Alexandre Gonçalves Dal-Bó

Synthesis of luminescent liquid crystals derived from gallic acid containing heterocyclic 1,3,4-oxadiazole

This article describes the synthesis, liquid crystalline and photophysical properties of luminescent liquid crystalline compounds, derived from gallic acid containing heterocyclic 1,3,4-oxadiazole. The mesophases of these compounds were characterised using polarising optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). All compounds showed high thermal stability and blue photoluminescence in solution, with emission maxima between 376 and 381 nm. For all compounds, the liquid crystalline behaviour was preserved on cooling from the isotropic state to room temperature. These characteristics make these materials good candidates for application in organic electronics.

Gold nanoparticles and/or N-acetylcysteine mediate carrageenan-induced inflammation and oxidative stress in a concentration-dependent manner

We report the effect of gold nanoparticles (AuNP) in an acute inflammation model induced by carrageenan (CG) and compared this effect with those induced by the antioxidant N-acetylcysteine (NAC) alone and by the synergistic effect of NAC and AuNP together. Male Wistar rats received saline or saline containing CG administered into the pleural cavity, and some rats also received NAC (20 mg/kg) subcutaneously and/or AuNP administered into the pleural cavity immediately after surgery. Four hours later, the rats were sacrificed and pleural exudates obtained for evaluation of cytokine levels and myeloperoxidase activities. Oxidative stress parameters were also evaluated in the lungs. The results demonstrated that the inflammatory process caused by the administration of CG into the pleural cavity resulted in a substantial increase in the levels of tumor necrosis factor-α, interleukin-1β, and myeloperoxidase and a reduction in interleukin-10 levels. These levels seem to be reversed after different treatments in animals. Antioxidant enzymes exhibited positive responses after treatment of NAC + AuNP, and all treatments were effective at reducing lipid peroxidation and oxidation of thiol groups induced by CG. These findings suggest that small compounds, such as NAC plus AuNP, may be useful in the treatment of conditions associated with local inflammation.

Syntheses and catalytic activities of new metallodendritic catalysts

This investigation presents the syntheses of new metallodendritic catalysts from a silsesquioxane core (Silsesq-PrNH3+Cl−) via a new route. For optimization of the syntheses of the catalysts, reaction times, thermodynamic effects, and the amounts of [Mo(η3-C3H5)Br(CO)2(NCCH3)2] (1) and [Mo(CO)3Br2(NCCH3)2] (2) complexes fixed on the second-generation dendrimer (PDG2.0) were studied. After the optimization studies and with the objective of application in catalysis, the catalysts were prepared by reaction of PDG2.0 with the organometallic complexes and characterized by elemental analysis (CNH), FTIR, 13C and 29Si NMR, XRD, TGA, SEM, EDS and BET. The metallodendritic catalysts were tested in the epoxidation of olefins and shown to be a vigorous catalyst with conversion rates between 76 and 97% for PDG2.0–[(Mo(η3-C3H5)(CO)2Br)8] and 30–80% for PDG2.0–[(Mo(CO)3Br2)5], and a high selectivity in the formation of epoxides using tertbutyl hydroperoxide (TBHP) as an oxidant. The catalysts remain highly active after being used for at least 5 cycles. To the best of our knowledge, this study is the first to have reported the preparation of these new dendritic catalysts, as well as the catalytic comparison with their previous generations in the epoxidation of 1-octene, cyclooctene, (S)-limonene, cis-3-hexen-1-ol, trans-3-hexen-1-ol and styrene.

Self-assembled carbohydrate-based vesicles for lectin targeting

This study examined the physicochemical interactions between vesicles formed by phosphatidylcholine (PC) and glycosylated polymeric amphiphile N-acetyl-β-d-glucosaminyl-PEG900-docosanate (C22PEG900GlcNAc) conjugated with Bauhinia variegata lectin (BVL). Lectins are proteins or glycoproteins capable of binding glycosylated membrane components. Accordingly, the surface functionalization by such entities is considered a potential strategy for targeted drug delivery. We observed increased hydrodynamic radii (RH) of PC+C22PEG900GlcNAc vesicles in the presence of lectins, suggesting that this aggregation was due to the interaction between lectins and the vesicular glycosylated surfaces. Furthermore, changes in the zeta potential of the vesicles with increasing lectin concentrations implied that the vesicular glycosylated surfaces were recognized by the investigated lectin. The presence of carbohydrate residues on vesicle surfaces and the ability of the vesicles to establish specific interactions with BVL were further explored using atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS) analysis. The results indicated that the thickness of the hydrophilic layer was to some extent influenced by the presence of lectins. The presence of lectins required a higher degree of polydispersity as indicated by the width parameter of the log-normal distribution of size, which also suggested more irregular structures. Reflectance Fourier transform infrared (HATR-FTIR), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR) and ultraviolet-visible (UV-vis.) analyses revealed that the studied lectin preferentially interacted with the choline and carbonyl groups of the lipid, thereby changing the choline orientation and intermolecular interactions. The protein also discretely reduced the intermolecular communication of the hydrophobic acyl chains, resulting in a disordered state.

Self-association of sodium deoxycholate with EHEC cellulose cooperatively induced by sodium dodecanoate.

Some aspects of ethyl (hydroxyethyl) cellulose (EHEC) aqueous behavior in the presence of ionic surfactants are described in the literature; however, most of the studies reported address moderately concentrated solutions. Few studies have been carried out in the dilute regime using mixtures of biosurfactants. The main purpose of this work is to investigate the interaction of EHEC in the dilute regime and to verify the mixture of two surfactants: sodium deoxycholate (NaDC) and sodium dodecanoate (SDoD). The parameters of the surfactant to polymer association processes such as the critical aggregation concentration (cac) and saturation of the polymer by surfactants (psp) were determined from the plots of surface tension and specific conductivity versus surfactant concentration in basic conditions. The cmc of NaDC-SDoD mixtures showed non-ideal behavior. However, EHEC added to mixtures of SDoD and NaDC acts as a stabilizer for the mixed aggregate during the association process.

Porous Ceramic Structures Obtained from Calcium Carbonate as Pore Generating Agent

The aim of this work is to present experimental results related to the use of calcium carbonate as pore generating agent. Four compositions containing 20 wt.% of limestone were used and characterized chemically and thermally. Each composition was homogenized in a porcelain ball mill, dried in a laboratory drier, humidified at 7 wt.%, and pressed in an uniaxial hydraulic press. Compacted samples were dried and heat treated with a suitable heating rate for the degasification of calcium carbonate and sintered at 800, 900, and 1050 °C. Sintered samples were characterized to determine the porosity, crystalline phases formed and microstructural features. The results showed that the porosity has increased with the sintering temperature of the compositions increasing due porosity generated by the calcium carbonate degasification and the material expansion.

Elucidating Bauhinia variegata lectin/phosphatidylcholine interactions in lectin-containing liposomes

Investigations focused on the interactions of nanoparticles with lectins are relevant since it is well accepted that such proteins can be recognized by carbohydrates as parts of cell membranes. This can ultimately enhance the cellular uptake of the produced assemblies. In this framework, the physical interactions of phosphatidylcholine (PC) liposomes and the Bauhinia variegate lectin (BVL) are reported here. BVL-liposome interactions were characterized by a variety of techniques to understand the influence of BVL in the structural features, thermodynamic and spectroscopic properties of the hybrid material. The produced system is composed of 56% w/w lectin, and the scattering techniques show the presence of stable vesicular structures with a mean diameter DH ∼ 100 nm. The FTIR and NMR results showed a strong lectin effect on the PC choline region, restricting the rotational motion of the lipid group. The BVL-liposome interaction promoted hardening of the protein as evidenced by circular dichroism spectroscopy. The photophysics results suggest higher rigidity of the system in the presence of BVL. The BVL may be present in the inner or outer polar surface of the liposomes. The system was shown to be relatively stable and therefore potentially useful for carbohydrate recognition of nanoparticles.

Synthesis, DNA Interaction and Genotoxic Evaluation of a Photoactive Benzothiadiazole with Potential Application in Photovoltaic Paint

A new fluorophore containing 2,1,3-benzothiadiazole unit with alkylated tetrazole terminal groups as electron donors connected through a π-conjugated system of the type (D-π-A-π-D) was synthesized using the Sonogashira coupling reaction with good yields. The genotoxicity of the two intermediate compounds and the final product was evaluated in vitro in consideration of the potential application of the new compound in the chemical production of photovoltaic paints. The new fluorophore did not show significant biological effects in the cell viability test and the comet assay when compared with the intermediate compounds that were obtained synthetically despite the ability to interact with deoxyribonucleic acid (DNA) as demonstrated in circular dichroism assays. Thus, the compound does not show toxic or genotoxic activity, and therefore, it can be applied as a pigment in photovoltaic paint.