Mass spectrometry as a powerful tool to study therapeutic metallodrugs speciation mechanisms: current frontiers and perspectives

Metal-based compounds form a promising class of therapeutic agents, whose mechanisms of action still need to be elucidated, and that are in general prone to undergo extensive speciation in physiological environment. Thus, determination of the fate of the metal compounds in complex biological systems, contributing to their overall pharmacological and toxicological profiles, is important to develop more rationalised and targeted metal-based drugs. To these aims, a number of spectroscopic and biophysical methods, as well as analytical techniques, are nowadays extensively applied to study the reactivity of metal complexes with different biomolecules (e.g. nucleic acids, proteins, buffer components). Among the various techniques, molecular mass spectrometry (MS) has emerged in the last decade as a major tool to characterise the interactions of metallodrugs at a molecular level. In this review, we present an overview of the information available on the reactivity of various families of therapeutic metallodrugs (mainly anticancer compounds based on Pt, Ru, Au and As) with biomolecules studied by different MS techniques, including high-resolution ESI-, MALDI- and ion mobility-MS among others. Representative examples on the potential of the MS approach to study non-covalent interactions are also discussed. The review is organized to present results obtained on samples with different degrees of complexity, from the interactions of metal compounds with small model nucleophiles (amino acids and nucleobases), model peptides/oligonucleotides, target proteins/nucleic acids, to the analysis of serum, cell extracts and tissue samples. The latter requiring combination of proteomic methods with advanced MS techniques. Correlations between molecular reactivity of metallodrugs and biological activity are hard to establish, but differences in the reactivity of metallodrugs to biomolecules and their different adducts, as revealed by MS methods, may indicate differences in their modes of action. Overall, the knowledge offered by MS methods on metallodrugs speciation is invaluable to establish new rules and define new trends in the periodic table aimed at rationalizing the behavior of metal compounds in complex living systems

Aquaporin modulators: a patent review (2010-2015)

Introduction: Since the discovery of aquaporin-1 (AQP1) as a water channel, more than 2,000 articles, reviews and chapters have been published. The wide tissue expression, functional and biological roles have documented the major and essential physiological importance of these channels both in health and disease. Thus, over the years, studies have revealed essential importance of aquaporins in mammalian pathophysiology revealing aquaporins as potential drug targets. Areas covered: Starting from a brief description of the main structural and functional features of aquaporins, their roles in physiology and pathophysiology of different human diseases, this review describes the main classes of small molecules and biologicals patented, published from 2010 to 2015, able to regulate AQPs for diagnostic and therapeutic applications. Expert opinion: Several patents report on AQP modulators, mostly inhibitors, and related pharmaceutical formulations, to be used for treatments of water imbalance disorders, such as edema. Noteworthy, a unique class of gold-based compounds as selective inhibitors of aquaglyceroporin isoforms may provide new chemical tools for therapeutic applications, especially in cancer. AQP4-targeted therapies for neuromyelitis optica, enhancement of AQP2 function for nephrogenic diabetes insipidus and AQP1-5 gene transfer for the Sjogren’s syndrome represent promising therapies that deserve further investigation by clinical trials

Gold compounds for catalysis and metal-mediated transformations in biological systems

One of the challenges of modern inorganic chemistry is translating the potential of metal catalysts to living systems to achieve controlled non-natural transformations. This field poses numerous issues associated with the metal compounds biocompatibility, stability, and reactivity in complex aqueous environment. Moreover, it should be noted that although referring to ‘metal catalysis’, turnover has not yet been fully demonstrated in most of the examples within living systems. Nevertheless, transition metal catalysts offer an opportunity of modulating bioprocesses through reactions that are complementary to enzymes. In this context, gold complexes, both coordination and organometallic, have emerged as promising tools for bio-orthogonal transformations, endowed with excellent reactivity and selectivity, compatibility within aqueous reaction medium, fast kinetics of ligand exchange reactions, and mild reaction conditions. Thus, a number of examples of gold-templated reactions in a biologically relevant context will be presented and discussed here in relation to their potential applications in biological and medicinal chemistry

Gold Complexes in Anticancer Therapy: From New Design Principles to Particle‐Based Delivery Systems

The discovery of the medicinal properties of gold complexes has fuelled the design and synthesis of new anticancer metallodrugs, which have received special attention due to their unique modes of action. Current research in the development of gold compounds with therapeutic properties is predominantly focused on the molecular design of drug leads with superior pharmacological activities, e.g., by introducing targeting features. Moreover, intensive research aims at improving the physicochemical properties of gold compounds, such as chemical stability and solubility in the physiological environment. In this regard, the encapsulation of gold compounds in nanocarriers or their chemical grafting onto targeted delivery vectors could lead to new nanomedicines that eventually reach clinical applications. Herein, we provide an overview of the state-of-the-art progress of gold anticancer compounds, andmore importantly we thoroughly revise the development of nanoparticle-based delivery systems for gold chemotherapeutics

Recent developments of supramolecular metal-based structures for applications in cancer therapy and imaging

The biomedical application of discrete supramolecular metal-based structures, including supramolecular coordination complexes (SCCs), is still an emergent field of study. However, pioneering studies over the last 10 years demonstrated the potential of these supramolecular compounds as novel anticancer drugs, endowed with different mechanisms of action compared to classical small-molecules, often related to their peculiar molecular recognition properties. In addition, the robustness and modular composition of supramolecular metal-based structures allows for an incorporation of different functionalities in the same system to enable imaging in cells via different modalities, but also active tumor targeting and stimuli-responsiveness. Although most of the studies reported so far exploit these systems for therapy, supramolecular metal-based structures may also constitute ideal scaffolds to develop multimodal theranostic agents. Of note, the host-guest chemistry of 3D self-assembled supramolecular structures – within the metallacages family - can also be exploited to design novel drug delivery systems for anticancer chemotherapeutics. In this review, we aim at summarizing the pivotal concepts in this fascinating research area, starting with the main design principles and illustrating representative examples while providing a critical discussion of the state-of-the-art. A section is also included on supramolecular organometallic complexes (SOCs) whereby the (organic) linker is forming the organometallic bond to the metal node, whose biological applications are still to be explored. Certainly, the myriad of possible supramolecular metal-based structures and their almost limitless modularity and tunability suggests that the biomedical applications of such complex chemical entities will continue along this already promising path

On the binding modes of metal NHC complexes with DNA secondary structures: implications for therapy and imaging

Organometallic compounds currently occupy an important place in the field of medicinal inorganic chemistry due to the unique chemical properties of metal coordination compounds. Particularly, metal compounds ligated by N-heterocyclic carbenes (NHC) have shown high potential for biomedical applications as antimicrobial and anticancer agents during the recent 15 years. Although further studies are necessary to validate the modes of action of this family of compounds, a number of biological targets have been identified, including DNA secondary structures. This perspective review aims at providing an overview of the most representative examples of metal NHC complexes reacting with nucleic acids via different binding modes. It is organized according to the type of DNA secondary structure targeted by metal NHCs, highlighting the possible advantages of biomedical applications, including therapy and imaging

The beauty of gold: knowledge of mechanisms leads to different applications of organogold compounds in medicine and catalysis

This review is aimed at providing a concise overview of the results obtained by our group in the field of organometallic chemistry of gold. Therefore, a selection of examples amongst the most extensively explored families of bioactive gold complexes — Au(I) N-heterocyclic carbenes and cyclometalated Au(III) compounds — is presented. Insights into the bio-inorganic mechanisms of reactivity of organogold compounds obtained by an integrated investigational approach, and knowledge of structure-activity relationships are discussed also in relation to novel applications of gold-based catalysts and metal-mediated transformations in aqueous environment

Supramolecular exo-functionalized palladium cages: fluorescent properties and biological activity

Metallosupramolecular systems are promising new tools for pharmaceutical applications. Thus, novel self-assembled Pd(II) coordination cages were synthesized which were exo-functionalized with naphthalene or anthracene groups with the aim to image their fate in cells. The cages were also investigated for their anticancer properties in human lung and ovarian cancer cell lines in vitro. While the observed cytotoxic effects hold promise and the cages resulted to be more effective than cisplatin in both cell lines, fluorescence emission properties were scarce. Therefore, using TD-DFT calculations, fluorescence quenching observed in the naphthalene-based system could be ascribed to a lower probability of a HOMO–LUMO excitation and an emission wavelength outside the visible region. Overall, the reported Pd2L4 cages provide new insights into the chemical–physical properties of this family of supramolecular coordination complexes whose understanding is necessary to achieve their applications in various fields