Juan Manuel Lázaro-Martínez

Dermatan sulfate/chitosan polyelectrolyte complex with potential application in the treatment and diagnosis of vascular disease

Cardiovascular disease is the largest single cause of morbid-mortality in the world. However, there is still no pharmaceutical treatment that directly targets the blood vessel wall instead of just controlling the risk factors. Here, we produced polyelectrolyte complexes (PECs) by a simple and reproducible polyelectrolyte complexation method between low molecular mass dermatan sulfate (polyanionic polysaccharide) and chitosan (polycationic polysaccharide), and evaluated the cellular uptake by vascular endothelial cells. The composition and the composition homogeneity of PECs were confirmed by (13)C-CP-MAS spectroscopy and by polyacrylamide gel electrophoresis, respectively. The hydrodynamic radius, determined by dynamic light scattering, was 729±11nm. PECs were not cytotoxic for a murine heart endothelium-derived cell line. Fluorescent confocal microscopy showed the specific uptake of fluorescently-labeled PECs by endothelial cells when they were cultured alone or in the presence of macrophages. Overall, these findings confirmed the potential of these PECs for targeting different agents to the vessel wall in the prevention, diagnosis, and therapy of vascular disease.

Generation and Stability of the gem-Diol Forms in Imidazole Derivatives Containing Carbonyl Groups. Solid-State NMR and Single-Crystal X-ray Diffraction Studies

The stability of gem-diol forms in imidazolecarboxaldehyde isomers was studied by solid-state nuclear magnetic resonance (ss-NMR) combined with single-crystal X-ray diffraction studies. These methodologies also allowed determining the factors governing the occurrence of such rare functionalization in carbonyl moieties. Results indicated that the position of the carbonyl group is the main factor that governs the generation of geminal diols, having a clear and direct effect on hydration, since, under the same experimental conditions, only 36% of 5-imidazolecarboxaldehydes and 5% of 4-imidazolecarboxaldehydes were hydrated, as compared to 2-imidazolecarboxaldehydes, with which a 100% hydration was achieved. Not only did trifluoroacetic acid favor the addition of water to the carbonyl group but also it allowed obtaining single crystals. Single crystals of the gem-diol and the hemiacetal forms 2-imidazolecarboxaldehyde and N-methyl-2-imidazolecarboxaldehyde, respectively, were isolated and studied through 1H ss-NMR. Mass spectrometry and solution-state NMR experiments were also performed to study the hydration process.

Phosphorus adsorption by a modified polyampholyte-diatomaceous earth material containing imidazole and carboxylic acid moieties: batch and dynamic studies

The aim of this study was to investigate phosphorus removal in water by using a polyampholyte obtained by the reaction of methacrylic acid, ethylene glycol diglycidyl ether and imidazole by a one step synthesis, mixed with diatomaceous earth. The material was characterized before and after phosphorus exposure using FT-IR, Raman, and solid state 31P-NMR and 13C-NMR spectroscopy concluding that the charged imidazole units were involved in the interaction between the phosphorus and the polyampholyte and that only the H2PO4− species was adsorbed. The point of zero charge value was 5.09. Concomitantly, the optimal pH for P adsorption was 5.0. As pH was increased, the polymer turned more negative, and the phosphate repulsion diminished the adsorption. In the batch experiments, the adsorption isotherms at pH values 5.0 and 7.0 were studied. The effects of different flow rates, P influent concentration and the interference of nitrate and sulfate in the breakthrough curves were studied. A shorter breakthrough time occurred at a higher flow rate. The q0 values not only increased from lower to higher influent levels but also showed a decrease in the presence of S and N as interferents demonstrating that there was a competition for the adsorption sites between those anions and the phosphate.

Thermo-responsive microgels based on encapsulated carbon quantum dots

In this work carbon quantum dot (CQD) nanoparticles are synthesized from D-lactose using a hydrothermal method and then they are coated with polyethylene glycol (CQDs@PEG). These particles exhibit a monodisperse spherical morphology with an average particle size of ∼4 nm. Nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopy showed the presence of the hydroxyl groups from the ethylene glycol molecules grafted onto the CQDs’ surfaces, which confirms that PEG was covalently attached to the nanoparticles’ surfaces. Fluorescence analysis demonstrates a shift in the emission at 495 nm after PEG coating. Modified carbon dots were introduced into thermo-responsive pNIPAM microgels. The resultant pNIPAM–CQDs@PEG hybrid system exhibits interesting fluorescence properties. Transmission electron microscopy (TEM), fluorescence microscopy, and energy-dispersive X-ray (EDX) spectroscopy confirm the incorporation of CQD particles into the microgels. Finally, dynamic light scattering (DLS) analysis confirms that further hybrid microgels based on pNIPAM are thermo-responsive, with a transition temperature similar to that of a system with an ionic component.

P-doped carbon nano-powders for fingerprint imaging

A simple, fast, and laboratory efficient doped P carbon nanoparticles synthesis is developed for fingerprint imaging, using 1,3-dihydroxyacetone and di-phosphorous pentoxide. Fluorescence nanoparticles, with an average size of 230 nm were obtained, without additional energy input or external heating. ATR, solid NMR, XPS and fluorescence spectroscopy revealed their surface functionalization; a reaction mechanism is proposed. Fluorescence measurements exhibited a maximum emission band at ca. 495 nm, when excited at 385 nm. The images obtained, on different surfaces such as mobile telephone screen, magnetic band and metallic surface of a credit card and a Euro banknote treated with the obtained nano-powders allows us to record positive matches, confirming that the experimental results illustrate the effectiveness of proposed method.

Enhanced electrochemical response of carbon quantum dot modified electrodes

A glassy carbon electrode (GCE) was surface-modified with carbon quantum dots (CQDs) and applied for the effective enhancement of the electrochemical signal for dopamine and uric acid determination. CQDs were prepared from graphite by a green modification of the Hummers method. They were characterized by FTIR-ATR, XPS, solid-state NMR, fluorescence and Raman spectroscopies. TPD-MS analysis was applied to characterize the functionalization of the surface. The CQDs were assembled on the glassy carbon electrode by adsorption because of the large number of carboxy groups on their surface warrants effective adsorption. The modified GCE exhibits a sensitivity that is almost 10 times better than of the bare GCE. The lower limits of detection are 1.3μM for uric acid and 2.7μM for dopamine.

Calcium alginate beads reinforced with synthetic oligomers, linear polyethylenimine and Cu(II): structural stability and potential applications

Calcium alginate beads were reinforced with linear polyethylenimine (PEI), Cu(II) and synthetic oligomers derived from a diepoxide, methacrylic acid and imidazole, to increase the resistance to stirring and vibration for environmental applications. The FT-IR and Raman spectra of the beads confirmed the presence of the organic reactants and their interactions. The SEM images of the lyophilized beads with an excess of oligomers exhibited an ordered core structure surrounded by a shell. The elemental mapping by EDAX showed a homogeneous distribution of Ca(II) and Cu(II), and a density influenced by PEI. The beads more resistant to sonication were those with the highest oligomer content. The enzyme soybean peroxidase (SBP) was immobilized in the beads for an environmental application that requires a stable matrix from chemical and structural points of view. The synergistic action of the entrapped SBP and Cu(II) on H2O2 activation induced the removal of an azo dye from aqueous solutions. Free radicals and O2 were released from Cu(II)-sites in the presence of the peroxide. The content of the oligomers determined the efficiency of the beads on dye removal.

Design, Characterization, and Environmental Applications of Hydrogels with Metal Ion Coordination Properties

In this chapter, we discuss the design and synthesis of hydrogels and related polymeric materials with metal ion coordination properties, with the aim to review the main synthetic strategies used in the area. Then, we focus on the solid-state nuclear magnetic reso‐ nance (ss-NMR) spectroscopic technique due to its importance as a structural elucida‐ tion tool in both powdered and hydrated state, with emphasis on cross-polarization magic angle spinning (CP-MAS) and high-resolution magic angle spinning (HRMAS). Also, we explain different adsorption models, with the aim to present the methods most common‐ ly used to analyze the uptake properties of hydrogel materials toward metal ions or organic compounds. Finally, we will discuss the applications of these materials for the removal of heavy metal ions and organic compounds, in terms of efficiency in the uptake of these ions and the different techniques commonly used to study the coordination process and the generation of reactive oxygen species (ROS) from hydrogen peroxide (H2O2). The main aim is to provide scientists with a review of the spectroscopic techniques most common‐ ly used for bulk and surface characterization of non-soluble materials.

A New Look at the Halogenation of Porphyrins

Fil: Gazzano, Emiliano R. A.. Universidad de Buenos Aires. Facultad de Farmacia y Bioquimica. Departamento de Quimica Organica; Argentina