Association between Diet Quality and Risk of Type 2 Diabetes Mellitus in Patients with Coronary Heart Disease: Findings from the CORDIOPREV Study.

The incidence of type 2 diabetes mellitus (T2DM) is growing in Western countries. Nutritional interventions that promote high-quality dietary patterns could help reverse this trend. We aimed to evaluate whether changes in Nutrient-Rich Food Index 9.3 (NRF9.3) were related to the risk of developing T2DM in patients with coronary heart disease (CHD). The study was carried out in the context of two healthy dietary interventions (a Mediterranean and a low-fat diet). For this purpose, we evaluated all the patients in the CORDIOPREV study without T2DM at baseline. Data were obtained during the first 5 years of dietary intervention. The score was calculated using the Food Frequency Questionnaires at baseline and after 1 year of intervention. After 5 years of follow-up, 106 patients developed T2DM (incident-T2DM), while 316 subjects did not (non-T2DM). Total NRF9.3 score and changes during the first year of intervention were compared between incident-T2DM and non-T2DM. Incident-T2DM showed less improvement in NRF9.3 than non-T2DM (p = 0.010). In the multi-adjusted Cox proportional hazard study, patients with greater improvement in NRF9.3 had over 50% less risk of developing T2DM compared with the lowest tertile (HR 2.10, 95%, CI = 1.12-3.56). In conclusion, improved diet quality in terms of nutrient density after the dietary intervention was associated with a lower risk of T2DM in patients with CHD.

Dietary antioxidant intake reduces carotid intima-media thickness in coronary heart disease patients: From the CORDIOPREV study.

BACKGROUND: Atherosclerosis is the leading underlying cause of coronary heart disease (CHD). In patients with CHD, intima-media thickness of common carotid arteries (IMT-CC) is a reliable, validated, and non-invasive marker of the progression of atherosclerosis. Dietary intervention may affect IMT-CC evolution through different pathways. There is a lack of clinical trials evaluating the effect of total dietary antioxidant content of diets on IMT-CC, especially in patients with CHD. OBJECTIVE: We evaluated the correlation between the diet's total antioxidant content and the changes in IMT-CC produced after 5 years of dietary intervention following two healthy diet models (Mediterranean diet and low-fat diet). We also evaluated whether the diet's total antioxidant content was related to the total redox capacity of the participants. METHODS: From the total participants of the CORDIOPREV study (clinical trial register NCT00924937), 805 participants completed the IMT-CC measurement and the dietary antioxidant evaluation at baseline and after 5 years of dietary intervention. IMT-CC was carried out by ultrasound and the dietary antioxidant evaluation was performed by the Dietary Antioxidant Index (DAI). Additionally, direct redox balance was evaluated in a subset of population by the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSH) by colorimetric assay. RESULTS: We observed an inverse correlation between evolution of DAI and IMT-CC after 5-years of dietary intervention. The mean of the DAI index augmented in the Mediterranean Diet group, whereas it decreased in the Low-fat group. DAI was correlated to the GSH/GSSG ratio, supporting DAI as an adequate estimator of diet's antioxidant content. When looking for individual components of the DAI that were associated to the changes in IMT-CC, an inverse correlation was found for carotenoids, vitamin E, vitamin C, and zinc and the IMT-CC. CONCLUSIONS: Our study indicates that, after five years of dietary intervention, changes in DAI inversely correlate with changes in IMT-CC in patients with CHD. Overall effect of Mediterranean diet resulted in an increase of DAI, conversely to low-fat. Specific elements included in the DAI index were inversely correlated with IMT-CC.

Mechanical Interlocking to Unlock the Reinforcing Potential of Carbon Nanotubes.

Single-walled carbon nanotubes (SWNTs) present extraordinary mechanical properties, with Youngs' modulus>1 TPa and tensile strength>50 GPa; this makes them ideal candidates as fillers for the reinforcement of polymers. However, the performance of SWNTs in this field has fallen behind expectations. This is due to a combination of imperfect individualization of the SWNTs and poor load transfer from the polymer to the SWNTs. Here, we study the reinforcement of polymers of different chemical nature using mechanically interlocked derivatives of single-walled carbon nanotubes (MINTs). We compare the mechanical properties of fibers made of poly (methyl methacrylate) (PMMA) and polysulfone (PSU) and their composites made with pristine SWNTs, MINTs, and the corresponding supramolecular models. With very low loading of MINTs (0.01 % w/w), improvements of more than 100 % on Youngs Modulus and the tensile strength are observed for both the nonpolar aliphatic PMMA and the very polar aromatic PSU polymers, while pristine carbon nanotubes and the supramolecular nanofillers showed smaller reinforcement. These data, together with our previous report on the reinforcement of polystyrene (nonpolar and aromatic), indicate that derivatization of SWNTs as MINTs is a valid general strategy to optimize the interaction between SWNT fillers and the polymer matrix.

Light-induced bi-directional switching of thermal conductivity in azobenzene-doped liquid crystal mesophases.

The development of systems that can be switched between states with different thermal conductivities is one of the current challenges in materials science. Despite their enormous diversity and chemical richness, molecular materials have been only scarcely explored in this regard. Here, we report a reversible, light-triggered thermal conductivity switching of ≈30-40% in mesophases of pure 4,4'-dialkyloxy-3-methylazobenzene. By doping a liquid crystal matrix with the azobenzene molecules, reversible and bidirectional switching of the thermal conductivity can be achieved by UV/Vis-light irradiation. Given the enormous variety of photoactive molecules and chemically compatible liquid crystal mesophases, this approach opens unforeseen possibilities for developing effective thermal switches based on molecular materials.

Mechanically interlocked derivatives of carbon nanotubes: synthesis and potential applications.

Single-walled carbon nanotubes (SWNTs) present one of the most interesting collections of properties among nanomaterials. Some sort of chemical modification of SWNTs is often used as a strategy to make the most of their intrinsic properties. In the last few years, the mechanical bond has been added to the chemistry toolbox for SWNT modification. In this Tutorial Review, we first discuss the characteristics of the mechanical bond that make it appealing for materials science in general and SWNTs in particular. We then describe the potential advantages of making mechanically-interlocked derivatives of SWNTs (MINTs), as compared to covalent or classic supramolecular derivatives of SWNTs. We go on to explain the different methods of synthesis of MINTs, highlighting their common features as an indication towards possible future synthetic strategies. Finally, we illustrate with examples how the making of MINTs can contribute to modifying the surface properties of SWNTs, modulating their electronic properties, and linking them to functional molecular fragments. The overall objective of this Review is to introduce the reader to the application of the chemistry of the mechanical bond to SWNTs: why it is relevant, how it is done in practice, what it has shown already as potential contributions towards applications, and what could be done in the future.

Mechanical interlocking of SWNTs with N-rich macrocycles for efficient ORR electrocatalysis.

Substitutional N-doping of single-walled carbon nanotubes is a common strategy to enhance their electrocatalytic properties in the oxygen-reduction reaction (ORR). Here, we explore the encapsulation of SWNTs within N-rich macrocycles as an alternative strategy to display electroactive sites on the surface of SWNTs. We design and synthesize four types of mechanically interlocked derivatives of SWNTs (MINTs) by combining two types of macrocycles and two types of SWNT samples. Comprehensive electrochemical characterization of these MINTs and their reference SWNTs allows us to establish structure-activity relationships. First, we show that all MINT samples are superior electrocatalysts compared to pristine SWNTs, which serves as general validation of our strategy. Secondly, we show that macrocycles displaying both N atoms and carbonyl groups perform better than those with N atoms only. Finally, we demonstrate that a tighter fit between macrocycles and SWNTs results in enhanced catalytic activity and stability, most likely due to a more effective charge-transfer between the SWNTs and the macrocycles. These results, focusing on the ORR as a testbed, show the possibility of understanding electrocatalytic performance of SWNTs at the molecular level and thus enable the design of more active and more stable catalysts in the future.

Single-Walled Carbon Nanotubes Encapsulated within Metallacycles.

Mechanically interlocked derivatives of carbon nanotubes (MINTs) are interesting nanotube products since they show high stability without altering the carbon nanotube structure. So far, MINTs have been synthesized using ring-closing metathesis, disulfide exchange reaction, H-bonding or direct threading with macrocycles. Here, we describe the encapsulation of single-walled carbon nanotubes within a palladium-based metallosquare. The formation of MINTs was confirmed by a variety of techniques, including high-resolution transmission electron microscopy. We find the making of these MINTs is remarkably sensitive to structural variations of the metallo-assemblies. When a metallosquare with a cavity of appropriate shape and size is used, the formation of the MINT proceeds successfully by both templated clipping and direct threading. Our studies also show indications on how supramolecular coordination complexes can help expand the potential applications of MINTs.

Reduction in Circulating Advanced Glycation End Products by Mediterranean Diet Is Associated with Increased Likelihood of Type 2 Diabetes Remission in Patients with Coronary Heart Disease: From the Cordioprev Study.

SCOPE: It is hypothesized that decreased advanced glycation end products (AGEs) levels could affect type 2 diabetes mellitus (T2DM) remission in newly diagnosed patients through the consumption of two healthy diets. METHODS AND RESULTS: Patients from CORDIOPREV study, all with previous cardiovascular events, with T2DM at the beginning of the study are included. Patients are randomized to a Mediterranean or a low-fat diet for five years. No different diabetes remission rates are found among diets. Serum methylglioxal (MG) and carboximethyllysine (CML), levels dietary AGE, as well as gene expression of AGER1 and RAGE are measured. Serum MG decreases only after the consumption of the Mediterranean diet. Moreover, a COX regression analysis shows that each SD decrease in the MG, occurring after the Mediterranean diet, increases the probability of T2DM remission with HR:2.56(1.02-6.25) and p = 0.046 and each SD increase in disposition index at baseline increases the probability of remission with HR:1.94(1.32-2.87) and p = 0.001. CONCLUSIONS: It is demonstrated that the reduction of serum AGEs levels and the modulation of its metabolism, occurring after the consumption of a Mediterranean diet, might be involved in the molecular mechanism underlying the T2DM remission of newly diagnosed patients with coronary heart disease.

Chemical sensing of water contaminants by a colloid of a fluorescent imine-linked covalent organic framework.

A two-dimensional imine-linked covalent organic framework bearing pyrene has been prepared and exfoliated in water as nanosheets to produce a stable water colloid. As a proof-of-concept, this COF colloid has been used to detect the presence of several organic dyes and polynitro-aromatic derivatives. These results show the high potential of these nanomaterials for applications in chemical sensing of pollutants directly in water.

Layer-Stacking-Driven Fluorescence in a Two-Dimensional Imine-Linked Covalent Organic Framework.

Schiff-condensation reactions carried out between 1,6-diaminopyrene (DAP) and the tritopical 1,3,5 benzenetricarbaldehyde (BTCA) or 2,4,6-triformylphloroglucinol (TP) ligands give rise to the formation of two-dimensional imine-based covalent-organic frameworks (COFs), named IMDEA-COF-1 and -2, respectively. These materials show dramatic layer-packing-driven fluorescence in solid state arising from the three-dimensional arrangement of the pyrene units among layers. Layer stacking within these 2D-COF materials to give either eclipsed or staggered conformations can be controlled, at an atomic level through chemical design of the building blocks used in their synthesis. Theoretical calculations have been used to rationalize the different preferential packing between both COFs. IMDEA-COF-1 shows green emission with absolute photoluminescence quantum yield of 3.5% in solid state. This material represents the first example of imine-linked 2D-COF showing emission in solid state.

Positive and negative regulation of carbon nanotube catalysts through encapsulation within macrocycles.

One of the most attractive applications of carbon nanomaterials is as catalysts, due to their extreme surface-to-volume ratio. The substitution of C with heteroatoms (typically B and N as p- and n-dopants) has been explored to enhance their catalytic activity. Here we show that encapsulation within weakly doping macrocycles can be used to modify the catalytic properties of the nanotubes towards the reduction of nitroarenes, either enhancing it (n-doping) or slowing it down (p-doping). This artificial regulation strategy presents a unique combination of features found in the natural regulation of enzymes: binding of the effectors (the macrocycles) is noncovalent, yet stable thanks to the mechanical link, and their effect is remote, but not allosteric, since it does not affect the structure of the active site. By careful design of the macrocycles' structure, we expect that this strategy will contribute to overcome the major hurdles in SWNT-based catalysts: activity, aggregation, and specificity.

Understanding Noncovalent Interactions of Small Molecules with Carbon Nanotubes.

We combine experimental methods, density functional theory (DFT) calculations, and molecular dynamics (MD) simulations in the quantitative analysis of noncovalent interactions between (6,5)-enriched single-walled carbon nanotubes (SWNTs), as hosts, and a set of pyrene derivatives with different electronic properties and surface areas, as guests. The experiments and calculations were carried out in two solvents with markedly different polarities, namely 1,1',2,2'-tetrachloroethane (TCE) and N,N-dimethylformamide (DMF). Our results show that dispersion forces govern the supramolecular association of small molecules with (6,5)-SWNTs, with negligible contributions from ground-state charge-transfer effects. In the nonpolar solvent (TCE), the binding constants are highly correlated with the contact area between the SWNT and the guests. In the polar solvent (DMF), the binding constants show a complex dependence on the chemical nature of the pyrene substituents, as demonstrated by MD simulations with the explicit inclusion of solvent molecules. The solvation of the small molecules is shown to play a leading role in the binding process. Remarkably, the binding constants obtained from the MD simulations for the five guest molecules correlate with those derived from experiment. Furthermore, the MD simulations also reveal the structure of the adsorbed guest from low to high SWNT surface coverage.

Threading through Macrocycles Enhances the Performance of Carbon Nanotubes as Polymer Fillers.

In this work, we study the reinforcement of polymers by mechanically interlocked derivatives of single-walled carbon nanotubes (SWNTs). We compare the mechanical properties of fibers made of polymers and of composites with pristine SWNTs, mechanically interlocked derivatives of SWNTs (MINTs), and the corresponding supramolecular models. Improvements of both Young's modulus and tensile strength of up to 200% were observed for the polystyrene-MINT samples with an optimized loading of just 0.01 wt %, while the supramolecular models with identical chemical composition and loading showed negligible or even detrimental influence. This behavior is found for three different types of SWNTs and two types of macrocycles. Molecular dynamics simulations show that the polymer adopts an elongated conformation parallel to the SWNT when interacting with MINT fillers, irrespective of the macrocycle chemical nature, whereas a more globular structure is taken upon facing with either pristine SWNTs or supramolecular models. The MINT composite architecture thus leads to a more efficient exploitation of the axial properties of the SWNTs and of the polymer chain at the interface, in agreement with experimental results. Our findings demonstrate that the mechanical bond imparts distinctive advantageous properties to SWNT derivatives as polymer fillers.

Determination of association constants towards carbon nanotubes.

Single-walled carbon nanotubes (SWNTs) are one of the most promising nanomaterials and their supramolecular chemistry has attracted a lot of attention. However, despite well over a decade of research, there is no standard method for the quantification of their noncovalent chemistry in solution/suspension. Here, we describe a simple procedure for the determination of association constants (Ka) between soluble molecules and insoluble and heterogeneous carbon nanotube samples. To test the scope of the method, we report binding constants between five different hosts and two types of SWNTs in four solvents. We have determined numeric values of Ka in the range of 1-104 M-1. Solvent effects as well as structural changes in both the host and guest result in noticeable changes of Ka. The results obtained experimentally were validated through state-of-the-art DFT calculations. The generalization of quantitative and comparable association constants data should significantly help advance the supramolecular chemistry of carbon nanotubes.

Pyrene-based mechanically interlocked SWNTs.

The synthesis of rotaxane-type species composed of pyrene macrocycles and SWNTs as linear components is described. Pyrene-SWNT interactions help template the ring-closing metathesis of U-shaped precursors around the nanotubes.

Biomimetic oxidation of pyrene and related aromatic hydrocarbons. Unexpected electron accepting abilities of pyrenequinones.

We present a mild catalytic method to oxidize PAHs and, in particular, pyrene. The pyrenediones are much better electron acceptors than benzoquinone in the gas phase and present similar accepting abilities in solution.