The aqueous structural speciation of binary thallium-hydroxycarboxylic acid systems. Structure-chemical (bio)reactivity correlations

Among transition and non-transition metals, thallium is a unique case of an element which, despite its known toxicity, provides interesting challenges through its biology and chemistry linked to diagnosis of human pathophysiologies. Poised to investigate in-depth the structural and electronic aspects of thallium involvement in physiological processes, the synthetic exploration of aqueous binary systems of Tl(I) with physiological binders from the family of hydroxycarboxylic acids (glycolic, lactic, mandelic and citric acid) was pursued in a pH-specific fashion. The isolated crystalline coordination polymers, emerging from that effort, were physicochemically characterized through elemental analysis, FT-IR, ESI-MS, ¹H-/¹³C-NMR, and X-ray crystallography. The coordination environment of thallium in each molecular Tl(I) assembly, along with lattice dimensionality (2D3D), reflects the contributions of the ligands, collectively exemplifying interactions probed into though BVS and Hirshfeld surface analysis. The results portray a well-defined solid-state and solution profile for all species investigated, thereby providing the basis for their subsequent selection into in vitro biological studies involving the (patho)physiological cell lines 3T3-L1, Saos-2, C2C12, and MCF-7. Biotoxicity profiles, encompassing cell viability, morphology, and cell growth support clearly a concentration-, time-, and cell tissue-specific behavior for the chosen Tl(I) compounds in a structure-specific fashion. Collectively, the chemical experimental data support the biological results in formulating a structure-specific behavior for Tl(I)-hydroxycarboxylato species with respect to biotoxicity mechanisms in a (patho)physiological environment. The accrued knowledge stands as the foreground for further investigation into the relevant biological chemistry of Tl(I) and molecular technologies targeting its sequestration and removal from cellular media.

Biomimetic activity of soluble, well-defined, aqueous Ti(IV)-citrate species toward adipogenesis. An in vitro study

Metal-organic complexes bearing physiological substrates have been the target of several investigations, probing into the potential of well-defined atoxic metalloforms to influence fundamental cellular processes overcoming insulin resistance in Diabetes mellitus 2. Outstanding cases of such metals include zinc and vanadium, both being the target of intense synthetic and biological studies toward insulin mimesis. Owing to the close proximity in the periodic table, an early transition metal, titanium, emerges as another potential candidate of biologically relevant complexation, reflecting species capable of promoting insulin mimetic activity. Driven by the so far explored aqueous synthetic chemistry of Ti(IV)-hydroxycaboxylato systems, a well-defined Ti(IV)-citrate compound was synthesized under physiological conditions, isolated, and characterized, followed by its introduction in biological assays, targeting adipogenic events linked to glucose uptake and catabolism. The mononuclear Ti(IV)-citrate complex was introduced to 3T3-L1 cells, thereby probing into its biological activity (toxicity, morphology, migration, and adipogenic capacity). The results project an atoxic profile for the Ti(IV)-citrate species, thus justifying further incorporation in cellular differentiation processes, leading to mature adipocytes in a time- and concentration-dependent fashion. The experiments suggest that Ti(IV)-citrate is a competent agent promoting fibroblast differentiation, as evidenced by key adipogenic biomarkers, while concurrently exhibiting synergistic/enhancing action with insulin. The collective results show, for the first time, that an appropriately configured soluble-bioavailable complex Ti(IV) form exhibits a distinctly unique bioprofile, thereby lending credence to the notion that titanium metallopharmaceuticals hold merit as competent agents in adipogenesis and insulin mimesis in Diabetes mellitus.

Binary-ternary Cd(II)-(hydroxycarboxylic acid)-(aromatic chelator) systems exhibit in vitro cytotoxic selectivity in a tissue-specific manner

Cadmium is a metallotoxin, amply encountered in the environment and derived through physical and anthropogenic activities. Its entry in various organisms leads through water and the food chain to humans, thereby inducing a plethora of pathophysiologies. Delineation of the interactive role of cadmium with physiological and physiologically relevant substrates, requires well-defined forms of cadmium arising from such interactions along with the ensuing chemical reactivity amounting to toxic manifestations and health aberrations. To implement such efforts, low molecular mass substrate metal ion binders are needed, forming species with enhanced solubility and bioavailability. To that end, α-hydroxy isobutyric acid (HIBAH₂) was used in pH-specific synthetic efforts involving bulky aromatic chelators 2,2'-bipyridine (2,2'-bipy) and 1,10-phenanthroline (phen), thus leading to new crystalline materials [Cd(C₄H₇O₃)₂]_n(1), [Cd(C₄H₇O₃)₂(H₂O)₂](2), [{Cd₂(C₄H₇O₃)₂(C₁₀H₈N₂)₂(H₂O)₂}(NO₃)₂]_n·nH₂O(3), and [{Cd₂(C₄H₇O₃)₂(C₁₂H₈N₂)₂(H₂O)₂}(NO₃)₂]_n·2nH₂O(4), which were physicochemically characterized (elemental analysis, FT-IR, NMR, ESI-MS, and X-ray crystallography) in the solid state and solution. Their physicochemical characteristics led to their employment in tissue-specific biological toxicity studies in three different cell lines. Their toxicity profile (cell viability, morphology, chemotacticity) was correlated through genetic biomarkers to apoptotic-necrotic processes, thereby shedding light on cadmium cellular toxicity processes. Finally, the cytoprotective action of specific chelators was examined, lending credence to the notion that appropriately structured chelators and antioxidants may be used as effective deterrent to cadmium toxicity. Collectively, structure-specificity linked to tissue-specific toxicity profiling in well-defined binary-ternary Cd(II)-HIBAH₂ systems exemplifies that metal ion's aberrant interactions in the cellular milieu, meriting further probing into the development of efficient chelators in cadmium detoxification.

V(v)-Schiff base species induce adipogenesis through structure-specific influence of genetic targets

Appropriately designed Schiff-base substrates enhance V(v)-bioavailability and insulin-mimetic biomolecular gene profiling, inducing adipogenesis in a structure-specific manner.

Comparative assessment of metal-specific adipogenic activity in zinc and vanadium-citrates through associated gene expression

Diabetes mellitus comprises a group of metabolic abnormalities due to insulin deficiency and/or resistance. Obesity contributes to diabetes, with a strong causal relationship existing between diabetes and insulin resistance, especially in patients with Diabetes mellitus II. Adipocytes emerge as key constituents of adipose tissue physiology. In their pre-mature form to mature state transformation, adipocytes fully exemplify one of the key adipogenic actions of insulin. Poised to a) gain insight into adipogenesis leading to antidiabetic factors, and b) investigate adipogenesis through careful examination of insulin contributions to interwoven mechanistic pathways, a systematic comparative study was launched involving well-defined metal-citrates (zinc and vanadium), the chemical reactivity of which was in line with their chemistry under physiological conditions. Selection of the specific compounds was based on their common aqueous coordination chemistry involving the physiological chelator citric acid. Cellular maturation of pre-adipocytes to their mature form was pursued in the presence-absence of insulin and employment of closely linked genetic targets, key to adipocyte maturation (Peroxisome proliferator-activated receptor gamma (PPAR-γ), Glucose transporter 1,3,4 (GLUT 1,3,4), Adiponectin (ADIPOQ), Glucokinase (GCK), and Insulin receptor (INS-R)). The results show a) distinct adipogenic biological profiles for the metalloforms involved in a dose-, time- and nature-dependent manner, and b) metal ion-specific adipogenic response-signals at the same or higher level than insulin toward all selected targets. Collectively, the foundations have been established for future exploitation of the distinct metal-specific adipogenic factors contributing to the functional maturation of adipose tissue and their use toward hyperglycemic control in Diabetes mellitus.

Synthetic investigation of binary-ternary Cr(III)-hydroxycarboxylic acid-aromatic chelator systems. Structure-specific influence on adipogenic biomarkers linked to insulin mimesis

In an attempt to understand the aqueous interactions of Cr(III) with low-molecular mass physiological ligands and examine its role as an adipogenic metallodrug agent in Diabetes mellitus II, the pH-specific synthesis in the binary-ternary Cr(III)-(HA = hydroxycarboxylic acid)-(N,N)-aromatic chelator (AC) (HA = 2-hydroxyethyl iminodiacetic acid/heidaH₂, quinic acid; AC = 1,10-phenanthroline/phen) systems was pursued, leading to four new crystalline compounds. All materials were characterized by elemental analysis, UV-Visible, FT-IR, and ESI-MS spectroscopy, cyclic voltammetry, and X-Ray crystallography. Concurrently, the aqueous speciation of the binary Cr(III)-(2-hydroxyethyl iminodiacetic acid) system, complemented by ESI-MS, provided key-details of the species in solution correlating with the solid-state species. The structurally distinct Cr(III) soluble species were subsequently used in an in vitro investigation of their cytotoxic activity in 3T3-L1 fibroblast cultures. Compound 1 exhibited solubility, bioavailability, and atoxicity over a wide concentration range (0.1-100 μΜ) in contrast to 3, which was toxic. The adipogenic potential of 1 was subsequently investigated toward transformation of pre-adipocytes into mature adipocytes. Confirmation of that capacity relied on molecular biological techniques a) involving genes (glucose transporter type 4, peroxisome proliferator-activated receptor gamma, glucokinase, and adiponectin) serving as sensors of the transformation process, b) comparing the Cr(III)-adipogenicity potential to that of insulin, and c) exemplifying the ultimate maturity of adipocytes poised to catabolize glucose. The collective effort points out salient structural features in the coordination sphere of Cr(III) inducing adipogenic transformation relevant to combating hyperglycemia. The multiply targeted mechanistic insight into such a process exemplifies the role of well-defined Cr(III) complex forms as potential insulin-mimetic adipogenic agents in Diabetes mellitus II.

In vitro structure-specific Zn(II)-induced adipogenesis and structure-function bioreactivity correlations

The advent of Zn(II) metallodrugs in metabolic syndrome pathologies generates a strong challenge toward synthetic endeavors targeting well-defined, atoxic and biologically active binary/ternary species of Zn(II). Proper formulation of that metal ion's coordination sphere sets the stage for construction of appropriately configured Schiff ligands based on tromethamine and variably modified vanillin core components. The arising Schiff ligands react with Zn(II) in a defined stoichiometry, thereby delivering new binary Zn(II)-L species with defined physicochemical properties. Analytical (elemental), spectroscopic (FT-IR, Thermogravimetric Analysis) and crystallographic techniques attest to the distinct nature of the derived binary-ternary materials, bearing defined Zn(II):L molecular stoichiometry, variable nuclearity, charge, bulk and balance mix of hydrophilicity-hydrophobicity, thereby providing the physicochemical profile based on which biological studies could ensue. The structurally based selection of species was applied onto in vitro 3T3-L1 cultures, essentially exploring toxicity, migration, morphology, cell differentiation and maturation. The systematic effort toward comparative work on appropriately defined Zn(II) species and insulin in inducing adipogenesis reveals the salient structural features in the Schiff family of ligands configuring Zn(II) so as to promote complex formation sufficient to engage biomolecular targets during the process of initiation and maturation. Molecular targets of importance in adipogenesis were examined under the influence of Zn(II) and their expression levels suggest the structural composition that a Zn(II) ion might have to optimally pursue cell differentiation. Thus, a well-defined selection of binary Zn(II)-L species is tightly associated with the incurred bioactivity, thereby setting the stage for the development of efficient Zn(II) metallodrugs to combat Diabetes mellitus II.

Synthetic endeavors on cadmium species bearing glycolate and aromatic chelators with structure-specific biotoxic correlations in vitro

Cadmium is a well-known metallotoxin widespread in the environment and easily reaching cellular targets in lower and higher organisms, including humans. The form(s) of that metal ion through which it interacts with biomolecular targets in a cellular milieu are critical in cell survival. Poised to investigate the structure-specific activity of Cd(II) in a cellular environment and delve into the associated biotoxic processes, binary and ternary systems of that metal ion in the presence of the physiological α-hydroxycarboxylic acid glycolic acid and aromatic (N,N')-binders 2,2'-bipyridine (2,2'-bipy) and 4,4'-bipyridine (4,4'-bipy) were examined synthetically in aqueous media and a pH-specific fashion. The arising new materials [Cd(C₂H₃O₃)₂]_n (1), [Cd(C₂H₃O₃)(C₁₀H₈N₂)(NO₃)]_n·nH₂O (2), and {[Cd(C₂H₃O₃)(C₁₀H₈N₂)(H₂O)](NO₃)}_n·2nH₂O (3) project coordination polymers, which were physicochemically characterized through elemental analysis, FT-IR, NMR, luminescence and X-ray crystallography. The distinct spectroscopic features of 1-3, with luminescence exemplifying distinct behavior (2,3), further corroborated by crystallographic analysis, lend credence to a structure-specific selection of species employed in ensuing in vitro biological studies. The emerging results in two different cell lines (3T3-L1, Saos-2) reveal a concentration-dependent, structure-specific and cell line-specific toxicity profile of Cd(II), reflecting its coordination composition and formulation, rendering it soluble and bioavailable (1,2). Mechanistic information riding on caspase-dependent investigation unravels that metal ion's specific behavior compromising cell survival and integrity. Employment of ethylenediamine tetraacetic acid (EDTA) a) shows efficient sequestration of Cd(II) away from its toxic reactivity denoting the strength of interactions involved, and b) lends credence to further development of appropriately configured organic binders, selectively providing molecular protection from Cd(II) toxicity.

Structure-specific adipogenic capacity of novel, well-defined ternary Zn(II)-Schiff base materials. Biomolecular correlations in zinc-induced differentiation of 3T3-L1 pre-adipocytes to adipocytes

Among the various roles of zinc discovered to date, its exogenous activity as an insulin mimetic agent stands as a contemporary challenge currently under investigation and a goal to pursue in the form of a metallodrug against type 2 Diabetes Mellitus. Poised to investigate the adipogenic potential of Zn(II) and appropriately configure its coordination sphere into well-defined anti-diabetic forms, (a) a series of new well-defined ternary dinuclear Zn(II)-L (L=Schiff base ligands with a variable number of alcoholic moieties) compounds were synthesized and physicochemically characterized, (b) their cytotoxicity and migration effect(s) in both pre- and mature adipocytes were assessed, (c) their ability to effectively induce cell differentiation of 3T3-L1 pre-adipocytes into mature adipocytes was established, and (d) closely linked molecular targets involving or influenced by the specific Zn(II) forms were perused through molecular biological techniques, cumulatively delineating factors involved in Zn(II)-induced adipogenesis. Collectively, the results (a) reveal the significance of key structural features of Schiff ligands coordinated to Zn(II), thereby influencing its (a)toxicity behavior and insulin-like activity, (b) project molecular targets influenced by the specific forms of Zn(II) formulating its adipogenic potential, and (c) exemplify the interwoven relationship between Zn(II)-L structural speciation and insulin mimetic biological activity, thereby suggesting ways of fine tuning structure-specific zinc-induced adipogenicity in future efficient antidiabetic drugs.