modified cellulose (CAC) with many carboxyl groups was used instead of conventional cellulose. The preparation began with mixing an acrylamide-based αCD host polymer (p-αCD) and a dodecanoic acid guest polymer (p-AADA) to form supramolecular hydrogels (p-αCD/p-AADA). However, when CAC was directly added to p-αCD/p-AADA to form biocomposite hydrogels (p-αCD/p-AADA/CAC), it showed weaker mechanical properties than p-αCD/p-AADA itself. This was caused by the strong intramolecular hydrogen bonding (H-bonding) within the CAC, which prevented the CAC reinforcing p-αCD/p-AADA in p-αCD/p-AADA/CAC. Then, calcium chloride solution (CaCl₂) was used to form calcium ion (Ca²⁺) complexes between the CAC and p-αCD/p-AADA. This approach successfully created supramolecular biocomposite hydrogels assisted by Ca²⁺ complexes (p-αCD/p-AADA/CAC/Ca²⁺) with improved mechanical properties relative to p-αCD/p-AADA hydrogels; the toughness was increased 6-fold, from 1 to 6 MJ/m³. The mechanical properties were improved because of the disruption of the intramolecular H-bonding within the CAC by Ca²⁺ and subsequent complex formation between the carboxyl groups of CAC and p-AADA. This mechanism is a new approach for improving the mechanical properties of hydrogels that can be broadly applied as biomaterials.

Development of nanoparticle drug-delivery systems for the inner ear

Hearing loss has become the most common sensory nerve disorder worldwide, with no effective treatment strategy. Low-permeability and limited blood supply to the blood-labyrinth barrier limit the effective delivery and efficacy of therapeutic drugs in the inner ear. Nanoparticle (NP)-based drugs have shown benefits of stable controlled release and functional surface modification, and NP-based delivery systems have become a research hotspot. In this review, we discuss the development of new targeted drug-delivery systems based on the biocompatibility and safety of different NPs in the cochlea, as well as the advantages and disadvantages of their prescription methods and approaches. We believe that targeted NP-based drug-delivery systems will be effective treatments for hearing loss.

Nanochitin/metal ion dual reinforcement in synthetic polyacrylamide network-based nanocomposite hydrogels

Nanocomposite hydrogels consisting of a synthetic matrix reinforced by nanosized crystalline polysaccharides offer significant potential in various fields. Different from nanocellulose, the combination of nanochitin with synthetic polymers to obtain nanocomposite hydrogels has not been extensively and systematically studied. Herein, a physically and chemically dual crosslinked nanocomposite hydrogel was successfully synthesized, where chitin nanowhiskers (ChNWs) and Zn²⁺ were incorporated within polyacrylamide (PAAm) matrix. Nanochitin/metal ion dual reinforcement imparts increased elasticity, enhanced mechanical properties, and improved recovery performance to PAAm network. The PAAm/ChNWs/Zn²⁺ hydrogel could be stretched to over 13 times its original length with tensile strength of 321.9 ± 8.2 kPa, and restore its original shape rapidly even when compressed at a strain of 95% with a corresponding compressive strength of 6.95 ± 0.20 MPa. The multiple crosslinks and interactions among ChNWs, Zn²⁺ and synthetic polymeric network were investigated. Moreover, the hydrogel was applied in drug release and soft bioelectronics.

Comprehensive understanding of magnetic hyperthermia for improving antitumor therapeutic efficacy

Magnetic hyperthermia (MH) has been introduced clinically as an alternative approach for the focal treatment of tumors. MH utilizes the heat generated by the magnetic nanoparticles (MNPs) when subjected to an alternating magnetic field (AMF). It has become an important topic in the nanomedical field due to their multitudes of advantages towards effective antitumor therapy such as high biosafety, deep tissue penetration, and targeted selective tumor killing. However, in order for MH to progress and to realize its paramount potential as an alternative choice for cancer treatment, tremendous challenges have to be overcome. Thus, the efficiency of MH therapy needs enhancement. In its recent 60-year of history, the field of MH has focused primarily on heating using MNPs for therapeutic applications. Increasing the thermal conversion efficiency of MNPs is the fundamental strategy for improving therapeutic efficacy. Recently, emerging experimental evidence indicates that MNPs-MH produces nano-scale heat effects without macroscopic temperature rise. A deep understanding of the effect of this localized induction heat for the destruction of subcellular/cellular structures further supports the efficacy of MH in improving therapeutic therapy. In this review, the currently available strategies for improving the antitumor therapeutic efficacy of MNPs-MH will be discussed. Firstly, the recent advancements in engineering MNP size, composition, shape, and surface to significantly improve their energy dissipation rates will be explored. Secondly, the latest studies depicting the effect of local induction heat for selectively disrupting cells/intracellular structures will be examined. Thirdly, strategies to enhance the therapeutics by combining MH therapy with chemotherapy, radiotherapy, immunotherapy, photothermal/photodynamic therapy (PDT), and gene therapy will be reviewed. Lastly, the prospect and significant challenges in MH-based antitumor therapy will be discussed. This review is to provide a comprehensive understanding of MH for improving antitumor therapeutic efficacy, which would be of utmost benefit towards guiding the users and for the future development of MNPs-MH towards successful application in medicine.

A Neutrophil-Inspired Supramolecular Nanogel for Magnetocaloric-Enzymatic Tandem Therapy

Neutrophils can responsively release reactive oxygen species (ROS) to actively combat infections by exogenous stimulus and cascade enzyme catalyzed bio-oxidation. A supramolecular nanogel is now used as an artificial neutrophil by enzymatic interfacial self-assembly of peptides (Fmoc-Tyr(H₂ PO₃ )-OH) with magnetic nanoparticles (MNPs) and electrostatic loading of chloroperoxidase (CPO). The MNPs within the nanogel can elevate H₂ O₂ levels in cancer cells under programmed alternating magnetic field (AMF) similar to the neutrophil activator, and the loaded CPO within protective peptides nanolayer converts the H₂ O₂ into singlet oxygen (¹ O₂ ) in a sustained manner for neutrophil-inspired tumor therapy. As a proof of concept study, both the H₂ O₂ and ¹ O₂ in cancer cells increase stepwise under a programmed alternating magnetic field. An active enzyme dynamic therapy by magnetically stimulated oxygen stress and sustained enzyme bio-oxidation is thus shown with studies on both cells and animals.

Wearable, Antifreezing, and Healable Epidermal Sensor Assembled from Long-Lasting Moist Conductive Nanocomposite Organohydrogel

Flexible wearable soft epidermal sensors assembled from conductive hydrogels have recently attracted tremendous research attention because of their extensive and significant applications in body-attachable healthcare monitoring, ultrasensitive electronic skins, and personal healthcare diagnosis. However, traditional conductive hydrogels inevitably face the challenge of long-term usage under room temperature and cold conditions, due to the lost water, elasticity, and conductivity at room temperature, and freezing at the water icing temperatures. It severely limits the applications in flexible electronics at room temperature or cold environment. Herein, we report a flexible, wearable, antifreezing, and healable epidermal sensor assembled from an antifreezing, long-lasting moist, and conductive organohydrogel. The nanocomposite organohydrogel is prepared from the conformal coating of functionalized reduced graphene oxide network by the hydrogel polymer networks consisting of poly(vinyl alcohol), phenylboronic acid grafted alginate, and polyacrylamide in the binary ethylene glycol (EG)/H₂O solvent system. The obtained organohydrogel exhibits excellent temperature tolerance (-40 °C), long-lasting moisture (20 days), reliable self-healing ability, and can be assembled as wearable sensor for an accurate detection of both large and tiny human activities under extreme environment. Thus, it paves the way for the design of highly sensitive wearable epidermal sensors with reliable long-lasting moisture and excellent temperature tolerance for potential versatile applications in electronic skins, wearable healthcare monitoring, and human-machine interaction.

Construction of Dopamine-Releasing Gold Surfaces Mimicking Presynaptic Membrane by On-Chip Electrochemistry

We report a strategy to construct a dopamine-releasing gold surface mimicking a presynaptic membrane on a microfluidic chip to simulate in vivo neural signaling. We constructed dopamine self-assembled monolayers (DA SAMs) by electrochemical deprotection of methyl group-protected DA SAMs on a gold surface. Electrochemically controllable release of DA SAMs can be realized by applying nonhydrolytic negative potential on the gold surface. Our method in constructing DA SAMs avoids the polymerization and protonation of DA molecules which may lead to the failure of the DA SAM formation. By combining microfluidics, we realized spatial and temporal controllable release of DA by electrochemistry from the gold surface. Furthermore, by culturing neurons on the patterned DA SAMs, the interface between the DA SAMs and the neurons could serve as a presynaptic membrane, and the spatiotemporal release of DA could modulate the neuron activity with high precision. Our study holds great promise in the fields of neurobiology research and drug screening.

Generalized On-Demand Production of Nanoparticle Monolayers on Arbitrary Solid Surfaces via Capillarity-Mediated Inverse Transfer

Century-old Langmuir monolayer deposition still represents the most convenient approach to the production of monolayers of colloidal nanoparticles on solid substrates for practical biological and chemical-sensing applications. However, this approach simply yields arbitrarily shaped large monolayers on a flat surface and is strongly limited by substrate topography and interfacial energy. Here, we describe a generalized and facile method of rapidly producing uniform monolayers of various colloidal nanoparticles on arbitrary solid substrates by using an ordinary capillary tube. Our method is based on an interesting finding of inversion phenomenon of a nanoparticle-laden air-water interface by flowing through a capillary tube in a manner that prevents the particles from adhesion to the capillary sidewall, thereby presenting the nanoparticles face-first at the tube's opposite end for direct and one-step deposition onto a substrate. We show that our method not only allows the placement of a nanoparticle monolayer at target locations of solid substrates regardless of their surface geometry and adhesion but also enables the production of monolayers containing nanoparticles with different size, shape, surface charge, and composition. To explore the potential of our approach, we demonstrate the facile integration of gold nanoparticle monolayers into microfluidic devices for the real-time monitoring of molecular Raman signals under dynamic flow conditions. Moreover, we successfully extend the use of our method to developing on-demand Raman sensors that can be built directly on the surface of consumer products for practical chemical sensing and fingerprinting. Specifically, we achieve both the pinpoint deposition of gold nanoparticle monolayers and sensitive molecular detection from the deposited region on clothing fabric for the detection of illegal drug substances, a single grain of rice and an orange for pesticide monitoring, and a $100 bill as a potential anti-counterfeit measure, respectively. We believe that our method will provide unique opportunities to expand the utility of colloidal nanoparticles and to greatly improve the accessibility of nanoparticle-based sensing technologies.

An acoustic strategy for gold nanoparticle loading in platelets as biomimetic multifunctional carriers

In recent years, a wide variety of bioinspired colloidal particles with novel cell mimetic functions have been the subject of extensive research in materials science, chemistry, biology, physics, and engineering. However, most of the approaches are derived from natural cell membrane coatings, which are still too primitive compared with living cells. In this study, we have chosen gold nanoparticles (GNPs) to explore the bioactivity response of living platelets and nanoparticle loading efficiency under different ultrasonic intensity and frequency treatment conditions. The results show that GNPs with no surface modification could be easily loaded into intra-platelets by both incubation (30 min) and ultrasonic exposure (1 min) methods. The amount of GNP loading was (4.4 ± 0.9) × 10^-3 and (5.8 ± 2.4) × 10^-3 pg per platelet upon incubation and acoustic triggering (1 MHz, 0.25 W cm^-2), respectively. Although the other US treatment intensities (0.75, 1.50 and 2.25 W cm^-2) also promoted higher amounts of GNPs in the platelets, the higher US intensity might bring about partial damage of the platelet membrane. Compared with 1 MHz ultrasonic exposure, the change of the GNP loading amount was not significantly higher upon ultrasonic frequency treatment of 45, 80 or 100 kHz. Therefore, it has been found that an US intensity of 0.25 W cm^-2 could facilitate the intra-platelet delivery efficacy of the GNPs without damaging the biological activity. Furthermore, two possible pathways of GNPs entering into platelets upon US treatment are presented: one is the endocytosis/open canalicular system (OCS), and the other is cell membrane permeability enhancement, which is proved by the SEM and TEM results. Finally, the GNP-loaded platelets have been demonstrated as useful probes for photoacoustic imaging (PAI) and dark-field microscopy (DFM)-based imaging, which might allow a wide range of potential applications in diagnostics and therapy of platelet-related diseases.

Poly(N-isopropylacrylamide)/polydopamine/clay nanocomposite hydrogels with stretchability, conductivity, and dual light- and thermo- responsive bending and adhesive properties

Conducting hydrogels have attracted attention as a special functional class of smart soft materials and have found applications in various advanced fields. However, acquiring all the characteristics such as conductivity, adequate adhesiveness, self-healing ability, stretchability, biocompatibility, and stimulating deformation responsiveness still remains a challenge. Inspired by the mechanism of bioadhesion in marine mussels, a multifunctional nanocomposite hydrogel with excellent adhesiveness to a broad range of substrates including human skin was developed with the help of synergistic multiple coordination bonds between clay, poly(N-isopropylacrylamide) (PNIPAM), and polydopamine nanoparticles (PDA-NPs). The prepared hydrogel showed controllable near-infrared (NIR) responsive deformation after incorporation of PDA-NPs as highly effective photothermal agents in the thermo-sensitive PNIPAM network. Meanwhile, the fabricated nanocomposite hydrogels showed excellent stretchability and conductivity, which make them attractive material candidates for application in various fields, such as electronic skin, wearable devices, and so on.

Electrically Responsive, Nanopatterned Surfaces for Triggered Delivery of Biologically Active Molecules into Cells

Polyelectrolyte multilayers (PEMs) assembled layer-by-layer have emerged as functional polymer films that are both stable and capable of containing drug molecules for controlled release applications. Most of these applications concentrate on sustained release, where the concentration of the released molecules remains rather constant with time. However, high-efficiency delivery requires obtaining high local concentrations at the vicinity of the cells, which is achieved by triggered release. Here, we show that a nanopatterned PEM platform demonstrates superior properties with respect to drug retention and triggered delivery. A chemically modified block copolymer film was used as a template for the selective deposition of poly(ethylene imine) and a charged derivative of the electroactive poly(3,4-ethylenedioxythiophene) together with a drug molecule. This nanopatterned PEM shows the following advantages: (1) high drug loading; (2) enhanced retention of the bioactive molecule; (3) release triggered by an electrochemical stimulus; (4) high efficacy of drug delivery to cells adsorbed on the surface compared to the delivery efficacy of a similar concentration of drug to cells suspended in a solution.

Magnetic Cell-Scaffold Interface Constructed by Superparamagnetic IONP Enhanced Osteogenesis of Adipose-Derived Stem Cells

One of the key factors in tissue engineering and regenerative medicine is to optimize the interaction between seed cells and scaffolds such that the cells can grow in naturally biomimetic conditions. Their similarity to macromolecules and many unique properties mean that functional nanoparticles have promising potential for the modification and improvement of traditional scaffolds to obtain excellent biocompatibility, tunable stiffness, physical sensing, and stimulus-response capabilities. In the present study, we report magnetic poly(lactic- co-glycolic acid)/polycaprolactone (PLGA/PCL) scaffolds that were fabricated using a combination of the electrospinning technique and layer-by-layer assembly of superparamagnetic iron oxide nanoparticles (IONPs). PLGA/PCL scaffolds assembled with gold nanoparticles were prepared using the same method for comparison. The results showed that the assembled film of nanoparticles on the surface greatly enhanced the hydrophilicity and increased the elastic modulus of the scaffold, which subsequently improved the osteogenesis of the stem cells. Furthermore, the magnetic property of the IONPs proved to be the key factor in enhancing osteogenic differentiation, which explained the superior osteogenic capacity of the magnetic scaffolds compared with that of the gold nanoparticle-assembled scaffold. These results demonstrated the importance of magnetic nanomaterials as a bioactive interface between cells and scaffolds and will promote the design of biomaterials to improve tissue engineering and regenerative medicine efficacy.

Langmuir-Blodgett self-assembly of ultrathin graphene quantum dot films with modulated optical properties

Multiple-color-emissive graphene quantum dots (GQDs) have great potential in diverse applications such as bioimaging, light emission, and photocatalysis. Growing interest in GQDs is largely focused on their macro-scale aggregations that could inherit the unique properties of individual dots. However, the lack of advanced fabrication methods limits the practical applications of GQDs. Here, we employed a Langmuir-Blodgett (LB) technique to fabricate ultrathin, high-quality GQD aggregated films with well-modulated optical properties in a wide range of wavelengths. Through the combination of a bottom-up synthesis of GQDs and the LB assembly method, uniform, closely packed, and ultra-thin GQD films can be self-assembled with a well-controlled thickness on different substrates. The photoluminescence (PL) spectra of ultra-thin GQD films have an obvious red-shift compared with isolated GQD solution. We then elucidate remarkably strong energy transfer in self-assembled GQDs. Furthermore, the ultra-thin GQD films exhibit a clear excitation-dependent PL that could almost cover the entire visible light. This convenient self-assembly method and systematic optical and physical studies of ultra-thin GQD films may provide a new direction for developing low-cost, GQD film-based light-emitting devices.

Muscle-Inspired Highly Anisotropic, Strong, Ion-Conductive Hydrogels

Biological tissues generally exhibit excellent anisotropic mechanical properties owing to their well-developed microstructures. Inspired by the aligned structure in muscles, a highly anisotropic, strong, and conductive wood hydrogel is developed by fully utilizing the high-tensile strength of natural wood, and the flexibility and high-water content of hydrogels. The wood hydrogel exhibits a high-tensile strength of 36 MPa along the longitudinal direction due to the strong bonding and cross-linking between the aligned cellulose nanofibers (CNFs) in wood and the polyacrylamide (PAM) polymer. The wood hydrogel is 5 times and 500 times stronger than the bacterial cellulose hydrogels (7.2 MPa) and the unmodified PAM hydrogel (0.072 MPa), respectively, representing one of the strongest hydrogels ever reported. Due to the negatively charged aligned CNF, the wood hydrogel is also an excellent nanofluidic conduit with an ionic conductivity of up to 5 × 10^-4 S cm^-1 at low concentrations for highly selective ion transport, akin to biological muscle tissue. The work offers a promising strategy to fabricate a wide variety of strong, anisotropic, flexible, and ionically conductive wood-based hydrogels for potential biomaterials and nanofluidic applications.

Ferumoxytol of ultrahigh magnetization produced by hydrocooling and magnetically internal heating co-precipitation

Ferumoxytol, which is originally intended for MRI and anemia treatment, is currently the only inorganic nanodrug approved by FDA for clinical application in vivo. Common ferumoxytol seems incapable of meeting the requirements for diverse applications. Thus, the development of a novel strategy based on co-precipitation to produce ferumoxytol with high quality is an imminent task. Herein, we proposed a physically assisted strategy, namely hydrocooling and magnetically internal heating co-precipitation, to optimize the properties of ferumoxytol and thus significantly enhance its magnetic performance. Magnetization of the newly developed ferumoxytol can reach 104-105 emu g-1 Fe, which is the highest value among the reported results. It has been found that the crystalline structures of the newly developed ferumoxytol have been greatly improved on the basis of pharmaceutical quality criteria.

A Water-Processable and Bioactive Multivalent Graphene Nanoink for Highly Flexible Bioelectronic Films and Nanofibers

The capabilities of conductive nanomaterials to be produced in liquid form with well-defined chemical, physical, and biological properties are highly important for the construction of next-generation flexible bioelectronic devices. Although functional graphene nanomaterials can serve as attractive liquid nanoink platforms for the fabrication of bioelectronics, scalable synthesis of graphene nanoink with an integration of high colloidal stability, water processability, electrochemical activity, and especially bioactivity remains a major challenge. Here, a facile and scalable synthesis of supramolecular-functionalized multivalent graphene nanoink (mGN-ink) via [2+1] nitrene cycloaddition is reported. The mGN-ink unambiguously displays a well-defined and flat 2D morphology and shows good water processability and bioactivity. The uniquely chemical, physical, and biological properties of mGN-ink endow the constructed bioelectronic films and nanofibers with high flexibility and durability, suitable conductivity and electrochemical activity, and most importantly, good cellular compatibility and a highly efficient control of stem-cell spreading and orientation. Overall, for the first time, a water-processable and bioactive mGN-ink is developed for the design of flexible and electrochemically active bioelectronic composites and devices, which not only presents manifold possibilities for electronic-cellular applications but also establishes a new pathway for adapting macroscopic usages of graphene nanomaterials in bionic, biomedical, electronic, and even energy fields.

Gold nanoparticles in injectable calcium phosphate cement enhance osteogenic differentiation of human dental pulp stem cells

In this study, a novel calcium phosphate cement containing gold nanoparticles (GNP-CPC) was developed. Its osteogenic induction ability on human dental pulp stem cells (hDPSCs) was investigated for the first time. The incorporation of GNPs improved hDPSCs behavior on CPC, including better cell adhesion (about 2-fold increase in cell spreading) and proliferation, and enhanced osteogenic differentiation (about 2-3-fold increase at 14 days). GNPs endow CPC with micro-nano-structure, thus improving surface properties for cell adhesion and subsequent behaviors. In addition, GNPs released from GNP-CPC were internalized by hDPSCs, as verified by transmission electron microscopy (TEM), thus enhancing cell functions. The culture media containing GNPs enhanced the cellular activities of hDPSCs. This result was consistent with and supported the osteogenic induction results of GNP-CPC. In conclusion, GNP-CPC significantly enhanced the osteogenic functions of hDPSCs. GNPs are promising to modify CPC with nanotopography and work as bioactive additives thus enhance bone regeneration.

Bioinspired Nanocomposite Hydrogels with Highly Ordered Structures

In the human body, many soft tissues with hierarchically ordered composite structures, such as cartilage, skeletal muscle, the corneas, and blood vessels, exhibit highly anisotropic mechanical strength and functionality to adapt to complex environments. In artificial soft materials, hydrogels are analogous to these biological soft tissues due to their "soft and wet" properties, their biocompatibility, and their elastic performance. However, conventional hydrogel materials with unordered homogeneous structures inevitably lack high mechanical properties and anisotropic functional performances; thus, their further application is limited. Inspired by biological soft tissues with well-ordered structures, researchers have increasingly investigated highly ordered nanocomposite hydrogels as functional biological engineering soft materials with unique mechanical, optical, and biological properties. These hydrogels incorporate long-range ordered nanocomposite structures within hydrogel network matrixes. Here, the critical design criteria and the state-of-the-art fabrication strategies of nanocomposite hydrogels with highly ordered structures are systemically reviewed. Then, recent progress in applications in the fields of soft actuators, tissue engineering, and sensors is highlighted. The future development and prospective application of highly ordered nanocomposite hydrogels are also discussed.