Hybrid-peptide hydrogel arrangements are a promising alternative to obtaining biocompatible structures at the nanoscopic scale. In this work, a new class of hybrid hydrogels was obtained through the sol-gel process based on the reaction between an amyloid-like octapeptide sequence [RF]4 (where R = arginine and F = phenylalanine) covalently bonded with glycine-linked alkoxysilanes, and hybrid silylated polyethylene glycol (PEG). 1H nuclear magnetic resonance (NMR), liquid chromatography-mass spectrometry (LC-MS), and Fourier transform infrared spectroscopy (FTIR) analyses were used, resulting in synthesized precursor/intermediate molecules. The structure of hybrid hydrogel fibers was studied by atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS), where the existence of two regions in the Guinier plot was observed, one being predominantly formed by polymer while the other one by peptide chains. The rheological measurements showed that viscoelastic parameters depend on both the amount of silane peptide in the hydrogel matrix and increased temperature. Also, the FTIR spectra indicated the coexistence of antiparallel and parallel β-sheet structure patterns into amyloid fibril hydrogels, which can be modulated by peptide-silane coupling in each formulation. The analyzed hydrogels showed thixotropic and shear-thinning rheology at physiological pH, leaving open the opportunity to topical drug delivery system applications in the future.

Hydrogels based on peptide nanostructures are biological entities that can be applied in a wide range of applications, such as scaffolds for tissue engineering, drug delivery, and biosensors. The aim of this research was to study peptide hydrogels based on N-(9-fluorenylmethoxycarbonyl)-L, L-diphenylalanine (Fmoc-FF) in two different media: water and phosphate buffer. These hydrogels were used for encapsulating Leishmania infantun chagasi soluble proteins. The structure of the matrices was investigated in detail through scanning and transmission electron microscopy, and small angle X-ray scattering (SAXS). The mechanical behavior of the hydrogels were assessed through rheology assays, demonstrating both the physical and chemical stability of the hydrogel scaffolds. The immunogenicity of immobilized antigens was studied using enzyme-linked immunosorbent assay (ELISA) detection after the reaction with positive and negative dog sera for Leishmania infantum chagasi. The hydrogel was efficient to encapsulate antigens, and can promote the development of novel devices that requires the storage of biomolecules under moist environmental conditions.

In this work, we describe the immobilization of the dinuclear compound [Cu2(apyhist)2Cl2](ClO4)2 (1) and its derived cations complexes, obtained in water solution or by deprotonation of the imidazolate moiety in the ligand leading to a cyclic tetranuclear species, in the Nafion® membrane on glass carbon electrode surface. After that, we studied the influence of the equilibrium in the electrocatalytic activity towards the reduction of H2O2 in the development of an amperometric sensor for the analytical determination of hydrogen peroxide. This strategy proved successful, and the electrochemical behaviour of the all complexes formed within the Nafion® coatings was characterized. We also provide evidence that its related cyclic tetranuclear imidazolate-bridged complex acts as a catalysts for the intramolecular, two-electron reduction of H2O2.

Este trabalho descreve a caracterização espectroscópica por infravermelho e o estudo da dinâmica de compensação de cargas do filme supramolecular FeTPPZFeCN derivado do ligante tetra-2-piridil-1,4-pirazina (TPPZ) com hexacianoferrato, bem como o filme híbrido envolvendo FeTPPZFeCN e uma matriz de polipirrol (PPy). Para o filme supramolecular, foi observado um aumento no fluxo de ânion em solução contendo K+ em relação ao Li+, que parece estar relacionado ao tamanho do raio iônico cristalino do K+. O processo de eletroneutralização é discutido em termos de interação eletrostática entre cátions e centros metálicos na matriz hospedeira. A natureza do processo de compensação de carga difere de outros eletrodos modificados derivados do azul da Prússia, onde somente cátions tais como K+ participam no processo de eletroneutralização. No caso do filme híbrido FeTPPZFeCN/PPy, a magnitude do fluxo de ânions é também dependente da identidade do ânion em diferentes eletrólitos de suporte.

This work describes the infrared spectroscopy characterization and the charge compensation dynamics in supramolecular film FeTPPZFeCN derived from tetra-2-pyridyl-1,4-pyrazine (TPPZ) with hexacyanoferrate, as well as the hybrid film formed by FeTPPZFeCN and polypyrrole (PPy). For supramolecular film, it was found that anion flux is greater in a K+ containing solution than in Li+ solution, which seems to be due to the larger crystalline ionic radius of K+. The electroneutralization process is discussed in terms of electrostatic interactions between cations and metallic centers in the hosting matrix. The nature of the charge compensation process differs from others modified electrodes based on Prussian blue films, where only cations such as K+ participate in the electroneutralization process. In the case of FeTPPZFeCN/PPy hybrid film, the magnitude of the anions’s flux is also dependent on the identity of the anion of the supporting electrolyte.

Novos complexos de cobre(II) com uma imina tridentada, bimpy (ou 2-(benzimidazolil)metileno-2-amino-1-etilpiridina), foram preparados e tiveram sua atividade catalítica na oxidação da N,N,N',N'-tetrametil-p-fenilenodiamina (TMPD) comparada. As espécies mononucleares, [Cu(bimpy)(H2O)2](NO3 )2, (1) e [Cu(bimpy)Cl2]·H2O, (2), assim como a espécie dinuclear contendo pontes cloreto, [Cu2(bimpy)2Cl2]X2·nH 2O preparada como sais perclorato 3, nitrato 4 e cloreto 5, respectivamente, foram isoladas e caracterizadas por técnicas espectroscópicas (UV/Vis, IV e EPR). O composto 2 teve sua estrutura determinada por cristalografia de raios-X. Em solventes não-aquosos predomina a espécie dinuclear, enquanto em solução aquosa, ou solventes contendo água, um equilíbrio entre a espécie dinuclear e a mononuclear 1 foi observado. Estudos cinéticos, em metanol, da oxidação catalisada de TMPD indicaram uma dependência de primeira-ordem da velocidade inicial com a concentração de catalisador e um efeito de saturação com aumento da concentração de substrato. O composto dinuclear é mais reativo que o mono-, e experimentos adicionais mostraram que o contra-íon cloreto afeta significativamente os parâmetros cinéticos, deslocando o equilíbrio envolvendo as espécies 2 e 5, além de estabilizar um par iônico com o substrato.

Some new copper(II) complexes with a tridentate imine ligand, bimpy (or 2-(benzimidazolyl)methylene-2-amino-1-ethylpyridine), were prepared, and had their catalytic activity in the N,N,N',N'-tetramethyl- p-phenylenediamine (TMPD) oxidation compared. Mononuclear species, [Cu(bimpy)(H2O)2](NO3 )2, (1) and [Cu(bimpy)Cl2]·H2O, (2), as well as the dinuclear species containing chloro-bridges, [Cu2(bimpy)2Cl2]X2·nH 2O as perchlorate 3, nitrate 4 and chloride 5 salts, respectively, were obtained and characterized by different techniques (UV/Vis, IR, EPR and X-ray crystallography). In non-aqueous solvents, the dinuclear species predominates; however, in aqueous solution or solvents containing water, equilibrium between dinuclear and correlated mononuclear species 1 was verified. Kinetic studies, in methanol solution, on the catalyzed TMPD oxidation indicated a first-order dependence of the initial rate with the catalyst concentration, and a saturation effect with increasing concentrations of the substrate. The dinuclear species was observed to be more reactive than the mononuclear one, and further experiments showed that the counter-ion chloride can significantly affect the kinetic parameters, mostly by shifting the mono-/dinuclear equilibrium, and stabilizing an ion-pair with the substrate.