Metal complexes containing natural and and artificial radioactive elements and their applications

Active Cu(II), Mn(II) and Ag(I) 1,10-phenanthroline/1,10-phenanthroline-5,6-dione/dicarboxylate chelates: effects on Scedosporium

Background: Scedosporium/Lomentospora species are human pathogens that are resistant to almost all antifungals currently available in clinical practice. Methods: The effects of 16 1,10-phenanthroline (phen)/1,10-phenanthroline-5,6-dione/dicarboxylate chelates containing Cu(II), Mn(II) and Ag(I) against Scedosporium apiospermum, Scedosporium minutisporum, Scedosporium aurantiacum and Lomentospora prolificans were evaluated. Results: To different degrees, all of the test chelates inhibited the viability of planktonic conidial cells, displaying MICs ranging from 0.029 to 72.08 μM. Generally, Mn(II)-containing chelates were the least toxic to lung epithelial cells, particularly [Mn2(oda)(phen)4(H2O)2][Mn2(oda)(phen)4(oda)2].4H2O (MICs: 1.62-3.25 μM: selectivity indexes >64). Moreover, this manganese-based chelate reduced the biofilm biomass formation and diminished the mature biofilm viability. Conclusion: [Mn2(oda)(phen)4(H2O)2][Mn2(oda)(phen)4(oda)2].4H2O opens a new chemotherapeutic avenue for the deactivation of these emergent, multidrug-resistant filamentous fungi.

Global Substance Registration System: consistent scientific descriptions for substances related to health

The US Food and Drug Administration (FDA) and the National Center for Advancing Translational Sciences (NCATS) have collaborated to publish rigorous scientific descriptions of substances relevant to regulated products. The FDA has adopted the global ISO 11238 data standard for the identification of substances in medicinal products and has populated a database to organize the agency's regulatory submissions and marketed products data. NCATS has worked with FDA to develop the Global Substance Registration System (GSRS) and produce a non-proprietary version of the database for public benefit. In 2019, more than half of all new drugs in clinical development were proteins, nucleic acid therapeutics, polymer products, structurally diverse natural products or cellular therapies. While multiple databases of small molecule chemical structures are available, this resource is unique in its application of regulatory standards for the identification of medicinal substances and its robust support for other substances in addition to small molecules. This public, manually curated dataset provides unique ingredient identifiers (UNIIs) and detailed descriptions for over 100 000 substances that are particularly relevant to medicine and translational research. The dataset can be accessed and queried at https://gsrs.ncats.nih.gov/app/substances.

Metal-Based Complexes as Pharmaceuticals for Molecular Imaging of the Liver

This article reviews the use of metal complexes as contrast agents (CA) and radiopharmaceuticals for the anatomical and functional imaging of the liver. The main focus was on two established imaging modalities: magnetic resonance imaging (MRI) and nuclear medicine, the latter including scintigraphy and positron emission tomography (PET). The review provides an overview on approved pharmaceuticals like Gd-based CA and ^99mTc-based radiometal complexes, and also on novel agents such as ⁶⁸Ga-based PET tracers. Metal complexes are presented by their imaging modality, with subsections focusing on their structure and mode of action. Uptake mechanisms, metabolism, and specificity are presented, in context with advantages and limitations of the diagnostic application and taking into account the respective imaging technique.

Antifungal Potential of Copper(II), Manganese(II) and Silver(I) 1,10-Phenanthroline Chelates Against Multidrug-Resistant Fungal Species Forming the Candida haemulonii Complex: Impact on the Planktonic and Biofilm Lifestyles

Candida haemulonii, Candida haemulonii var. vulnera and Candida duobushaemulonii, which form the C. haemulonii complex, are emerging etiologic agents of fungal infections known to be resistant to the most commonly used antifungals. The well-established anti-Candida potential of metal complexes containing 1,10-phenanthroline (phen) ligands encouraged us to evaluate different copper(II), manganese(II), and silver(I) phen chelates for their ability to inhibit planktonic growth and biofilm of C. haemulonii species complex. Two novel coordination complexes, {[Cu(3,6,9-tdda)(phen)₂].3H₂O.EtOH}_n and [Ag₂(3,6,9-tdda)(phen)₄].EtOH (3,6,9-tddaH₂ = 3,6,9-trioxaundecanedioic acid), were synthesized in a similar fashion to the other, previously documented, sixteen copper(II), manganese(II), and silver(I) chelates employed herein. Three isolates of each C. haemulonii species complex were used and the effect of the metal chelates on viability was determined utilizing the CLSI standard protocol and on biofilm-growing cells using the XTT assay. Cytotoxicity of the chelates was evaluated by the MTT assay, employing lung epithelial cells. The majority of the metal chelates were capable of interfering with the viability of planktonic-growing cells of all the fungal isolates. The silver complexes were the most effective drugs (overall geometric mean of the minimum inhibitory concentration (GM-MIC) ranged from 0.26 to 2.16 μM), followed by the manganese (overall GM-MIC ranged from 0.87 to 10.71 μM) and copper (overall GM-MIC ranged from 3.37 to >72 μM) chelates. The manganese chelates (CC₅₀ values ranged from 234.51 to >512 μM) were the least toxic to the mammalian cells, followed by the silver (CC₅₀ values ranged from 2.07 to 13.63 μM) and copper (CC₅₀ values ranged from 0.53 to 3.86 μM) compounds. When tested against mature biofilms, the chelates were less active, with MICs ranging from 2- to 33-fold higher levels when compared to the planktonic MIC counterparts. Importantly, manganese(II), copper(II), and silver(I) phen chelates are relatively cheap and easy to synthesize and they offer significant antifungal chemotherapeutic potential for the treatment of highly resistant pathogens.

Anti-Pseudomonas aeruginosa activity of 1,10-phenanthroline-based drugs against both planktonic- and biofilm-growing cells

OBJECTIVES

The beneficial antimicrobial properties of 1,10-phenanthroline (phen)-based drugs, together with the imperative need to develop new chemotherapeutic options for prevention/treatment of infections caused by MDR Gram-negative bacteria, led us to evaluate the effects of phen, 1,10-phenanthroline-5,6-dione (phendione), [Ag(phendione)2]ClO4 and [Cu(phendione)3](ClO4)2·4H2O on planktonic- and biofilm-growing Pseudomonas aeruginosa.

METHODS

Thirty-two non-duplicated Brazilian clinical isolates of P. aeruginosa with distinct genetic backgrounds were used in all experiments. The effect of test compounds on planktonic bacterial proliferation was determined as recommended by CLSI protocol. The effect on biofilm formation was evaluated by crystal violet incorporation (biomass determination) and XTT (viability assay). Mature biofilm disorganization was evidenced by staining with crystal violet.

RESULTS

Phen-based compounds presented anti-P. aeruginosa activity, but with different potencies concerning the geometric mean MIC: [Cu(phendione)3](2+) (7.76 μM) > [Ag(phendione)2](+) (14.05 μM) > phendione (31.15 μM) > phen (579.28 μM). MICs of each compound were similar irrespective of whether the P. aeruginosa isolates were susceptible or resistant to classical antimicrobials (ceftazidime, meropenem and imipenem). The pretreatment of bacteria with phen, phendione and phendione's metal derivatives at 0.5 × MIC value inhibited biofilm formation, particularly the use of [Cu(phendione)3](2+) and [Ag(phendione)2](+), which significantly reduced both biomass (48% and 44%, respectively) and viability (78% and 77%, respectively). The compounds studied also disrupted mature biofilm in a dose-dependent manner, especially [Ag(phendione)2](+) and [Cu(phendione)3](2+) (IC50, 9.39 and 10.16 μM, respectively).

CONCLUSIONS

Coordination of phendione to Ag(+) and Cu(2+) represents a new promising group of anti-infective agents, which revealed a potent anti-P. aeruginosa action against both planktonic- and biofilm-growing cells.

Special issue: practical applications of metal complexes

In 1913 Alfred Werner received the Nobel Prize in Chemistry for his work that was of great importance for the development of coordination chemistry. In the years that followed numerous complexes consisting of metal ions and organic ligands were isolated, thus building a strong connection between inorganic and organic chemistry. Coordination compounds have many interesting properties which find diverse applications in numerous aspects of human life. Fourteeen contributions were received for this Special Issue covering very different aspects of metal complexes and their practical applications. The highest number of manuscripts deals with the biological activity of complexes which might potentially be used in the clinical practice. Authors have tested their cytotoxicity, antibacterial activity and enzyme inhibition. Their optical properties were studied in view of their potential use in photodynamic therapy. Moreover, optical properties could also be used for bioanalysis. It is also known that metal complexes are useful catalysts and a few such examples are also described herein. Many other interesting properties and facts about the isolated and described complexes are also reported (radioactivity, design of metal-organic frameworks, etc.).