Sustainable Thermal Regulation of Electronics via Mitigated Supercooling of Porous Gallium-Based Phase Change Materials

Gallium liquid metal is one of the promising phase change materials for passive thermal management of electronics due to their high thermal conductivity and latent heat per volume. However, it suffers from severe supercooling, in which molten gallium does not return to solid due to the lack of nucleation. It may require 28.2 °C lower temperature than the original freezing point to address supercooling, leading to unstable thermal regulation performance along fluctuations of cooling condition. Here, gallium is infused into porous copper in an oxide-free environment, forming intermetallic compound impurities at the interfaces to reduce the activation energy for heterogeneous nucleation. The porous-shaped gallium provides ≈63% smaller supercooling than that of the bulk type due to large specific surface area (≈9,070 cm2 per cm3) and high wetting characteristics (≈16° of contact angle) on CuGa2 intermetallic layer. During repetitive heating-cooling cycles, porous-shaped gallium consistently shows propagation of crystallization at even near room temperature (≈25 °C) while maintaining stable performance as thermal buffer, whereas droplet-shaped gallium is gradually degraded due to partial-supercooled state. The findings will improve the responsive thermal regulation performance to relieve a rapid increase in temperature of semiconductors/batteries, and also have a potential for energy storage applications.

Impact of Catalysis-Relevant Oxidation and Annealing Treatments on Nanostructured GaRh Alloys

In this study, we examine the surface-derived electronic and chemical structures of nanostructured GaRh alloys as a model system for supported catalytically active liquid metal solutions (SCALMS), a novel catalyst candidate for dehydrogenation reactions that are important for the petrochemical and hydrogen energy industry. It is reported that under ambient conditions, SCALMS tends to form a gallium oxide shell, which can be removed by an activation treatment at elevated temperatures and hydrogen flow to enhance the catalytic reactivity. We prepared a 7 at. % Rh containing the GaRh sample and interrogated the evolution of the surface chemical and electronic structure by photoelectron spectroscopy (complemented by scanning electron microscopy) upon performing surface oxidation and (activation treatment mimicking) annealing treatments in ultrahigh vacuum conditions. The initially pronounced Rh 4d and Fermi level-derived states in the valence band spectra disappear upon oxidation (due to formation of a GaOx shell) but reemerge upon annealing, especially for temperatures of 600 °C and above, i.e., when the GaOx shell is efficiently being removed and the Ga matrix is expected to be liquid. At the same temperature, new spectroscopic features at both the high and low binding energy sides of the Rh 3d5/2 spectra are observed, which we attribute to new GaRh species with depleted and enriched Rh contents, respectively. A liquefied and GaOx-free surface is also expected for GaRh SCALMS at reaction conditions, and thus the revealed high-temperature properties of the GaRh alloy provide insights about respective catalysts at work.

Continuous isomerisation of 2,5-dimethylfuran to 2,4-dimethylfuran over Ga-silicate

2,4-dimethylfuran has a rare disubstitution pattern in the five-membered heterocyclic furan ring that is highly interesting chemically but challenging to access synthetically. We present a heterogeneously catalysed route to synthesise 2,4-dimethylfuran from commonly available 2,5-dimethylfuran using a zeolite packed-bed flow reactor. As supported by DFT calculations, the reaction occurs inside the zeolite channels, where the acid sites catalyse proton transfer followed by migration of a methyl group. The zeotype Ga-silicate (MFI type) appears superior to an aluminium-containing ZSM-5 by demonstrating higher selectivities and slower catalyst deactivation. This work provides new opportunities for the continuous valorisation of bio-feedstock molecules in the perspective of the emerging biorefinery era.

Breaking Iron Homeostasis: Iron Capturing Nanocomposites for Combating Bacterial Biofilm

Given the scarcity of novel antibiotics, the eradication of bacterial biofilm infections poses formidable challenges. Upon bacterial infection, the host restricts Fe ions, which are crucial for bacterial growth and maintenance. Having coevolved with the host, bacteria developed adaptive pathways like the hemin-uptake system to avoid iron deficiency. Inspired by this, we propose a novel strategy, termed iron nutritional immunity therapy (INIT), utilizing Ga-CT@P nanocomposites constructed with gallium, copper-doped tetrakis (4-carboxyphenyl) porphyrin (TCPP) metal-organic framework, and polyamine-amine polymer dots, to target bacterial iron intakes and starve them. Owing to the similarity between iron/hemin and gallium/TCPP, gallium-incorporated porphyrin potentially deceives bacteria into uptaking gallium ions and concurrently extracts iron ions from the surrounding bacteria milieu through the porphyrin ring. This strategy orchestrates a "give and take" approach for Ga3+/Fe3+ exchange. Simultaneously, polymer dots can impede bacterial iron metabolism and serve as real-time fluorescent iron-sensing probes to continuously monitor dynamic iron restriction status. INIT based on Ga-CT@P nanocomposites induced long-term iron starvation, which affected iron-sulfur cluster biogenesis and carbohydrate metabolism, ultimately facilitating biofilm eradication and tissue regeneration. Therefore, this study presents an innovative antibacterial strategy from a nutritional perspective that sheds light on refractory bacterial infection treatment and its future clinical application.

Fabrication of 3D-printed scaffolds loaded with gallium acetylacetonate for potential application in osteoclastic bone resorption

We recently reported the potential of a new gallium compound, gallium acetylacetonate (GaAcAc) in combating osteoclastic bone resorption through inhibition of osteoclast differentiation and function. Herein, we focused on 3D-printed polylactic acid scaffolds that were loaded with GaAcAc and investigated the impact of scaffold pretreatment with polydopamine (PDA) or sodium hydroxide (NaOH). We observed a remarkable increase in scaffold hydrophilicity with PDA or NaOH pretreatment while biocompatibility and in vitro degradation were not affected. NaOH-pretreated scaffolds showed the highest amount of GaAcAc loading when compared to other scaffolds (p < 0.05). NaOH-pretreated scaffolds with GaAcAc loading showed effective reduction of osteoclast counts and size. The trend was supported by suppression of key osteoclast differentiation markers such as NFAT2, c-Fos, TRAF6, & TRAP. All GaAcAc-loaded scaffolds, regardless of surface pretreatment, were effective in inhibiting osteoclast function as evidenced by reduction in the number of resorptive pits in bovine cortical bone slices (p < 0.01). The suppression of osteoclast function according to the type of scaffold followed the ranking: GaAcAc loading without surface pretreatment > GaAcAc loading with NaOH pretreatment > GaAcAc loading with PDA pretreatment. Additional studies will be needed to fully elucidate the impact of surface pretreatment on the efficacy and safety of GaAcAc-loaded 3D-printed scaffolds.

Metabolic Nanoregulator Remodels Gut Microenvironment for Treatment of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is strongly related to the occurrence of accumulation of toxic reactive oxygen species (ROS), inflammation of the mucosa, and an imbalance of intestinal microbes. However, current treatments largely focus on a single factor, yielding unsatisfactory clinical outcomes. Herein, we report a biocompatible and IBD-targeted metabolic nanoregulator (TMNR) that synergistically regulates cellular and bacterial metabolism. The TMNR comprises a melanin-gallium complex (MNR) encapsulated within a thermosensitive and colitis-targeting hydrogel, all composed of natural and FDA-approved components. The TMNR confers superior broad-spectrum antioxidant properties, effectively scavenging reactive oxygen species (ROS) and blocking inflammatory signaling pathways. The presence of Ga3+ in TMNR selectively disrupts iron metabolism in pathogenic microorganisms due to its structural resemblance to the iron atom. Additionally, incorporating a thermosensitive injectable hydrogel enables targeted delivery of TMNR to inflammatory regions, prolonging their retention time and providing a physical barrier function for optimizing IBD treatment efficacy. Collectively, TMNR effectively modulates the redox balance of inflamed colonic epithelial tissue and disrupts iron metabolism in pathogenic microorganisms, thereby eliminating inflammation and restoring intestinal homeostasis against IBD. Hence, this work presents a comprehensive approach for precise spatiotemporal regulation of the intestinal microenvironmental metabolism for IBD treatment.

Gallium Hydride-Catalyzed Selective Hydroboration of Unsaturated Organic Substrates

The first examples of tetrasubstituted conjugated bis-guanidinate (CBG) supported monomeric and thermally stable gallium dihalides [LGaX2], (X=Cl (Ga-Cl), I (Ga-I)) and dihydride (Ga-H) [LGaH2] (where L={(ArHN)(ArN)-C=N-C=(NAr)(NHAr)}; Ar=2,6-Et2-C6H3) compounds are reported. The reaction of in situ generated LLi with 1.0 equiv. GaX3 (X=Cl, I) afforded compounds Ga-Cl and Ga-I. The reaction between Ga-Cl and Li[HBEt3] in benzene yielded the dihydride compound Ga-H. All reported compounds (Ga-Cl, Ga-I, and Ga-H) were characterized by NMR, HRMS, and single-crystal X-ray diffraction studies. Ga-H was probed for the hydroboration of carbodiimides (CDI), isocyanates, and isothiocyanates with HBpin. Compound Ga-H was also found effective for the catalytic hydroboration of imines, nitriles, alkynes, esters, and formates, affording the corresponding products in quantitative yields. Stoichiometric reactions with a CDI were performed to establish the catalytic cycle.

Implantation of Gallium into Layered WS2 Nanostructures is Facilitated by Hydrogenation

Bombarding WS2 multilayered nanoparticles and nanotubes with focused ion beams of Ga+ ions at high doses, larger than 1016 cm-2 , leads to drastic structural changes and melting of the material. At lower doses, when the damage is negligible or significantly smaller, the amount of implanted Ga is very small. A substantial increase in the amount of implanted Ga, and not appreciable structural damage, are observed in nanoparticles previously hydrogenated by a radio-frequency activated hydrogen plasma. Density functional calculations reveal that the implantation of Ga in the spaces between adjacent layers of pristine WS2 nanoparticles is difficult due to the presence of activation barriers. In contrast, in hydrogenated WS2 , the hydrogen molecules are able to intercalate in between adjacent layers of the WS2 nanoparticles, giving rise to the expansion of the interlayer distances, that in practice leads to the vanishing of the activation barrier for Ga implantation. This facilitates the implantation of Ga atoms in the irradiation experiments.

Structure and Role of a Ga-Promoter in Ni-Based Catalysts for the Selective Hydrogenation of CO2 to Methanol

Supported, bimetallic catalysts have shown great promise for the selective hydrogenation of CO2 to methanol. In this study, we decipher the catalytically active structure of Ni-Ga-based catalysts. To this end, model Ni-Ga-based catalysts, with varying Ni:Ga ratios, were prepared by a surface organometallic chemistry approach. In situ differential pair distribution function (d-PDF) analysis revealed that catalyst activation in H2 leads to the formation of nanoparticles based on a Ni-Ga face-centered cubic (fcc) alloy along with a small quantity of GaOx. Structure refinements of the d-PDF data enabled us to determine the amount of both alloyed Ga and GaOx species. In situ X-ray absorption spectroscopy experiments confirmed the presence of alloyed Ga and GaOx and indicated that alloying with Ga affects the electronic structure of metallic Ni (viz., Niδ-). Both the Ni:Ga ratio in the alloy and the quantity of GaOx are found to minimize methanation and to determine the methanol formation rate and the resulting methanol selectivity. The highest formation rate and methanol selectivity are found for a Ni-Ga alloy having a Ni:Ga ratio of ∼75:25 along with a small quantity of oxidized Ga species (0.14 molNi-1). Furthermore, operando infrared spectroscopy experiments indicate that GaOx species play a role in the stabilization of formate surface intermediates, which are subsequently further hydrogenated to methoxy species and ultimately to methanol. Notably, operando XAS shows that alloying between Ni and Ga is maintained under reaction conditions and is key to attaining a high methanol selectivity (by minimizing CO and CH4 formation), while oxidized Ga species enhance the methanol formation rate.

Silver-Assisted Hydrogen Evolution from Aluminum Oxidation in Saline Media

A swarf of aluminum alloy with high corrosion resistance and ductility was successfully converted into fine hydro reactive powders via ball milling with silver powder and either lithium chloride or gallium. The latter substances significantly intensified particle size reduction, while silver formed 'cathodic' sites (Ag, Ag2Al), promoting Al corrosion in aqueous saline solutions with hydrogen generation. The diffraction patterns, microphotographs, and elemental analysis results demonstrated partial aluminum oxidation in the samples and their contamination with tungsten carbide from milling balls. Those factors were responsible for obtaining lower hydrogen yields than expected. For AlCl3 solution at 60 °C, Al-LiCl-Ag, Al-LiCl, Al-Ga-Ag, and Al-Ga composites delivered (84.6 ± 0.2), (86.8 ± 1.4), (80.2 ± 0.5), and (76.7 ± 0.7)% of the expected hydrogen, respectively. Modification with Ag promoted Al oxidation, thus providing higher hydrogen evolution rates. The samples with Ag were tested in a CaCl2 solution as well, for which the reaction proceeded much more slowly. At a higher temperature (80 °C) after 3 h of experiment, the corresponding hydrogen yields for Al-LiCl-Ag and Al-Ga-Ag powders were (46.7 ± 2.1) and (31.8 ± 1.9)%. The tested Ag-modified composite powders were considered promising for hydrogen generation and had the potential for further improvement to deliver higher hydrogen yields.

Potent in vivo efficacy of oral gallium maltolate in treatment-resistant glioblastoma

Background

Treatment-resistant glioblastoma (trGBM) is an aggressive brain tumor with a dismal prognosis, underscoring the need for better treatment options. Emerging data indicate that trGBM iron metabolism is an attractive therapeutic target. The novel iron mimetic, gallium maltolate (GaM), inhibits mitochondrial function via iron-dependent and -independent pathways.

Methods

In vitro irradiated adult GBM U-87 MG cells were tested for cell viability and allowed to reach confluence prior to stereotactic implantation into the right striatum of male and female athymic rats. Advanced MRI at 9.4T was carried out weekly starting two weeks after implantation. Daily oral GaM (50mg/kg) or vehicle were provided on tumor confirmation. Longitudinal MRI parameters were processed for enhancing tumor ROIs in OsiriX 8.5.1 (lite) with Imaging Biometrics Software (Imaging Biometrics LLC). Statistical analyses included Cox proportional hazards regression models, Kaplan-Meier survival plots, linear mixed model comparisons, and t-statistic for slopes comparison as indicator of tumor growth rate.

Results

In this study we demonstrate non-invasively, using longitudinal MRI surveillance, the potent antineoplastic effects of GaM in a novel rat xenograft model of trGBM, as evidenced by extended suppression of tumor growth (23.56 mm3/week untreated, 5.76 mm3/week treated, P < 0.001), a blunting of tumor perfusion, and a significant survival benefit (median overall survival: 30 days untreated, 56 days treated; P < 0.001). The therapeutic effect was confirmed histologically by the presence of abundant cytotoxic cellular swelling, a significant reduction in proliferation markers (P < 0.01), and vessel normalization characterized by prominent vessel pruning, loss of branching, and uniformity of vessel lumina. Xenograft tumors in the treatment group were further characterized by an absence of an invasive edge and a significant reduction in both, MIB-1% and mitotic index (P < 0.01 each). Transferrin receptor and ferroportin expression in GaM-treated tumors illustrated cellular iron deprivation. Additionally, treatment with GaM decreased the expression of pro-angiogenic markers (von Willebrand Factor and VEGF) and increased the expression of anti-angiogenic markers, such as Angiopoietin-2.

Conclusion

Monotherapy with the iron-mimetic GaM profoundly inhibits trGBM growth and significantly extends disease-specific survival in vivo.

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.

Passivation-Free, Liquid-Metal-Based Electrosynthesis of Aluminum Metal-Organic Frameworks Mediated by Light Metal Activation

The production of aluminum (Al) metal-organic frameworks (MOFs) by electrosynthesis using solid-state Al electrodes always faces significant challenges due to the formation of a passivating aluminum oxide layer in the process. Here, we developed a liquid-metal-based method to electrosynthesize an aluminum Al-MOF (MIL-53). This method uses a liquid-state gallium (Ga) anode as a reservoir and activator for a light metal, Al, in the form of Al-Ga alloys that releases Al3+ for the electrosynthesis of Al-MOFs. Introducing Ga into the system inhibits the formation of aluminum oxide passivation layer and promotes the electrochemical reaction for Al-MOF synthesis. The electrosynthesis using liquid Al-Ga alloy is conducted at ambient temperatures for long durations without requiring pretreatment for aluminum oxide removal. We show that the Al-MOF products synthesized from 0.40 wt % Al in liquid Ga lead to the highest crystallinity and possess a specific surface area greater than 800 m2 g-1 and a low capacity for CO2 adsorption that can be used as a potential matrix for CO2/N2 separation. This work provides evidence that employing liquid-metal electrodes offers a viable pathway to circumvent surface passivation effects that inevitably occur when using conventional solid metals. It also introduces an efficient electrosynthesis method based on liquid metals for producing atomically porous materials.

Towards High Efficiency and Rapid Production of Room-Temperature Liquid Metal Wires Compatible with Electronic Prototyping Connectors

We present in this work new methodologies to produce, refine, and interconnect room-temperature liquid-metal-core thermoplastic elastomer wires that have extreme extendibility (>500%), low production time and cost at scale, and may be integrated into commonly used electrical prototyping connectors like a Japan Solderless Terminal (JST) or Dupont connectors. Rather than focus on the development of a specific device, the aim of this work is to demonstrate strategies and processes necessary to achieve scalable production of liquid-metal-enabled electronics and address several key challenges that have been present in liquid metal systems, including leak-free operation, minimal gallium corrosion of other electrode materials, low liquid metal consumption, and high production rates. The ultimate goal is to create liquid-metal-enabled rapid prototyping technologies, similar to what can be achieved with Arduino projects, where modification and switching of components can be performed in seconds, which enables faster iterations of designs. Our process is focused primarily on fibre-based liquid metal wires contained within thermoplastic elastomers. These fibre form factors can easily be integrated with wearable sensors and actuators as they can be sewn or woven into fabrics, or cast within soft robotic components.

Gallium-doped thermochemically treated titanium reduces osteoclastogenesis and improves osteodifferentiation

Excessive bone resorption is one of the main causes of bone homeostasis alterations, resulting in an imbalance in the natural remodeling cycle. This imbalance can cause diseases such as osteoporosis, or it can be exacerbated in bone cancer processes. In such cases, there is an increased risk of fractures requiring a prosthesis. In the present study, a titanium implant subjected to gallium (Ga)-doped thermochemical treatment was evaluated as a strategy to reduce bone resorption and improve osteodifferentiation. The suitability of the material to reduce bone resorption was proven by inducing macrophages (RAW 264.7) to differentiate to osteoclasts on Ga-containing surfaces. In addition, the behavior of human mesenchymal stem cells (hMSCs) was studied in terms of cell adhesion, morphology, proliferation, and differentiation. The results proved that the Ga-containing calcium titanate layer is capable of inhibiting osteoclastogenesis, hypothetically by inducing ferroptosis. Furthermore, Ga-containing surfaces promote the differentiation of hMSCs into osteoblasts. Therefore, Ga-containing calcium titanate may be a promising strategy for patients with fractures resulting from an excessive bone resorption disease.

aeruginosa biofilms

Intravenous gallium nitrate therapy is a novel therapeutic strategy deployed to combat chronic Pseudomonas aeruginosa biofilm infections in the lungs of cystic fibrosis (CF) patients by interfering with iron (Fe3+) uptake. The therapy is a source of Ga3+, which competes with Fe3+ for siderophore binding, subsequently disrupting iron metabolism and inhibiting biofilm proliferation in vivo. It was recently demonstrated that the Pseudomonas quinolone signal (PQS) can chelate Fe3+ to assist in bacterial iron uptake. However, it is unknown whether exogenous gallium also targets [Fe(PQS)3] uptake, which, in turn, would extend the mechanism of gallium therapy beyond siderophore competition, potentially supporting use of the therapy against P. aeruginosa mutants deficient in siderophore uptake proteins. To that end, the thermodynamic feasibility of iron-for-gallium cation exchange into [Fe(PQS)3] was evaluated using quantum chemical density functional theory (DFT) modelling and verified experimentally using 1H nuclear magnetic resonance (NMR). We demonstrate here that Ga3+ can strongly bind to three PQS molecules and, furthermore, displace and substitute Fe3+ from the native chelate pocket within PQS complexes, through a Trojan horse mechanism, retaining the key structural features present within the native ferric complex. As such, [Fe(PQS)3] complexes, in addition to ferric-siderophore complexes, represent another target for gallium therapy.

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.

Aluminium and Gallium Silylimides as Nitride Sources

Terminal aluminium and gallium imides of the type K[(NON)M(NR)], bearing heteroatom substituents at R, have been synthesised via reactions of anionic aluminium(I) and gallium(I) reagents with silyl and boryl azides (NON=4,5-bis(2,6-diisopropyl-anilido)-2,7-di-tert-butyl-9,9-dimethyl-xanthene). These systems vary significantly in their lability in solution: the N(Sii Pr3 ) and N(Boryl) complexes are very labile, on account of the high basicity at nitrogen. Phenylsilylimido derivatives provide greater stabilization through the π-acceptor capabilities of the SiR3 group. K[(NON)AlN(Sit BuPh2 )] offers a workable compromise between stability and solubility, and has been completely characterized by spectroscopic, analytical and crystallographic methods. The silylimide species examined feature minimal π-bonding between the imide ligand and aluminium/gallium, with the HOMO and HOMO-1 orbitals effectively comprising orthogonal lone pairs centred at N. Reactivity-wise, both aluminium and gallium silylimides can act as viable sources of nitride, [N]3- , with systems derived from either metal reacting with CO to afford cyanide complexes. By contrast, only the gallium system K[(NON)Ga{N(SiPh3 )}] is capable of effecting a similar transformation with N2 O to yield azide, N3 - , via formal oxide/nitride metathesis. The aluminium systems instead generate RN3 via transfer of the imide fragment [RN]2- .

Yttrium Complexes with Group 13 Heterobenzene-Type Ligands

The yttrium gallabenzene complex [(1-Me-3,5-tBu2 -C5 H3 Ga)(μ-Me)Y(2,4-dtbp)] is accessible from Y(GaMe4 )3 and K(2,4-dtbp) via a tandem salt metathesis/methane elimination (2,4-dtbp=2,4-di-tert-butyl-pentadienyl). The pentadienyl ligand in [(1-Me-3,5-tBu2 -C5 H3 E)(μ-Me)Y(2,4-dtbp)] (E=Al, Ga) is easily displaced by salt metathesis with KC5 Me5 and KTpMe,Me (TpMe,Me =tris(pyrazolyl-Me2 -3,5)borato) affording [(1-Me-3,5-tBu2 -C5 H3 E)(μ-Me)Y(TpMe,Me )] and [(1-Me-3,5-tBu2 -C5 H3 E)(μ-Me)Y(C5 Me5 )]. The yttrium center in [(1-Me-3,5-tBu2 -C5 H3 E)(μ-Me)Y(2,4-dtbp)] readily forms adducts with neutral Lewis bases like 4-DMAP (4-dimethylaminopyridine), PMe3 , DMPE (1,2-bis(dimethylphosphino)ethane), and DME (1,2-dimethoxyethane). In stark contrast, addition of TMEDA (N,N,N',N'-tetramethylethylenediamine) results in methyl/pentadienyl exchange between aluminum and yttrium resulting in [(1-(2,4-dtbp)-1-Me-3,5-tBu2 -C5 H3 Al)Y(Me)(tmeda)]. The bonding features of the newly synthesized complexes are analyzed by single-crystal X-ray diffraction (SCXRD) and heteronuclear (89 Y, 31 P) NMR spectroscopy.

Investigation of surface orientation dependent sputtering of Ag

Sputtering of metal surfaces can be both a beneficial phenomenon, for instance in the coating industry, or an undesired side-effect, for instant materials subjected to irradiation. While the average sputtering yields are well known in common metals, recent studies have shown that the yields can depend on the crystallographic orientation of the surface much stronger than commonly appreciated. In this study, we investigate by computational means, molecular dynamics, the sputtering of single crystalline Ag surfaces under various incoming energies. The results at low and high energy are compared to experimental results for single crystalline Ag nanocubes of different orientations. We observe strong differences between the sputtering yields of different surface directions and ion energies. We analyze the results in terms of the atom cluster size of the sputtered materials, and show that the cluster size distribution is a key factor to understand the correspondence between simulations and experiments. At low energies mainly single atoms are sputtered, whereas at higher energies the sputtered material is mainly in atom clusters.

Gallium-Doped Hydroxyapatite: Shape Transformation and Osteogenesis Activity

In this study, we employed a chemical precipitation method to successfully synthesize nanoparticles of gallium-doped hydroxyapatite (Ga-HAp). The microstructure of Ga-HAp was precisely tailored by modulating the concentration of gallium ions. Our findings unequivocally demonstrate that gallium ions exert a pronounced inhibitory influence on the growth of HAp crystals, and this inhibitory potency exhibits a direct correlation with the concentration of gallium. Furthermore, gallium ions facilitate the metamorphosis of HAp nanoparticles, transitioning them from nanoneedles to nanosheets. It is worth noting, however, that gallium ions exhibit a limited capacity to substitute for calcium ions within the crystal lattice of HAp, with the maximum substitution rate capped at 4.85%. Additionally, gallium plays a pivotal role in constraining the release of ions from HAp, and this behavior remains consistent across samples with varying Ga doping concentrations. Our in vitro experiments confirm that Ga-doped HAp amplifies both the proliferation and osteogenic differentiation of bone marrow mesenchymal stem cells.

Microstructure and Properties of Magnesium Alloy Joints Bonded by Using Gallium with the Assistance of Ultrasound at Room Temperature

Although magnesium alloys show potential as structural and functional materials, they are difficult to join using traditional welding methods because of their low melting points and active chemical properties. Their poor weldability impedes their universal application. Ultrasound-assisted transient liquid-phase bonding (U-TLP) is a novel method used for magnesium alloy bonding, but in almost all related studies, a heating device has been required, and the types of solders are limited. In this study, gallium was used as solder to bond AZ31 magnesium alloy with ultrasonic assistance at room temperature (without a heating device) due to the low melting temperature of gallium and its compatibility with other metals when forming intermetallic compounds (IMCs). The variations in the products, microstructure, fracture characteristics, and shear strength of the joints were investigated. A reliable joint composed of IMCs (Mg2Ga5, H-MgGa2, and Mg2Ga) and a eutectic structure was obtained after an ultrasonic duration of 3 s. Significantly, the plasticity of the joint was improved due to ultrasonic effects, which included the accelerated element diffusion process, the refinement of grains to nanometer particles, and the homogenization of organization. Thus, the highest shear strength of 14.65 MPa at 4 s was obtained, with obvious cleavage fracture characteristics in the region of the IMCs.

In Vivo Trafficking of the Anticancer Drug Tris(8-Quinolinolato) Gallium (III) (KP46) by Gallium-68/67 PET/SPECT Imaging

KP46 (tris(hydroxyquinolinato)gallium(III)) is an experimental, orally administered anticancer drug. Its absorption, delivery to tumours, and mode of action are poorly understood. We aimed to gain insight into these issues using gallium-67 and gallium-68 as radiotracers with SPECT and PET imaging in mice. [67Ga]KP46 and [68Ga]KP46, compared with [68Ga]gallium acetate, were used for logP measurements, in vitro cell uptake studies in A375 melanoma cells, and in vivo imaging in mice bearing A375 tumour xenografts up to 48 h after intravenous (tracer level) and oral (tracer and bulk) administration. 68Ga was more efficiently accumulated in A375 cells in vitro when presented as [68Ga]KP46 than as [68Ga]gallium acetate, but the reverse was observed when intravenously administered in vivo. After oral administration of [68/67Ga]KP46, absorption of 68Ga and 67Ga from the GI tract and delivery to tumours were poor, with the majority excreted in faeces. By 48 h, low but measurable amounts were accumulated in tumours. The distribution in tissues of absorbed radiogallium and octanol extraction of tissues suggested trafficking as free gallium rather than as KP46. We conclude that KP46 likely acts as a slow releaser of gallium ions which are inefficiently absorbed from the GI tract and trafficked to tissues, including tumour and bone.

Activation of the GaI Cation for Bond Activation: from Oxidative Additions into C-Cl and H-P Bonds to Reversible Insertion into P4

Although the discovery of the GaI complex salt [Ga(PhF)2-3 ][Al(ORF )4 ] (RF =C(CF3 )3 , PhF=C6 H5 F) invoked the preparation of a diverse library of cationic Ga(I) coordination complexes and clusters, studies on small molecule activation with low-valent GaI cations are scarce. Herein, a first experimental study on the reactivity of a monomeric Ga(I) cation activated with a pyridine-diimine pincer ligand (in [Ga(PDIdipp )][Al(ORF )4 ]) towards small-molecules is reported. First controlled oxidative additions of the GaI cation into C-Cl, H-P and P-P bonds are presented. Moreover, the [4+1]cycloaddition to butadienes was achieved. Intriguingly, the isolated, blue insertion product into the P-P bond of P4 allows for the quantitative release of the P4 molecule upon reaction with AlEt3 and butadienes. Reversible P4 insertion of main-group metals has previously been reported for Ge and Sn, respectively. The experimental study is supported by high-level computational analysis of the in-part reversible oxidative additions at the DLPNO-CCSD(T)/def2-TZVPP//PBEh-3c/def2-mSVP level of theory with COSMO-RS solvation in 1,2-difluorobenzene.

Liquid Metal Interface for Two-Precursor Autogenous Deposition of Metal Telluride-Tellurium Networks

Liquid metal-electrolyte can offer electrochemically reducing interfaces for the self-deposition of low-dimensional nanomaterials. We show that implementing such interfaces from multiprecursors is a promising pathway for achieving nanostructured films with combinatory properties and functionalities. Here, we explored the liquid metal-driven interfacial growth of metal tellurides using eutectic gallium-indium (EGaIn) as the liquid metal and the cation pairs Ag+-HTeO2+ and Cu2+-HTeO2+ as the precursors. At the EGaIn-electrolyte interface, the precursors were reduced and self-deposited autogenously to form interconnected nanoparticle networks. The deposited materials consisted of metal telluride and tellurium with their relative abundance depending on the metal ion type (Ag+ and Cu2+) and the metal-to-tellurium ion ratios. When used as electrode modifiers, the synthesized materials increased the electroactive surface area of unmodified electrodes by over 10 times and demonstrated remarkable activity for model electrochemical reactions, including HexRu(III) responses and dopamine sensing. Our work reveals the promising potential of the liquid metal-templated deposition method for synthesizing complex material systems for electrochemical applications.

Unravelling the Surface Oxidation-Induced Evolution of the Electronic Structure of Gallium

Gallium is widely used in liquid metal catalyst fabrication, and its oxidized species is a well-known dielectric material. In the past decades, these two species have been well studied separately. However, the surface oxide layer-induced impact on the chemical and electronic structure of (liquid) gallium is still mostly unclear because of the extreme fast formation of thermodynamically stable surface Ga2O3. In this study, we used a combination of direct and inverse photoemission complemented by scanning electron microscopy to examine the surface properties of Ga and Ga oxide (on a SiOx/Si support) and the evolution of the surface structure upon stepwise oxidation and subsequent reduction at an elevated temperature. We find oxidation time-dependent self-limited formation of a substoichiometric Ga2O3-δ surface layer on the Ga nanoparticles. The valence band maximum (conduction band minimum) for this Ga2O3-δ is located at -3.8 (±0.1) eV [1.4 (±0.2) eV] with respect to the Fermi level, resulting in an electronic surface band gap of 5.2 (±0.2) eV. Upon annealing in ultrahigh vacuum conditions, the Ga2O3-δ surface layer can efficiently be removed when using temperatures of 600 °C and higher. This study reveals how the surface properties of Ga nanoparticles are influenced by stepwise oxidation-reduction, providing detailed insights that will benefit the optimization of this material class for different applications.

A Study on the Interfacial Reactions between Gallium and Cu/Ni/Au(Pd) Multilayer Metallization

This research introduces low-temperature soldering of Ga with practical metallization structures, namely, Cu/Ni/Pd and Cu/Ni/Au, applied to contemporary microelectronic packages. Through these multilayer configurations, the study investigates the stability of the Ni diffusion barrier by examining changes in the interfacial microstructure as Ni is consumed. The interfacial reactions are conducted across a temperature spectrum of 160, 200, 240, and 280 °C, with reaction durations ranging from 30 to 270 min. Valuable insights for low-temperature soldering with Ga are extracted from the data. At lower reaction temperatures, the presence of Ga-rich intermetallic compounds (IMCs), specifically GaxNi (x = 89 to 95 at%), on the Ga7Ni3 layer is notably confirmed. As the reaction temperature and duration increase, the gradual consumption of the Ni layer occurs. This gives rise to the formation of Ga-Cu IMCs, specifically CuGa2 and γ3-Cu9Ga4, beneath the Ga-Ni IMC layer. Concurrently, the gap between the Ga-Ni and Ga-Cu IMC layers widens, allowing molten Ga to infiltrate. The rate of Ga7Ni3 growth follows a time exponent ranging approximately from 1.1 to 1.7. This highlights the significant influence of interface reaction-controlled kinetics on Ga7Ni3 IMC growth. The activation energy for Ga7Ni3 growth is determined to be 61.5 kJ/mol. The growth of Ga7Ni3 is believed to be primarily driven by the diffusion of Ga atoms along grain boundaries, with the porous microstructure inherent in the Ga7Ni3 layer providing additional diffusion pathways.

Liquid-Metal Solvents for Designing Hierarchical Nanoporous Metals at Low Temperatures

Metallic nanoarchitectures hold immense value as functional materials across diverse applications. However, major challenges lie in effectively engineering their hierarchical porosity while achieving scalable fabrication at low processing temperatures. Here we present a liquid-metal solvent-based method for the nanoarchitecting and transformation of solid metals. This was achieved by reacting liquid gallium with solid metals to form crystalline entities. Nanoporous features were then created by selectively removing the less noble and comparatively softer gallium from the intermetallic crystals. By controlling the crystal growth and dealloying conditions, we realized the effective tuning of the micro-/nanoscale porosities. Proof-of-concept examples were shown by applying liquid gallium to solid copper, silver, gold, palladium, and platinum, while the strategy can be extended to a wider range of metals. This metallic-solvent-based route enables low-temperature fabrication of metallic nanoarchitectures with tailored porosity. By demonstrating large-surface-area and scalable hierarchical nanoporous metals, our work addresses the pressing demand for these materials in various sectors.

Inhalable Capsular Polysaccharide-Camouflaged Gallium-Polyphenol Nanoparticles Enhance Lung Cancer Chemotherapy by Depleting Local Lung Microbiota

Local lung microbiota is closely associated with lung tumorigenesis and therapeutic response. It is found that lung commensal microbes induce chemoresistance in lung cancer by directly inactivating therapeutic drugs via biotransformation. Accordingly, an inhalable microbial capsular polysaccharide (CP)-camouflaged gallium-polyphenol metal-organic network (MON) is designed to eliminate lung microbiota and thereby abrogate microbe-induced chemoresistance. As a substitute for iron uptake, Ga3+ released from MON acts as a "Trojan horse" to disrupt bacterial iron respiration, effectively inactivating multiple microbes. Moreover, CP cloaks endow MON with reduced immune clearance by masquerading as normal host-tissue molecules, significantly increasing residence time in lung tissue for enhanced antimicrobial efficacy. In multiple lung cancer mice models, microbe-induced drug degradation is remarkably inhibited when drugs are delivered by antimicrobial MON. Tumor growth is sufficiently suppressed and mouse survival is prolonged. The work develops a novel microbiota-depleted nanostrategy to overcome chemoresistance in lung cancer by inhibiting local microbial inactivation of therapeutic drugs.

Gallium Nitrate Enhances Antimicrobial Activity of Colistin against Klebsiella pneumoniae by Inducing Reactive Oxygen Species Accumulation

Klebsiella pneumoniae, a pathogen of critical clinical concern, urgently demands effective therapeutic options owing to its drug resistance. Polymyxins are increasingly regarded as a last-line therapeutic option for the treatment of multidrug-resistant (MDR) Gram-negative bacterial infections. However, polymyxin resistance in K. pneumoniae is an emerging issue. Here, we report that gallium nitrate (GaNt), an antimicrobial candidate, exhibits a potentiating effect on colistin against MDR K. pneumoniae clinical isolates. To further confirm this, we investigated the efficacy of combined GaNt and colistin in vitro using spot dilution and rapid time-kill assays and growth curve inhibition tests and in vivo using a murine lung infection model. The results showed that GaNt significantly increased the antimicrobial activity of colistin, especially in the iron-limiting media. Mechanistic studies demonstrated that bacterial antioxidant activity was repressed by GaNt, as revealed by RNA sequencing (RNA-seq), leading to intracellular accumulation of reactive oxygen species (ROS) in K. pneumoniae, which was enhanced in the presence of colistin. Therefore, oxidative stress induced by GaNt and colistin augments the colistin-mediated killing of wild-type cells, which can be abolished by dimethyl sulfoxide (DMSO), an effective ROS scavenger. Collectively, our study indicates that GaNt has a notable impact on the antimicrobial activity of colistin against K. pneumoniae, revealing the potential of GaNt as a novel colistin adjuvant to improve the treatment outcomes of bacterial infections. IMPORTANCE This study aimed to determine the antimicrobial activity of GaNt combined with colistin against Klebsiella pneumoniae in vitro and in vivo. Our results suggest that by combining GaNt with colistin, antioxidant activity was suppressed and reactive oxygen species accumulation was induced in bacterial cells, enhancing antimicrobial activity against K. pneumoniae. We found that GaNt functioned as an antibiotic adjuvant when combined with colistin by inhibiting the growth of multidrug-resistant K. pneumoniae. Our study provides insight into the use of an adjuvant to boost the antibiotic potential of colistin for treating infections caused by multidrug-resistant K. pneumoniae.

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.

Combination Therapy with Gallium Protoporphyrin and Gallium Nitrate Exhibits Enhanced Antimicrobial Activity In Vitro and In Vivo against Methicillin-Resistant Staphylococcus aureus

There is a major need for the development of new therapeutics to combat antibiotic-resistant Staphylococcus aureus. Recently, gallium (Ga)-based complexes have shown promising antimicrobial effects against various bacteria, including multidrug-resistant organisms, by targeting multiple heme/iron-dependent metabolic pathways. Among these, Ga protoporphyrin (GaPP) inhibits bacterial growth by targeting heme pathways, including aerobic respiration. Ga(NO3)3, an iron mimetic, disrupts elemental iron pathways. Here, we demonstrate the enhanced antimicrobial activity of the combination of GaPP and Ga(NO3)3 against methicillin-resistant S. aureus (MRSA) under iron-limited conditions, including small colony variants (SCV). This therapy demonstrated significant antimicrobial activity without inducing slow-growing SCV. We also observed that the combination of GaPP and Ga(NO3)3 inhibited the MRSA catalase but not above that seen with Ga(NO3)3 alone. Neither GaPP nor Ga(NO3)3 alone or their combination inhibited the dominant superoxide dismutase expressed (SodA) under the iron-limited conditions examined. Intranasal administration of the combination of the two compounds improved drug biodistribution in the lungs compared to intraperitoneal administration. In a murine MRSA lung infection model, we observed a significant increase in survival and decrease in MRSA lung CFUs in mice that received combination therapy with intranasal GaPP and Ga(NO3)3 compared to untreated control or mice receiving GaPP or Ga(NO3)3 alone. No drug-related toxicity was observed as assessed histologically in the spleen, lung, nasal cavity, and kidney for both single and repeated doses of 10 mg Ga /Kg of mice over 13 days. Our results strongly suggest that GaPP and Ga(NO3)3 in combination have excellent synergism and potential to be developed as a novel therapy for infections with S. aureus.

Temporal Variability of Gallium in Natural Plants

The aim of the research was to study the distribution of gallium (Ga) in rhizosphere soil and in plants growing under natural conditions in uncontaminated sites, with an emphasis on temporal fluctuations of Ga concentration in plants. For this purpose, two field experiments were conducted in St. Petersburg, Russia, in 2019 and 2020, at two sites. Three widespread grasses (couch grass, plantain, and dandelion) were chosen for the experiments. ICP-MS analytical technique was applied for the determination of Ga. All plants were capable of accumulating Ga, but the uptake of Ga was different in different plant species, although the plants grew under the same conditions. It can be assumed that one of the main reasons for such differences was the belonging of the plants to different botanical classes, where biochemical processes can proceed differently. The concentration of Ga in plants and rhizosphere soil varied in the daytime. The daily fluctuations of Ga in different plant species were often completely different and did not resemble the temporal fluctuations of Ga in rhizosphere soil. These short-term variations were due to natural reasons and should be considered when collecting plant and soil samples.

Metallacage-based enhanced PDT strategy for bacterial elimination via inhibiting endogenous NO production

Antibiotics are among the most used weapons in fighting microbial infections and have greatly improved the quality of human life. However, bacteria can eventually evolve to exhibit antibiotic resistance to almost all prescribed antibiotic drugs. Photodynamic therapy (PDT) develops little antibiotic resistance and has become a promising strategy in fighting bacterial infection. To augment the killing effect of PDT, the conventional strategy is introducing excess ROS in various ways, such as applying high light doses, high photosensitizer concentrations, and exogenous oxygen. In this study, we report a metallacage-based PDT strategy that minimizes the use of ROS by jointly using gallium-metal organic framework rods to inhibit the production of bacterial endogenous NO, amplify ROS stress, and enhance the killing effect. The augmented bactericidal effect was demonstrated both in vitro and in vivo. This proposed enhanced PDT strategy will provide a new option for bacterial ablation.

Comparison of micromorphological changes in enamel using SEM analysis after conventional and erbium, chromium:yttrium, scandium, gallium, and garnet hard-tissue laser fissurotomy: An in vitro study

Background

Well articulated by John Knowles - "Everything has to evolve or else it perishes." With the paradigm shift of emphasis toward the prevention of dental caries, it has been proven that laser irradiation protects against both caries initiation and caries progression.

Aim

The aim of the study was to evaluate and compare the micromorphology of caries-free extracted premolars using a Scanning electron microscope (SEM) after fissurotomy by conventional fissurotomy bur and erbium, chromium: yttrium, scandium, gallium, and garnet (ER, CR: YSGG) hard-tissue laser.

Methodology

Sixty caries-free premolars extracted atraumatically for orthodontic treatment were included in the study. The samples were divided into two groups randomly (Group 1: fissurotomy by bur, n = 30, and Group 2: fissurotomy by hard-tissue laser, n = 30). Each sample was further divided into halves from the occlusal surface wherein one-half of the occlusal surface received fissurotomy procedure and the other half was control. Samples were analyzed by scanning electron microscopy (SEM) for micromorphological changes.

Results

Profile image of control samples revealed the disorganization of enamel surface at the junction of fissures forming a heterogeneous tissue and agglomeration of enamel with deep pit and fissure. On the contrary, the image of experimented samples (with laser fissurotomy) showed smooth enamel surface and homogeneous enamel subsurface with wider pit and fissure owing to self-cleansing ability.

Conclusion

On the grounds of the present study results, it could be concluded that the intervention of ER, CR: YSGG hard-tissue laser possesses self-cleansable pit and fissures for caries prevention and has the potential to irradicate the smear layer entirely for superior attachment of remineralizing agents.

Chemical-genomic profiling identifies genes that protect yeast from aluminium, gallium, and indium toxicity

Aluminium, gallium, and indium are group 13 metals with similar chemical and physical properties. While aluminium is one of the most abundant elements in the Earth's crust, gallium and indium are present only in trace amounts. However, the increased use of the latter metals in novel technologies may result in increased human and environmental exposure. There is mounting evidence that these metals are toxic, but the underlying mechanisms remain poorly understood. Likewise, little is known about how cells protect themselves from these metals. Aluminium, gallium, and indium are relatively insoluble at neutral pH, and here we show that they precipitate in yeast culture medium at acidic pH as metal-phosphate species. Despite of this, the dissolved metal concentrations are sufficient to induce toxicity in the yeast Saccharomyces cerevisiae. By chemical-genomic profiling of the S. cerevisiae gene deletion collection, we identified genes that maintain growth in the presence of the three metals. We found both shared and metal-specific genes that confer resistance. The shared gene-products included functions related to calcium metabolism and Ire1/Hac1-mediated protection. Metal-specific gene-products included functions in vesicle-mediated transport and autophagy for aluminium, protein folding and phospholipid metabolism for gallium, and chorismate metabolic processes for indium. Many of the identified yeast genes have human orthologues involved in disease processes. Thus, similar protective mechanisms may act in yeast and humans. The protective functions identified in this study provides a basis for further investigations into toxicity and resistance mechanisms in yeast, plants, and humans.

Dual-Action Effect of Gallium and Silver Providing Osseointegration and Antibacterial Properties to Calcium Titanate Coatings on Porous Titanium Implants

Previously, functional coatings on 3D-printed titanium implants were developed to improve their biointegration by separately incorporating Ga and Ag on the biomaterial surface. Now, a thermochemical treatment modification is proposed to study the effect of their simultaneous incorporation. Different concentrations of AgNO₃ and Ga(NO₃)₃ are evaluated, and the obtained surfaces are completely characterized. Ion release, cytotoxicity, and bioactivity studies complement the characterization. The provided antibacterial effect of the surfaces is analyzed, and cell response is assessed by the study of SaOS-2 cell adhesion, proliferation, and differentiation. The Ti surface doping is confirmed by the formation of Ga-containing Ca titanates and nanoparticles of metallic Ag within the titanate coating. The surfaces generated with all combinations of AgNO₃ and Ga(NO₃)₃ concentrations show bioactivity. The bacterial assay confirms a strong bactericidal impact achieved by the effect of both Ga and Ag present on the surface, especially for Pseudomonas aeruginosa, one of the main pathogens involved in orthopedic implant failures. SaOS-2 cells adhere and proliferate on the Ga/Ag-doped Ti surfaces, and the presence of gallium favors cell differentiation. The dual effect of both metallic agents doping the titanium surface provides bioactivity while protecting the biomaterial from the most frequent pathogens in implantology.

Dynamics of the Ligand Excited States Relaxation in Novel β-Diketonates of Non-Luminescent Trivalent Metal Ions

Complexes emitting in the blue spectral region are attractive materials for developing white-colored light sources. Here, we report the luminescence properties of novel coordination compounds based on the trivalent group 3, 13 metals, and the 1-phenyl-3-methyl-4-cyclohexylcarbonyl-pyrazol-5-onate (Q^CH) ligand. [M(Q^CH)₃] (M = Al, Ga, and In), [M(Q^CH)₃(H₂O)] (M = Sc, Gd, and Lu), [Lu(Q^CH)₃(DMSO)], and [La(Q^CH)₃(H₂O)(EtOH)] complexes were synthesized and structurally characterized by a single-crystal X-ray diffraction study. It has been found that the luminescence quantum yields of the ligand increase by one order of magnitude upon metal coordination. A significant correspondence between the energies of the ligand's excited states and the luminescence quantum yields to the metal ion's atomic numbers was found using molecular spectroscopy techniques. The replacement of the central ion with the heavier one leads to a monotonic increase in singlet state energy, while the energy of the triplet state is similar for all the complexes. Time-resolved measurements allowed us to estimate the intersystem crossing (ISC) rate constants. It was shown that replacing the Al³⁺ ion with the heavier diamagnetic Ga³⁺ and In³⁺ ions decreased the ISC rate, while the replacement with the paramagnetic Gd³⁺ ion increased the ISC rate, which resulted in a remarkably bright and room-temperature phosphorescence of [Gd(Q^CH)₃(H₂O)].

Neutron Irradiation to Transmute Zinc into Gallium

Modified ²⁴¹Am-Be neutron beams showed an ability to change the optical properties of zinc oxide (ZnO) photoluminescence (PL) spectra by transmuting zinc (Zn) into gallium (Ga) after irradiation. This study investigates the time required by slow neutron irradiation to register the transmutation of the Zn into Ga. Two series of samples from different suppliers hydrothermally (HT) grown by TEW Tokyo Denpa Co. Ltd., Tokyo, Japan, and MTI corporation, China, are irradiated for 6, 12, 18, and 24 days on the Zn-polar face of each sample to specify the relationship between the irradiation intensity and transmutation.

Effects of Central Elements on the Properties of Group 13 Dialdiminate Complexes

The series of luminescent complexes with the dialdimine ligand were prepared by changing the central atom in the group 13 elements. In the solution states, their absorption wavelengths and responses to Lewis bases apparently depended on the central atom. The aluminum complexes exhibited the blue-shift of the absorption maxima compared to the gallium and indium congeners. It is probably because the aluminum complex has lower-lying highest-occupied molecular orbital than other complexes. Additionally, the emission intensity was clearly changed in response to a Lewis base, especially in the case of the aluminum complex. Quantum chemical calculations suggested that these element-dependent optical properties could be originated from the difference in the electric charges on the central elements. Interestingly, the ligand exchange reactions were observed in the indium complexes together with the changes in the optical properties and controlled by the addition of InCl3 and InMe3. Furthermore, all the complexes showed the aggregation-induced emission enhancement (AIEE) and crystallization-induced emission enhancement (CIEE) properties. These results lead to proposing a practical strategy for manipulating the optoelectronic properties coupled with the reactivities of complexes by choosing the central elements in the same group.

Photoactive p-Type Spinel CuGa2O4 Nanocrystals

Herein we report the synthesis and characterization of spinel copper gallate (CuGa₂O₄) nanocrystals (NCs) with an average size of 3.7 nm via a heat-up colloidal reaction. CuGa₂O₄ NCs have a band gap of ∼2.5 eV and marked p-type character, in agreement with ab initio simulations. These novel NCs are demonstrated to be photoactive, generating a clear and reproducible photocurrent under blue light irradiation when deposited as thin films. Crucially, the ability to adjust the Cu/Ga ratio within the NCs, and the effect of this on the optical and electronic properties of the NCs, was also demonstrated. These results position CuGa₂O₄ NCs as a novel material for optoelectronic applications, including hole transport and light harvesting.

Development of Gallium(III) as an Antimicrobial Drug Targeting Pathophysiologic Iron Metabolism of Human Pathogens

The treatment of infections is becoming more difficult due to emerging resistance of pathogens to existing drugs. As such, alternative druggable targets, particularly those that are essential for microbe viability and thus make it harder to develop resistance, are desperately needed. In turn, once identified, safe and effective agents that disrupt these targets must be developed. Microbial acquisition and use of iron is a promising novel target for antimicrobial drug development. In this Review we look at the various facets of iron metabolism critical to human infection with pathogenic microbes and the various ways in which it can be targeted, altered, disrupted, and taken advantage of to halt or eliminate microbial infections. Although a variety of agents will be touched upon, the primary focus will be on the potential use of one or more gallium complexes as a new class of antimicrobial agents. In vitro and in vivo data on the activity of gallium complexes against a variety of pathogens including ESKAPE pathogens, mycobacteria, emerging viruses, and fungi will be discussed in detail, as well as pharmacokinetics, novel formulations and delivery approaches, and early human clinical results.

A New, Thorough Look on Unusual and Neglected Group III-VI Compounds Toward Novel Perusals

The attention on group III-VI compounds in the last decades has been centered on the optoelectronic properties of indium and gallium chalcogenides. These outstanding properties are leading to novel advancements in terms of fundamental and applied science. One of the advantages of these compounds is to present laminated structures, which can be exfoliated down to monolayers. Despite the large knowledge gathered toward indium and gallium chalcogenides, the family of the group III-VI compounds embraces several other noncommon compounds formed by the other group III elements. These compounds present various crystal lattices, among which a great deal is offered from layered structures. Studies on aluminium chalcogenides show interesting potential as anodes in batteries and as semiconductors. Thallium (Tl), which is commonly present in the +1 oxidation state, is one of the key components in ternary chalcogenides. However, binary Tl-Q (Q = S, Se, Te) systems and derived films are still studied for their semiconducting and thermoelectric properties. This review aims to summarize the biggest features of these unusual materials and to shed some new light on them with the perspective that in the future, novel studies can revive these compounds in order to give rise to a new generation of technology.

NHC-Stabilised Parent Tripentelyltrielanes

A missing family of the extremely air sensitive tripentelyltrielanes was discovered. Their stabilisation was achieved by using the bulky NHC IDipp (NHC=N-heterocyclic carbene, IDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene). The tripentelylgallanes and tripentelylalanes IDipp ⋅ Ga(PH₂ )₃ (1 a), IDipp ⋅ Ga(AsH₂ )₃ (1 b), IDipp ⋅ Al(PH₂ )₃ (2 a) and IDipp ⋅ Al(AsH₂ )₃ (2 b) were synthesised by salt metathesis of IDipp ⋅ ECl₃ (E=Al, Ga, In) with alkali metal pnictogenides such as NaPH₂ /LiPH₂ ⋅ DME and KAsH₂ , respectively. Moreover, the detection of the first NHC-stabilised tripentelylindiumane IDipp ⋅ In(PH₂ )₃ (3) was possible by multinuclear NMR spectroscopy. Initial investigations of the coordination ability of these compounds resulted in the successful isolation of the coordination compound [IDipp ⋅ Ga(PH₂ )₂ (μ₃ -PH₂ {HgC₆ F₄ }₃ )] (4) by reaction of 1 a with (HgC₆ F₄ )₃ . The compounds were characterised by multinuclear NMR spectroscopy as well as single crystal X-ray diffraction studies. Supporting computational studies highlight the electronic features of the products.

Recent Trends in the Development of Novel Metal-Based Antineoplastic Drugs

Since the accidental discovery of the anticancer properties of cisplatin more than half a century ago, significant efforts by the broad scientific community have been and are currently being invested into the search for metal complexes with antitumor activity. Coordination compounds of transition metals such as platinum (Pt), ruthenium (Ru) and gold (Au) have proven their effectiveness as diagnostic and/or antiproliferative agents. In recent years, experimental work on the potential applications of elements including lanthanum (La) and the post-transition metal gallium (Ga) in the field of oncology has been gaining traction. The authors of the present review article aim to help the reader "catch up" with some of the latest developments in the vast subject of coordination compounds in oncology. Herewith is offered a review of the published scientific literature on anticancer coordination compounds of Pt, Ru, Au, Ga and La that has been released over the past three years with the hope readers find the following article informative and helpful.

Encapsulation and Delivery of an Osteosarcoma Stem Cell Active Gallium(III)-Diflunisal Complex Using Polymeric Micelles

Here we report the encapsulation of an osteosarcoma stem cell (OSC) potent gallium(III)-diflunisal complex 1 into polymeric nanoparticles, and its delivery into osteosarcoma cells. At the optimum feed (20 %, 1 NP²⁰ ), nanoparticle encapsulation of 1 enhances potency towards bulk osteosarcoma cells and OSCs (cultured in monolayer and three-dimensional systems). Strikingly, the nanoparticle formulation exhibits up to 5645-fold greater potency towards OSCs than frontline anti-osteosarcoma drugs, doxorubicin and cisplatin. The nanoparticle formulation evokes a similar mechanism of action as the payload, which bodes well for future translation. Specifically, the nanoparticle formulation induces nuclear DNA damage, cyclooxygenase-2 downregulation, and caspase-dependent apoptosis. To the best of our knowledge, this is the first study to demonstrate that polymeric nanoparticles can be used to effectively deliver an OSC-active metal complex into osteosarcoma cells.

AAZTA-Like Ligands Bearing Phenolate Arms as Efficient Chelators for 68 Ga Labelling in vitro and in vivo

The introduction of a phenolate pendant arm in place of an acetate on AAZTA- and DATA-like ligands resulted in hepta- and hexadentate chelators able to form Ga(III) complexes with thermodynamic stability and kinetic inertness higher than that of other Ga(III) complexes based on the parent 6-amino-6-methylperhydro-1,4-diazepine scaffold. In particular, the heptadentate AAZ3A-endoHB with a phenolate arm on an endocyclic N-atom shows a logK_GaL of 27.35 and a remarkable resistance to hydroxide coordination up to basic pH (pH>9). This behaviour allows to also improve the kinetic inertness of the complex showing a dissociation half-life (t_1/2 ) at pH 7.4 of 76 h. Although also the hexadentate AAZ2A-exoHB chelator forms a stable (logK_GaL =24.69) and inert (t_1/2 =33 h at pH 7.4) Ga(III) complex, the ⁶⁸ Ga labelling showed a better radiochemical yield with AAZ3A-endoHB, especially at room temperature. Thus, a bifunctional chelator of AAZ3A-endoHB was synthesized bearing an isothiocyanate group that was conjugated to the N-terminus of a c(RGD) peptide for integrin receptor targeting. Finally, the conjugate was successfully labelled with ⁶⁸ Ga isotope, and the resulting radiotracer tested for its stability in human serum and then in vivo for targeting B16-F10 tumours with miniPET imaging.

Exploring the Co-Crystallization of Kojic Acid with Silver(I), Copper(II), Zinc(II), and Gallium(III) for Potential Antibacterial Applications

Co-crystallization of kojic acid (HKA) with silver(I), copper(II), zinc(II), or gallium(III) salts yielded three 1D coordination polymers and one 0D complex in which kojic acid was present as a neutral or anionic terminal or bridging ligand. All reactions were conducted mechanochemically via ball milling and manual grinding, or via slurry. All solids were fully characterized via single-crystal and/or powder X-ray diffraction. As kojic acid is a mild antimicrobial compound that is widely used in cosmetics, and the metal cations possess antibacterial properties, their combinations were tested for potential antibacterial applications. The minimal inhibition concentrations (MICs) and minimal biocidal concentrations (MBCs) for all compounds were measured against standard strains of the bacteria P. aeruginosa, S. aureus, and E. coli. All compounds exerted appreciable antimicrobial activity in the order of silver, zinc, copper, and gallium complexes.

Gallium-Doped Hydroxyapatite Shows Antibacterial Activity against Pseudomonas aeruginosa without Affecting Cell Metabolic Activity

Calcium phosphates (CaPs) have been used in bone regeneration for decades. Among the described CaPs, synthetic hydroxyapatite (HAp) has a chemical composition similar to that of natural bone. Gallium-containing compounds have been studied since the 1970s for the treatment of autoimmune diseases and have shown beneficial properties, such as antibacterial activity and inhibition of osteoclast activity. In this study, we synthesized hydroxyapatite (HAp) powder with Ga doping ratios up to 6.9 ± 0.5 wt% using the wet chemical precipitation method. The obtained products were characterized using XRD, BET, FTIR, and ICP-MS. Ga³⁺ ion release was determined in the cell culture media for up to 30 days. Antibacterial activity was assessed against five bacterial species: Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis, and Streptococcus pyogenes. The biocompatibility of the GaHAp samples was determined in human fibroblasts (hTERT-BJ1) through direct and indirect tests. The structure of the synthesized products was characteristic of HAp, as revealed with XRD and FTIR, although the addition of Ga caused a decrease in the crystallite size. Ga³⁺ was released from GaHAp paste in a steady manner, with approximately 40% being released within 21 days. GaHAp with the highest gallium contents, 5.5 ± 0.1 wt% and 6.9 ± 0.5 wt%, inhibited the growth of all five bacterial species, with the greatest activity being against Pseudomonas aeruginosa. Biocompatibility assays showed maintained cell viability (~80%) after seven days of indirect exposure to GaHAp. However, when GaHAp with Ga content above 3.3 ± 0.4 wt% was directly applied on the cells, a decrease in metabolic activity was observed on the seventh day. Overall, these results show that GaHAp with Ga content below 3.3 ± 0.4 wt% has attractive antimicrobial properties, without affecting the cell metabolic activity, creating a material that could be used for bone regeneration and prevention of infection.

Reactivity of E4 (E4 =P4 , As4 , AsP3 ) towards Low-Valent Al(I) and Ga(I) Compounds

The reactivity of yellow arsenic and the interpnictogen compound AsP₃ towards low-valent group 13 compounds was investigated. The reactions of [LAl] (1, L=[{N(C₆ H₃ ⁱ Pr₂ -2,6)C(Me)}₂ CH]^- ) with As₄ and AsP₃ lead to [(LAl)₂ (μ,η^1:1:1:1 -E₄ )] (E₄ =As₄ (3 b), AsP₃ (3 c)) by insertion of two fragments [LAl] into two of the six E-E edges of the E₄ tetrahedra. Furthermore, the reaction of [LGa] (2) with E₄ afforded [LGa(η^1:1 -E₄ )] (E₄ =As₄ (4 b), AsP₃ (4 c)). In these compounds, only one E-E bond of the E₄ tetrahedra was cleaved. These compounds represent the first examples of the conversion of yellow arsenic and AsP₃ , respectively, with group 13 compounds. Furthermore, the reactivity of the gallium complexes towards unsaturated transition metal units or polypnictogen (E_n ) ligand complexes was investigated. This leads to the heterobimetallic compounds [(LGa)(μ,η^2:1:1 -P₄ )(LNi)] (5 a), [(Cp'''Co)(μ,η^4:1:1 -E₄ )(LGa)] (E=P (6 a), As (6 b), Cp'''=η⁵ -C₅ H₂ ^t Bu₃ ) and [(Cp'''Ni)(η^3:1:1 -E₃ )(LGa)] (E=P (7 a), As (7 b)), which combine two different ligand systems in one complex (nacnac and Cp) as well as two different types of metals (main group and transition metals). The products were characterized by crystallographic and spectroscopic methods.