A Liquid Metal Mediated Metallic Coating for Antimicrobial and Antiviral Fabrics

Potential activity of nanomaterials to combat SARS-CoV-2 and mucormycosis ‎coinfection‎

INTRODUCTION

Mucormycosis, popularly known as the black fungus, has become a worldwide concern in the continuing COVID-19 pandemic, causing increased morbidity and death in immunocompromised people. Due to multi-drug resistance and the limited number of antifungals, surgical interventions, ‎including the excision of infected tissue, remain a standard treatment option‎. Surgical treatment usually results in the loss of organs or their function, long-term intensive care, and a significant risk of reinfection during the procedure. A comprehensive approach is needed to treat the disease, and nanomaterials can be a powerful alternative therapeutic approach.

AREAS COVERED

We searched PubMed, Scopus, and Google Scholar with the keywords 'emerging role of nanomaterials,' and 'combating COVID-19-related mucormycosis,' and reviewed the related research paper. Antifungal nanomaterials and their delivery can significantly impact the treatment of COVID-19-related fungal infections like mucormycosis. However, the therapeutic options for mucormycosis are limited and drug resistance is also reported.

EXPERT OPINION

The current review encompasses a detailed overview of the recent developments in antifungal/antiviral nanomaterials and the properties of these therapeutic nanomaterials that may contribute to formulating an efficient strategy against invasive mucormycosis. Further extensive research is needed to develop nano-based therapeutics for the management of mucormycosis-viral coinfection with a definitive end-point.

In Vitro Assessment of Gallium Nanoalloy Hydrogels for Antimicrobial and Wound Healing Applications

Chronic and recurring wounds pose a significant challenge in modern healthcare, leading to substantial morbidity. These wounds allow pathogens to colonize, potentially resulting in local and systemic infections. Current interventions need to be revised and become increasingly less reliable due to the emergence of antibiotic resistance. In the present study, we aim to address these issues by fabricating hydrogels impregnated with gallium-based nanoalloys for their antimicrobial activity. Gallium liquid metal nanoparticles (approximately 100 nm in diameter) were alloyed in different combinations with bismuth and silver ions through a galvanic replacement reaction. These multimetallic hydrogels showed favorable antibacterial activity against the Gram-positive Staphylococcus aureus and the Gram-negative Pseudomonas aeruginosa, as observed with fluorescence microscopy and inhibition assays. The multimetallic hydrogels showed no toxicity against murine macrophages or human dermal fibroblasts and enhanced in vitro wound healing. The development of these innovative gallium-based hydrogels represents a promising strategy to combat chronic wounds and their associated complications, offering an effective alternative to current antimicrobial treatments amidst rising antibiotic resistance.

Review of Liquid Metal Fiber Based Biosensors and Bioelectronics

Liquid metal, as a novel material, has become ideal for the fabrication of flexible conductive fibers and has shown great potential in the field of biomedical sensing. This paper presents a comprehensive review of the unique properties of liquid metals such as gallium-based alloys, including their excellent electrical conductivity, mobility, and biocompatibility. These properties make liquid metals ideal for the fabrication of flexible and malleable biosensors. The article explores common preparation methods for liquid metal conductive fibers, such as internal liquid metal filling, surface printing with liquid metal, and liquid metal coating techniques, and their applications in health monitoring, neural interfaces, and wearable devices. By summarizing and analyzing the current research, this paper aims to reveal the current status and challenges of liquid metal conductive fibers in the field of biosensors and to look forward to their development in the future, which will provide valuable references and insights for researchers in the field of biomedical engineering.

Trash into Treasure: Nano-coating of Catheter Utilizes Urine to Deprive H2S Against Persister and Rip Biofilm Matrix

Bacteria-derived hydrogen sulfide (H2S) often contributes to the emergence of antibiotic-recalcitrant bacteria, especially persister (a sub-population of dormant bacteria), thus causing the treatment failure of Catheter-associated urinary tract infection (CAUTI). Here, an H2S harvester nanosystem to prevent the generation of persister bacteria and disrupt the dense biofilm matrix by the self-adaptive ability of shape-morphing is prepared. The nanosystem possesses a core-shell structure that is composed of liquid metal nanoparticle (LM NP), AgNPs, and immobilized urease. The nanosystem decomposes urea contained in urine to generate ammonia for eliminating bacteria-derived H2S. Depending on the oxidative layer of liquid metal, the nanosystem also constitutes a long-lasting reservoir for temporarily storing bacteria-derived H2S, when urease transiently overloads or in the absence of urine in a catheter. Depriving H2S can prevent the emergence of persistent bacteria, enhancing the bacteria-killing efficiency of Ga3+ and Ag+ ions. Even when the biofilm has formed, the urine flow provides heat to trigger shape morphing of the LM NP, tearing the biofilm matrix. Collectively, this strategy can turn trash (urea) into treasure (H2S scavengers and biofilm rippers), and provides a new direction for the antibacterial materials application in the medical field.

A Liquid Metal-Based Temperature-Responsive Low-Toxic Smart Coating for Anti-Biofouling Applications in Marine Engineering

Titanium alloys have been widely used in marine engineering fields. However, because of high biocompatibility, they are vulnerable to biofouling. In this work, based on the micro-arc oxidation technology and spontaneous galvanic replacement reaction, a temperature-responsive low-toxic smart coating consisting of liquid metal particles is designed to control the release of Ga3+, Cu2+, and Cu1+ ions in different temperatures. This technology can ensure the full release of active ingredients within the target temperature range, intelligently maintaining the excellent anti-biofouling performance, while saving active ingredients. After being immersed in culture media with Sulfate-Reducing Bacteria (SRB) for 14 days at 10, 20, and 30 °C, at the optimal activity temperature of 30 °C for SRB, the best sample releases the highest amounts of Ga3+, Cu2+, and Cu1+ ions, demonstrating a 99.9% bactericidal rate. When the temperature decreases to 10 °C, the activity level of SRB is very low, and the smart coating can also reduce the released ions correspondingly, still with a 97.3% bactericidal rate. The remarkable anti-biofouling performance is attributed to the physical damage and lethal ions interaction. Furthermore, the best sample exhibits good corrosion resistance. This work presents a design route for smart anti-biofouling coatings for temperature-responsive.

Orally administrated liquid metal agents for inflammation-targeted alleviation of inflammatory bowel diseases

Rapid drug clearance and off-target effects of therapeutic drugs can induce low bioavailability and systemic side effects and gravely restrict the therapeutic effects of inflammatory bowel diseases (IBDs). Here, we propose an amplifying targeting strategy based on orally administered gallium (Ga)-based liquid metal (LM) nano-agents to efficiently eliminate reactive oxygen and nitrogen species (RONS) and modulate the dysregulated microbiome for remission of IBDs. Taking advantage of the favorable adhesive activity and coordination ability of polyphenol structure, epigallocatechin gallate (EGCG) is applied to encapsulate LM to construct the formulations (LM-EGCG). After adhering to the inflamed tissue, EGCG not only eliminates RONS but also captures the dissociated Ga to form EGCG-Ga complexes for enhancive accumulation. The detained composites protect the intestinal barrier and modulate gut microbiota for restoring the disordered enteral microenvironment, thereby relieving IBDs. Unexpectedly, LM-EGCG markedly decreases the Escherichia_Shigella populations while augmenting the abundance of Akkermansia and Bifidobacterium, resulting in favorable therapeutic effects against the dextran sulfate sodium-induced colitis.

Sustainable Biofilm Inhibition Using Chitosan-Mesoporous Nanoparticle-Based Hybrid Slippery Composites

In recent decades, extensive research has been directed toward mitigating microbial contamination and preventing biofilm formation. However, many conventional antibiofilm methods rely on hazardous and toxic substances, neglecting potential risks to human health and the environment. Moreover, these approaches often rely on single-strategy mechanisms, utilizing either bactericidal or fouling-resistant agents, which have shown limited efficacy in long-term biofilm suppression. In this study, we propose an efficient and sustainable biofilm-resistant slippery hybrid slippery composite. This composite integrates nontoxic and environmentally friendly materials including chitosan, silicone oil-infused polydimethylsiloxane, and mesoporous silica nanoparticles in a synergistic manner. Leveraging the bacteria-killing properties of chitosan and the antifouling capabilities of the silicone oil layer, the hybrid composite exhibits robust antibiofilm performance against both Gram-positive and Gram-negative bacteria. Furthermore, the inclusion of mesoporous silica nanoparticles enhances the oil absorption capacity and self-replenishing properties, ensuring exceptional biofilm inhibition even under harsh conditions such as exposure to high shear flow and prolonged incubation (7 days). This approach offers promising prospects for developing effective biofilm-resistant materials with a reduced environmental impact and improved long-term performance.

Arene-Arene Coupled Disulfamethazines (or Sulfadiazine)-Phenanthroline-Metal(II) Complexes were Synthesized by In Situ Reactions and Inhibited the Growth and Development of Triple-Negative Breast Cancer through the Synergistic Effect of Antiangiogenesis, Anti-Inflammation, Pro-Apoptosis, and Cuproptosis

The novel metal(II)-based complexes HA-Cu, HA-Co, and HA-Ni with phenanthroline, sulfamethazine, and aromatic-aromatic coupled disulfamethazines as ligands were synthesized and characterized. HA-Cu, HA-Co, and HA-Ni all showed a broad spectrum of cytotoxicity and antiangiogenesis. HA-Cu was superior to HA-Co and HA-Ni, and even superior to DDP, showing significant inhibitory effect on the growth and development of tripe-negative breast cancer in vivo and in vitro. HA-Cu exhibited observable synergistic effects of antiproliferation, antiangiogenesis, anti-inflammatory, pro-apoptosis, and cuproptosis to effectively inhibited tumor survival and development. The molecular mechanism was confirmed that HA-Cu could downregulate the expression of key proteins in the VEGF/VEGFR2 signaling pathway and the expression of inflammatory cytokines, enhance the advantage of pro-apoptotic protein Bax, and enforce cuproptosis by weakening the expression of FDX1 and enhancing the expression of HSP70. Our research will provide a theoretical and practical reference for the development of metal-sulfamethazine and its derivatives as chemotherapy drugs for cancer treatment.

Gallium-based liquid metals as reaction media for nanomaterials synthesis

Gallium-based liquid metals (LMs) and their alloys have gained prominence in the realm of flexible and stretchable electronics. Recent advances have expanded the interest to explore the electron-rich core and interface of LMs to synthesize various nanomaterials, where Ga-based LMs serve as versatile reaction media. In this paper, we delve into the latest developments within this burgeoning field. Our discussion begins by elucidating the unique attributes of LMs that render them suitable as reaction media, including their high metal solubility, low standard reduction potential, self-limiting oxidation and ultra-smooth and "layer" surface. We then provide a comprehensive categorized summary of utilizing these features to fabricate a variety of nanomaterials, including pure metallic materials (metal alloys, metal crystals, porous metals, high-entropy alloys and metallic single atoms), metal-inorganic compounds (2D metal oxides, 2D metallic inorganic compounds and 2D graphitic materials), as well as metal-organic composites (metal-organic frameworks). This paper concludes by discussing the current challenges in this field and exploring potential future directions. The versatility and unique properties of Ga-based LMs are poised to play a pivotal role in the future of nanomaterial science, paving the way for more efficient, sustainable, and innovative technological solutions.

Antimicrobial and Antifouling Effects of Petal-Like Nanostructure by Evaporation-Induced Self-Assembly for Personal Protective Equipment

Although the personal protective equipment (PPE) used by healthcare workers (HCWs) effectively blocks hazardous substances and pathogens, it does not fully rule out the possibility of infection, as pathogens surviving on the fabric surface pose a substantial risk of cross-infection through unintended means. Therefore, PPE materials that exhibit effective biocidal activity while minimizing contamination by viscous body fluids (e.g., blood and saliva) and pathogen-laden droplets are highly sought. In this study, petal-like nanostructures (PNSs) are synthesized through the vertical rearrangement of colloidal lamellar bilayers via evaporation-induced self-assembly of octadecylamine, silica-alumina sol, and diverse photosensitizer. The developed method is compatible with various fabrics and imparts visible-light-activated antimicrobial and superhydrophobic-based antifouling activities. PNS-coated fabrics could provide a high level of protection and effectively block pathogen transmission as exemplified by their ability to roll off viscous body fluids reducing bacterial droplet adhesion and to inactivate various microorganisms. The combination of antifouling and photobiocidal activities results in the complete inactivation of sprayed pathogen-laden droplets within 30 min. Thus, this study paves the way for effective contagious disease management and the protection of HCWs in general medical environments, inspiring further research on the fabrication of materials that integrate multiple useful functionalities.

Nanogallium-poly(L-lactide) Composites with Contact Antibacterial Action

In diverse biomedical and other applications of polylactide (PLA), its bacterial contamination and colonization are unwanted. For this reason, this biodegradable polymer is often combined with antibacterial agents or fillers. Here, we present a new solution of this kind. Through the process of simple solvent casting, we developed homogeneous composite films from 28 ± 5 nm oleic-acid-capped gallium nanoparticles (Ga NPs) and poly(L-lactide) and characterized their detailed morphology, crystallinity, aqueous wettability, optical and thermal properties. The addition of Ga NPs decreased the ultraviolet transparency of the films, increased their hydrophobicity, and enhanced the PLA structural ordering during solvent casting. Albeit, above the glass transition, there is an interplay of heterogeneous nucleation and retarded chain mobility through interfacial interactions. The gallium content varied from 0.08 to 2.4 weight %, and films with at least 0.8% Ga inhibited the growth of Pseudomonas aeruginosa PAO1 in contact, while 2.4% Ga enhanced the effect of the films to be bactericidal. This contact action was a result of unwrapping the top film layer under biological conditions and the consequent bacterial contact with the exposed Ga NPs on the surface. All the tested films showed good cytocompatibility with human HaCaT keratinocytes and enabled the adhesion and growth of these skin cells on their surfaces when coated with poly(L-lysine). These properties make the nanogallium-polyl(L-lactide) composite a promising new polymer-based material worthy of further investigation and development for biomedical and pharmaceutical applications.

Antibacterial and Angiogenic (2A) Bio-Heterojunctions Facilitate Infectious Ischemic Wound Regeneration via an Endogenous-Exogenous Bistimulatory Strategy

In infectious ischemic wounds, a lack of blood perfusion significantly worsens microbe-associated infection symptoms and frequently complicates healing. To overcome this daunting issue, antibacterial and angiogenic (2A) bio-heterojunctions (bio-HJs) consisting of CuS/MXene heterojunctions and a vascular endothelial growth factor (VEGF)-mimicking peptide (VMP) are devised and developed to accelerate infectious cutaneous regeneration by boosting angiogenesis via an endogenous-exogenous bistimulatory (EEB) strategy. Assisted by near-infrared irradiation, the bio-HJ platform exhibits versatile synergistic photothermal, photodynamic, and chemodynamic effects for robust antibacterial efficacy. In addition, copper ions liberated from 2A bio-HJs elevate VEGF secretion from fibroblasts, which provokes VEGF receptors (VEGFR) activation through an endogenous pathway, whereas VMP itself promotes an exogenous pathway to facilitate endothelial cell multiplication and tube formation by directly activating the VEGFR signaling pathway. Moreover, employing an in vivo model of infectious ischemic wounds, it is confirmed that the EEB strategy can considerably boost cutaneous regeneration through pathogen elimination, angiogenesis promotion, and collagen deposition. As envisaged, this work leads to the development of a powerful 2A bio-HJ platform that can serve as an effective remedy for bacterial invasion-induced ischemic wounds through the EEB strategy.

Activating Tumor-Selective Liquid Metal Nanomedicine through Galvanic Replacement

Advanced chemotherapeutic strategies including prodrug and nanocatalytic medicine have significantly advanced tumor-selective theranostics, but delicate prodrug screening, tedious synthesis, low degradability/biocompatibility of inorganic components, and unsatisfied reaction activity complicate treatment efficacies. Here, the intrinsic anticancer bioactivity of liquid metal nanodroplets (LMNDs) is explored through galvanic replacement. By utilizing a mechano-degradable ligand, the resultant size of the aqueous LMND is unexpectedly controlled as small as ≈20 nm (LMND20). It is demonstrated that LMND20 presents excellent tumor penetration and biocompatibility and activates tumor-selective carrier-to-drug conversion, synchronously depleting Cu2+ ions and producing Ga3+ ions through galvanic replacement. Together with abundant generation of reactive oxygen species, multiple anticancer pathways lead to selective apoptosis and anti-angiogenesis of breast cancer cells. Compared to the preclinical/clinical anticancer drugs of tetrathiomolybdate and Ga(NO3 )3 , LMND20 administration significantly improves the therapeutic efficacy and survival in a BCap-37 xenograft mouse model, yet without obvious side effects.

Liquid metal biomaterials: translational medicines, challenges and perspectives

Until now, significant healthcare challenges and growing urgent clinical requirements remain incompletely addressed by presently available biomedical materials. This is due to their inadequate mechanical compatibility, suboptimal physical and chemical properties, susceptibility to immune rejection, and concerns about long-term biological safety. As an alternative, liquid metal (LM) opens up a promising class of biomaterials with unique advantages like biocompatibility, flexibility, excellent electrical conductivity, and ease of functionalization. However, despite the unique advantages and successful explorations of LM in biomedical fields, widespread clinical translations and applications of LM-based medical products remain limited. This article summarizes the current status and future prospects of LM biomaterials, interprets their applications in healthcare, medical imaging, bone repair, nerve interface, and tumor therapy, etc. Opportunities to translate LM materials into medicine and obstacles encountered in practices are discussed. Following that, we outline a blueprint for LM clinics, emphasizing their potential in making new-generation artificial organs. Last, the core challenges of LM biomaterials in clinical translation, including bio-safety, material stability, and ethical concerns are also discussed. Overall, the current progress, translational medicine bottlenecks, and perspectives of LM biomaterials signify their immense potential to drive future medical breakthroughs and thus open up novel avenues for upcoming clinical practices.

I-GLAD: a new strategy for fabricating antibacterial surfaces

The paper uses inverted glancing angle deposition (I-GLAD) for creating antibacterial surfaces. Antibacterial surfaces are found in nature, such as on insect wings, eyes, and plant leaves. Since the bactericidal mechanism is purely physical for these surfaces, the antimicrobial resistance of bacteria to traditional chemical antibiotics can be overcome. The technical problem is how to mimic, synthesize, and scale up the naturally occurring antibacterial surfaces for practical applications, given the fact that most of those surfaces are composed of three-dimensional hierarchical micro-nano structures. This paper proposes to use I-GLAD as a novel bottom-up nanofabrication technique to scale up bio-inspired nano-structured antibacterial surfaces. Our innovative I-GLAD nanofabrication technique includes traditional GLAD deposition processes alongside the crucial inverting process. Following fabrication, we explore the antibacterial efficacy of I-GLAD surfaces using two types of bacteria: Escherichia coli (E. coli), a gram-negative bacterium, and Staphylococcus aureus (S. aureus), a gram-positive bacterium. Scanning electron microscopy (SEM) shows the small tips and flexible D/P (feature size over period) ratio of I-GLAD nanoneedles, which is required to achieve the desired bactericidal mechanism. Antibacterial properties of the I-GLAD samples are validated by achieving flat growth curves of E. coli and S. aureus, and direct observation under SEM. The paper bridges the knowledge gaps of seeding techniques for GLAD, and the control/optimization of the I-GLAD process to tune the morphologies of the nano-protrusions. I-GLAD surfaces are effective against both gram-negative and gram-positive bacteria, and they have tremendous potentials in hospital settings and daily surfaces.

Metallic Gallium Droplets Exhibit Poor Antibacterial Properties

The rise of antibiotic resistance in pathogenic bacteria requires new therapeutics to be developed. Several metallic nanoparticles such as those made from silver, copper, and zinc have shown significant antibacterial activity, in part due to metal ion leaching. Ga3+ containing compounds have also been shown to have antibacterial properties. Accordingly, it is estimated that metallic Ga droplets may be antibacterial, and some studies to date have confirmed this. Here, multiple concentrations of Ga droplets were tested against the antibiotic resistant Gram-positive bacteria methicillin-resistantStaphylococcus aureus (MRSA) and the Gram-negative bacteria Pseudomonas aeruginosa (P. aeruginosa) Despite a high concentration (2 mg/mL), Ga droplets had only modest antibacterial activity against both bacteria after 24 h of interaction. Finally, we demonstrated that Ga droplets were easily functionalized through a galvanic replacement reaction to develop antibacterial particles with copper and silver demonstrating a total detectable reduction of MRSA and >96% reduction ofP. aeruginosa. Altogether, these results contradict previous literature and show that Ga droplets demonstrate no antibacterial activity at concentrations comparable to those of conventional antibiotics and well-established antibacterial nanomaterials and only modest antibacterial activity at very high concentrations. However, we demonstrate that their antibacterial activity can be easily enhanced by functionalization.

Tungsten Oxide Coated Liquid Metal Electrodes via Galvanic Replacement as Heavy Metal Ion Sensors

Gallium liquid metals (LMs) like Galinstan and eutectic Gallium-Indium (EGaIn) have seen increasing applications in heavy metal ion (HMI) sensing, because of their ability to amalgamate with HMIs like lead, their high hydrogen potential, and their stable electrochemical window. Furthermore, coating LM droplets with nanopowders of tungsten oxide (WO) has shown enhancement in HMI sensing owing to intense electrical fields at the nanopowder-liquid-metal interface. However, most LM HMI sensors are droplet based, which show limitations in scalability and the homogeneity of the surface. A scalable approach that can be extended to LM electrodes is therefore highly desirable. In this work, we present, for the first time, WO-Galinstan HMI sensors fabricated via photolithography of a negative cavity, Galinstan brushing inside the cavity, lift-off, and galvanic replacement (GR) in a tungsten salt solution. Successful GR of Galinstan was verified using optical microscopy, SEM, EDX, XPS, and surface roughness measurements of the Galinstan electrodes. The fabricated WO-Galinstan electrodes demonstrated enhanced sensitivity in comparison with electrodes structured from pure Galinstan and detected lead at concentrations down to 0.1 mmol·L-1. This work paves the way for a new class of HMI sensors using GR of WO-Galinstan electrodes, with applications in microfluidics and MEMS for a toxic-free environment.

Gallium-Containing Materials and Their Potential within New-Generation Titanium Alloys for Biomedical Applications

With the rising demand for implantable orthopaedic medical devices and the dominance of device-associated infections, extensive research into the development of novel materials has been prompted. Among these, new-generation titanium alloys with biocompatible elements and improved stiffness levels have received much attention. Furthermore, the development of titanium-based materials that can impart antibacterial function has demonstrated promising results, where gallium has exhibited superior antimicrobial action. This has been evidenced by the addition of gallium to various biomaterials including titanium alloys. Therefore, this paper aims to review the antibacterial activity of gallium when incorporated into biomedical materials, with a focus on titanium-based alloys. First, discussion into the development of new-generation Ti alloys that possess biocompatible elements and reduced Young's moduli is presented. This includes a brief review of the influence of alloying elements, processing techniques and the resulting biocompatibilities of the materials found in the literature. The antibacterial effect of gallium added to various materials, including bioglasses, liquid metals, and bioceramics, is then reviewed and discussed. Finally, a key focus is given to the incorporation of gallium into titanium systems for which the inherent mechanical, biocompatible, and antibacterial effects are reviewed and discussed in more detail, leading to suggestions and directions for further research in this area.

Highly Antibacterial and Self-Healing Janus Fabric for Effective Body Moisture/Thermal Management and Durable Waterproof

Despite the development of many functional fabrics, they are unable to meet practical needs due to their monolithic functions and low durability. Therefore, a multifunctional waterborne polyurethane nanodroplet containing disulfide bonds (WSPU) was synthesized using a simple and environmentally friendly approach. The functional WSPU nanodroplet coating endowed fabrics with a variety of properties, including exceptional hydrophobicity, antibacterial properties, self-healing at room temperature, directional transport, etc. The functionalized fabric demonstrated durable mechanical and chemical stabilities due to the combined effects of disulfide bond reconstruction and hydrophobic chain migration. It exhibited the ability to regain its hydrophobic properties at room temperature after 50 friction cycles were performed without requiring external stimulation. Furthermore, the fabric maintained a water contact angle above 140°, even after being subjected to washing, boiling, and immersion in acid and alkali solutions. In addition, as a result of the fabric's Janus-like wettability, it performed various functions in accordance with varying weather conditions, in terms of wearing comfort and breathability. In hot weather or during exercise, the Janus fabric with the hydrophilic side facing outward enhances the process of sweat-directed perspiration, resulting in a notable cooling effect. On rainy days, the Janus fabric, when positioned with the hydrophobic side facing outward, exhibited excellent waterproof performance. This study presents an opportunity to explore the development of multifunctional fabrics through the combined effects of several functions.

Voltage-Driven Chemical Reactions Enable the Synthesis of Tunable Liquid Ga-Metal Nanoparticles

Nanosized particles of liquid metals are emerging materials that hold promise for applications spanning from microelectronics to catalysis. Yet, knowledge of their chemical reactivity is largely unknown. Here, we study the reactivity of liquid Ga and Cu nanoparticles under the application of a cathodic voltage. We discover that the applied voltage and the spatial proximity of these two particle precursors dictate the reaction outcome. In particular, we find that a gradual voltage ramp is crucial to reduce the native oxide skin of gallium and enable reactive wetting between the Ga and Cu nanoparticles; instead, a voltage step causes dewetting between the two. We determine that the use of liquid Ga/Cu nanodimer precursors, which consist of an oxide-covered Ga domain interfaced with a metallic Cu domain, provides a more uniform mixing and results in more homogeneous reaction products compared to a physical mixture of Ga and Cu NPs. Having learned this, we obtain CuGa2 alloys or solid@liquid CuGa2@Ga core@shell nanoparticles by tuning the stoichiometry of Ga and Cu in the nanodimer precursors. These products reveal an interesting complementarity of thermal and voltage-driven syntheses to expand the compositional range of bimetallic NPs. Finally, we extend the voltage-driven synthesis to the combination of Ga with other elements (Ag, Sn, Co, and W). By rationalizing the impact of the native skin reduction rate, the wetting properties, and the chemical reactivity between Ga and other metals on the results of such voltage-driven chemical manipulation, we define the criteria to predict the outcome of this reaction and set the ground for future studies targeting various applications for multielement nanomaterials based on liquid Ga.

Meta-Aerogel Electric Trap Enables Instant and Continuable Pathogen Killing in Face Masks

The tremendous menace of the COVID-19 pandemic has underscored the urgency for antipathogen masks to stop the transmission of airborne infectious diseases. Most prevailing antipathogen masks manifest a slower sterilization rate that lags behind the pathogen momentum traversing the masks, thereby engendering an elevated susceptibility to infection. Here we tailor nanofibrous meta-aerogel electric traps, 3D-assembled from self-knotted carbon nanotube networks in an all rigid nanofibrous skeleton. This superior configuration revolves around the creation of numerous "dielectrophoretic-aerodynamic grippers", which are capable of directional manipulation of microbes toward the region of the lethal intensive electric field. Based on this, we present a disinfection unit comprising a pair of aerogel electrodes that demonstrate a rapid killing rate (>99.99% biocidal efficacy within 0.016 s) and long-term durability (12 h of continuous operation). Additionally, a microbutton lithium cell is employed as a power supply to fabricate an antipathogen face mask with this disinfection unit, which exhibits superior pathogen inactivation efficacy compared to commercial masks. This scalable biocidal protective equipment holds great potential for use in emergency medical services.

Nonleaching Antimicrobial Cotton Fabrics Finished with Hyperbranched Polylysine

The choice of the antimicrobial agent and finishing process is very important for the activity, durability, and safety of antimicrobial fabrics. Here, a novel antimicrobial cotton fabric (HPL-CF) was constructed by covalently bonding an antimicrobial agent, hyperbranched polylysine (HPL), onto the surface of a cotton fabric (CF) pretreated with a silane coupling agent, 3-chloropropyltrimethoxysilane (CPTMS). The multiple amino groups contained in the periphery of HPL make it possible to react with the CF to form multiple bonds, which is beneficial to improve the durability and safety of HPL-CFs. The obtained HPL-CFs exhibited excellent antimicrobial activities against Escherichia coli (E. coli, Gram-negative bacteria), Staphylococcus aureus (S. aureus, Gram-positive bacteria), and Candida albicans (C. albicans, fungi) even when the CF was treated with HPL solution at the concentration of 0.5 wt %. HPL2.0-CFs maintained 98, >99, and >99% of antimicrobial ratios for E. coli, S. aureus, and C. albicans, respectively, after 50 equiv of domestic laundering cycles, surpassing the requirements of the AAA class. The halo method, cell compatibility, and skin irritation assays all prove the fine safety of HPL-CFs. This work demonstrates the great advantages of applying HPL in the antimicrobial finishing of fabrics.

High-Performance Supramolecular Organogel Adhesives for Antimicrobial Applications in Diverse Conditions

Supramolecular organogel coatings that can disinfect the deposited microbial pathogens are emerging as an effective vehicle to prevent pathogen transmission. However, the development of anti-pathogen supramolecular adhesives with mechanical robustness and controlled oil inclusion is technically challenging. Here, we report supramolecular adhesives with mechanical integrity and robust interfacial adhesion over a wide range of biogenic antimicrobial oil. Bifunctional monomers are synthesized and assembled into linear polymers with semicrystalline stackings through hierarchical hydrogen bonds, where incorporated bioactive oil could regulate the semicrystalline stackings into nanosized crystalline domains through intermolecular hydrogen bonds. The abundant bonding motifs provided by the supramolecular cross-linked networks could accommodate oil molecules with high inclusion capability and provide more interfacial binding sites with high adhesion strength, and the nanosized crystalline domains could stabilize the organogel network and compensate for the interactions with oil molecules to enhance structural and mechanical stability. In addition, rapid healing, robust adhesion, and antimicrobial and antiviral properties of the resultant organogel coatings are demonstrated. This study paves the way for the development of high-performance antimicrobial supramolecular adhesives with controlled oil inclusion, showing potential applications in soft robotics, tissue engineering, and biomedical devices.

Rapid In Situ Thermal Decontamination of Wearable Composite Textile Materials

Pandemics stress supply lines and generate shortages of personal protective equipment (PPE), in part because most PPE is single-use and disposable, resulting in a need for constant replenishment to cope with high-volume usage. To better prepare for the next pandemic and to reduce waste associated with disposable PPE, we present a composite textile material capable of thermally decontaminating its surface via Joule heating. This material can achieve high surface temperatures (>100 °C) and inactivate viruses quickly (<5 s of heating), as evidenced experimentally with the surrogate virus HCoV-OC43 and in agreement with analytical modeling for both HCoV-OC43 and SARS-CoV-2. Furthermore, it does not require doffing because it remains relatively cool near the skin (<40 °C). The material can be easily integrated into clothing and provides a rapid, reusable, in situ decontamination method capable of reducing PPE waste and mitigating the risk of supply line disruptions in times of need.

Antiviral efficacy of nanomaterial-treated textiles in real-life like exposure conditions

Due to the growing interest towards reducing the number of potentially infectious agents on critical high-touch surfaces, the popularity of antimicrobially and antivirally active surfaces, including textiles, has increased. The goal of this study was to create antiviral textiles by spray-depositing three different nanomaterials, two types of CeO2 nanoparticles and quaternary ammonium surfactant CTAB loaded SiO2 nanocontainers, onto the surface of a knitted polyester textile and assess their antiviral activity against two coronaviruses, porcine transmissible gastroenteritis virus (TGEV) and severe acute respiratory syndrome virus (SARS CoV-2). Antiviral testing was carried out in small droplets in semi-dry conditions and in the presence of organic soiling, to mimic aerosol deposition of viruses onto the textiles. In such conditions, SARS CoV-2 stayed infectious at least for 24 h and TGEV infected cells even after 72h of semi-dry deposition suggesting that textiles exhibiting sufficient antiviral activity before or at 24 h, can be considered promising. The antiviral efficacy of nanomaterial-deposited textiles was compared with the activity of the same nanomaterials in colloidal form and with positive control textiles loaded with copper nitrate and CTAB. Our results indicated that after deposition onto the textile, CeO2 nanoparticles lost most of their antiviral activity, but antiviral efficacy of CTAB-loaded SiO2 nanocontainers was retained also after deposition. Copper nitrate deposited textile that was used as a positive control, showed relatively high antiviral activity as expected. However, as copper was effectively washed away from the textile already during 1 h, the use of copper for creating antiviral textiles would be impractical. In summary, our results indicated that antiviral activity of textiles cannot be predicted from antiviral efficacy of the deposited compounds in colloid and attention should be paid on prolonged efficacy of antivirally coated textiles.

Wearable bioelectronics fabricated in situ on skins

In recent years, wearable bioelectronics has rapidly expanded for diagnosing, monitoring, and treating various pathological conditions from the skin surface. Although the devices are typically prefabricated as soft patches for general usage, there is a growing need for devices that are customized in situ to provide accurate data and precise treatment. In this perspective, the state-of-the-art in situ fabricated wearable bioelectronics are summarized, focusing primarily on Drawn-on-Skin (DoS) bioelectronics and other in situ fabrication methods. The advantages and limitations of these technologies are evaluated and potential future directions are suggested for the widespread adoption of these technologies in everyday life.

Nanoheterostructure by Liquid Metal Sandwich-Based Interfacial Galvanic Replacement for Cancer Targeted Theranostics

Nanoheterostructures with exquisite interface and heterostructure design find numerous applications in catalysis, plasmonics, electronics, and biomedicine. In the current study, series core-shell metal or metal oxide-based heterogeneous nanocomposite have been successfully fabricated by employing sandwiched liquid metal (LM) layer (i.e., LM oxide/LM/LM oxide) as interfacial galvanic replacement reaction environment. A self-limiting thin oxide layer, which would naturally occur at the metal-air interface under ambient conditions, could be readily delaminated onto the surface of core metal (Fe, Bi, carbonyl iron, Zn, Mo) or metal oxide (Fe₃ O₄ , Fe₂ O₃ , MoO₃ , ZrO₂ , TiO₂ ) nano- or micro-particles by van der Waals (vdW) exfoliation. Further on, the sandwiched LM layer could be formed immediately and acted as the reaction site of galvanic replacement where metals (Au, Ag, and Cu) or metal oxide (MnO₂ ) with higher reduction potential could be deposited as shell structure. Such strategy provides facile and versatile approaches to design and fabricate nanoheterostructures. As a model, nanocomposite of Fe@Sandwiched-GaIn-Au (Fe@SW-GaIn-Au) is constructed and their application in targeted magnetic resonance imaging (MRI) guided photothermal tumor ablation and chemodynamic therapy (CDT), as well as the enhanced radiotherapy (RT) against tumors, have been systematically investigated.

Facile Process for the Development of Antiviral Cotton Fabrics with Nano-Embossed Copper Oxide

Metallic or metal oxide-based nanoparticles have the potential to inactivate viruses. Among various metals, copper has shown edge over others. One of the rapidly evolving areas is to combine nanoscience for production of self-sanitizing antiviral surfaces. In this study, we designed antiviral-coated fabrics to combat the spread of viruses. Copper oxide nanoparticles were sonochemically synthesized and subsequently deposited using the dip-coat process to modify the surface of fabric. The morphology and structure of uncoated and coated fabrics were examined by scanning electron microscopy, X-ray diffraction, FTIR, and elemental analysis. The findings show that small, agglomerated rugby ball structures made of copper oxide (CuO) nanoparticles (16 ± 1.6 nm, according to the Scherrer equation) develop on the surface of fabric, resulting in nano-embossing and a hydrophobic (contact angle > 140°) surface. The CuO-coated fabric yielded the maximum zone of inhibition for antibacterial activity. The virucidal activity (against human adenovirus-B) of CuO nanoparticle-fabricated fabric against adenovirus shows decreased 99.99% according to the ISO 18184 testing standard. With the dip and dry approach, any textile industry can use the simple coating procedure without having to change its textile operations. This fabric can be widely used in the face mask, clothing, bedding, and aprons, and the coating remains efficient over more than 25 washes.

Preparation of Highly Stable and Cost-Efficient Antiviral Materials for Reducing Infections and Avoiding the Transmission of Viruses such as SARS-CoV-2

The current global pandemic due to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has demonstrated the necessity to develop novel materials with antimicrobial and antiviral activities to prevent the infection. One significant route for the spread of diseases is by the transmission of the virus through contact with contaminated surfaces. Antiviral surface treatments can help to reduce or even avoid these hazards. In particular, the development of active-virucidal fabrics or paints represents a very important challenge with multiple applications in hospitals, public transports, or schools. Modern, cutting-edge methods for creating antiviral surface coatings use either materials with a metal base or sophisticated synthetic polymers. Even if these methods are effective, they will still face significant obstacles in terms of large-scale applicability. Here, we describe the preparation of fabrics and paints treated with a scaled-up novel nanostructured biohybrid material composed of very small crystalline phosphate copper(II) nanoparticles, synthesized based on a technology that employs the use of a small amount of biological agent for its formation at room temperature in aqueous media. We demonstrate the efficient inactivation of the human coronavirus 229E (HCoV-229E), the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus, and non-enveloped human rhinovirus 14 (HRV-14) (>99.9%) using an inexpensive, ecologically friendly coating agent. The reactive oxygen species produced during the oxidation of water or the more intensive reaction with hydrogen peroxide are believed to be the cause of the antiviral mechanism of the nanostructured material. In contrast to the release of a specific antiviral drug, this process does not consume the surface coating and does not need regeneration. A 12-month aging research that revealed no decline in antiviral activity is proof that the coating is durable in ambient circumstances. Also, the coated fabric can be reused after different washing cycles, even at moderate to high temperatures.

Shaping a Soft Future: Patterning Liquid Metals

This review highlights the unique techniques for patterning liquid metals containing gallium (e.g., eutectic gallium indium, EGaIn). These techniques are enabled by two unique attributes of these liquids relative to solid metals: 1) The fluidity of the metal allows it to be injected, sprayed, and generally dispensed. 2) The solid native oxide shell allows the metal to adhere to surfaces and be shaped in ways that would normally be prohibited due to surface tension. The ability to shape liquid metals into non-spherical structures such as wires, antennas, and electrodes can enable fluidic metallic conductors for stretchable electronics, soft robotics, e-skins, and wearables. The key properties of these metals with a focus on methods to pattern liquid metals into soft or stretchable devices are summari.

Liquid Metal as Bioinspired and Unusual Modulator in Bioorthogonal Catalysis for Tumor Inhibition Therapy

Bioorthogonal catalysis mediated by Pd-based transition metal catalysts has sparked increasing interest in combating diseases. However, the catalytic and therapeutic efficiency of current Pd⁰ catalysts is unsatisfactory. Herein, inspired by the concept that ligands around metal sites could enable enzymes to catalyze astonishing reactions by changing their electronic environment, a LM-Pd catalyst with liquid metal (LM) as an unusual modulator has been designed to realize efficient bioorthogonal catalysis for tumor inhibition. The LM matrix can serve as a "ligand" to afford an electron-rich environment to stabilize the active Pd⁰ and promote nucleophilic turnover of the π-allylpalladium species to accelerate the uncaging process. Besides, the photothermal properties of LM can lead to the enhanced removal of tumor cells by photo-enhanced catalysis and photothermal effect. We believe that our work will broaden the application of LM and motivate the design of bioinspired bioorthogonal catalysts.

Functional Textile Materials for Blocking COVID-19 Transmission

The outbreak of COVID-19 provided a warning sign for society worldwide: that is, we urgently need to explore effective strategies for combating unpredictable viral pandemics. Protective textiles such as surgery masks have played an important role in the mitigation of the COVID-19 pandemic, while revealing serious challenges in terms of supply, cross-infection risk, and environmental pollution. In this context, textiles with an antivirus functionality have attracted increasing attention, and many innovative proposals with exciting commercial possibilities have been reported over the past three years. In this review, we illustrate the progress of textile filtration for pandemics and summarize the recent development of antiviral textiles for personal protective purposes by cataloging them into three classes: metal-based, carbon-based, and polymer-based materials. We focused on the preparation routes of emerging antiviral textiles, providing a forward-looking perspective on their opportunities and challenges, to evaluate their efficacy, scale up their manufacturing processes, and expand their high-volume applications. Based on this review, we conclude that ideal antiviral textiles are characterized by a high filtration efficiency, reliable antiviral effect, long storage life, and recyclability. The expected manufacturing processes should be economically feasible, scalable, and quickly responsive.

Liquid Metal-Based Electronics for On-Skin Healthcare

Wearable devices are receiving growing interest in modern technologies for realizing multiple on-skin purposes, including flexible display, flexible e-textiles, and, most importantly, flexible epidermal healthcare. A 'BEER' requirement, i.e., biocompatibility, electrical elasticity, and robustness, is first proposed here for all the on-skin healthcare electronics for epidermal applications. This requirement would guide the designing of the next-generation on-skin healthcare electronics. For conventional stretchable electronics, the rigid conductive materials, e.g., gold nanoparticles and silver nanofibers, would suffer from an easy-to-fail interface with elastic substrates due to a Young's modulus mismatch. Liquid metal (LM) with high conductivity and stretchability has emerged as a promising solution for robust stretchable epidermal electronics. In addition, the fundamental physical, chemical, and biocompatible properties of LM are illustrated. Furthermore, the fabrication strategies of LM are outlined for pure LM, LM composites, and LM circuits based on the surface tension control. Five dominant epidermal healthcare applications of LM are illustrated, including electrodes, interconnectors, mechanical sensors, thermal management, and biomedical and sustainable applications. Finally, the key challenges and perspectives of LM are identified for the future research vision.

Liquid-Metal-Induced Hydrogen Insertion in Photoelectrodes for Enhanced Photoelectrochemical Water Oxidation

Fast charge separation and transfer (CST) is essential for achieving efficient solar conversion processes. This CST process requires not only a strong driving force but also a sufficient charge carrier concentration, which is not easily achievable with traditional methods. Herein, we report a rapid hydrogenation method enabled by gallium-based liquid metals (GBLMs) to modify the prototypical WO₃ photoelectrode to enhance the CST for a PEC process. Protons in solution are controllably embedded into the WO₃ photoanode accompanied by electron injection due to the strong reduction capability of GBLMs. This process dramatically increases the carrier concentration of the WO₃ photoanode, leading to improved charge separation and transfer. The hydrogenated WO₃ photoanode exhibits over a 229% improvement in photocurrent density with long-term stability. The effectiveness of GBLMs treatment in accelerating the CST process is further proved using other more general semiconductor photoelectrodes, including Nb₂O₅ and TiO₂.

Lignin: A Sustainable Antiviral Coating Material

Transmission of viruses through contact with contaminated surfaces is an important pathway for the spread of infections. Antiviral surface coatings are useful to minimize such risks. Current state-of-the-art approaches toward antiviral surface coatings either involve metal-based materials or complex synthetic polymers. These approaches, however, even if successful, will have to face great challenges when it comes to large-scale applications and their environmental sustainability. Here, an antiviral surface coating was prepared by spin-coating lignin, a natural biomass residue of the paper production industry. We show effective inactivation of herpes simplex virus type 2 (>99% after 30 min) on a surface coating that is low-cost and environmentally sustainable. The antiviral mechanism of the lignin surface was investigated and is attributed to reactive oxygen species generated upon oxidation of lignin phenols. This mechanism does not consume the surface coating (as opposed to the release of a specific antiviral agent) and does not require regeneration. The coating is stable in ambient conditions, as demonstrated in a 6 month aging study that did not reveal any decrease in antiviral activity. This research suggests that natural compounds may be used for the development of affordable and sustainable antiviral coatings.

Assembly of surface-independent polyphenol/liquid gallium composite nanocoatings

The development of functional nanocoatings using natural compounds is a hallmark of sustainable strategies in the field of green synthesis. Herein, we report a surface-independent nanocoating strategy using natural polyphenols and gallium-based room temperature liquid metal nanoparticles. The nanocoating matrix is composed of tannic acid, crosslinked with group (IV) transition metal ions. Liquid gallium nanoparticles are incorporated into the coatings as a gallium ion releasing depot. The coating deposition is rapid and can be applied to a range of substrates including glass, plastics, paper, and metal surfaces, owing to the versatile adhesive nature of the catechol/gallol functional groups of tannic acid. The coating thickness can be controlled from 100 to 700 nm and the content of liquid gallium nanoparticles can be modulated. This enables the tunable release behaviour of gallium ions into the surrounding from the composite coatings. The coatings are highly biocompatible and display antioxidant and antibacterial properties that can be useful for diverse applications.

Violacein-embedded nanofiber filters with antiviral and antibacterial activities

Most respiratory masks are made of fabrics, which only capture the infectious virus carriers into the matrix. However, these contagious viruses stay active for a long duration (∼7 days) within the fabric matrix possibly inducing post-contact transmissions. Moreover, conventional masks are vulnerable to bacterial growth with prolonged exposure to exhaled breaths. Herein, we combined violacein, a naturally-occurring antimicrobial agent, with porous nanofiber membranes to develop a series of functional filters that autonomously sterilizes viruses and bacteria. The violacein-embedded membrane inactivates viruses within 4 h (99.532 % reduction for influenza and 99.999 % for human coronavirus) and bacteria within 2 h (75.5 % reduction). Besides, its nanofiber structure physically filters out the nanoscale (<0.8 μm) and micron-scale (0.8 μm - 3 μm) particulates, providing high filtration efficiencies (99.7 % and 100 % for PM 1.0 and PM 10, respectively) with long-term stability (for 25 days). In addition, violacein provides additional UV-resistant property, which protects the skin from sunlight. The violacein-embedded membrane not only proved the sterile efficacy of microbe extracted pigments for biomedical products but also provided insights to advance the personal protective equipment (PPE) to fight against contagious pathogens.

Bifunctional Amphiphilic Nanospikes with Antifogging and Antibiofouling Properties

Over the past few decades, extensive research efforts have been devoted to developing surfaces with unique functionalities, such as controlled wettability, antibiofouling, antifogging, and anti-icing behavior, for applications in a wide range of fields, including biomedical devices, optical instruments, microfluidics, and energy conservation and harvesting. However, many of the previously reported approaches have limitations with regard to eco-friendliness, multifunctionality, long-term stability and efficacy, and cost effectiveness. Herein, we propose a scalable bifunctional surface that simultaneously exhibits excellent antifogging and antibiofouling properties based on the synergistic integration of an eco-friendly and bio-friendly polyethylene glycol (PEG) hydrogel, oleamide (OA), and nanoscale architectures in a single flexible platform. We demonstrate that the PEG-OA-nanostructure hybrid exhibits excellent antifogging performance owing to its enhanced water absorption and spreading properties. We further show that the triple hybrid exhibits notable biofilm resistance without the use of toxic biocides or chemicals by integrating the "fouling-resistant" mechanism of the PEG hydrogel, the "fouling-release" mechanism of OA, and the "foulant-killing" mechanism of the nanostructures.

Gallium-Based Liquid Metal Materials for Antimicrobial Applications

The hazards caused by drug-resistant bacteria are rocketing along with the indiscriminate use of antibiotics. The development of new non-antibiotic antibacterial drugs is urgent. The excellent biocompatibility and diverse multifunctionalities of liquid metal have stimulated the studies of antibacterial application. Several gallium-based antimicrobial agents have been developed based on the mechanism that gallium (a type of liquid metal) ions disorder the normal metabolism of iron ions. Other emerging strategies, such as physical sterilization by directly using LM microparticles to destroy the biofilm of bacteria or thermal destruction via infrared laser irradiation, are gaining increasing attention. Different from traditional antibacterial agents of gallium compounds, the pronounced property of gallium-based liquid metal materials would bring innovation to the antibacterial field. Here, LM-based antimicrobial mechanisms, including iron metabolism disorder, production of reactive oxygen species, thermal injury, and mechanical destruction, are highlighted. Antimicrobial applications of LM-based materials are summarized and divided into five categories, including liquid metal motors, antibacterial fabrics, magnetic field-responsive microparticles, liquid metal films, and liquid metal polymer composites. In addition, future opportunities and challenges towards the development and application of LM-based antimicrobial materials are presented.

Liquid-Metal-Coated Magnetic Particles toward Writable, Nonwettable, Stretchable Circuit Boards, and Directly Assembled Liquid Metal-Elastomer Conductors

Liquid metal is a promising conductor material for producing soft and stretchable circuit "boards" that can enable next-generation electronics by electrically connecting and mechanically supporting electronic components. While liquid metal in general can be used to fabricate soft and stretchable circuits, magnetic liquid metal is appealing because it can be used for self-healing electronics and actuators by external magnetic fields. Liquid metal can be rendered into particles that can then be used for sensors and catalysts through sonication. We used this feature to produce "novel" conductive and magnetic particles. Mixing ferromagnetic iron particles into the liquid metal (gallium) produces conductive ferrofluids that can be rendered into gallium-coated iron particles by sonication. The gallium shell of the particles is extremely soft, while the rigid iron core can induce high friction in response to mechanical pressure; thus, hand-sintering of the particles can be used to directly write the conductive traces when the particles are cast as a film on elastic substrates. The surface topography of the particles can be manipulated by forming GaOOH crystals through sonication in DI water, thus resulting in nonwettable circuit boards. These gallium-coated iron particles dispersed in uncured elastomer can be assembled to form conductive microwires with the application of magnetic fields.

A Personalized Electronic Tattoo for Healthcare Realized by On-the-Spot Assembly of an Intrinsically Conductive and Durable Liquid-Metal Composite

Conventional electronic (e-) skins are a class of thin-film electronics mainly fabricated in laboratories or factories, which is incapable of rapid and simple customization for personalized healthcare. Here a new class of e-tattoos is introduced that can be directly implemented on the skin by facile one-step coating with various designs at multi-scale depending on the purpose of the user without a substrate. An e-tattoo is realized by attaching Pt-decorated carbon nanotubes on gallium-based liquid-metal particles (CMP) to impose intrinsic electrical conductivity and mechanical durability. Tuning the CMP suspension to have low-zeta potential, excellent wettability, and high-vapor pressure enables conformal and intimate assembly of particles directly on the skin in 10 s. Low-cost, ease of preparation, on-skin compatibility, and multifunctionality of CMP make it highly suitable for e-tattoos. Demonstrations of electrical muscle stimulators, photothermal patches, motion artifact-free electrophysiological sensors, and electrochemical biosensors validate the simplicity, versatility, and reliability of the e-tattoo-based approach in biomedical engineering.

Application of Fluconazole-Loaded pH-Sensitive Lipid Nanoparticles for Enhanced Antifungal Therapy

Cryptococcus neoformans is a yeast-like fungus that can cause the life-threatening disease cryptococcal meningitis. Numerous reports have shown increased resistance of this fungus against antifungal treatments, such as fluconazole (Fluc), contributing to an 80% global mortality rate. This work presents a novel approach to improve the delivery of the antifungal agent Fluc and increase the drug's targetability and availability at the infection site. Exploiting the acidic environment surrounding a C. neoformans infected site, we have developed pH-sensitive lipid nanoparticles (LNP) encapsulating Fluc to inhibit the growth of resistant C. neoformans. The LNP-Fluc delivery system consists of a neutral lipid monoolein (MO) and a novel synthetic ionizable lipid 2-morpholinoethyl oleate (O2ME). At neutral pH, because of the presence of O2ME, the nanoparticles are neutral and exhibit a liquid crystalline hexagonal nanostructure (hexosomes). At an acidic pH, they are positively charged with a cubic nanostructure (cubosomes), which facilitates the interaction with the negatively charged fungal cell wall. This interaction results in the MIC50 and MIC90 values of the LNP-Fluc being significantly lower than that of the free-Fluc control. Confocal laser scanning microscopy and scanning electron microscopy further support the MIC values, showing fungal cells exposed to LNP-Fluc at acidic pH were heavily distorted, demonstrating efflux of cytoplasmic molecules. In contrast, fungal cells exposed to Fluc alone showed cell walls mostly intact. This current study represents a significant advancement in delivering targeted antifungal therapy to combat fungal antimicrobial resistance.

Gallium Nanodroplets are Anti-Inflammatory without Interfering with Iron Homeostasis

Gallium (Ga) compounds, as the source of Ga ions (Ga³⁺), have been historically used as anti-inflammatories. Currently, the widely accepted mechanisms of the anti-inflammatory effects for Ga³⁺ are rationalized on the basis of their similarities to ferric ions (Fe³⁺), which permits Ga³⁺ to bind with Fe-binding proteins and subsequently disturbs the Fe homeostasis in the immune cells. Here in contrast to the classic views, our study presents the mechanisms of Ga as anti-inflammatory by delivering Ga nanodroplets (GNDs) into lipopolysaccharide-induced macrophages and exploring the processes. The GNDs show a selective inhibition of nitric oxide (NO) production without affecting the accumulation of pro-inflammatory mediators. This is explained by GNDs disrupting the synthesis of inducible NO synthase in the activated macrophages by upregulating the levels of eIF2α phosphorylation, without interfering with the Fe homeostasis. The Fe³⁺ transferrin receptor-independent endocytosis of GNDs by the cells prompts a fundamentally different mechanism as anti-inflammatories in comparison to that imparted by Ga³⁺. This study reveals the fundamental molecular basis of GND-macrophage interactions, which may provide additional avenues for the use of Ga for anti-inflammatory and future biomedical and pharmaceutical applications.

Gallium-Strontium Phosphate Conversion Coatings for Promoting Infection Prevention and Biocompatibility of Magnesium for Orthopedic Applications

Device-associated infections remain a clinical challenge. The common strategies to prevent bacterial infection are either toxic to healthy mammalian cells and tissue or involve high doses of antibiotics that can prompt long-term negative consequences. An antibiotic-free coating strategy to suppress bacterial growth is presented herein, which concurrently promotes bone cell growth and moderates the dissolution kinetics of resorbable magnesium (Mg) biomaterials. Pure Mg as a model biodegradable material was coated with gallium-doped strontium-phosphate through a chemical conversion process. Gallium was distributed in a gradual manner throughout the strontium-phosphate coating, with a compact structure and a gallium-rich surface. It was demonstrated that the coating protected the underlying Mg parts from significant degradation in minimal essential media at physiological conditions over 9 days. In terms of bacteria culture, the liberated gallium ions from the coatings upon Mg specimens, even though in minute quantities, inhibited the growth of Gram-positiveStaphylococcus aureus, Gram-negative Escherichia coli, andPseudomonas aeruginosa ─ key pathogens causing infection and early failure of the surgical implantations in orthopedics and trauma. More importantly, the gallium dopants displayed minimal interferences with the strontium-phosphate-based coating which boosted osteoblasts and undermined osteoclasts in in vitro co-cultures. This work provides a new strategy to prevent bacterial infection and control the degradation behavior of Mg-based orthopedic implants, while preserving osteogenic features of the devices.

Surface Functionalities of Polymers for Biomaterial Applications

Changes of a material biointerface allow for specialized cell signaling and diverse biological responses. Biomaterials incorporating immobilized bioactive ligands have been widely introduced and used for tissue engineering and regenerative medicine applications in order to develop biomaterials with improved functionality. Furthermore, a variety of physical and chemical techniques have been utilized to improve biomaterial functionality, particularly at the material interface. At the interface level, the interactions between materials and cells are described. The importance of surface features in cell function is then examined, with new strategies for surface modification being highlighted in detail.

How to Make Personal Protective Equipment Spontaneously and Continuously Antimicrobial (Incorporating Oxidase-like Catalysts)

The inability of commercial personal protective equipment (PPE) to inactivate microbes in the droplets/aerosols they intercept makes used PPE a potential source of cross-contamination. To make PPE spontaneously and continuously antimicrobial, we incorporate PPE with oxidase-like catalysts, which efficiently convert O₂ into reactive oxygen species (ROS) without requiring any externally applied stimulus. Using a single-atom catalyst (SAC) nanoparticle containing atomically dispersed copper atoms as the reactive centers (Cu-SAC) and a silver-palladium bimetallic alloy nanoparticle (AgPd_0.38) as models for oxidase-like catalysts, we show that the incorporation of oxidase-like catalysts enables PPE to inactivate bacteria in the droplets/aerosols they intercept without requiring any externally applied stimulus. Notably, this approach works both for PPE that are fibrous and woven such as a commercial KN95 facial respirator and for those made of solid plastics such as an apron. This work suggests a feasible and global approach for preventing PPE from spreading infectious diseases.

A core-shell liquid metal-Cu nanoparticle with glutathione consumption via an in situ replacement strategy for tumor combination treatment of chemodynamic, microwave dynamic and microwave thermal therapy

The presence of high content glutathione (GSH) provides an effective "protective shield" for tumor cells, which undoubtedly is a huge impediment to reactive oxygen species (ROS)-based treatment. Fortunately, divalent copper (Cu²⁺) can not only consume GSH, destroying the protection mechanism of GSH, but also can be reduced to Cu⁺ with excellent Fenton-like reaction activity. Hence, capitalizing on the properties of liquid metals, we introduced Cu with three different valances via an in situ replacement reaction. A stable core-shell liquid-metal based "Cu storage pool" was obtained. It can effectively deplete GSH within the cells, and simultaneously produce ·OH through a Fenton-like reaction, further improving the effect of chemodynamic therapy (CDT). Under microwave irradiation, it is also capable of producing a large amount of ROS to promote tumor treatment. In addition, the loading of ionic liquid endows LZC@IL nanoparticles with certain microwave heating performance, which is able to augment microwave thermal therapy (MWTT). With the combination of CDT, microwave dynamic therapy (MDT) and MWTT, LZC@IL has an excellent effect on tumor elimination. This work offers a new idea for the application of liquid metals and the combined treatment of tumors, which has potential application value.

Antibacterial Longevity of a Novel Gallium Liquid Metal/Hydroxyapatite Composite Coating Fabricated by Plasma Spray

Hydroxyapatite (HAp)-coated metallic implants are known for their excellent bioactivity and osteoconductivity. However, infections associated with the microstructure of the HAp coatings may lead to implant failures as well as increased morbidity and mortality. This work addresses the concerns about infections by developing novel composite coatings of HAp and gallium liquid metal (GaLM) using atmospheric plasma spray (APS) as the coating technique. Five weight percent Ga was mixed into a commercially supplied HAp powder using an orbital shaker; then, the HAp-Ga particle feedstock was coated onto Ti₆Al₄V substrates using the APS technique. The X-ray diffraction results indicated that Ga did not form any Ga-related phases in either the HAp-Ga powder or the respective coating. The GaLM filled the pores of the HAp coating presented both on the top surface and within the coating, especially at voids and cracks, to prevent failures of the coating at these locations. The wettability of the surface was changed from hydrophobic for the HAp coating to hydrophilic for the HAp-Ga composite coating. Finally, the HAp-Ga coating presented excellent antibacterial efficacies against both initial attachments and established biofilms generated from methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa after 18 h and 7 days of incubation in comparison to the control HAp coating. This study shows that GaLM improves the antibacterial properties of HAp-based coatings without sacrificing the beneficial properties of conventional HAp coatings. Thus, the HAp-Ga APS coating is a viable candidate for antibacterial coatings.