Glioblastoma, an aggressive cancer, is difficult to treat due to its location, late detection, drug resistance, and poor absorption of chemotherapeutics. Intratumoral drug administration offers a promising potential treatment alternative with localized delivery and minimal systemic toxicity. Vanadium(V) coordination complexes, incorporating Schiff base and catecholate ligands, have shown effects as antiproliferative agents with tunable efficacy and reactivity, stability, steric bulk, hydrophobicity, uptake, and toxicity optimized for the intratumoral administration vehicle. A new series of oxovanadium(V) Schiff base–catecholate complexes were synthesized and characterized using nuclear magnetic resonance (NMR), UV-Vis, and infrared spectroscopy and mass spectrometry. Stability under physiological conditions was assessed via UV-Vis spectroscopy, and the antiproliferative activity was evaluated in T98G glioblastoma and SVG p12 normal glial cells using viability assays. The newly synthesized [VO(3-tBuHSHED)(TIPCAT)] complex was more stable (t1/2 ~ 4.5 h) and had strong antiproliferative activity (IC50 ~ 1.5 µM), comparing favorably with the current lead compound, [VO(HSHED)(DTB)]. The structural modifications enhanced stability, hydrophobicity, and steric bulk through substitution with iso-propyl and tert-butyl groups. The improved properties were attributed to steric hindrance associated with the new Schiff base and catecholato ligands, as well as the formation of non-toxic byproducts upon degradation. The [VO(3-tBuHSHED)(TIPCAT)] complex emerges as a promising candidate for glioblastoma therapy by demonstrating enhanced stability and a greater selectivity, which highlights the role of strategic ligand design in developing localized therapies for the treatment of resistant cancers. In reporting the new class of compounds effective against T98G glioblastoma cells, we describe the generally desirable properties that potential drugs being developed for intratumoral administration should have.

IntroductionCatechol moieties are common in natural bioactive molecules, and their ability to bind metal ions is widely explored both naturally with siderophores and in the development of metal-based drugs. The reactivities and biology activities of a sterically hindered model catechol compound, 3,5-di-tert-butylcatechol (dtbH2) and its oxidation product 3,5-di-tert-butyl-o-quinone (dtbQ), were studied in cell culture medium to understand better the medicinal roles of this class of molecules.MethodsAnti-proliferative activities of dtbH2 and dtbQ in fresh and aged solutions of the molecules were studied in two common human cancer cell lines, T98G (glioblastoma) and A549 (lung carcinoma). Electrospray mass spectrometry and UV/Vis spectroscopy were used to study the reactivities of the molecules in buffer solutions and cell culture medium, in the presence and absence of glutathione and imidazole.Results and DiscussionThe dtbH2 and dtbQ molecules showed high anti-proliferative activity (IC50 < 10 μM in 72 h assays) in T98G and A549 cell lines in the absence of added metal ions. The activity was observed when dtbH2 and dtbQ were freshly added to cell culture medium, while pre-incubation with the medium for 24 h reduced their activity 5-10-fold. This deactivation was avoided when the biological reductant, glutathione (GSH), was added to the medium at a physiologically relevant intracellular concentration (5.0 mM). These results were explained by speciation studies (UV/Vis spectroscopy and mass spectrometry) of dtbH2 and dtbQ in cell culture medium, aqueous buffers, or organic solvents in the presence or absence of GSH. These studies showed that a redox equilibrium was established between dtbH2 and dtbQ, with the latter rapidly coupling the GSH in an oxidative manner. The resultant adduct is likely to be responsible for the high toxicity of dtbH2 and dtbQ in GSH-rich cancer cells via oxygen-dependent radical chain reactions. Deactivation of dtbH2 and dtbQ in cell culture medium in the absence of GSH was due to the reactions of dtbQ with nucleophiles, such as amino acids, followed by the formation of polymeric species. The reported high anti-proliferative activity of V(V)-catecholato complexes can be explained by a combination of their efficient cellular uptake and rapid decomposition in thiol-rich intracellular environment with the formation of active V(V) and dtbH2/dtbQ adducts with thiols (mainly GSH). Slower decomposition and deactivation of the complexes was observed in thiol-poor extracellular environments. These data show that speciation in cell culture medium is crucial for the biological activity not only of metal complexes but also of their ligands when the complexes dissociates.

Halogenated non-innocent vanadium( v ) Schiff base mono-substituted catecholates have a low stability and anti-proliferative properties similar to vanadate. A linear correlation between complex redox potential and the catechol p K a was observed.

Selective staining of extracellular vesicles (EVs) is a major challenge for diagnostic and therapeutic applications. Herein, the EV labeling properties of a new class of tetranuclear polypyridylruthenium(II) complexes, Rubb7-TNL and Rubb7-TL, as phosphorescent stains are described. These new stains have many advantages over standard stains to detect and characterize EVs, including: high specificity for EV staining versus cell staining; high phosphorescence yields; photostability; and a lack of leaching from EVs until incorporation with target cells. As an example of their utility, large EVs released from control (basal) or lipopolysaccharide (LPS)-stimulated THP-1 monocytic leukemia cells were studied as a model of immune system EVs released during bacterial infection. Key findings from EV staining combined with flow cytometry were as follows: (i) LPS-stimulated THP-1 cells generated significantly larger and more numerous large EVs, as compared with those from unstimulated cells; (ii) EVs retained native EV physical properties after staining; and (iii) the new stains selectively differentiated intact large EVs from artificial liposomes, which are models of cell membrane fragments or other lipid-containing debris, as well as distinguished two distinct subpopulations of monocytic EVs within the same experiment, as a result of biochemical differences between unstimulated and LPS-stimulated monocytes. Comparatively, the staining patterns of A549 epithelial lung carcinoma-derived EVs closely resembled those of THP-1 cell line-derived EVs, which highlighted similarities in their selective staining despite their distinct cellular origins. This is consistent with the hypothesis that these new phosphorescent stains target RNA within the EVs.

Rhenium(I) tricarbonyl complexes are widely studied for their cell imaging properties and anti-cancer and anti-microbial activities, but the complexes with S-donor ligands remain relatively unexplored. A series of six fac-[Re(NN)(CO)3(SR)] complexes, where (NN) is 2,2'-bipyridyl (bipy) or 1,10-phenanthroline (phen), and RSH is a series of thiocarboxylic acid methyl esters, have been synthesized and characterized. Cellular uptake and anti-proliferative activities of these complexes in human breast cancer cell lines (MDA-MB-231 and MCF-7) were generally lower than those of the previously described fac-[Re(NN)(CO)3(OH2)]+ complexes; however, one of the complexes, fac-[Re(CO)3(phen)(SC(Ph)CH2C(O)OMe)] (3b), was active (IC50 ∼ 10 μM at 72 h treatment) in thiol-depleted MDA-MB-231 cells. Moreover, unlike fac-[Re(CO)3(phen)(OH2)]+, this complex did not lose activity in the presence of extracellular glutathione. Taken together these properties show promise for further development of 3b and its analogues as potential anti-cancer drugs for co-treatment with thiol-depleting agents. Conversely, the stable and non-toxic complex, fac-[Re(bipy)(CO)3(SC(Me)C(O)OMe)] (1a), predominantly localized in the lysosomes of MDA-MB-231 cells, as shown by live cell confocal microscopy (λex = 405 nm, λem = 470-570 nm). It is strongly localized in a subset of lysosomes (25 μM Re, 4 h treatment), as shown by co-localization with a Lysotracker dye. Longer treatment times with 1a (25 μM Re for 48 h) resulted in partial migration of the probe into the mitochondria, as shown by co-localization with a Mitotracker dye. These properties make complex 1a an attractive target for further development as an organelle probe for multimodal imaging, including phosphorescence, carbonyl tag for vibrational spectroscopy, and Re tag for X-ray fluorescence microscopy.

Introduction: Glioblastoma is a brain cancer difficult to treat but recently mixed-ligand vanadium(V) Schiff base/catecholato complexes have exhibited high in vitro anti-proliferative activity. Hence, we explored the activity of [VVOL1L2], which contains two iron chelating ligands, 2-hydroxy-1-naphthylaldehyde iso-nicotinoyhydrazone (L1H2) and clioquinol (L2H). This complex was previously reported to be very effective against Trypanosoma cruzi, the causative agent of Chagas disease. These studies explored the possibility that a compound with efficacy against Trypanosoma cruzi also has efficacy against human glioblastoma cancer cells. Since [VVOL1L2] was poorly soluble in water and the clioquinol ligand dissociated from the complex upon addition to an aqueous environment, an understanding of the speciation was very important to interpret its biological activity.Methods: Stability studies in cell media were followed by UV/Vis spectroscopy to determine speciation of relevance to the in vitro anti-proliferative activity of the complex with T98G glioblastoma cells, which was also measured in the absence and presence of Fe(III).Results and Discussion: The current work demonstrated that the mixed-ligand vanadium coordination complex had high in vitro anti-proliferative activity against the human glioblastoma (T98G) cell line. The enhanced anti-proliferative effects of the mixed-ligand vanadium complex against T98G cells could be due to either hydrolysis of complex and release of the toxic clioquinol, or the rapid uptake of the lipophilic complex prior to hydrolysis. The speciation studies showed that at least part of the potent toxicity of the mixed-ligand coordination complex stemmed from release of the bioactive clioquinol ligand from the complex, which depended on whether Fe(III) was present. The studies also showed that the [VV(O)2 (L1H)] coordination complex was the most potent complex that remained intact and, hence, the complex that is the most biological active. Thus, future development of complexes should focus on the one-ligand intact complexes or making any mixed-ligand complex more water soluble, stable in aqueous solution, or designed to be rapidly taken up by diseased cells prior to hydrolysis.

This review focusses on the significance of fluorescent, phosphorescent labelling and tracking of extracellular vesicles (EVs) for unravelling their biology, pathophysiology, and potential diagnostic and therapeutic uses. Various labeling strategies, such as lipid membrane, surface protein, luminal, nucleic acid, radionuclide, quantum dot labels, and metal complex-based stains, are evaluated for visualizing and characterizing EVs. Direct labelling with fluorescent lipophilic dyes is simple but generally lacks specificity, while surface protein labelling offers selectivity but may affect EV-cell interactions. Luminal and nucleic acid labelling strategies have their own advantages and challenges. Each labelling approach has strengths and weaknesses, which require a suitable probe and technique based on research goals, but new tetranuclear polypyridylruthenium(II) complexes as phosphorescent probes have strong phosphorescence, selective staining, and stability. Future research should prioritize the design of novel fluorescent probes and labelling platforms that can significantly enhance the efficiency, accuracy, and specificity of EV labeling, while preserving their composition and functionality. It is crucial to reduce false positive signals and explore the potential of multimodal imaging techniques to gain comprehensive insights into EVs.

Two new series of complexes with pyridine-containing Schiff bases, [VVO(SALIEP)L] and [VVO(Cl-SALIEP)L] (SALIEP=N-(salicylideneaminato)-2-(2-aminoethylpyridine; Cl-SALIEP=N-(5-chlorosalicylideneaminato)-2-(2-aminoethyl)pyridine, L=catecholato(2-) ligand) have been synthesized. Characterization by 1H and 51V NMR and UV-Vis spectroscopies confirmed that: 1) most complexes form two major geometric isomers in solution, and [VVO(SALIEP)(DTB)] (DTB=3,5-di-tert-butylcatecholato(2-)) forms two isomers that equilibrate in solution; and 2) tert-butyl substituents were necessary to stabilize the reduced VIV species (EPR spectroscopy and cyclic voltammetry). The pyridine moiety within the Schiff base ligands significantly changed their chemical properties with unsubstituted catecholate ligands compared with the parent HSHED (N-(salicylideneaminato)-N '-(2-hydroxyethyl)-1,2-ethanediamine) Schiff base complexes. Immediate reduction to VIV occurred for the unsubstituted-catecholato VV complexes on dissolution in DMSO. By contrast, the pyridine moiety within the Schiff base significantly improved the hydrolytic stability of [VVO(SALIEP)(DTB)] compared with [VVO(HSHED)(DTB)]. [VVO(SALIEP)(DTB)] had moderate stability in cell culture media. There was significant cellular uptake of the intact complex by T98G (human glioblastoma) cells and very good anti-proliferative activity (IC50 6.7 +/- 0.9 mu M, 72 h), which was approximately five times higher than for the non-cancerous human cell line, HFF-1 (IC50 34 +/- 10 mu M). This made [VVO(SALIEP)(DTB)] a potential drug candidate for the treatment of advanced gliomas by intracranial injection. Vanadium(V) catecholates are promising agents for intratumoral injections to treat glioblastoma, an aggressive form of brain cancer. We report a novel promising analog abbreviated [VO(SALIEP)(DTB)] that is highly selective towards glioblastoma cells and nontoxic to normal cells due to the presence of the pyridine ring on the Schiff base. This is the first structure-activity study to establish this scaffold, which allows high toxicity against glioblastoma (T98G) cells.image

Tumour cell heterogeneity affects cisplatin but not doxorubicin cytotoxicity in two phenotypes of the triple-negative breast cancer (TNBC) cell line, MDA-MB-231. A mesenchymal MDA-MB-231 phenotype was three times less sensitive to cisplatin than an epithelial-type phenotype from the same cell line, which has important implications in the success of TNBC chemotherapies.

Internationally, the value and usefulness of museum zoological specimens are compromised when supporting contextual data are lost or disconnected from the specimen. In this pilot study, twelve Macropodidae Thylogale (pademelon) skins with known provenance from the Australian Museum (Sydney) were analysed using portable X-ray fluorescence spectroscopy and principal component analysis. Elemental composition of preservative residues was assessed to establish if common patterns existed and could be associated with particular field collectors. Specimens were differentiated, and the field collector deduced, based on elemental analysis of preservative residues on skins. Each of the nineteenth century field collectors, in this study, were found to have applied the same or similar preservatives to zoological specimens over a number of years, which showed a consistent pattern of practice. Additionally, the specimens obtained by each of the field collectors could be distinguished from one another based on the preservative residues. These discoveries provide exciting prospects for the use of X-ray fluorescence spectroscopy to couple museum specimens with unknown contextual data via their field collector and associated archival evidence, and hence, enable a considerable enhancement of their value as museum and research objects.

As shown by IncuCyte Zoom imaging proliferation assays, invasive triple-negative human breast MDA-MB-231 cancer cells treated with sub-toxic doses (5.0-20 mu M, 72h) of [GaQ(3)] (Q=8-hydroxyquinolinato) caused profound morphological changes and inhibition of cell migration, which were likely due to terminal cell differentiation or similar phenotypical change. This is the first demonstration of potential use of a metal complex in differentiation anti-cancer therapy. Additionally, a trace amount of Cu(II) (0.20 mu M) added to the medium dramatically increased [GaQ(3)] cytotoxicity (IC50 similar to 2 mu M, 72h) due to its partial dissociation and the action of the HQ ligand as a Cu(II) ionophore, as shown with electrospray mass spectrometry and fluorescence spectroscopy assays in the medium. Hence, cytotoxicity of [GaQ(3)] is strongly linked to ligand binding of essential metal ions in the medium, for example, Cu(II). Appropriate delivery mechanisms of such complexes and their ligands could enable a powerful new triple therapeutic approach for cancer chemotherapy, including cytotoxicity against primary tumour, arrest of metastases, and activation of innate and adaptive immune responses.

Twelve Re(I) tricarbonyl diimine (2,2'-bipyridine and 1,10-phenanthroline) complexes with thiotetrazolato ligands have been synthesised and fully characterised. Structural characterisation revealed the capacity of the tetrazolato ligand to bind to the Re(I) centre through either the S atom or the N atom with crystallography revealing most complexes being bound to the N atom. However, an example where the Re(I) centre is linked via the S atom has been identified. In solution, the complexes exist as an equilibrating mixture of linkage isomers, as suggested by comparison of their NMR spectra at room temperature and 373 K, as well as 2D exchange spectroscopy. The complexes are photoluminescent in fluid solution at room temperature, with emission either at 625 or 640 nm from the metal-to-ligand charge transfer excited states of triplet multiplicity, which seems to be exclusively dependent on the nature of the diimine ligand. The oxygen-sensitive excited state lifetime decay ranges between 12.5 and 27.5 ns for the complexes bound to 2,2'-bipyrdine, or between 130.6 and 155.2 ns for those bound to 1.10-phenanthroline. Quantum yields were measured within 0.4 and 1.5%. The complexes were incubated with human lung (A549), brain (T98g), and breast (MDA-MB-231) cancer cells, as well as with normal human skin fibroblasts (HFF-1), revealing low to moderate cytotoxicity, which for some compounds exceeded that of a standard anti-cancer drug, cisplatin. Low cytotoxicity combined with significant cellular uptake and photoluminescence properties provides potential for their use as cellular imaging agents. Furthermore, the complexes were assessed in disc diffusion and broth microdilution assays against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), Escherichia coli (E. coli), and Pseudomonas aeruginosa (P. aeruginosa) bacterial strains, which revealed negligible antibacterial activity in the dark or after irradiation.

Limited stability of most transition-metal complexes in biological media has hampered their medicinal applications but also created a potential for novel cancer treatments, such as intratumoral injections of cytotoxic but short-lived anticancer drugs. Two related V(V) complexes, [VO(Hshed)(dtb)] (1) and [VO(Hshed)(cat)] (2), where H2shed = N-(salicylideneaminato)-N'-(2-hydroxyethyl)-1,2-ethanediamine, H2dtb = 3,5-di-tert-butylcatechol, and H2cat = 1,2-catechol, decomposed within minutes in cell culture medium at 310 K (t1/2 = 43 and 9 s for 1 and 2, respectively). Despite this, both complexes showed high antiproliferative activities in triple-negative human breast cancer (MDA-MB-231) cells, but the mechanisms of their activities were radically different. Complex 1 formed noncovalent adducts with human serum albumin, rapidly entered cells via passive diffusion, and was nearly as active in a short-term treatment (IC50 = 1.9 ± 0.2 μM at 30 min) compared with a long-term treatment (IC50 = 1.3 ± 0.2 μM at 72 h). The activity of 1 decreased about 20-fold after its decomposition in cell culture medium for 30 min at 310 K. Complex 2 showed similar activities (IC50 ≈ 12 μM at 72 h) in both fresh and decomposed solutions and was inactive in a short-term treatment. The activity of 2 was mainly due to the reactions among V(V) decomposition products, free catechol, and O2 in cell culture medium. As a result, the activity of 1 was less sensitive than that of 2 to the effects of hypoxic conditions that are characteristic of solid tumors and to the presence of apo-transferrin that acts as a scavenger of V(V/IV) decomposition products in blood serum. In summary, complex 1, but not 2, is a suitable candidate for further development as an anticancer drug delivered via intratumoral injections. These results demonstrate the importance of fine-tuning the ligand properties for the optimization of biological activities of metal complexes.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Vanadium pyridine-containing Schiff base catecholate complexes are selectively cytotoxic against glioblastoma cells with increasing efficacy as the hydrophobicity and sterics of the complexes increase. More information can be found in the Research Article by P. A. Lay, D. C. Crans and co-workers (DOI: 10.1002/chem.202302271). Image by Nidhi Kumari.

The regular incremental secretion of enamel and dentine can be interrupted during periods of stress resulting in accentuated growth lines. These accentuated lines, visible under light microscopy, provide a chronology of an individual's stress exposure. Previously, we showed that small biochemical changes along accentuated growth lines detected by Raman spectroscopy, coincided with the timing of medical history events and disruptions of weight trajectory in teeth from captive macaques. Here, we translate those techniques to study biochemical changes related to illness and prolonged medical treatment during early infancy in humans. Chemometric analysis revealed biochemical changes related to known stress-induced changes in circulating phenylalanine as well as other biomolecules. Changes in phenylalanine are also known to affect biomineralization which is reflected in changes in the wavenumbers of hydroxyapatite phosphate bands associated with stress in the crystal lattice. Raman spectroscopy mapping of teeth is an objective, minimally-destructive technique that can aid in the reconstruction of an individual's stress response history and provide important information on the mixture of circulating biochemicals associated with medical conditions, as applied in epidemiological and clinical samples.

A new photoluminescent polypyridylruthenium(II) stain for extracellular vesicles (EVs) released from lipopolysaccharide-stimulated THP-1 monocytes enabled important new insights into how the bacteria-induced immune system affects the blood-brain barrier (BBB). These included previously unknown aspects of EV interactions with BBB microvascular endothelial cells and the extracellular matrix relevant to human brain diseases.

A hydrophobic Schiff base catecholate vanadium complex was recently discovered to have anticancer properties superior to cisplatin and suited for intratumoral administration. This [VO(HSHED)(DTB)] complex, where HSHED is N-(salicylideneaminato)-N'-(2-hydroxyethyl)-1,2-ethanediamine and the non-innocent catecholato ligand is di-t-butylcatecholato (DTB), has higher stability compared to simpler catecholato complexes. Three new chloro-substituted Schiff base complexes of vanadium(V) with substituted catecholates as co-ligands were synthesized for comparison with their non-chlorinated Schiff base vanadium complexes, and their properties were characterized. Up to four geometric isomers for each complex were identified in organic solvents using 51V and 1H NMR spectroscopies. Spectroscopy was used to characterize the structure of the major isomer in solution and to demonstrate that the observed isomers are exchanged in solution. All three chloro-substituted Schiff base vanadium(V) complexes with substituted catecholates were also characterized by UV-vis spectroscopy, mass spectrometry, and electrochemistry. Upon testing in human glioblastoma multiforme (T98g) cells as an in vitro model of brain gliomas, the most sterically hindered, hydrophobic, and stable compound [t1/2 (298 K) = 15 min in cell medium] was better than the two other complexes (IC50 = 4.1 ± 0.5 μM DTB, 34 ± 7 μM 3-MeCat, and 19 ± 2 μM Cat). Furthermore, upon aging, the complexes formed less toxic decomposition products (IC50 = 9 ± 1 μM DTB, 18 ± 3 μM 3-MeCat, and 8.1 ± 0.6 μM Cat). The vanadium complexes with the chloro-substituted Schiff base were more hydrophobic, more hydrolytically stable, more easily reduced compared to their corresponding parent counterparts, and the most sterically hindered complex of this series is only the second non-innocent vanadium Schiff base complex with a potent in vitro anticancer activity that is an order of magnitude more potent than cisplatin under the same conditions.

Injections of highly cytotoxic or immunomodulating drugs directly into the inoperable tumor is a procedure that is increasingly applied in the clinic and uses established Pt-based drugs. It is advantageous for less stable anticancer metal complexes that fail administration by the standard intravenous route. Such hydrophobic metal-containing complexes are rapidly taken up into cancer cells and cause cell death, while the release of their relatively non-toxic decomposition products into the blood has low systemic toxicity and, in some cases, may even be beneficial. This concept was recently proposed for V(V) complexes with hydrophobic organic ligands, but it can potentially be applied to other metal complexes, such as Ti(IV), Ga(III) and Ru(III) complexes, some of which were previously unsuccessful in human clinical trials when administered via intravenous injections. The potential beneficial effects include antidiabetic, neuroprotective and tissue-regenerating activities for V(V/IV); antimicrobial activities for Ga(III); and antimetastatic and potentially immunogenic activities for Ru(III). Utilizing organic ligands with limited stability under biological conditions, such as Schiff bases, further enhances the tuning of the reactivities of the metal complexes under the conditions of intratumoral injections. However, nanocarrier formulations are likely to be required for the delivery of unstable metal complexes into the tumor.