Metal-based molecules for biomedical applications: investigation of their biological activities in cancer cells

Cisplatin, a platinum(II) based drug exhibiting potent cytotoxic effects in highly dividing and proliferating cells, is widely applied as chemotherapeutic agent against several forms of cancer. However, current drawbacks and limitations such as its severe nephrotoxicity and increased drug resistance are still of great concern. This doctoral research aimed to address these issues by exploring the potential of new families of metal-based molecules for biomedical applications as either anticancer agents or anticancer drug delivery vehicles for the aforementioned Pt(II) drug. Two strategies were then deployed. The first part of the thesis describes the study of small molecule gold(III) complexes with different scaffolds designed as aquaporin (AQP) inhibitors. AQP are membrane proteins enabling permeation of water, but also of small solutes, such as glycerol and hydrogen peroxide, across biomembranes, and their expression has been correlated to several types of cancer, making them attractive as diagnostic and therapeutic targets. Based on preliminary data on AQP modulation (inhibition) by metal-based compounds, two series of gold(III) complexes, either coordination or organometallics, were investigated for their ability to target these membrane proteins using different spectroscopic methods, and the compounds’ cytotoxic effect were also studied in vitro. The second part of this thesis focuses on another strategy to improve cisplatin`s selectivity and targeting without altering its structure/properties via the use of new generation metal-based drug delivery systems, which are able to protect the drug from metabolism (speciation) and to facilitate its uptake in cancer cells. Therefore, supramolecular coordination complexes (SCCs), specifically three dimensional (3D) metallacages, were chosen. These discrete supramolecular entities, formed via selfassembly of ligands and appropriate metal precursors, can not only be exploited for their host-guest properties to achieve drug encapsulation, but they can also be exofunctionalized with targeting moieties to improve their delivery at a tumour site. Our study provides the proof-of-concept that a specific family of metallacages of general formula [Pd2L4] 4+ (L= ligand), bioconjugated to integrin targeting ligands, can encapsulate cisplatin and increase its potency in human cancer cells overexpressing the integrin receptors. Moreover, the metallacages can be functionalized with fluorophores to enable the study of their uptake and intracellular distribution by iv fluorescence microscopy. As such, the mechanism of accumulation of [Pd2L4] 4+ cages labelled with fluorescent BODIPY moieties was investigated in vitro

Aquaporins in cancer development: opportunities for bioinorganic chemistry to contribute novel chemical probes and therapeutic agents

Metal ions and complexes can interfere with the transcellular water flow but also with the cellular transport of glycerol and hydrogen peroxide,viainhibition of the ubiquitous aquaporin channels.</p

Exploring the reactivity and biological effects of heteroleptic N-Heterocyclic carbene gold(I)-Alkynyl complexes

Two families of heteroleptic N‐heterocyclic carbene gold(I)‐alkynyl complexes have been synthesized and characterized by different methods. Their reactivity with model thiols has been studied by NMR spectroscopy and DFT calculations. Moreover, preliminary studies on the compounds' reactivity with DNA and antiproliferative effects have been conducted

Mechanisms of irreversible aquaporin-10 inhibition by organogold compounds studied by combined biophysical methods and atomistic simulations

The inhibition of glycerol permeation via human aquaporin-10 (hAQP10) by organometallic gold complexes has been studied by stopped-flow fluorescence spectroscopy, and its mechanism has been described using molecular modelling and atomistic simulations. The most effective hAQP10 inhibitors are cyclometalated Au(III) C^N compounds known to efficiently react with cysteine residues leading to the formation of irreversible C–S bonds. Functional assays also demonstrate the irreversibility of the binding to hAQP10 by the organometallic complexes. The obtained computational results by metadynamics show that the local arylation of Cys209 in hAQP10 by one of the gold inhibitors is mapped into a global change of the overall free energy of glycerol translocation across the channel. Our study further pinpoints the need to understand the mechanism of glycerol and small molecule permeation as a combination of local structural motifs and global pore conformational changes, which are taking place on the scale of the translocation process and whose study, therefore, require sophisticated molecular dynamics strategies

Highly luminescent metallacages featuring bispyridyl ligands functionalised with BODIPY for imaging in cancer cells

Recently, 3-dimentional supramolecular coordination complexes of the metallacage type have been shown to hold promise as drug delivery systems for different cytotoxic agents, including the anticancer drug cisplatin. However, so far only limited information is available on their uptake and sub-cellular localisation in cancer cells. With the aim of understanding the fate of metallacages in cells by fluorescence microscopy, three fluorescent Pd2L4 metallacages were designed and synthesised by self-assembly of two types of bispyridyl ligands (L), exo-functionalised with boron dipyrromethene (BODIPY) moieties, with Pd(II) ions. The cages show high quantum yields and are moderately stable in the presence of physiologically relevant concentration of glutathione. Furthermore, the cages are able to encapsulate the anticancer drug cisplatin, as demonstrated by NMR spectroscopy. Preliminary cytotoxicity studies in a small panel of human cancer cells showed that the metallacages are scarcely toxic in vitro. The marked fluorescence due to BODIPY allowed us to visualise the cages' uptake and sub-cellular localisation inside melanoma cells using fluorescence microscopy, highlighting uptake via active transport mechanisms and accumulation in cytoplasmic vesicles

Construçao do masculino na Curitiba das décadas de 1940 e 1950 tornar-se homem

Orientadora : Maria Luiza AndreazzaAutor não autorizou a divulgação do arquivo digitalDissertaçao (mestrado) - Universidade Federal do Paraná, Setor de Ciencias Humanas, Letras e ArtesInclui referência

Organometallic Pillarplexes That Bind DNA 4-Way Holliday Junctions and Forks

Holliday 4-way junctions are key to important biological DNA processes (insertion, recombination, and repair) and are dynamic structures that adopt either open or closed conformations, the open conformation being the biologically active form. Tetracationic metallo-supramolecular pillarplexes display aryl faces about a cylindrical core, an ideal structure to interact with open DNA junction cavities. Combining experimental studies and MD simulations, we show that an Au pillarplex can bind DNA 4-way (Holliday) junctions in their open form, a binding mode not accessed by synthetic agents before. Pillarplexes can bind 3-way junctions too, but their large size leads them to open up and expand that junction, disrupting the base pairing, which manifests in an increased hydrodynamic size and lower junction thermal stability. At high loading, they rearrange both 4-way and 3-way junctions into Y-shaped forks to increase the available junction-like binding sites. Isostructural Ag pillarplexes show similar DNA junction binding behavior but lower solution stability. This pillarplex binding contrasts with (but complements) that of metallo-supramolecular cylinders, which prefer 3-way junctions and can rearrange 4-way junctions into 3-way junction structures. The pillarplexes’ ability to bind open 4-way junctions creates exciting possibilities to modulate and switch such structures in biology, as well as in synthetic nucleic acid nanostructures. In human cells, the pillarplexes do reach the nucleus, with antiproliferative activity at levels similar to those of cisplatin. The findings provide a new roadmap for targeting higher-order junction structures using a metallo-supramolecular approach, as well as expanding the toolbox available to design bioactive junction binders into organometallic chemistry

Insights into the mechanisms of aquaporin-3 inhibition by gold(III) complexes: the importance of non-coordinative adduct formation

A series of six new Au(III) coordination compounds with phenanthroline ligands have been synthesized and studied for the inhibition of the water and glycerol channel aquaporin-3 (AQP3). From a combination of different experimental and computational approaches, further insights into the mechanisms of AQP3 inhibition by gold compounds at a molecular level have been gained. The results evidence the importance of noncoordinative adduct formation, prior to “covalent” protein binding, to achieve selective AQP3 inhibition

Bioconjugation of supramolecular metallacages to integrin ligands for targeted delivery of cisplatin

Cisplatin occupies a crucial role in the treatment of various malignant tumours. However, its efficacy and applicability are heavily restricted by severe systemic toxicities and drug resistance. Our study exploits the active targeting of supramolecular metallacages to enhance the activity of cisplatin in cancer cells while reducing its toxicity. Thus, Pd2L4 cages (L = ligand) have been conjugated to four integrin ligands with different binding affinity and selectivity. Cage formation and encapsulation of cisplatin was proven by NMR spectroscopy. Upon encapsulation, cisplatin showed increased cytotoxicity in vitro, in melanoma A375 cells overexpressing αvβ3 integrins. Moreover, ex vivo studies in tissue slices indicated reduced toxicity towards healthy liver and kidney tissues for cage-encapsulated cisplatin. Analysis of metal content by ICP-MS demonstrated that encapsulated drug is less accumulated in these organs compared to the ‘free’ one