Melatonin-loaded mesoporous zinc- and gallium-doped hydroxyapatite nanoparticles to control infection and bone repair

Effective treatment of infected bone defects resulting from multi-drug resistant bacteria (MDR) has emerged as a significant clinical challenge, highlighting the pressing demand for potent antibacterial bone graft substitutes. Mesoporous nanoparticles have been introduced as a promising class of biomaterials offering significant properties for treating bone infections. Herein, we synthesize antibacterial mesoporous hydroxyapatite substituted with zinc and gallium (Zn-Ga:mHA) nanoparticles using a facile sol-gel method. The resulting mesoporous nanoparticles are applied for the controlled release of melatonin (Mel). Zn-Ga:mHA nanoparticles with an average particle size of 36 ± 3 nm and pore size of 10.6 ± 0.4 nm reveal a Mel loading efficiency of 58 ± 1%. Results show that 50% of Mel is released within 20 h and its long-term release is recorded up to 50 h. The Zn-Ga:mHA nanoparticles exhibit highly effective antibacterial performance as reflected by a 19 ± 1% and 8 ± 2% viability reduction in Escherichia coli and Staphylococcus bacteria, respectively. Noticeably, Mel-loaded Zn-Ga:mHA nanoparticles are also cytocompatible and stimulate in vitro osteogenic differentiation of human mesenchymal stem cells (hMSCs) without any osteoinductive factor. In vivo studies in a rabbit skull also show significant regeneration of bone during 14 days. In summary, Mel-loaded Zn-Ga:mHA nanoparticles provide great potential as an antibacterial and osteogenic component in bone substitutes like hydrogels, scaffolds, and coatings.

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.

Gallium-based liquid metals as smart responsive materials: Morphological forms and stimuli characterization

Gallium-based liquid metals (GaLMs) have garnered monumental attention from the scientific community due to their diverse actuation characteristics. These metals possess remarkable characteristics, including high surface tension, excellent electrical and thermal conductivity, phase transformation behaviour, minimal viscosity and vapour pressure, lack of toxicity, and biocompatibility. In addition, GaLMs have melting points that are either lower or near room temperature, making them incredibly beneficial when compared to solid metals since they can be easily deformed. Thus, there has been significant progress in developing multifunctional devices using GaLMs, including bio-devices, flexible and self-healing circuits, and actuators. Despite numerous reports on these liquid metals (LMs), there is an urgent need for consolidated and coherent literature regarding their actuation principles linked to the targeted application. This will ensure that the reader gets the flavour of physics behind the actuation mechanism and how it can be utilized in diverse fields. Moreover, the actuation mechanism has been scattered in the literature, and thus, the primary motive of this review is to provide a one-stop solution for the actuation mechanism and the associated dynamics while directing the readers to specialized literature. Thus, addressing this issue, we thoroughly examine and present a detailed account of the actuation mechanisms of GaLMs while highlighting the science behind them. We also discuss the various morphologies of GaLMs and their crucial physical characteristics which decide their targeted application. Furthermore, we also delve into commonly held beliefs about GaLMs in the literature, such as their toxicity and antibacterial properties, to offer readers a more accurate understanding. Finally, we have explored several key unanswered aspects of the LM that should be explored in future research. The core strength of this review lies in its simplistic approach in offering a starting point for researchers venturing this innovative field, while we make use of existing literature to develop a comprehensive understanding.

Effect of gallium nitrate on the antibacterial activity of vancomycin in methicillin-sensitive and resistant Staphylococcus aureus

The extension of multidrug-resistant strains of Staphylococcus aureus (S. aureus) is one of the main health challenges in the world, which requires serious solutions to deal with it. Combination therapies using conventional antibiotics and new antibacterial compounds that target different bacterial pathways are effective methods against resistant bacterial infections. Gallium is an iron-like metal that competes with iron for uptake into bacteria and has the potential to disrupt iron-dependent vital processes in bacteria. In this study, we explored the antibacterial effects of gallium nitrate (Ga(NO3)3) and vancomycin alone and in combination with each other on methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) using microdilution assay and checkerboard test, respectively. Then, their effect on the formation and destruction of biofilms was investigated. Finally, the amount of ROS production in the presence of these two compounds in bacteria was evaluated. The results indicated that the vancomycin/ Ga(NO3)3 combination reduced the MIC of vancomycin in the MRSA strain and had an additive effect on it. Vancomycin plus Ga(NO3)3 reduced the formation of biofilms and increased the destruction of biofilms formed in both strains, especially in the MRSA strain. ROS production was also higher in the combination of vancomycin with Ga(NO3)3 compared to vancomycin alone, especially in MRSA. Therefore, our results showed that Ga(NO3)3 enhances the antibacterial activity of vancomycin and this combination therapy can be considered as a new strategy for the treatment of MRSA infections.

Recent advances and progress on the design, fabrication and biomedical applications of Gallium liquid metals-based functional materials

Gallium (Ga) is a well-known liquid metals (LMs) that possesses the features, such as fluidity, low viscosity, high electrical and thermal conductivity, and relative low toxicity. Owing to the weak interactions between Ga atoms, Ga LMs can be adopted for fabrication of various Ga LMs-based functional materials via ultrasonic treatment and mechanical grinding. Moreover, many organic compounds/polymers can be coated on the surface of LMs-based materials through coordination between oxidized outlayers of Ga LMs and functional groups of organic components. Over the past decades, different strategies have been reported for synthesizing Ga LMs-based functional materials and their biomedical applications have been intensively investigated. Although some review articles have published over the past few years, a concise review is still needed to advance the latest developments in biomedical fields. The main context can be majorly divided into two parts. In the first section, various strategies for fabrication of Ga LMs-based functional materials via top-down strategies were introduced and discussed. Following that, biomedical applications of Ga LMs-based functional materials were summarized and design Ga LMs-based functional materials with enhanced performance for cancer photothermal therapy (PTT) and PTT combined therapy were highlighted. We trust this review article will be beneficial for scientists to comprehend this promising field and greatly advance future development for fabrication of other Ga LMs-based functional materials with better performance for biomedical applications.

In Situ Synthesis of Liquid Metal Conductive Fibers toward Smart Cloth

To meet the diverse needs of humans, smart cloth has become a potential research hotspot to replace traditional cloth. However, it is challenging to manufacture a flexible fabric with multiple functions. Here, we introduce a smart cloth based on liquid metal (LM) conductive fibers. Ga2O3 nanoparticles are obtained through ultrasonic pretreatment. Furthermore, a coordination bond is formed between thiol groups on the surface of protein fibers and Ga2O3 through a scraping method, allowing Ga2O3 particles to be grafted onto the surface of protein fibers in situ. Finally, LM conductive fibers are encapsulated using a photocuring adhesive. In addition, a wearable smart cloth integrated with multiple sensors has been developed based on LM conductive fibers. Users can not only monitor their movement trajectory and the surrounding environment in real time but also have their data supervised by family members through a client, achieving remote and continuous monitoring. The development of this wearable smart cloth provides strong support for future wearable, flexible electronic devices.

A review of recent advances in the use of complex metal nanostructures for biomedical applications from diagnosis to treatment

Complex metal nanostructures represent an exceptional category of materials characterized by distinct morphologies and physicochemical properties. Nanostructures with shape anisotropies, such as nanorods, nanostars, nanocages, and nanoprisms, are particularly appealing due to their tunable surface plasmon resonances, controllable surface chemistries, and effective targeting capabilities. These complex nanostructures can absorb light in the near-infrared, enabling noteworthy applications in nanomedicine, molecular imaging, and biology. The engineering of targeting abilities through surface modifications involving ligands, antibodies, peptides, and other agents potentiates their effects. Recent years have witnessed the development of innovative structures with diverse compositions, expanding their applications in biomedicine. These applications encompass targeted imaging, surface-enhanced Raman spectroscopy, near-infrared II imaging, catalytic therapy, photothermal therapy, and cancer treatment. This review seeks to provide the nanomedicine community with a thorough and informative overview of the evolving landscape of complex metal nanoparticle research, with a specific emphasis on their roles in imaging, cancer therapy, infectious diseases, and biofilm treatment. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Diagnostic Tools > Diagnostic Nanodevices.

Regenerated silk fibroin coating stable liquid metal nanoparticles enhance photothermal antimicrobial activity of hydrogel for wound infection repair

The integration of liquid metal (LM) and regenerated silk fibroin (RSF) hydrogel holds great potential for achieving effective antibacterial wound treatment through the LM photothermal effect. However, the challenge of LM's uncontrollable shape-deformability hinders its stable application. To address this, we propose a straightforward and environmentally-friendly ice-bath ultrasonic treatment method to fabricate stable RSF-coated eutectic gallium indium (EGaIn) nanoparticles (RSF@EGaIn NPs). Additionally, a double-crosslinked hydrogel (RSF-P-EGaIn) is prepared by incorporating poly N-isopropyl acrylamide (PNIPAAm) and RSF@EGaIn NPs, leading to improved mechanical properties and temperature sensitivity. Our findings reveal that RSF@EGaIn NPs exhibit excellent stability, and the use of near-infrared (NIR) irradiation enhances the antibacterial behavior of RSF-P-EGaIn hydrogel in vivo. In fact, in vivo testing demonstrates that wounds treated with RSF-P-EGaIn hydrogel under NIR irradiation completely healed within 14 days post-trauma infection, with the formation of new skin and hair. Histological examination further indicates that RSF-P-EGaIn hydrogel promoted epithelialization and well-organized collagen deposition in the dermis. These promising results lay a solid foundation for the future development of drug release systems based on photothermal-responsive hydrogels utilizing RSF-P-EGaIn.

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.

Using chitosan nanofibers to synergistically construct a highly stretchable multi-functional liquid mental-based hydrogel for assembling strain sensor with high sensitivity and broad working range

Liquid metal (LM) microdroplets have garnered significant interest as conductive materials for initiating free radical polymerization in the development of conductive hydrogels suited for strain sensors. However, crafting multi-functional conductive hydrogels that boast both high stretchability and superior sensing capabilities remains as a challenge. In this study, we have successfully synthesized LM-based conductive hydrogels characterized by remarkable stretchability and sensing performance employing acrylic acid (AA) to evenly distribute chitosan nanofibers (CSFs) and to subsequently catalyze the free radical polymerization of AA. The resultant polymer network was crosslinked within situ polyacrylic acid (PAA), facilitated by Ga3+ in conjunction with guar gum (GG)-stabilized Ga droplets. The strategic interplay between the rigid, and protonated CSFs and the pliable PAA matrix, coupled with the ionic crosslinking of Ga3+, endows the resulting GG-Ga-CSF-PAA hydrogel with high stretchability (3700 %), ultrafast self-healing, robust moldability, and strong adhesiveness. When deployed as a strain sensing material, this hydrogel exhibits a high gauge factor (38.8), a minimal detection threshold, enduring durability, and a broad operational range. This versatility enables the hydrogel-based strain sensor to monitor a wide spectrum of human motions. Remarkably, the hydrogel maintains its stretchability and sensing efficacy under extreme temperatures after a simple glycerol solution treatment.

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.

Self-healing and durable antifouling zwitterionic hydrogels based on functionalized liquid metal microgels

Hydrogels are a promising new class of antifouling materials. But their utility is constrained by low mechanical strength and unsatisfactory antifouling performance over the long term. Herein, we successfully prepared zwitterionic polymer PEIS cross-linked gallium-based liquid metal microgels-based (PEIS-Gel@PMPC-GLM) hydrogels via UV-curing and amidation reaction. The as-prepared hydrogels showed preferable mechanical properties and superior hydrophilicity to the original hydrogels. The PEIS-Gel@PMPC-GLM hydrogels could prevent the adhesion of more than 90 % of microalgae and nearly 100 % of bacteria in a short-term antifouling test. PEIS-Gel@PMPC-GLM hydrogels also performed exceptionally well in the high concentration antibacterial test and the long-term antifouling test (remove more than 90 % bacteria and 80 % microalgae). In addition to releasing a high concentration of gallium ions, as shown by the ICP-OES test, PEIS-Gel@PMPC-GLM hydrogels also exhibitedexcellent lubrication performance, as demonstrated by the friction test (coefficient of friction as low as 0.023). Therefore, the antifouling effect of gallium ions combined with the strong hydration ability of the surfaces endowed the hydrogels remarkable antibacterial and antifouling properties. As a result of the exposed gallium atoms inducing further crosslinking of residual vinyl monomer in hydrogels, PEIS-Gel@PMPC-GLM hydrogels revealed certain self-healing performance.

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.

Gallium-based metal-organic frameworks loaded with antimicrobial peptides for synergistic killing of drug-resistant bacteria

Increased antibiotic resistance has made bacterial infections a global concern, which requires novel non-antibiotic-dependent antibacterial strategies to address the menace. Antimicrobial peptides (AMPs) are a promising antibiotic alternative, whose antibacterial mechanism is mainly to destroy the membrane of bacteria. Gallium ions exhibit an antibacterial effect by interfering with the iron metabolism of bacteria. With the rapid development of nanotechnology, it is worth studying the potential of gallium-AMP-based nanocomposites for treating bacterial infections. Herein, novel gallium-based metal-organic frameworks (MOFs) were synthesized at room temperature, followed by in situ loading of the model AMP melittin. The obtained nanocomposites exhibited stronger antibacterial activity than pure MEL and gallium ions, achieving the effects of "one plus one is greater than two". Moreover, the nanocomposites showed favorable biocompatibility and accelerated healing of a wound infected by methicillin-resistant Staphylococcus aureus by down-regulation of inflammatory cytokines IL-6 and TNF-α. This work presents an innovative antibacterial strategy to overcome the antibiotic resistance crisis and expand the application of AMPs.

Gallium Liquid Metal: Nanotoolbox for Antimicrobial Applications

The proliferation of drug resistance in microbial pathogens poses a significant threat to human health. Hence, treatment measures are essential to surmount this growing problem. In this context, liquid metal nanoparticles are promising. Gallium, a post-transition metal notable for being a liquid at physiological temperature, has drawn attention for its distinctive properties, high antimicrobial efficacy, and low toxicity. Moreover, gallium nanoparticles demonstrate anti-inflammatory properties in immune cells. Gallium can alloy with other metals and be prepared in various composites to modify and tailor its characteristics and functionality. More importantly, the bactericidal mechanism of gallium liquid metal could sidestep the threat of emerging drug resistance mechanisms. Building on this rationale, gallium-based liquid metal nanoparticles can enable impactful and innovative strategic pathways in the battle against antimicrobial resistance. This review outlines the characteristics of gallium-based liquid metals at the nanoscale and their corresponding antimicrobial mechanisms to provide a comprehensive yet succinct overview of their current antimicrobial applications. In addition, challenges and opportunities that require further research efforts have been identified and discussed.

Constructing liquid metal/metal-organic framework nanohybrids with strong sonochemical energy storage performance for enhanced pollutants removal

With endogenous redox systems and multiple enzymes, the storage and utilization of external energy is general in living cells, especially through photo/ultrasonic synthesis/catalysis due to in-situ generation of abundant reactive oxygen species (ROS). However, in artificial systems, because of extreme cavitation surroundings, ultrashort lifetime and increased diffusion distance, sonochemical energy is rapidly dissipated via electron-hole pairs recombination and ROS termination. Here, we integrate zeolitic imidazolate framework-90 (ZIF-90) and liquid metal (LM) with opposite charges by convenient sonosynthesis, and the resultant nanohybrid (LMND@ZIF-90) can efficiently capture sonogenerated holes and electrons, and thus suppress electron-hole pairs recombination. Unexpectedly, LMND@ZIF-90 can store the ultrasonic energy for over ten days and exhibit acid-responsive release to trigger persistent generation of various ROS including superoxide (O₂•^-), hydroxyl radicals (•OH), and singlet oxygen (¹O₂), presenting significantly faster dye degradation rate (short to seconds) than previously reported sonocatalysts. Moreover, unique properties of gallium could additionally facilitate heavy metals removal through galvanic replacement and alloying. In summary, the LM/MOF nanohybrid constructed here demonstrates strong capacity for storing sonochemical energy as long-lived ROS, enabling enhanced water decontamination without energy input.

Green Synthesis of Liquid Metal-Doped Carbon Dots for Treating Multidrug-Resistant Gram-Negative Bacteria

Global emergence of multidrug-resistant (MDR) gram-negative bacteria triggers severe infections that result in an epidemic. It is urgent to discover novel classes of antibacterial agents. Here, a green route for synthesizing polyethylene glycol-based carbon dots (PEG-CDs) doped with liquid metal (LM-Cdots) via a solvent-free system is presented. LM-Cdots synthesized via ultrasound exhibit great antibacterial activity against gram-negative bacteria (E. coli, P. aeruginosa, K. pneumoniae, and A. baumannii) and their multidrug-resistant (MDR) clinical isolates. In the in vitro antibacterial test with MDR K. pneumoniae, LM-Cdots show an extremely low minimum inhibition concentration (MIC) of 0.63 µg mL-1 . Compared to naked PEG-CDs, the MIC is improved by 1000 times. In vivo results reveal that LM-Cdots can accelerate wound healing with low biotoxicity and inflammation.

A liquid metal-polydopamine composite for cell culture and electro-stimulation

Gallium (Ga) is a low melting point metal in the liquid state in the biological environment which presents a unique combination of fluidity, softness, and metallic electrical and thermal properties. In this work, liquid Ga is proposed as a biocompatible electrode material for cell culture by electro-stimulation since the cytotoxicity of Ga is generally considered low and some Ga compounds have been reported to exhibit anti-bacterial and anti-inflammatory activities. Complementarily, polydopamine (PDA) was coated on liquid Ga to increase the attachment capability of cells on the liquid Ga electrode and provide enhanced biocompatibility. The liquid Ga layer could be readily painted at room temperature on a solid inert substrate, followed by the formation of a nanoscale PDA coating layer resulting in a conformable and biocompatible composite electrode. The PDA layer was shown to coordinate with Ga³⁺, which is sourced from liquid Ga, providing electrical conductivity in the cell culture medium. The PDA-Ga³⁺ composite acted as a conductive substrate for advanced electro-stimulation for cell culture methods of representative animal fibroblasts. The cell proliferation was observed to increase by ∼143% as compared to a standard glass coverslip at a low potential of 0.1 V of direct coupling stimulation. This novel PDA-Ga³⁺ composite has potential applications in cell culture and regenerative medicine.

Liquid metal integrated PU/CNT fibrous membrane for human health monitoring

Wearable flexible sensors are widely used in several applications such as physiological monitoring, electronic skin, and telemedicine. Typically, flexible sensors that are made of elastomeric thin-films lack sufficient permeability, which leads to skin inflammation, and more importantly, affects signal detection and consequently, reduces the sensitivity of the sensor. In this study, we designed a flexible nanofibrous membrane with a high air permeability (6.10 mm/s), which could be effectively used to monitor human motion signals and physiological signals. More specifically, a flexible membrane with a point (liquid metal nanoparticles)-line (carbon nanotubes)-plane (liquid metal thin-film) multiscale conductive structure was fabricated by combining liquid metal (LM) and carbon nanotubes (CNTs) with a polyurethane (PU) nanofibrous membrane. Interestingly, the excellent conductivity and fluidity of the liquid metal enhanced the sensitivity and stability of the membrane. More precisely, the gauge factor (GF) values of the membrane is 3.0 at 50% strain and 14.0 at 400% strain, which corresponds to a high strain sensitivity within the whole range of deformation. Additionally, the proposed membrane has good mechanical properties with an elongation at a break of 490% and a tensile strength of 12 MPa. Furthermore, the flexible membrane exhibits good biocompatibility and can efficiently monitor human health signals, thereby indicating potential for application in the field of wearable electronic devices.

Defect-Modified nano-BaTiO3 as a Sonosensitizer for Rapid and High-Efficiency Sonodynamic Sterilization

Multidrug-resistant bacteria caused by the unlimited overuse of antibiotics pose a great challenge to global health. An antibacterial method based on reactive oxygen species (ROS) is one of the effective strategies without inducing bacterial resistance. Owing to the ability of generating ROS, piezocatalytic material-mediated sonodynamic therapy (SDT) has drawn much attention. However, its major challenge is the low ROS generation efficiency in the piezocatalytic process due to the poor charge carrier concentration of piezoelectric materials. Vacancy engineering can regulate the charge density and largely promote ROS generation under ultrasound (US) irradiation. Herein, a US-responsive self-doped barium titanate with controlled oxygen vacancy (Vo) concentrations was successfully synthesized through a facile thermal reduction treatment at different temperatures (i.e., 350, 400, and 450 °C), and the corresponding samples were named as BTO-350, BTO-400, and BTO-450, respectively. Then, the effect of Vo concentrations on ROS generation efficiency during the piezocatalytic process was systematically studied. And BTO-400 was found to possess the highest piezocatalytic activity and excellent sonodynamic antibacterial performance against Escherichia coli and Staphylococcus aureus. Furthermore, its antibacterial mechanism was confirmed that the ROS generated under US could damage bacterial cell membrane and cause considerable leakage of cytoplasmic components and irreversible death of bacteria. Notably, the in vivo results illustrated that the BTO-400 could serve as an effective antibacterial agent and accelerate skin healing via SDT therapy. In all, the Vo defect-modified nano-BaTiO₃ has a noticeable potential to induce a rapid and efficient sterilization as well as skin tissue repair by SDT.

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.

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.

Magnetic Microswarm and Fluoroscopy-Guided Platform for Biofilm Eradication in Biliary Stents

Biofilm eradication from medical implants is of fundamental importance, and the treatment of biofilm-associated pathogen infections on inaccessible biliary stents remains challenging. Magnetically driven microrobots with controlled motility, accessibility to the tiny lumen, and swarm enhancement effects can physically disrupt the deleterious biostructures while not developing drug resistance. Magnetic urchin-like capsule robots (MUCRs) loaded with magnetic liquid metal droplets (MLMDs, antibacterial agents) are designed using natural sunflower pollen, and the therapeutic effect of swarming MUCR@MLMDs is explored for eradicating complex mixtures of bacterial biofilm within biliary stents collected from patients. The external magnetic field triggers the emergence of the microswarm and induces MLMDs to transform their shape into spheroids and rods with sharp edges. The inherent natural microspikes of MUCRs and the obtained sharp edges of MLMDs actively rupture the dense biological matrix and multiple species of embedded bacterial cells by exerting mechanical force, finally achieving synergistic biofilm eradication. The microswarm is precisely and rapidly deployed into the biliary stent via endoscopy in 10 min. Notably, fluoroscopy imaging is used to track and navigate the locomotion of microswarm in biliary stents in real-time. The microswarm has great potential for treating bacterial biofilm infections associated with medical implants.

Advancement of Gallium and Gallium-Based Compounds as Antimicrobial Agents

With the abuse and misuse of antibiotics, antimicrobial resistance has become a challenging issue in the medical system. Iatrogenic and non-iatrogenic infections caused by multidrug-resistant (MDR) pathogens pose serious threats to global human life and health because the efficacy of traditional antibiotics has been greatly reduced and the resulting socio-economic burden has increased. It is important to find and develop non-antibiotic-dependent antibacterial strategies because the development of new antibiotics can hardly keep pace with the emergence of resistant bacteria. Gallium (III) is a multi-target antibacterial agent that has an excellent antibacterial activity, especially against MDR pathogens; thus, a gallium (III)-based treatment is expected to become a new antibacterial strategy. However, some limitations of gallium ions as antimicrobials still exist, including low bioavailability and explosive release. In recent years, with the development of nanomaterials and clathrates, the progress of manufacturing technology, and the emergence of synergistic antibacterial strategies, the antibacterial activities of gallium have greatly improved, and the scope of application in medical systems has expanded. This review summarizes the advancement of current optimization for these key factors. This review will enrich the knowledge about the efficiency and mechanism of various gallium-based antibacterial agents and provide strategies for the improvement of the antibacterial activity of gallium-based compounds.

Advancing of 3D-Printed Titanium Implants with Combined Antibacterial Protection Using Ultrasharp Nanostructured Surface and Gallium-Releasing Agents

This paper presents the development of advanced Ti implants with enhanced antibacterial activity. The implants were engineered using additive manufacturing three-dimensional (3D) printing technology followed by surface modification with electrochemical anodization and hydrothermal etching, to create unique hierarchical micro/nanosurface topographies of microspheres covered with sharp nanopillars that can mechanically kill bacteria in contact with the surface. To achieve enhanced antibacterial performance, fabricated Ti implant models were loaded with gallium nitrate as an antibacterial agent. The antibacterial efficacy of the fabricated substrates with the combined action of sharp nanopillars and locally releasing gallium ions (Ga³⁺) was evaluated toward Staphylococcus aureus and Pseudomonas aeruginosa. Results confirm the significant antibacterial performance of Ga³⁺-loaded substrates with a 100% eradication of bacteria. The nanopillars significantly reduced bacterial attachment and prevented biofilm formation while also killing any bacteria remaining on the surface. Furthermore, 3D-printed surfaces with microspheres of diameter 5-30 μm and interspaces of 12-35 μm favored the attachment of osteoblast-like MG-63 cells, as confirmed via the assessment of their attachment, proliferation, and viability. This study provides important progress toward engineering of next-generation 3D-printed implants, that combine surface chemistry and structure to achieve a highly efficacious antibacterial surface with dual cytocompatibility to overcome the limitations of conventional Ti implants.

Assessment of in vitro Cytotoxic, iNOS, Antioxidant and Photodynamic Antimicrobial Activities of Water-soluble Sulfonated Phthalocyanines

In recent years, much effort has been devoted to the development of effective anticancer agents. In this manner, the utilization of water-soluble sulfonated phthalocyanines is crucial for many cancer cell lines. In this study, phthalonitrile and metallophthalocyanine compounds linked by benzenesulfonic acid groups have been prepared. Antimicrobial behaviors of those compounds were investigated by performing disk diffusion and photodynamic assays on gram-positive and negative bacteria. Indium phthalocyanine (InClPc) (3) showed inhibition activity against B. cereus, B. subtilis and S. aureus with disk diffusion assay. Also, gallium and indium phthalocyanines (2 and 3) exhibited inhibitory activity on both gram-positive and -negative microorganisms after light activation. Increasing the inhibitor concentration and light exposure time increased the inhibition activity for both molecules. GaClPc (2) demonstrated the maximum reducing power capacity among studied compounds, and CoPc (4) showed even better DPPH radical scavenging ability than the standard molecule Trolox at 2000 µg mL^-1 concentration. The dose-dependent effect of compounds on cytotoxicity was studied against cancer cells PANC-1, MDA-MB-231, HepG2, A549, HeLa, CaCo-2 and non-tumorigenic cells HEK-293. All compounds showed no significant cytotoxic effect on any cell line up to the highest treated concentration at 50 µg mL^-1 . However, all phthalocyanines had significant nitric oxide inhibition activity, and only in copper phthalocyanine (CuPc) (5), the MTT IC₅₀ value was reached on LPS-activated RAW 264.7 macrophage cells. The lowest inducible nitric oxide synthase (iNOS) IC₅₀ values were defined as 6 ± 1 μg mL^-1 and 7 ± 0.5 μg mL^-1 for CuPc (5) and InClPc (3), respectively.

Polydopamine Shell as a Ga3+ Reservoir for Triggering Gallium-Indium Phase Separation in Eutectic Gallium-Indium Nanoalloys

Low melting point eutectic systems, such as the eutectic gallium-indium (EGaIn) alloy, offer great potential in the domain of nanometallurgy; however, many of their interfacial behaviors remain to be explored. Here, a compositional change of EGaIn nanoalloys triggered by polydopamine (PDA) coating is demonstrated. Incorporating PDA on the surface of EGaIn nanoalloys renders core-shell nanostructures that accompany Ga-In phase separation within the nanoalloys. The PDA shell keeps depleting the Ga³⁺ from the EGaIn nanoalloys when the synthesis proceeds, leading to a Ga³⁺-coordinated PDA coating and a smaller nanoalloy. During this process, the eutectic nanoalloys turn into non-eutectic systems that ultimately result in the solidification of In when Ga is fully depleted. The reaction of Ga³⁺-coordinated PDA-coated nanoalloys with nitrogen dioxide gas is presented as an example for demonstrating the functionality of such hybrid composites. The concept of phase-separating systems, with polymeric reservoirs, may lead to tailored materials and can be explored on a variety of post-transition metals.

Tailoring Additively Manufactured Titanium Implants for Short-Time Pediatric Implantations with Enhanced Bactericidal Activity

Paediatric titanium (Ti) implants are used for the short-term fixation of fractures, after which they are removed. However, bone overgrowth on the implant surface can complicate their removal. The current Ti implants research focuses on improving their osseointegration and antibacterial properties for long-term use while overlooking the requirements of temporary implants. This paper presents the engineering of additively manufactured Ti implants with antibacterial properties and prevention of bone cell overgrowth. 3D-printed implants were fabricated followed by electrochemical anodization to generate vertically aligned titania nanotubes (TNTs) on the surface with specific diameters (∼100 nm) to reduce cell attachment and proliferation. To achieve enhanced antibacterial performance, TNTs were coated with gallium nitrate as antibacterial agent. The physicochemical characteristics of these implants assessed by the attachment, growth and viability of osteoblastic MG-63 cells showed significantly reduced cell attachment and proliferation, confirming the ability of TNTs surface to avoid cell overgrowth. Gallium coated TNTs showed strong antibacterial activity against S. aureus and P. aeruginosa with reduced bacterial attachment and high rates of bacterial death. Thus a new approach for the engineering of temporary Ti implants with enhanced bactericidal properties with reduced bone cell attachment is demonstrated as a new strategy toward a new generation of short-term implants in paediatrics.

Magnetic liquid metal loaded nano-in-micro spheres as fully flexible theranostic agents for SMART embolization

Transcatheter arterial chemoembolization (TACE) has become one of the preferred choices for advanced liver cancer patients. Current clinically used microsphere embolic agents, such as PVA, gelatin, and alginate microspheres, have limited therapeutic efficacy and lack the function of real-time imaging. In this work, we fabricated magnetic liquid metal nanoparticle (Fe@EGaIn NP) loaded calcium alginate (CA) microspheres (denoted as Fe@EGaIn/CA microspheres), which integrate CT/MR dual-modality imaging and photothermal/photodynamic functions of the Fe@EGaIn NP core, as well as embolization and drug-loading functions of CA microspheres. Namely, such nano-in-micro spheres can be used as fully flexible theranostic agents to achieve smart-chemoembolization. It has been confirmed by in vitro and in vivo experiments that Fe@EGaIn/CA microspheres have advantageous morphology, favorable biocompatibility, splendid versatility, and advanced embolic efficacy. Benefiting from these properties, excellent therapeutic efficiency was achieved with a tumor growth-inhibiting value of 100% in tumor-bearing rabbits. As a novel microsphere embolic agent with promising therapeutic efficacy and diagnostic capability, Fe@EGaIn/CA microspheres have shown potential applications in clinical transcatheter arterial chemoembolization. And the preparation strategy presented here provides a generalized paradigm for achieving multifunctional and fully flexible theranostics.