Gallium and its competing roles with iron in biological systems

Efficient density functional theory directed identification of siderophores with increased selectivity towards indium and germanium

Siderophores are promising ligands for application in novel recycling and bioremediation technologies, as they can selectively complex a variety of metals. However, with over 250 known siderophores, the selection of suiting complexants in the wet lab is impractical. Thus, this study established a density functional theory (DFT) based approach to efficiently identify siderophores with increased selectivity towards target metals on the example of germanium and indium. Considering 239 structures, chemically similar siderophores were clustered, and their complexation reactions modeled utilizing DFT. The calculations revealed siderophores with, compared to the reference siderophore desferrioxamine B (DFOB), up to 128 % or 48 % higher selectivity for indium or germanium, respectively. Experimental validation of the method was conducted with fimsbactin A and agrobactin, demonstrating up to 40 % more selective indium binding and at least sevenfold better germanium binding than DFOB, respectively. The results generated in this study open the door for the utilization of siderophores in eco-friendly technologies for the recovery of many different critical metals from various industry waters and leachates or bioremediation approaches. This endeavor is greatly facilitated by applying the herein-created database of geometry-optimized siderophore structures as de novo modeling of the molecules can be omitted.

Wake biofilm up to enhance suicidal uptake of gallium for chronic lung infection treatment

The hypometabolic and nutrient-limiting condition of dormant bacteria inside biofilms reduces their susceptibility to antibacterial agents, making the treatment of biofilm-dominating chronic infections difficult. Herein, we demonstrate an intratracheal aerosolized maltohexaose-modified catalase-gallium integrated nanosystem that can 'wake up' dormant Pseudomonas aeruginosa biofilm to increase the metabolism and nutritional iron demand by reconciling the oxygen gradient. The activated bacteria then enhance suicidal gallium uptake since gallium acts as a 'Trojan horse' to mimic iron. The internalized gallium ions disrupt biofilms by interfering with the physiological processes of iron ion acquisition and utilization, biofilm formation, and quorum sensing. Furthermore, aerosol microsprayer administration and bacteria-specific maltohexaose modification enable accumulation at biofilm-infected lung and targeted release of gallium into bacteria to improve the therapeutic effect. This work provides a potential strategy for treating infection by reversing the dormant biofilm's resistance condition.

Natural organic matter (NOM) can increase the uptake fluxes of three critical metals (Ga, La, Pt) in a unicellular green alga

Critical metals such as gallium, lanthanum and platinum are considered essential in a modern economy and for the required energy transition. Their relatively recent and increasing use in new technologies have led to an increase in their environmental mobility. As they reach aquatic systems, these metals can interact with organic ligands and especially Natural Organic Matter (NOM). The formation of organic complexes would be expected to reduce metal bioavailability and uptake by living cells, according to the Biotic Ligand Model (BLM). However, exceptions to this model have been determined for several critical metals in the past. The present work compared internalization kinetics of Ga, La and Pt in the green alga Chlamydomonas reinhardtii in the presence of NOMs from different origins: humic and fulvic acids from Suwannee River as well as NOMs from Ontario (Bannister Lake and Luther Marsh). Complexation was determined using a partial ultrafiltration method allowing for a normalization of data based on speciation to compare all conditions based on the concentration of the metal that was not bound to NOM. While internalization metal fluxes varied greatly from one NOM source to the other, uptake was almost always significantly higher than expected based on metal speciation. Quite often, metal internalization fluxes were even significantly increased in the presence of NOM, for the same total metal exposure concentration. For instance, Pt internalization was twice greater in the presence of Bannister Lake NOM than it was in the absence of NOM. The assumption that such exceptions could be explained by NOM characteristics was contradicted by the variable results from one metal to another. To further explore this phenomenon, internalization mechanisms for these individual metals need to be elucidated. This is a necessary step to accurately estimate the risk posed by the presence of these metals in humic aquatic systems.

A review of organic small-molecule fluorescent probes for the gallium(III) ion

Gallium metal and gallium compounds play significant roles in industry and medicine; however, their pollution and residue can pose potential risks to plants, animals and human health. Moreover, accurately detecting Ga3+ during tumor treatment holds great clinical significance. Therefore, it is crucial to reliably determine the content of Ga3+ in environmental and biological samples. Organic small-molecule fluorescent probe technology offers high selectivity and sensitivity, rapid detection speed, and non-destructive in situ bioimaging capabilities, making it an ideal approach for Ga3+ detection. The numerous reported probes for detecting Ga3+ highlight the immense application potential of fluorescent probes in this field. However, due to limited development of Ga3+-specific fluorescent probes thus far, several challenges associated with their design and development remain. This paper presents a comprehensive overview of the performance achieved by Ga3+ fluorescent probes, while addressing existing issues and proposing corresponding solutions. Additionally, future directions for developing highly efficient Ga3+ fluorescent probes are outlined as valuable guidance.

Antimicrobial Activity of Gallium(III) Compounds: Pathogen-Dependent Targeting of Multiple Iron/Heme-Dependent Biological Processes

Metals play vital roles in biological systems, with iron/heme being essential for cellular and metabolic functions necessary for survival and/or virulence in many bacterial pathogens. Given the rise of bacterial resistance to current antibiotics, there is an urgent need for the development of non-toxic and novel antibiotics that do not contribute to resistance to other antibiotics. Gallium, which mimics iron, has emerged as a promising antimicrobial agent, offering a novel approach to combat bacterial infections. Gallium does not have any known functions in biological systems. Gallium exerts its effects primarily by replacing iron in redox enzymes, effectively inhibiting bacterial growth by targeting multiple iron/heme-dependent biological processes and suppressing the development of drug resistance. The aim of this review is to highlight recent findings on the mechanisms of action of gallium and provide further insights into the development of gallium-based compounds. Understanding the mechanisms underlying gallium's biological activities is crucial for designing drugs that enhance their therapeutic therapies while minimizing side effects, offering promising avenues for the treatment of infectious diseases.

Beyond transition block metals: exploring the reactivity of phosphine PTA and its oxide [PTA(O)] towards gallium(iii)

The water-soluble cage-like phosphine PTA (1,3,5-triaza-7-phosphaadamantane) and its phosphine oxide derivative [PTA(O)] (1,3,5-triaza-7-phosphaadamantane-7-oxide) were used to explore their reactivity towards two gallium(iii)-halide precursors, namely GaCl3 and GaI3, for the first time. By using various reaction conditions, a series of N-mono-protonated phosphine salts with [GaCl4]- or [I]- as counterions were obtained in all cases, while the formation of coordinated Ga-PTA and Ga-[PTA(O)] complexes was not observed. All compounds were characterized in solution using multinuclear NMR spectroscopy (1H, 13C{1H}, 31P{1H} and 71Ga) and in the solid state using FT-IR spectroscopy and X-ray crystal diffraction. The new Ga-phosphine salts resulted stable and highly soluble in aqueous solution at room temperature. Density functional theory (DFT) calculations were also performed to further rationalize the coordination features of PTA with Ga3+ metal ion, highlighting that the phosphorus-gallium bond is about twice weaker than the phosphorus-metal bond commonly established by PTA with transition metals such as gold. Furthermore, the mono-protonation of PTA (or [PTA(O)]) makes the formation of ionic gallium-PTA coordination complexes thermodynamically unstable, as confirmed experimentally by the formation of Ga-phosphine salts reported herein.

Biofilm Microenvironment Activated Antibiotic Adjuvant for Implant-Associated Infections by Systematic Iron Metabolism Interference

Hematoma, a risk factor of implant-associated infections (IAIs), creates a Fe-rich environment following implantation, which proliferates the growth of pathogenic bacteria. Fe metabolism is a major vulnerability for pathogens and is crucial for several fundamental physiological processes. Herein, a deferiprone (DFP)-loaded layered double hydroxide (LDH)-based nanomedicine (DFP@Ga-LDH) that targets the Fe-rich environments of IAIs is reported. In response to acidic changes at the infection site, DFP@Ga-LDH systematically interferes with bacterial Fe metabolism via the substitution of Ga3+ and Fe scavenging by DFP. DFP@Ga-LDH effectively reverses the Fe/Ga ratio in Pseudomonas aeruginosa, causing comprehensive interference in various Fe-associated targets, including transcription and substance metabolism. In addition to its favorable antibacterial properties, DFP@Ga-LDH functions as a nano-adjuvant capable of delaying the emergence of antibiotic resistance. Accordingly, DFP@Ga-LDH is loaded with a siderophore antibiotic (cefiderocol, Cefi) to achieve the antibacterial nanodrug DFP@Ga-LDH-Cefi. Antimicrobial and biosafety efficacies of DFP@Ga-LDH-Cefi are validated using ex vivo human skin and mouse IAI models. The pivotal role of the hematoma-created Fe-rich environment of IAIs is highlighted, and a nanoplatform that efficiently interferes with bacterial Fe metabolism is developed. The findings of the study provide promising guidance for future research on the exploration of nano-adjuvants as antibacterial agents.

O-versus S-Metal Coordination of the Thiocarboxylate Group: An NMR Study of the Two Tautomeric Forms of the Ga(III)-Photoxenobactin E Complex

Photoxenobactin E (1) is a natural product with an unusual thiocarboxylic acid terminus recently isolated from an entomopathogenic bacterium. The biosynthetic gene cluster associated with photoxenobactin E, and other reported derivatives, is very similar to that of piscibactin, the siderophore responsible for the iron uptake among bacteria of the Vibrionaceae family, including potential human pathogens. Here, the reisolation of 1 from the fish pathogen Vibrio anguillarum RV22 cultured under iron deprivation, its ability to chelate Ga(III), and the full NMR spectroscopic characterization of the Ga(III)-photoxenobactin E complex are presented. Our results show that Ga(III)-photoxenobactin E in solution exists in a thiol-thione tautomeric equilibrium, where Ga(III) is coordinated through the sulfur (thiol form) or oxygen (thione form) atoms of the thiocarboxylate group. This report represents the first NMR study of the chemical exchange between the thiol and thione forms associated with thiocarboxylate-Ga(III) coordination, including the kinetics of the interconversion process associated with this tautomeric exchange. These findings show significant implications for ligand design as they illustrate the potential of the thiocarboxylate group as a versatile donor for hard metal ions such as Ga(III).

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.

Nanoparticles in plant resistance against bacterial pathogens: current status and future prospects

Nanoparticles (NPs) serve immense roles in various fields of science. They have vastly upgraded conventional methods in the fields of agriculture and food sciences to eliminate growing threats of crop damage and disease, caused by various phytopathogens including bacteria, fungi, viruses, and some insects. Bacterial diseases resulted in mass damage of crops by adopting antibacterial resistance, which has proved to be a major threat leading to food scarcity. Therefore, numerous NPs with antibacterial potentials have been formulated to overcome the problem of antibiotic resistance alongside an increase in crop yield and boosting plant immunity. NPs synthesized through green synthesis techniques have proved to be more effective and environment-friendly than those synthesized via chemical methods. NPs exhibit great roles in plants ranging from enhanced crop yield to disease suppression, to targeted drug and pesticide deliveries inside the plants and acting as biosensors for pathogen detection. NPs serves major roles in disruption of cellular membranes, ROS production, altering of DNA and protein entities and changing energy transductions. This review focuses on the antibacterial effect of NPs on several plant bacterial pathogens, mostly, against Pseudomonas syringe, Ralstonia solanacearum, Xanthomonas axonopodis, Clavibacter michiganensisand Pantoea ananatis both in vivo and ex vivo, thereby minimizing their antibacterial resistance and enhancing the plants acquired immunity. Therefore, NPs present a safer and more reliable bactericidal activity against various disease-causing bacteria in plants.

Effect of trace element mixtures on the outcome of patients with esophageal squamous cell carcinoma: a prospective cohort study in Fujian, China

BACKGROUND

The evidence about the effects of trace elements on overall survival(OS) of patients with esophageal squamous cell carcinoma(ESCC) is limited. This study aims to evaluate mixed effects of plasma trace elements on OS of ESCC.

METHODS

This prospective cohort analysis included 497 ESCC patients with a median follow-up of 52.3 months. The concentrations of 17 trace elements were measured. We fitted Cox's proportional hazards regression, factor analysis and Bayesian kernel machine regression (BKMR) models to estimate the association between trace elements and OS.

RESULTS

Our analysis found that in the single-element model, Co, Ni, and Cd were associated with an increased risk of death, while Ga, Rb, and Ba were associated with a decreased risk. Cd had the strongest risk effect among all elements. As many elements were found to be mutually correlated, we conducted a factor analysis to identify common factors and investigate their associations with survival time. The factor analysis indicated that the factor with high factor loadings in Ga, Ba and B was linked to a decreased risk of death, while the factor with high factor loadings in Co, Ti, Cd and Pb was associated with a borderline significantly increased risk. Using BKMR analysis to disentangle the interaction between elements in significant factors, we discovered that Ga interacted with Ba and both elements had U-shaped effects with OS. Cd, on the other hand, had no interaction with other elements and independently increased the risk of death.

CONCLUSIONS

Our analysis revealed that Ga, Ba and Cd were associated with ESCC outcome, with Ga and Ba demonstrating an interaction. These findings provide new insights into the impact of trace elements on the survival of patients with ESCC.

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.

Enhanced antibacterial activity of dimethyl gallium quinolinolates toward drug-resistant Klebsiella pneumoniae in low iron environments

A series of dimethylgallium quinolinolate [GaMe2L] (L = 5-chloroquinolinolate, 5, 7-dichloroquinolinolate, 5, 7-dibromoquinolinolate or 5, 7-doiodoquinolinolate) complexes, shown previously to be active toward the Leishmania parasite, have been studied for their antibacterial activity toward a reference and drug resistant strain of Klebsiella pneumoniae (KP). The assays were conducted in standard iron-rich LB media and in the iron depleted RPMI and RPMI-HS media to better understand the effect of Fe concentration on the activity of the Ga complexes. In LB broth the parent quinolinols and the gallium complexes were inactive up to the highest concentration tested, 100 μM. In the more physiologically relevant 'iron-poor' RPMI-HS media the quinolonols remained inactive, however, the gallium complexes showed exceptional activity in the range 48-195 nM. Only in RPMI without any added HS did both the quinolinols and the gallium complexes show good activity. The significant differences in activity across the various media types suggest that the unnaturally high iron content of conventional LB media may provide false negative results for potentially potent Ga therapeutics. A protein binding assay on the organometallic gallium complexes showed a much slower uptake of Ga by Fe-binding proteins than is typically observed for gallium salts. This indicates that their greater lipophilicity and greater hydrolytic stability could account for their increased biological activity in RPMI-HS media.

First Gallium and Indium Crystal Structures of Curcuminoid Homoleptic Complexes: All-Different Ligand Stereochemistry and Cytotoxic Potential

The crystal structure determination of metal complexes of curcuminoids is a relevant topic to assess their unequivocal molecular structure. We report herein the first two X-ray crystal structures of homoleptic metal complexes of a curcuminoid, namely Dimethoxycurcumin (DiMeOC), with gallium and indium. Such successful achievement can be attributed to the suppression of interactions from the phenolic groups, which favor an appropriate molecular setup, rendering Dimethoxycurcumin gallium ((DiMeOC)2-Ga) and Dimethoxycurcumin indium ((DiMeOC)3-In) crystals. Surprisingly, the conformation of ligands in the crystal structures shows differences in each metal complex. Thus, the ligands in the (DiMeOC)2-Ga complex show two different conformers in the two molecules of the asymmetric unit. However, the ligands in the (DiMeOC)3-In complex exhibit three different conformations within the same molecule of the asymmetric unit, constituting the first such case described for an ML3 complex. The cytotoxic activity of the (DiMeOC)2-Ga complex is 4-fold higher than cisplatin against the K562 cell line and has comparable activity towards U251 and PC-3 cell lines. Interestingly, this complex exhibit three times lesser toxicity than cisplatin and even slightly lesser cytotoxicity than curcumin itself.

Structure-activity effects in the anti-leishmanial activity of di-alkyl gallium quinolin-8-olates

Six (G1-G6) novel organogallium complexes of the general formula [Ga(R)2quin] (where R = Et, iPr, nBu, tBu, sBu and hexyl; quin = quinolin-8-olate, C9H6NO) have been synthesised and fully characterised. Single crystal X-ray diffraction shows the complexes adopt a five-coordinate geometry through dimerisation. Complexes G1-G5 were analytically pure and could undergo further biological analysis. [Ga(hex)2quin] G6 could not be satisfactorily purified and was excluded from biological assays. 1H NMR spectroscopy indicated the complexes are stable to hydrolysis over 24 hours in 'wet' d6-DMSO. Complexes G1-G5 were assessed for their anti-leishmanial activity towards three separate strains: L. major, L. amazonensis and L. donovani, with varied results toward the promastigote form. G1 and G2 were found to be the most selective with little to no toxicity towards mammalian cell lines. Amastigote invasion assays on the three strains showed that [Ga(nBu)2quin] G3 and [Ga(tBu)2quin] G4 gave the best all round anti-parasitic activity with percentage infection ranges of 1.50-3.00% and 3.25-7.50% respectively, with G3 out-performing the drug control amphotericin B in all three assays. The activity was found to correlate with lipophilicity and water solubility, with the most effective G3 proving the most lipophilic and least water soluble.

Development of Biocompatible Ga2(HPO4)3 Nanoparticles as an Antimicrobial Agent with Improved Ga Resistance Development Profile against Pseudomonas aeruginosa

Ga(III) can mimic Fe(III) in the biological system due to its similarities in charge and ionic radius to those of Fe(III) and can exhibit antimicrobial activity by disrupting the acquisition and metabolism of Fe in bacterial cells. For example, Ga(NO3)3 has been proven to be effective in treating chronic lung infections by Pseudomonas aeruginosa (P. aeruginosa) in cystic fibrosis patients in a recent phase II clinical trial. However, Ga(NO3)3 is an ionic compound that can hydrolyze to form insoluble hydroxides at physiological pH, which not only reduces its bioavailability but also causes potential renal toxicity when it is used as a systemic drug. Although complexion with suitable chelating agents has offered a varying degree of success in alleviating the hydrolysis of Ga(III), the use of nanotechnology to deliver this metallic ion should constitute an ultimate solution to all the above-mentioned problems. Thus far, the development of Ga-based nanomaterials as metalloantibiotics is an underexploited area of research. We have developed two different synthetic routes for the preparation of biocompatible Ga2(HPO4)3 NPs and shown that both the PVP- or PEG-coated Ga2(HPO4)3 NPs exhibit potent antimicrobial activity against P. aeruginosa. More importantly, such polymer-coated NPs do not show any sign of Ga-resistant phenotype development after 30 passes, in sharp contrast to Ga(NO3)3, which can rapidly develop Ga-resistant phenotypes of P. aeruginosa, indicating the potential of using Ga2(HPO4)3 NPs a new antimicrobial agent in place of Ga(NO3)3.

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.

Gallium reactivates first and second generation quinolone antibiotics towards drug-resistant Klebsiella pneumoniae

Herein, we report on a series of homoleptic [GaL3] and heteroleptic organometallic [GaMe2L] complexes of inactive quinolone antibiotics; nalidixic acid, oxolinic acid and norfloxacin with their antibacterial activity (MIC 0.024-0.781 μM) towards four multi-drug resistant strains of Klebsiella pneumoniae through complexation to gallium.

Gallium Triggers Ferroptosis through a Synergistic Mechanism

The gallium ion (Ga3+ ) has long been believed to disrupt ferric homeostasis in the body by competing with iron cofactors in metalloproteins, ultimately leading to cell death. This study revealed that through an indirect pathway, gallium can trigger ferroptosis, a type of non-apoptotic cell death regulated by iron. This is exemplified by the gallium complex of the salen ligand (Ga-1); we found that Ga-1 acts as an effective anion transporter that can affect the pH gradient and change membrane permeability, leading to mitochondrial dysfunction and the release of ferrous iron from the electron transfer chain (ETC). In addition, Ga-1 also targeted protein disulfide isomerases (PDIs) located in the endoplasmic reticulum (ER) membrane, preventing the repair of the antioxidant glutathione (GSH) system and thus enforcing ferroptosis. Finally, a combination treatment of Ga-1 and dietary polyunsaturated fatty acids (PUFAs), which enhances lipid peroxidation during ferroptosis, showed a synergistic therapeutic effect both in vitro and in vivo. This study provided us with a strategy to synergistically induce Ferroptosis in tumor cells, thereby enhancing the anti-neoplastic effect.

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 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.

Synthesis of Antimicrobial Gallium Nanoparticles Using the Hot Injection Method

Antibiotic resistance continues to be an ongoing problem in global public health despite interventions to reduce antibiotic overuse. Furthermore, it threatens to undo the achievements and progress of modern medicine. To address these issues, the development of new alternative treatments is needed. Metallic nanoparticles have become an increasingly attractive alternative due to their unique physicochemical properties that allow for different applications and their various mechanisms of action. In this study, gallium nanoparticles (Ga NPs) were tested against several clinical strains of Pseudomonas aeruginosa (DFU53, 364077, and 365707) and multi-drug-resistant Acinetobacter baumannii (MRAB). The results showed that Ga NPs did not inhibit bacterial growth when tested against the bacterial strains using a broth microdilution assay, but they exhibited effects in biofilm production in P. aeruginosa DFU53. Furthermore, as captured by atomic force microscopy imaging, P. aeruginosa DFU53 and MRAB biofilms underwent morphological changes, appearing rough and irregular when they were treated with Ga NPs. Although Ga NPs did not affect planktonic bacterial growth, their effects on both biofilm formation and established biofilm demonstrate their potential role in the race to combat antibiotic resistance, especially in biofilm-related infections.

Targeting Iron-Sulfur Clusters in Cancer: Opportunities and Challenges for Ferroptosis-Based Therapy

Iron dysregulation is a hallmark of cancer, characterized by an overexpression of genes involved in iron metabolism and iron-sulfur cluster (ISC) biogenesis. Dysregulated iron homeostasis increases intracellular labile iron, which may lead to the formation of excess cytotoxic radicals and make it vulnerable to various types of regulated cell death, including ferroptosis. The inhibition of ISC synthesis triggers the iron starvation response, increasing lipid peroxidation and ferroptosis in cancer cells treated with oxidative stress-inducing agents. Various methods, such as redox operations, iron chelation, and iron replacement with redox-inert metals, can destabilize or limit ISC formation and function, providing potential therapeutic strategies for cancer treatment. Targeting ISCs to induce ferroptosis represents a promising approach in cancer therapy. This review summarizes the state-of-the-art overview of iron metabolism and ferroptosis in cancer cells, the role of ISC modulation in ferroptosis, and the potential of targeting ISCs for ferroptosis induction in cancer therapy. Further research is necessary to develop and validate these strategies in clinical trials for various cancers, which may ultimately lead to the development of novel and effective treatments for cancer patients.

Iron Acquisition and Metabolism as a Promising Target for Antimicrobials (Bottlenecks and Opportunities): Where Do We Stand?

The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) infections is one of the most crucial challenges currently faced by the scientific community. Developments in the fundamental understanding of their underlying mechanisms may open new perspectives in drug discovery. In this review, we conducted a systematic literature search in PubMed, Web of Science, and Scopus, to collect information on innovative strategies to hinder iron acquisition in bacteria. In detail, we discussed the most interesting targets from iron uptake and metabolism pathways, and examined the main chemical entities that exhibit anti-infective activities by interfering with their function. The mechanism of action of each drug candidate was also reviewed, together with its pharmacodynamic, pharmacokinetic, and toxicological properties. The comprehensive knowledge of such an impactful area of research will hopefully reflect in the discovery of newer antibiotics able to effectively tackle the antimicrobial resistance issue.

Deferiprone and Iron-Maltol: Forty Years since Their Discovery and Insights into Their Drug Design, Development, Clinical Use and Future Prospects

The historical insights and background of the discovery, development and clinical use of deferiprone (L1) and the maltol-iron complex, which were discovered over 40 years ago, highlight the difficulties, complexities and efforts in general orphan drug development programs originating from academic centers. Deferiprone is widely used for the removal of excess iron in the treatment of iron overload diseases, but also in many other diseases associated with iron toxicity, as well as the modulation of iron metabolism pathways. The maltol-iron complex is a recently approved drug used for increasing iron intake in the treatment of iron deficiency anemia, a condition affecting one-third to one-quarter of the world's population. Detailed insights into different aspects of drug development associated with L1 and the maltol-iron complex are revealed, including theoretical concepts of invention; drug discovery; new chemical synthesis; in vitro, in vivo and clinical screening; toxicology; pharmacology; and the optimization of dose protocols. The prospects of the application of these two drugs in many other diseases are discussed under the light of competing drugs from other academic and commercial centers and also different regulatory authorities. The underlying scientific and other strategies, as well as the many limitations in the present global scene of pharmaceuticals, are also highlighted, with an emphasis on the priorities for orphan drug and emergency medicine development, including the roles of the academic scientific community, pharmaceutical companies and patient organizations.

Mechanisms of iron homeostasis in Pseudomonas aeruginosa and emerging therapeutics directed to disrupt this vital process

Pseudomonas aeruginosa is an opportunistic pathogen able to infect any human tissue. One of the reasons for its high adaptability and colonization of host tissues is its capacity of maintaining iron homeostasis through a wide array of iron acquisition and removal mechanisms. Due to their ability to cause life-threatening acute and chronic infections, especially among cystic fibrosis and immunocompromised patients, and their propensity to acquire resistance to many antibiotics, the World Health Organization (WHO) has encouraged the scientific community to find new strategies to eradicate this pathogen. Several recent strategies to battle P. aeruginosa focus on targeting iron homeostasis mechanisms, turning its greatest advantage into an exploitable weak point. In this review, we discuss the different mechanisms used by P. aeruginosa to maintain iron homeostasis and the strategies being developed to fight this pathogen by blocking these mechanisms. Among others, the use of iron chelators and mimics, as well as disruption of siderophore production and uptake, have shown promising results in reducing viability and/or virulence of this pathogen. The so-called 'Trojan-horse' strategy taking advantage of the siderophore uptake systems is emerging as an efficient method to improve delivery of antibiotics into the bacterial cells. Moreover, siderophore transporters are considered promising targets for the developing of P. aeruginosa vaccines.

The elements of life: A biocentric tour of the periodic table

Living systems are built from a small subset of the atomic elements, including the bulk macronutrients (C,H,N,O,P,S) and ions (Mg,K,Na,Ca) together with a small but variable set of trace elements (micronutrients). Here, we provide a global survey of how chemical elements contribute to life. We define five classes of elements: those that are (i) essential for all life, (ii) essential for many organisms in all three domains of life, (iii) essential or beneficial for many organisms in at least one domain, (iv) beneficial to at least some species, and (v) of no known beneficial use. The ability of cells to sustain life when individual elements are absent or limiting relies on complex physiological and evolutionary mechanisms (elemental economy). This survey of elemental use across the tree of life is encapsulated in a web-based, interactive periodic table that summarizes the roles chemical elements in biology and highlights corresponding mechanisms of elemental economy.

Biological Use of Nanostructured Silica-Based Materials Functionalized with Metallodrugs: The Spanish Perspective

Since the pioneering work of Vallet-Regí's group on the design and synthesis of mesoporous silica-based materials with therapeutic applications, during the last 15 years, the potential use of mesoporous silica nanostructured materials as drug delivery vehicles has been extensively explored. The versatility of these materials allows the design of a wide variety of platforms that can incorporate numerous agents of interest (fluorophores, proteins, drugs, etc.) in a single scaffold. However, the use of these systems loaded with metallodrugs as cytotoxic agents against different diseases and with distinct therapeutic targets has been studied to a much lesser extent. This review will focus on the work carried out in this field, highlighting both the pioneering and recent contributions of Spanish groups that have synthesized a wide variety of systems based on titanium, tin, ruthenium, copper and silver complexes supported onto nanostructured silica. In addition, this article will also discuss the importance of the structural features of the systems for evaluating and modulating their therapeutic properties. Finally, the most interesting results obtained in the study of the potential therapeutic application of these metallodrug-functionalized silica-based materials against cancer and bacteria will be described, paying special attention to preclinical trials in vivo.

Gallium Metal-Organic Nanoparticles with Albumin-Stabilized and Loaded Graphene for Enhanced Delivery to HCT116 Cells

Background

Gallium (III) metal-organic complexes have been shown to have the ability to inhibit tumor growth, but the poor water solubility of many of the complexes precludes further application. The use of materials with high biocompatibility as drug delivery carriers for metal-organic complexes to enhance the bioavailability of the drug is a feasible approach.

Methods

Here, we modified the ligands of gallium 8-hydroxyquinolinate complex with good clinical anticancer activity by replacing the 8-hydroxyquinoline ligands with 5-bromo-8-hydroxyquinoline (HBrQ), and the resulting Ga(III) + HBrQ complex had poor water solubility. Two biocompatible materials, bovine serum albumin (BSA) and graphene oxide (GO), were used to synthesize the corresponding Ga(III) + HBrQ complex nanoparticles (NPs) BSA/Ga/HBrQ NPs and GO/Ga/HBrQ NPs in different ways to enhance the drug delivery of the metal complex.

Results

Both of BSA/Ga/HBrQ NPs and GO/Ga/HBrQ NPs can maintain stable existence in different solution states. In vitro cytotoxicity test showed that two nanomedicines had excellent anti-proliferation effect on HCT116 cells, which shown higher level of intracellular ROS and apoptosis ratio than that of cisplatin and oxaliplatin. In addition, the superior emissive properties of BSA/Ga/HBrQ NPs and GO/Ga/HBrQ NPs allow their use for in vivo imaging showing highly effective therapy in HCT116 tumor-bearing mouse models.

Conclusion

The use of biocompatible materials for the preparation of NPs against poorly biocompatible metal-organic complexes to construct drug delivery systems is a promising strategy that can further improve drug delivery and therapeutic efficacy.

Synthesis of a Bifunctional Cross-Bridged Chelating Agent, Peptide Conjugation, and Comparison of 68 Ga Labeling and Complex Stability Characteristics with Established Chelators

[68 Ga]Ga3+ can be introduced into receptor-specific peptidic carriers via different chelators to obtain radiotracers for Positron Emission Tomography imaging and the chosen chelating agent considerably influences the in vivo pharmacokinetics of the corresponding radiopeptides. A chelator that should be a valuable alternative to established chelating agents for 68 Ga-radiolabeling of peptides would be a backbone-functionalized variant of the chelator CB-DO2A. Here, the bifunctional cross-bridged chelating agent CB-DO2A-GA was developed and compared to the established chelators DOTA, NODA-GA and DOTA-GA. For this purpose, CB-DO2A-GA(tBu)2 was introduced into the peptide Tyr3 -octreotate (TATE) and in direct comparison to the corresponding DOTA-, NODA-GA-, and DOTA-GA-modified TATE analogs, CB-DO2A-GA-TATE required harsher reaction conditions for 68 Ga-incorporation. Regarding the hydrophilicity profile of the resulting radiopeptides, a decrease in hydrophilicity from [68 Ga]Ga-DOTA-GA-TATE (logD(7.4) of -4.11±0.11) to [68 Ga]Ga-CB-DO2A-GA-TATE (-3.02±0.08) was observed. Assessing the stability against metabolic degradation and complex challenge, [68 Ga]Ga-CB-DO2A-GA demonstrated a very high kinetic inertness, exceeding that of [68 Ga]Ga-DOTA-GA. Therefore, CB-DO2A-GA is a valuable alternative to established chelating agents for 68 Ga-radiolabeling of peptides, especially when the formation of a very stable, positively charged 68 Ga-complex is pursued.

Toxicity and Biocompatibility of Liquid Metals

Recently, room-temperature liquid metals have attracted increasing attention from researchers owing to their excellent material properties. Systematic interpretation of the potential toxicity issues involved is essential for a wide range of applications, especially in the biomedical and healthcare fields. However, even with the exponential growth of related studies, investigation of the toxicological impact and possible hazards of liquid metals to organisms is still in its infancy. This review aims to provide a comprehensive summary of the current frontier of knowledge on liquid metal toxicology and biocompatibility in different environments. Based on recent studies, this review focuses on Ga and Bi-based in different states. It is necessary to evaluate their toxicity considering the rapid increase in research and utilization of such liquid metal composites. Finally, existing challenges are discussed and suggestions are provided for further investigation of liquid metal toxicology to clarify the toxicological mechanisms and strategies are provided to avoid adverse effects. In addition to resolving the doubts of public concern about the toxicity of liquid metals, this review is expected to promote the healthy and sustainable development of liquid metal-based materials and their use in diverse areas, especially those related to health care.

Nanoengineered Gallium Ion Incorporated Formulation for Safe and Efficient Reversal of PARP Inhibition and Platinum Resistance in Ovarian Cancer

Platinum-based chemotherapy remains the main systemic treatment of ovarian cancer (OC). However, the inevitable development of platinum and poly (adenosine diphosphate-ribose) polymerase inhibitor (PARPi) resistance is associated with poor outcomes, which becomes a major obstacle in the management of this disease. The present study developed "all-in-one" nanoparticles that contained the PARPi olaparib and gallium (Ga) (III) (olaparib-Ga) to effectively reverse PARPi resistance in platinum-resistant A2780-cis and SKOV3-cis OC cells and in SKOV3-cis tumor models. Notably, the olaparib-Ga suppressed SKOV3-cis tumor growth with negligible toxicity. Moreover, the suppression effect was more evident when combining olaparib-Ga with cisplatin or carboplatin, as evaluated in A2780-cis and SKOV3-cis cells. Mechanistically, the combined treatment induced DNA damage, which elicited the activation of ataxia telangiectasia mutated (ATM)/AMT- and Rad3-related (ATR) checkpoint kinase 1 (Chk1)/Chk2 signal transduction pathways. This led to the arrest of cell cycle progression at S and G₂/M phases, which eventually resulted in apoptosis and cell death due to unrepairable DNA damage. In addition, effective therapeutic responses to olaparib-Ga and cisplatin combination or olaparib-Ga and carboplatin combination were observed in SKOV3-cis tumor-bearing animal models. Altogether, the present findings demonstrate that olaparib-Ga has therapeutic implications in platinum-resistant OC cells, and the combination of olaparib-Ga with cisplatin or carboplatin may be promising for treating patients with OC who exhibit resistance to both PARPi and platinum.

Advances and Innovations of 3D Bioprinting Skin

Three-dimensional (3D) bioprinted skin equivalents are highlighted as the new gold standard for alternative models to animal testing, as well as full-thickness wound healing. In this review, we focus on the advances and innovations of 3D bioprinting skin for skin regeneration, within the last five years. After a brief introduction to skin anatomy, 3D bioprinting methods and the remarkable features of recent studies are classified as advances in materials, structures, and functions. We will discuss several ways to improve the clinical potential of 3D bioprinted skin, with state-of-the-art printing technology and novel biomaterials. After the breakthrough in the bottleneck of the current studies, highly developed skin can be fabricated, comprising stratified epidermis, dermis, and hypodermis with blood vessels, nerves, muscles, and skin appendages. We hope that this review will be priming water for future research and clinical applications, that will guide us to break new ground for the next generation of skin regeneration.

Fate and biological impact of persistent luminescence nanoparticles after injection in mice: a one-year follow-up

Persistent luminescence nanoparticles (PLNPs) are attracting growing interest for non-invasive optical imaging of tissues with a high signal to noise ratio. PLNPs can emit a persistent luminescence signal through the tissue transparency window for several minutes, after UV light excitation before systemic administration or directly in vivo through visible irradiation, allowing us to get rid of the autofluorescence signal of tissues. PLNPs constitute a promising alternative to the commercially available optical near infrared probes thanks to their versatile functionalization capabilities for improvement of the circulation time in the blood stream. Nevertheless, while biodistribution for a short time is well known, the long-term fate and toxicity of the PLNP's inorganic core after injection have not been dealt with in depth. Here we extend the current knowledge on ZnGa_1.995O₄Cr_0.005 NPs (or ZGO) with a one-year follow-up of their fate after a single systemic administration in mice. We investigated the organ tissue uptake of ZGO with two different coatings and determined their intracellular processing up to one year after injection. The biopersistence of ZGO was assessed, with a long-term retention, quantified by ICP-MS, mostly in the liver and spleen, parallel with a loss of their luminescence properties. The analysis of the toxicity related to combining an animal's weight, key hematological and metabolic markers, histological observations of liver tissues and quantification of the expression of 31 genes linked to different metabolic reactions did not reveal any signs of noxiousness, from the macro scale to the molecular level. Therefore, the ZGO imaging probe has been proven to be a safe and relevant candidate for preclinical studies, allowing its long term use without any in vivo disturbance of the general metabolism.

Gallium containing bioactive materials: A review of anticancer, antibacterial, and osteogenic properties

The incorporation of gallium into bioactive materials has been reported to enhance osteogenesis, to influence blood clotting, and to induce anti-cancer and anti-bacterial activity. Gallium-doped biomaterials prepared by various techniques include melt-derived and sol-gel-derived bioactive glasses, calcium phosphate bioceramics, metals and coatings. In this review, we summarize the recently reported developments in antibacterial, anticancer, osteogenesis, and hemostasis properties of Ga-doped biomaterials and briefly outline the mechanisms leading to Ga biological effects. The key finding is that gallium addition to biomaterials has great potential for treating bone-related diseases since it can be efficiently transferred to the desired region at a controllable rate. Besides, it can be used as a potential substitute for antibiotics for the inhibition of infections during the initial and advanced phases of the wound healing process. Ga is also used as an anticancer agent due to the increased concentration of gallium around excessive cell proliferation (tumor) sites. Moreover, we highlight the possibility to design different therapeutic approaches aimed at increasing the efficiency of the use of gallium containing bioactive materials for multifunctional applications.

Gallium ions incorporated silk fibroin hydrogel with antibacterial efficacy for promoting healing of Pseudomonas aeruginosa-infected wound

The continual resistance to antibiotics and the generation of a series of bacterial infections has emerged as a global concern, which requires appropriate measures and therapeutics to address such a menace. Herein, we report on Silk fibroin (SF) hydrogel with good biocompatibility and biodegradability fabricated through the crosslinking of the SF of different concentrations with Gallium nitrate (Ga (NO3)3) against Pseudomonas aeruginosa. However, the SF: Ga = 500: 1 (w/w) (SF/Ga) demonstrated a good bactericidal and wound healing effect as a result of the moderate and prolonged release of the Ga3+ following the gradual degradation of the hydrogel. The Ga3+, known for its innovative nature acted as a crosslinked agent and a therapeutic agent employing the “Trojan horse” strategy to effectively deal with the bacteria. Also, the Ga3+, which is positively charged neutralizes the negative potential value of the SF particles to reduce the charge and further induce the β-sheet formation in the protein structure, a characteristic of gelation in SF. The morphology showed a fabricated homogenous structure with greater storage modulus- G’ with low loss modulus- G'' modulus demonstrating the mechanical performance and the ability of the SF/Ga hydrogel to hold their shape, at the same time allowing for the gradual release of Ga3+. A demonstration of biocompatibility, biodegradability, bactericidal effect and wound healing in in vitro and in vivo present the SF/Ga hydrogel as an appropriate platform for therapeutic and for antibacterial wound dressing.

Cancer Inhibition and In Vivo Osteointegration and Compatibility of Gallium-Doped Bioactive Glasses for Osteosarcoma Applications

Traditional osteosarcoma therapies tend to focus solely on eradicating residual cancer cells and often fail to promote local bone regeneration and even inhibit it due to lack of precise control over target cells, i.e., the treatment affects both normal and cancer cells. Typically, multistep procedures are required for optimal efficacy. Here, we found that a silica-based bioactive material containing 3 mol % gallium oxide selectively kills human osteosarcoma cells and presents excellent in vivo osteointegration, while showing no local or systemic toxicity. Cell culture media conditioned with the proposed material was able to kill 41% of osteosarcoma cells, and no significant deleterious effect on normal human osteoblasts was observed. In addition, rats treated with the gallium-doped material showed excellent material-bone integration with no sign of local toxicity or implant rejection. Systemic biocompatibility investigation did not indicate any sign of toxicity, with no presence of fibrosis or cellular infiltrate in the histological microstructure of the liver and kidneys after 56 days of observation. Taken together, these results show that synergistic bone regeneration and targeted cancer therapy can be combined, paving the way toward new bone cancer treatment approaches.

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.

Gallium containing calcium phosphates: potential antibacterial agents or fictitious truth

Amidst an ever-increasing demand for the enhancement of the lifestyle and the modulation of modern diseases, the functionalization of biomaterials is of utmost importance. One of the leading materials for the aforementioned purpose have been calcium phosphates (CaPs). They have been widely used in bone regeneration displaying favourable regenerative potential and biological properties. Many studies have placed their entire focus on facilitating the osteogenic differentiation of stem cells and bone progenitor cells, while the aspect of antibacterial properties has been surmounted. Nevertheless, increasing antibiotic resistance of bacteria requires the development of new materials and the usage of alternative approaches such as ion doping. Gallium (Ga) has been the potential star on the rise among the ions. However, the obstacle that accompanies gallium is the scarcity of research performed and the variety of amalgamations. The question that imposes itself is how a growing field of therapeutics can be further entwined with advances in material science, and how will the incorporation of gallium bring a new outlook. The present study offers a comprehensive overview of state-of-the-art gallium containing calcium phosphates (GaCaPs), their synthesis methods, antibacterial properties, and biocompatibility. Considering their vast potential as antibacterial agents, the need for a methodical perspective is highly necessary to determine if it is a direction on the brink of recognition or a fruitless endeavour. STATEMENT OF SIGNIFICANCE: : Although several studies have been published on various metal ions-containing calcium phosphates, to this date there is no systematic overview pointing out the properties and benefits of gallium containing calcium phosphates. Here we offer a critical overview, including synthesis, structure and biological properties of gallium containing calcium phosphates.

Polymeric Nanosystems Applied for Metal-Based Drugs and Photosensitizers Delivery: The State of the Art and Recent Advancements

Nanotechnology-based approaches for targeting the delivery and controlled release of metal-based therapeutic agents have revealed significant potential as tools for enhancing the therapeutic effect of metal-based agents and minimizing their systemic toxicities. In this context, a series of polymer-based nanosized systems designed to physically load or covalently conjugate metal-based therapeutic agents have been remarkably improving their bioavailability and anticancer efficacy. Initially, the polymeric nanocarriers were applied for platinum-based chemotherapeutic agents resulting in some nanoformulations currently in clinical tests and even in medical applications. At present, these nanoassemblies have been slowly expanding for nonplatinum-containing metal-based chemotherapeutic agents. Interestingly, for metal-based photosensitizers (PS) applied in photodynamic therapy (PDT), especially for cancer treatment, strategies employing polymeric nanocarriers have been investigated for almost 30 years. In this review, we address the polymeric nanocarrier-assisted metal-based therapeutics agent delivery systems with a specific focus on non-platinum systems; we explore some biological and physicochemical aspects of the polymer–metallodrug assembly. Finally, we summarize some recent advances in polymeric nanosystems coupled with metal-based compounds that present potential for successful clinical applications as chemotherapeutic or photosensitizing agents. We hope this review can provide a fertile ground for the innovative design of polymeric nanosystems for targeting the delivery and controlled release of metal-containing therapeutic agents.

Iron limitation in M. tuberculosis has broad impact on central carbon metabolism

Mycobacterium tuberculosis (Mtb), the cause of the human pulmonary disease tuberculosis (TB), contributes to approximately 1.5 million deaths every year. Prior work has established that lipids are actively catabolized by Mtb in vivo and fulfill major roles in Mtb physiology and pathogenesis. We conducted a high-throughput screen to identify inhibitors of Mtb survival in its host macrophage. One of the hit compounds identified in this screen, sAEL057, demonstrates highest activity on Mtb growth in conditions where cholesterol was the primary carbon source. Transcriptional and functional data indicate that sAEL057 limits Mtb’s access to iron by acting as an iron chelator. Furthermore, pharmacological and genetic inhibition of iron acquisition results in dysregulation of cholesterol catabolism, revealing a previously unappreciated linkage between these pathways. Characterization of sAEL057’s mode of action argues that Mtb’s metabolic regulation reveals vulnerabilities in those pathways that impact central carbon metabolism.

An inhibitor of Mycobacterium tuberculosis (Mtb) survival acts as an iron chelator, demonstrating that iron deprivation alters Mtb cholesterol and central carbon metabolism.

Gallium Nanodroplets are Anti-Inflammatory without Interfering with Iron Homeostasis

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

Highly efficient magnetic ablation and the contrast of various imaging using biocompatible liquid-metal gallium

Background

Although the powerful clinical effects of radiofrequency and microwave ablation have been established, such ablation is associated with several limitations, including a small ablation size, a long ablation time, the few treatment positioning, and biosafety risks. To overcome these limitations, biosafe and efficient magnetic ablation was achieved in this study by using biocompatible liquid gallium as an ablation medium and a contrast medium for imaging.

Results

Magnetic fields with a frequency (f) lower than 200 kHz and an amplitude (H) × f value lower than 5.0 × 10⁹ Am⁻¹ s⁻¹ were generated using the proposed method. These fields could generate an ablation size of 3 cm in rat liver lobes under a temperature of approximately 300 °C and a time of 20 s. The results of this study indicate that biomedical gallium can be used as a contrast medium for the positioning of gallium injections and the evaluation of ablated tissue around a target site. Liquid gallium can be used as an ablation medium and imaging contrast medium because of its stable retention in normal tissue for at least 3 days. Besides, the high anticancer potential of gallium ions was inferred from the self-degradation of 100 µL of liquid gallium after around 21 days of immersion in acidic solutions.

Conclusions

The rapid wireless ablation of large or multiple lesions was achieved through the simple multi-injection of liquid gallium. This approach can replace the currently favoured procedure involving the use of multiple ablation probes, which is associated with limited benefits and several side effects.

Methods

Magnetic ablation was confirmed to be highly efficient by the consistent results obtained in the simulation and in vitro tests of gallium and iron oxide as well as the electromagnetic specifics and thermotherapy performance comparison detailed in this study Ultrasound imaging, X-ray imaging, and magnetic resonance imaging were found to be compatible with the proposed magnetic ablation method. Self-degradation analysis was conducted by mixing liquid gallium in acidic solutions with a pH of approximately 5–7 (to imitate a tumour-containing microenvironment). X-ray diffraction was used to identify the gallium oxides produced by degraded gallium ions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12938-022-01003-9.

Polysaccharide-Based Theranostic Systems for Combined Imaging and Cancer Therapy: Recent Advances and Challenges

Designing novel systems for efficient cancer treatment and improving the quality of life for patients is a prime requirement in the healthcare sector. In this regard, theranostics have recently emerged as a unique platform, which combines the benefits of both diagnosis and therapeutics delivery. Theranostics have the desired contrast agent and the drugs combined in a single carrier, thus providing the opportunity for real-time imaging to monitor the therapy results. This helps in reducing the hazards related to treatment overdose or underdose and gives the possibility of personalized therapy. Polysaccharides, as natural biomolecules, have been widely explored to develop theranostics, as they act as a matrix for simultaneously loading both contrast agents and drugs for their utility in drug delivery and imaging. Additionally, their remarkable physicochemical attributes (biodegradability, satisfactory safety profile, abundance, and diversity in functionality and charge) can be tuned via postmodification, which offers numerous possibilities to develop theranostics with desired characteristics. Hence, we provide an overview of recent advances in polysaccharide matrix-based theranostics for drug delivery combined with magnetic resonance imaging, computed tomography, positron emission tomography, single photon emission computed tomography, and ultrasound imaging. Herein, we also summarize the toxicity assessment of polysaccharides, associated contrast agents, and nanotoxicity along with the challenges and future research directions.

M. de Rosales R. Direct Cell Radiolabeling for in Vivo Cell Tracking with PET and SPECT Imaging

The arrival of cell-based therapies is a revolution in medicine. However, its safe clinical application in a rational manner depends on reliable, clinically applicable methods for determining the fate and trafficking of therapeutic cells in vivo using medical imaging techniques─known as in vivo cell tracking. Radionuclide imaging using single photon emission computed tomography (SPECT) or positron emission tomography (PET) has several advantages over other imaging modalities for cell tracking because of its high sensitivity (requiring low amounts of probe per cell for imaging) and whole-body quantitative imaging capability using clinically available scanners. For cell tracking with radionuclides, ex vivo direct cell radiolabeling, that is, radiolabeling cells before their administration, is the simplest and most robust method, allowing labeling of any cell type without the need for genetic modification. This Review covers the development and application of direct cell radiolabeling probes utilizing a variety of chemical approaches: organic and inorganic/coordination (radio)chemistry, nanomaterials, and biochemistry. We describe the key early developments and the most recent advances in the field, identifying advantages and disadvantages of the different approaches and informing future development and choice of methods for clinical and preclinical application.

Non-invasive radionuclide imaging of trace metal trafficking in health and disease: "PET metallomics"

Several specific metallic elements must be present in the human body to maintain health and function. Maintaining the correct quantity (from trace to bulk) and location at the cell and tissue level is essential. The study of the biological role of metals has become known as metallomics. While quantities of metals in cells and tissues can be readily measured in biopsy and autopsy samples by destructive analytical techniques, their trafficking and its role in health and disease are poorly understood. Molecular imaging with radionuclides - positron emission tomography (PET) and single photon emission computed tomography (SPECT) - is emerging as a means to non-invasively study the acute trafficking of essential metals between organs, non-invasively and in real time, in health and disease. PET scanners are increasingly widely available in hospitals, and methods for producing radionuclides of some of the key essential metals are developing fast. This review summarises recent developments in radionuclide imaging technology that permit such investigations, describes the radiological and physicochemical properties of key radioisotopes of essential trace metals and useful analogues, and introduces current and potential future applications in preclinical and clinical investigations to study the biology of essential trace metals in health and disease.

Combinatorial Delivery of Gallium (III) Nitrate and Curcumin Complex-Loaded Hollow Mesoporous Silica Nanoparticles for Breast Cancer Treatment

The main aims in the development of a novel drug delivery vehicle is to efficiently carry therapeutic drugs in the body's circulatory system and successfully deliver them to the targeted site as needed to safely achieve the desired therapeutic effect. In the present study, a passive targeted functionalised nanocarrier was fabricated or wrapped the hollow mesoporous silica nanoparticles with 3-aminopropyl triethoxysilane (APTES) to prepare APTES-coated hollow mesoporous silica nanoparticles (HMSNAP). A nitrogen sorption analysis confirmed that the shape of hysteresis loops is altered, and subsequently the pore volume and pore diameters of GaC-HMSNAP was reduced by around 56 and 37%, respectively, when compared with HMSNAP. The physico-chemical characterisation studies of fabricated HMSNAP, Ga-HMSNAP and GaC-HMSNAP have confirmed their stability. The drug release capacity of the fabricated Ga-HMSNAP and GaC-HMSNAP for delivery of gallium and curcumin was evaluated in the phosphate buffered saline (pH 3.0, 6.0 and 7.4). In an in silico molecular docking study of the gallium-curcumin complex in PDI, calnexin, HSP60, PDK, caspase 9, Akt1 and PTEN were found to be strong binding. In vitro antitumor activity of both Ga-HMSNAP and GaC-HMSNAP treated MCF-7 cells was investigated in a dose and time-dependent manner. The IC₅₀ values of GaC-HMSNAP (25 µM) were significantly reduced when compared with free gallium concentration (40 µM). The mechanism of gallium-mediated apoptosis was analyzed through western blotting and GaC-HMSNAP has increased caspases 9, 6, cleaved caspase 6, PARP, and GSK 3β(S9) in MCF-7 cells. Similarly, GaC-HMSNAP is reduced mitochondrial proteins such as prohibitin1, HSP60, and SOD1. The phosphorylation of oncogenic proteins such as Akt (S473), c-Raf (S249) PDK1 (S241) and induced cell death in MCF-7 cells. Furthermore, the findings revealed that Ga-HMSNAP and GaC-HMSNAP provide a controlled release of loaded gallium, curcumin and their complex. Altogether, our results depicted that GaC-HMNSAP induced cell death through the mitochondrial intrinsic cell death pathway, which could lead to novel therapeutic strategies for breast adenocarcinoma therapy.