Publications

Abstract The present study reports the production and characterization of PEG-coated silica nanoparticles (SiNP-PEG) containing insulin for oral administration. High (PEG 20,000) and low (PEG 6000) PEG molecular weights were used in the preparations. SiNP were produced by sol gel technology followed by PEG adsorption and characterized for in vitro release by Franz diffusion cells. In vitro permeation profile was assessed using everted rat intestine. HPLC method has been validated for the determination of insulin released and permeated. Insulin secondary structure was performed by circular dichroism (CD). Uncoated SiNP allowed slower insulin release in comparison to SiNP PEG. The coating with high molecular weight PEG did not significantly (p>0.05) alter insulin release. The slow insulin release is attributed to the affinity of insulin for silanol groups at silica surface. Drug release followed second order kinetics for uncoated and SiNP PEG at pH 2.0. On the other hand, at pH 6.8, the best fitting was first-order for SiNP PEG, except for SiNP which showed a Boltzmann behavior. Comparing the values of half-live, SiNP PEG 20,000 showed a faster diffusion followed by Si-PEG 6000 and SiNP. CD studies showed no conformational changes occurring after protein release from the nanoparticles under gastrointestinal simulated conditions.

Abstract This study aims to investigate the effects of O-3 in protein content and immunoglobulin E (IgE)-binding profiles of Acer negundo, Platanus x acerifolia and Quercus robur pollen. Pollen was exposed to O-3 in an environmental chamber, at half, equal and four times the limit value for the human health protection in Europe. Pollen total soluble protein was determined with Coomassie Protein Assay Reagent, and the antigenic and allergenic properties were investigated by SDS-PAGE and immunological techniques using patients' sera. O-3 exposure affected total soluble protein content and some protein species within the SDS-PAGE protein profiles. Most of the sera revealed increased IgE reactivity to proteins of A. negundo and Q. robur pollen exposed to the pollutant compared with the non-exposed one, while the opposite was observed in P. x acerifolia pollen. So, the modifications seem to be species dependent, but do not necessarily imply that increase allergenicity would occur in atopic individuals.

Abstract The outcome of the Suzuki-Miyaura cross-coupling for the direct competition reaction between two boronic acids was evaluated under routine synthesis conditions. The reaction selectivity was found to depend on the amount of the base used, with fewer bases favoring the reactivity of the boronic acid with lower pK(a) (stronger acid). The dependence of the reaction selectivity on base stoichiometry was found to increase with the increase in the difference in the pK(a) values of the competing boronic acids. These results confirm a relationship between acid-base chemistry and the Suzuki-Miyaura reaction catalytic cycle. Moreover, the results indicate that under these specific conditions, the most reactive organoboron species toward transmetalation is the borate anion RB(OH)(3)(-) instead of the neutral boronic acid RB(OH)(2). Hence, the main role of the base in the reaction mechanism is to increase the reactivity of the boronic acid toward the Pd-halide complex by converting it into the respective organoborate. In addition, boric acid, an important reaction byproduct, affects the selectivity in the Suzuki reaction because its gradual formation in the reaction medium disturbs the acid-base equilibrium.

Abstract Freeze-drying has widely been applied to improve the stabilization of colloidal drug carriers. In the present study, the effect of cryoprotectants on the physicochemical characteristics of silica nanoparticles (SiNP) during the freeze-drying process has been extensively investigated. SiNP were synthesized by sol–gel technology and freeze-dried in the presence of sorbitol, trehalose, and/or mannitol at different concentrations and ratios. Dynamic light scattering (DLS), atomic force microscopy (AFM), X-ray diffraction analysis (XRD), and differential scanning calorimetry (DSC) have been used for particle characterization after freeze-drying. Based on the obtained results, SiNP in the presence of mannitol showed a more crystalline behavior in comparison to nanoparticles with sorbitol or trehalose (confirmed by DSC and XRD). SiNP in the presence of trehalose showed a more crystalline structure than SiNP in the presence of sorbitol. However, trehalose was more efficient in preserving the particle size of nanoparticles during the freeze-drying process. The optimal concentration of trehalose for preserving silica nanoparticles was 10 % at a ratio of (1:1). During the freeze-drying process, trehalose is able to replace water molecules due to the strong interaction via hydrogen bounds between silanol groups present in SiNP surface and the sugar, forming a stable layer around the particle and thus preserving the particle physical properties.

Abstract The self-association equilibrium constants, K-ass, for the dimerization of some small oligothiophenes in acetone, acetonitrile and chloroform were measured by H-1 NMR spectroscopy. The gas phase interaction energies for some oligothiophene dimers were determined by computational quantum chemistry. The H-1 NMR results indicate that K-ass generally increases with the chain length (the number of thienyl rings, n) and solvent polarity; however, K-ass for thiophene (n = 1) was found to be higher than for the bithiophenes (n = 2). The linear oligothiophenes 2,2'-bithiophene and 2,2',5',2 ''-terthiophene were found to self-associate less than their corresponding nonlinear isomers 3,30-bithiophene and 3,2',5',3 ''-terthiophene in solution and in the gas phase. For a-quaterthiophene (n = 4) K-ass in solution was found to be smaller than expected. The non-linear dependence of the standard molar Gibbs energy of self-association, Delta(ass)G(m)(0), on the chain length in solution could be nicely reproduced and related to the conformational entropy change of dimerization. It was observed that the melting properties of oligothiophenes correlate well with their tendency to self-associate, with more self-association leading to increased liquid stability, and thus lower melting temperatures. These results highlight the relevance of self-association in isotropic systems for the correct molecular interpretation of phase equilibria.

Abstract An experimental and theoretical study on the phase and molecular stability of Mq(3) (M = Al, Ga, and In; q = 8-hydroxyquinoline) is presented. The results suggest that the energy difference between the meridional and facial isomers of Mq(3) shall be significantly lower than previously though and provide an explanation for the reported mer-fac solid-solid transition. The first accurate vapor pressure measurements for Alq(3), Gaq(3), and Inq(3) are presented, which are of great relevance for the manufacturing of thin films by vacuum deposition. Phase transition thermodynamics indicates higher cohesive energies of the mer-isomers and an entropic differentiation that can be associated with the different molecular symmetry of the mer- and fac-isomers.

Abstract Vapor pressures of 1,3-dimethylimidazolium bis(trifluoromethylsulfonyl) imide, ([C(1)C(1)im][NTf2]) and 1ethyl-3-propylimidazolium bis(trifluoromethylsulfonyl) imide, ([C(2)C(3)im][NTf2]) ionic liquids were measured as a function of temperature using a Knudsen effusion apparatus combined with a quartz crystal microbalance. Enthalpies and entropies of vaporization were derived from the fitting of vapor pressure and temperature results to the Clarke and Glew equation. [C(1)C(1)im][NTf2] presents a higher enthalpy and entropy of vaporization than the neighboring members of the series. The enthalpy of vaporization of [C(2)C(3)im][NTf2] lies in between the asymmetric and symmetric ionic liquid series, reflecting a decrease in the electrostatic interactions due to a decrease of the charge accessibility between the ionic pairs when the methyl group is replaced by an ethyl group. The obtained higher volatility of [C(2)C(3)im][NTf2] arises from its asymmetric character, leading to an higher entropic contribution that compensates the enthalpic penalty. The border conditions ([C(1)C(1)im][NTf2], [C(2)C(1)im][NTf2] and [C(2)C(2)im][NTf2]), topology ([C(2)C(3)im][NTf2]) and symmetry/asymmetry of the ILs effect were evaluated and rationalized based on a comparative analysis of the thermodynamic properties, enthalpies and entropies of vaporization.

Abstract The standard (p(o) = 0.1 MPa) molar enthalpy of formation of 6-propyl-2-thiouracil was derived from its standard molar energy of combustion, in oxygen, to yield CO2 (g), N-2 (g) and H2SO4 center dot 115H(2)O (I), at T = 298.15 K, measured by rotating bomb combustion calorimetry. The vapor pressures as function of temperature were measured by the Knudsen effusion technique and the standard molar enthalpy of sublimation, Delta H-g(cr)m(o). at T = 298.15 K, was derived by the Clausius-Clapeyron equation. These two thermodynamic parameters yielded the standard molar enthalpy of formation, in the gaseous phase, at T= 298.15 K: -(142.5 +/- 1.9) kJ mol(-1). This value was compared with estimates obtained from very accurate computational calculations using the G3 and G4 composite methods.

Abstract Biofilms are a problem to food industries, causing equipment damage, increased energy costs, and food spoilage, and they are a potential harbour of pathogenic microorganisms. Their extreme antimicrobial resistance means that novel control strategies are necessary. Plant secondary metabolites (phyto-chemicals) have demonstrated promising antimicrobial properties when applied against planktonic cells and biofilms. The aim of this study was to test the effectiveness of two phenolic acids: ferulic (FA) and sali-cylic (SA), alone and in combination (FSA) on the prevention and control of Bacillus cereus and Pseudomonas fluorescens biofilms. Additional tests were performed to ascertain the effects of FA and SA on bacterial motility, surface properties (physicochemical properties and surface charge), and quorum sensing inhibition (QSI). The effects of a concentration two times the minimum inhibitory concentration (500 mu g mL(-1)) were assessed on single- and dual-species biofilms. The results demonstrated that only swimming was affected by FA and SA and no clear relationship was obtained between the effects of phenolic acids on motility and biofilm prevention. The bacterial physicochemical surface properties and charge were affected by the phenolic acids. Salicylic acid demonstrated capacity for QSI. However, both bacteria were able to form single- and dual-species biofilms in the presence of the phenolic acids. The application of FA and SA (single and combined) to biofilms caused low to moderate inactivation and removal. However, dual-species biofilms formed in the presence of phenolic acids were highly susceptible to a second exposure to the chemicals. The continuous exposure of dual-species biofilms to the phenolic acids decreased their resilience and resistance to inactivation and removal. This study clarifies the role of FA and SA in the prevention and control of biofilms formed by two important food spoilage bacteria.

Abstract The purpose of the present study was to assess the antibacterial activity of phenyl isothiocyanate (PITC), a synthetic isothiocyanate, on biofilms of Escherichia coli and Staphylococcus aureus. The effects of PITC on bacterial free energy of adhesion and motility were also investigated. Biofilm formation in 96-well polystyrene microtiter plates was quantified by crystal violet staining and the metabolic activity of those biofilms was assessed with alamar blue. The viability and culturability of the biofilm bacteria after exposure to PITC were determined. The highest removal and metabolic activity reduction of biofilms with PITC was around 90% for both bacteria. Treatment with PITC enabled 4.5 and 4.0 log(10) reductions of the number of viable cells for E. coli and S. aureus, respectively; and no colony forming units (CFUs) were detected. PITC also affected the adhesion process and motility of bacteria, greatly preventing biofilm formation. In conclusion, PITC enabled both biofilm prevention and control, promoting high biofilm removal and inactivation activities, suggesting that this compound is a promising disinfectant.