Intra-tracheal administration increases gallium availability in lung: implications for antibacterial chemotherapy

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

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

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.

Synthesis, characterization and in vitro cytotoxicity of gallium(III)-dithiocarbamate complexes

A library of homoleptic mononuclear Ga(III) complexes of the general formula [Ga(DTC)3], where DTC is an alicyclic or a linear dithiocarbamate chelator, is reported. The complexes were prepared in high yields starting from Ga(NO3)3·6H2O and fully characterized by elemental analysis and IR and NMR spectroscopy. Crystals of five of these complexes were obtained. The antitumor activity of the newly synthesized compounds against a panel of human cancer cell lines was evaluated. The chemical nature of the DTC does not have a marked impact on the structural features of the final compound. X-ray crystal structure analyses revealed that all these complexes have a trigonal prismatic geometry with three identical chelating DTCs coordinating the Ga(III) ion. It is noteworthy that in complex 22, [Ga(NHEt)3] (NHEt = N-ethyldithiocarbamate), the asymmetric unit is formed by two independent and structurally different molecules. Cellular studies showed that all the synthesized Ga-DTC complexes exhibit marked cytotoxic activity, even against human colon cancer cells that are less sensitive to cisplatin. Among the tested compounds, 6 ([Ga(CEPipDTC)3], CEPipDTC = (ethoxycarbonyl)-piperidinedithiocarbamate) and 21 ([Ga(Pr-13)3], PR13 = 4 and N-(2-ethoxy-2-oxoethyl)-N-methyldithiocarbamate) are very promising derivatives, but they have no selectivity towards cancer cells. Nevertheless, the obtained data provide a foundation for developing gallium-dithiocarbamate complexes as anticancer agents.

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.

Variable Susceptibility to Gallium Compounds of Major Cystic Fibrosis Pathogens

The decreasing efficacy of existing antibiotics against pulmonary pathogens that affect cystic fibrosis (CF) patients calls for the development of novel antimicrobials. Iron uptake and metabolism are vital processes for bacteria, hence potential therapeutic targets. Gallium [Ga(III)] is a ferric iron-mimetic that inhibits bacterial growth by disrupting iron uptake and metabolism. In this work we evaluate the efficacy of three Ga(III) compounds, namely, Ga(NO₃)₃, (GaN), Ga(III)-maltolate (GaM), and Ga(III)-protoporphyrin IX (GaPPIX), against a collection of CF pathogens using both reference media and media mimicking biological fluids. All CF pathogens, except Streptococcus pneumoniae, were susceptible to at least one Ga(III) compound. Notably, Mycobacterium abscessus and Stenotrophomonas maltophilia were susceptible to all Ga(III) compounds. Achromobacter xylosoxidans, Burkholderia cepacia complex, and Pseudomonas aeruginosa were more susceptible to GaN and GaM, whereas Staphylococcus aureus and Haemophilus influenzae were more sensitive to GaPPIX. The results of this study support the development of Ga(III)-based therapy as a broad-spectrum strategy to treat CF lung infections.