Leire Ruiz-Rubio

Preparation and characterization of soluble branched ionic β-cyclodextrins and their inclusion complexes with triclosan

This study aims to synthesize, characterize and investigate the water solubility and cytotoxicity of branched anionic/cationic β-cyclodextrins (bβCDs) obtained by reaction with epichlorohydrin and chloroacetic acid or choline chloride, respectively, by a single step polycondensation reaction. Obtained ionic bβCDs were investigated as an attempt to comparatively study anionic and cationic bβCDs. Water solubility of both ionic derivatives was similar (400 mg/mL) at neutral and basic pHs and remarkably higher than that of their neutral homologues. Additionally, a pH-dependent solubility of anionic bβCDs was observed. Cytotoxicity of ionic bβCDs was evaluated on Human colon carcinoma Caco-2 cells and high cell viability (>99%) was observed in the range of 0-100 mg/mL for anionic and cationic samples, in the same range of that of neutral and parent β-CDs. Additionally, complexes formation capacity with triclosan, a poor water soluble antimicrobial agent, was confirmed by several techniques observing a complexation limit around 4 mg/mL for both systems and higher stability constant for anionic bβCDs than cationic derivatives.

Branched and ionic β-Cyclodextrins multilayer assembling onto polyacrylonitrile membranes for removal and controlled release of triclosan

The present study summarizes the formation and characterization of multilayers of polyacrylonitrile (PAN) membranes with β-cyclodextrin derivatives in order to be potentially interesting for triclosan (TR) controlled delivery with antibacterial purposes, as well as, for the removal of TR from wastewater. With this object, cationic and anionic branched β-cyclodextrins (bβCDs) were incorporated by layer-by-layer (LbL) process onto previously synthesized and hydrolyzed PAN membranes. FTIR, XPS and labelling with fluoresceinamine (FA) let to study the formation and stability of the prepared multilayered systems. TR is a widely used antibacterial and antifungal agent with proven ability to inhibit bacterial growth that, however, recently has shown a potential toxicity. The ability of obtained bβCDs/PAN multilayered membranes to retain TR in water was evaluated by two different loading procedures. The delivery kinetic profile of TR from loaded membranes was also analyzed showing the maximum release in the first 24h.

Polymer–polymer complexes of poly(N-isopropylacrylamide) and poly(N,N-diethylacrylamide) with poly(carboxylic acids): a comparative study

In this manuscript, the complexation process between two polyacids, poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA), and two different polyacrylamides, poly(N-isopropylacrylamide) (PNiPAm) and poly(N,N-diethylacrylamide) (PNdEAm), in organic solvents, has been studied. The influence of polymer chemical structure and the effect of polymer–solvent interactions on the complex formation in solution have been analyzed. Specific interactions were studied by Fourier transform infrared (FTIR) spectroscopy, and the composition of the obtained complexes was determined by elemental analysis. The calorimetric study of the interpolymer complexes shows a unique glass transition temperature for all systems except for PNdEAm/PMAA system in which phase separation was observed after thermal treatment.

From isolated to 2D coordination polymers based on 6-aminonicotinate and 3d-metal ions: towards field-induced single-ion-magnets

We report herein the synthesis and structural and chemical characterization of six new compounds consisting of 6-aminonicotinate (6ani) ligands and first-row transition metal ions, namely, [Mn2(μ-6ani)2(H2O)8](6ani)2 (1), [Co(6ani)(bipy)2(H2O)3](6ani)·5H2O (2), [M(μ-6ani)(6ani)(H2O)3]·2H2O [MII = Co (3), Ni (4)], and [M(μ-6ani)2]·H2O [MII = Co (5), Cu (6)] (where bipy = 4,4′-bipyridine). Compounds 1 and 2 consist of isolated dimeric and monomeric entities held together by supramolecular interactions governed by 6ani free anions. The rigid and low symmetry of 6ani ligands, in addition to their coordination as terminal and bridging ligands to octahedral metal geometries, gives rise to chiral 1D chains of compounds 3 and 4. 2D sql layers are formed (5 and 6) when 6ani ligands act as ligands bridging the metal ions, which precludes the presence of water molecules in the framework. Despite the wide structural diversity observed, all architectures share the occurrence of magnetically isolated 3d metal ions, given the poor exchange achieved through 6ani bridges, as confirmed by dc susceptibility measurements and DFT calculations. Dynamic ac susceptibility measurements reveal best-in-class field-induced slow magnetic relaxation behaviour in Co-based compounds with easy-plane magnetic anisotropy. The effective energy barriers (Ueff) of 39.6 K and 18.7 K for 3 and 5, respectively, estimated using the Arrhenius law are remarkably high among CoII-SIM coordination polymers reported so far.

Influence of α-methyl substitutions on interpolymer complexes formation between poly(meth)acrylic acids and poly(N-isopropyl(meth)acrylamide)s

The influence of α-methyl substitutions on the interpolymer complexation between polyisopropylacrylamides (poly(N-isopropylacrylamide) and poly(N-isopropylmethacrylamide)) and polyacrylic acids (poly(acrylic acid) and poly(methacrylic acid)) has been studied. The influence of solvents on the complexation process and, therefore, the effect of polymer–solvent interactions on the complex formation have been analyzed. Specific interactions were analyzed by Fourier transform infrared spectroscopy, and the composition of the obtained complexes was determined by elemental analysis. Finally, the thermal behavior of the obtained interpolymer complexes has been studied by calorimetry and thermogravimetry.

Towards the development of eco-friendly disposable polymers: ZnO-initiated thermal and hydrolytic degradation in poly(L-lactide)/ZnO nanocomposites

In this work poly(L-lactide)/ZnO nanocomposites with homogeneously distributed nanoparticles have been fabricated by a solvent-precipitation method. The obtained nanocomposites have been submitted to thermal and hydrolytic degradation processes in order to elucidate the catalytic effect of ZnO nanoparticles. The resulting degradation products from the thermally-initiated catalysis have been identified by Fourier transform infrared spectroscopy (FTIR). It has been found that the presence of ZnO gives rise to a 65-fold increase in the formation of CO2 in comparison to acetaldehyde. FTIR results of hydrolytically degraded nanocomposites show an increased amount of carboxylic acid groups as ZnO concentration increases, while the CO stretching band splitting denoted larger crystalline regions as degradation proceeds. The obtained results are explained from the viewpoint of lattice oxygen vacancies in ZnO. Upon thermodegradation nanoparticles initiate unzipping depolymerization/intermolecular transesterification reactions in PLLA, while during hydrolytic degradation H2O is dissociated on oxygen vacancy sites, giving hydroxyl groups that initiate the hydrolysis of ester bonds, and thus reducing PLLA to soluble monomers. The obtained findings are expected to allow the development of eco-friendly disposable polymeric waste by opening new possibilities in the use of naturally-available materials as efficient catalysts for feedstock recycling of biopolymers by common chemical processes.

Associative and segregative phase behaviour in mixtures of poly(N-tert-butylacrylamide) and poly(N,N-diethylacrylamide) with poly(4-vinylphenol): effect of solvent and concentration

Interpolymer complexation behaviour between poly(4-vinylphenol) (PVPh), as proton donor, and polyacrylamide derivatives, poly(N-tert-butylacrylamide) and poly(N,N-diethylacrylamide) (PNdEAm), as proton acceptor polymers, with both hydrogen bonding and hydrophobic properties, have been studied. Most mixtures studied in this work resulted in coprecipitation, that is, an associative phase separation. However, for the system PNdEAm/PVPh in aprotic solvents, tetrahydrofuran, acetone and 1,4-dioxane, either an associative (coprecipitation) or a segregative (precipitation of one polymer in presence of the other) behaviour is observed depending on concentration.

Active Release Coating of Multilayer Assembled Branched and Ionic β-Cyclodextrins onto Poly(ethylene terephthalate)

Branched ionic cyclodextrins multilayers were assembled onto the surface of previously aminolyzed poly(ethylene terephthalate) in order to construct local drug delivery tailored platforms with potential applicability as materials for indwelling medical devices. The construction of the multilayers took place by the alternate deposition of ionic cyclodextrin derivatives and was characterized by surface zeta-potential measurements, X-ray photoelectron spectroscopy and, after fluorescent labeling of anionic branched cyclodextrins, by UV-vis spectroscopy and confocal fluorescence spectroscopy. Transmission electron microscopy is used for the first time to show the deposited coating, and an average thickness of ∼270nm for 20 bilayered covering was measured. Contact angle measurements showed great differences in the films as the number of cyclodextrin layers was increased, and highly hydrophilic (19.7±1.5° for 10 bilayers) surfaces were obtained. The loading and release capacity of the antimicrobial triclosan, as hydrophobic model molecule, from PET coated surfaces was also studied.

U-Shaped and Surface Functionalized Polymer Optical Fiber Probe for Glucose Detection

In this work we show an optical fiber evanescent wave absorption probe for glucose detection in different physiological media. High selectivity is achieved by functionalizing the surface of an only-core poly(methyl methacrylate) (PMMA) polymer optical fiber with phenilboronic groups, and enhanced sensitivity by using a U-shaped geometry. Employing a supercontinuum light source and a high-resolution spectrometer, absorption measurements are performed in the broadband visible light spectrum. Experimental results suggest the feasibility of such a fiber probe as a low-cost and selective glucose detector.

Polysaccharide-Based Superabsorbents: Synthesis, Properties, and Applications

Traditional absorbent hydrogels are based on the copolymerization of petroleumbased synthetic vinyl monomers such as acrylic acid, methacrylic acid, and acrylamide derivatives. Nevertheless, these materials are usually expensive, poorly degradable, and non-environmentally friendly. On the contrary, natural polysaccharides display significant advantages such as availability, low production cost, nontoxicity, biocompatibility, and biodegradability. Accordingly, polysaccharides emerge as an interesting sustainable alternative to traditionally employed polymers. In addition, polysaccharides can easily form hydrogels by chemical or physical crosslinking (including hydrogen bonding and ionic interactions) or a combination of both, which makes the crosslinking of natural polysaccharides a versatile and promising approach for superabsorbent hydrogel (SAH) production. Therefore, in the last years, numerous polysaccharides including starch, cellulose, alginate, chitosan, and guar gum, among others, have been employed in SAH fabrication. Polysaccharide-based SAHs have been used in agriculture, hygiene products, waste treatment, crack mitigation in building applications, tissue engineering, and controlled release, for biomedical and soil conditioning applications. Despite of the evident commercial and environmental advantages of polysaccharide-based SAHs, they also display some drawbacks that make them continue appearing as a challenge research field. In this sense, although the biodegradability of polysaccharide-based hydrogels is a key characteristic for some applications because it avoids pollution-related issues and enables enhanced controlled release, at the same time, it could delay the development of longtime sustained release systems. Moreover, polysaccharide crosslinking leads to hydrogels with poor mechanical stability which is another associated disadvantage of these types of materials that needs to be overcome. Therefore an increasing amount of investigations about new synthetic approaches to improve the properties of polysaccharide-based hydrogels have been reported in the last years. In this chapter, the recent progress of this type of hydrogels is reviewed. The synthetic methods employed to obtain SAHs from the most common polysaccharides and the main properties of these materials with a special emphasis on swelling and mechanical properties are studied. Furthermore, the applications of SAHs have been summarized highlighting the most outstanding and promising uses.