Publications

Abstract In this work, we studied the effect of anion and cation properties on the interaction of alcohols with ionic liquids (ILs), using propan-1-ol as a molecular probe. The enthalpies of solution at infinite dilution of propan-1-ol in several ILs were measured by isothermal titration calorimetry (ITC). The calorimetric results were analysed together with molecular dynamics simulation and quantum chemical calculations of the interaction of the hydroxyl group of propan-1-ol with the anions. The results evidenced the role of the anion's basicity in the intermolecular interactions of alcohols and ionic liquids and further revealed a secondary effect of the cation nature on the solvation process. The effect of the anion basicity on the strength of the interaction of alcohols with ionic liquids was evaluated by comparing the results obtained for ILs with the same cation and different anions, [C(4)C(1)im][anion] (anions NTf2, PF6, FAP, DCA and TFA). The effect of the cation (size, aromaticity, charge distribution, and acidity) was explored using five different cations of the NTf2 series, [cation][NTf2] (cations C(4)C(1)im, C(4)C(1)pirr, C(4)py, C(4)C(1)pip, and C(3)C(1)C(1)im).

Abstract The uptake and transport of dietary antioxidants remains the most important setback for their application in therapy. To overcome the limitations, a PEGylated-based platform was developed to improve the delivery properties of two dietary hydroxycinnamic (HCA) antioxidants caffeic and ferulic acids. The antioxidant properties of the new polymer antioxidant conjugates (PEGAntiOxs), prepared by linking poly(ethylene glycol) (PEG) to the cinnamic acids by a one-step Knovenagel condensation reaction, were evaluated. PEGAntiOxs present a higher lipophilicity than the parent compounds (caffeic and ferulic acids) and similar, or higher, antioxidant properties. PEGAntiOxs were not cytotoxic at the tested concentrations in SH-SYSY, Caco-2, and hCMEC/D3 cells. By contrast, cytotoxic effects in hCMEC/D3 and SH-SYSY cells were observed, at 50 and 100/3M, for caffeic and ferulic acids. PEGAntiOxs operate as antioxidants against several oxidative stress-cellular inducers in a neuronal cell-based model, and were able to inhibit glycoprotein-P in Caco-2 cells. PEGAntiOxs can cross hCMEC/D3 mono layer cells, a model of the blood-brain barrier (BBB) endothelial membrane. In summary, PEGAntiOxs are valid antioxidant prototypes that can uphold the antioxidant properties of HCAs, reduce their cytotoxicity, and improve their BBB permeability. PEGAntiOxs can be used in the near future as drug candidates to prevent or slow oxidative stress associated with neurodegenerative diseases.

Abstract Mitochondrial oxidative damage is related to diverse pathologies, including cancer and neurodegenerative diseases. Shielding mitochondria from oxidative damage with mitochondriotropic antioxidants is by now considered an effective therapeutic strategy. Despite the success of the approach, some concerns related with cytotoxicity have been reported. For instance, AntiOxCIN(6) is a mitochondriotropic antioxidant based on caffeic acid (CAF) that is cytotoxic in hepatocarcinoma (HepG2) cell lines. PEGylation, often used to enhance drug pharmacologic and pharmaceutical properties, was herein applied to modulate AntiOxCIN(6) toxicity drawbacks. So, a dual-functionalization of polyethylene glycol (PEG) with TPP+ and CAF as targeting and antioxidant arms, respectively, was performed by a two-step amidation strategy using ethyl chloroformate and EDC/NHS as coupling reagents. The data showed that the antioxidant properties related with CAF moiety were maintained in the CAF-PEG-TPP conjugate (CPTPP) and that PEGylation process reverted the loss of ability to chelate iron observed with AntiOxCIN(6). In cellular studies, CPTPP was nontoxic to human HepG2 and neuronal (SH-SY5Y) cells, while both CAF and AntiOxCIN(6) demonstrated harmful effects in the same cell lines. The lack of cytotoxic events linked to oxidative stress levels observed with CPTPP suggested that PEGylation process somehow modulates the putative toxicity related with the presence of a catechol moiety and/or the TPP+ cation. In addition, the mitochondrial oxygen consumption was not significantly affected by CPTPP treatment in SH-SY5Y cells when compared with nontreated cells. CPTPP showed remarkable antioxidant effects in cell-based assays against several oxidative stress-induced agents (H2O2, t-BHP, and FeNTA). From the data it can be concluded that PEGylation technology can modulate the toxicity of mitochondriotropic antioxidants without disturbing the antioxidant profile of the core antioxidant. PEGylation can be considered a relevant tool to hasten the difficulties related to the design and development of mitochondrial nontoxic and operative drug candidates.

Abstract An understanding of the mechanism of action of antimicrobial peptides is fundamental to the development of new and more active antibiotics. In the present work, we use a wide range of techniques (SANS, SAXD, DSC, ITC, CD, and confocal and electron microscopy) in order to fully characterize the interaction of a cecropin A-melittin hybrid antimicrobial peptide, CA(1-7)M(2-9), of known antimicrobial activity, with a bacterial model membrane of POPE/POPG in an effort to unravel its mechanism of action. We found that CA(1-7)M(2-9) disrupts the vesicles, inducing membrane condensation and forming an onionlike structure of multilamellar stacks, held together by the intercalated peptides. SANS and SAXD revealed changes induced by the peptide in the lipid bilayer thickness and the bilayer stiffening in a tightly packed liquid-crystalline lamellar phase. The analysis of the observed abrupt changes in the repeat distance upon the phase transition to the gel state suggests the formation of an L-gamma phase. To the extent of our knowledge, this is the first time that the L-gamma phase is identified as part of the mechanism of action of antimicrobial peptides. The energetics of interaction depends on temperature, and ITC results indicate that CA(1-7)M(2-9) interacts with the outer leaflet. This further supports the idea of a surface interaction that leads to membrane condensation and not to pore formation. As a result, we propose that this peptide exerts its antimicrobial action against bacteria through extensive membrane disruption that leads to cell death.

Abstract Pseudomonas aeruginosa is one of the most dreaded human pathogens, because of its intrinsic resistance to a number of commonly used antibiotics and ability to form sessile communities (biofilms). Innovative treatment strategies are required and that can rely on the attenuation of the pathogenicity and virulence traits. The interruption of the mechanisms of intercellular communication in bacteria (quorum sensing) is one of such promising strategies. A cobalt coordination compound (Co(HL)(2)) synthesized from (E)-2-(2-(pyridin-2-ylmethylene) hydrazinyl)-4-(p-tolyl) thiazole (HL) is reported herein for the first time to inhibit P. aeruginosa 3-oxo-C12-HSL-dependent QS system (LasI/LasR system) and underling phenotypes (biofilm formation and virulence factors). Its interactions with a possible target, the transcriptional activator protein complex LasR-3-oxo-C12-HSL, was studied by molecular modeling with the coordination compound ligand having stronger predicted interactions than those of co-crystallized ligand 3-oxo-C12-HSL, as well as known-binder furvina. Transition metal group 9 coordination compounds may be explored in antipathogenic/antibacterial drug design.

Abstract Steady-state and time-resolved fluorescence techniques were used to study excited-state proton transfer (ESPT) to water of the reversible photoacid 2-naphthol-8-sulfonate (2N8S) in acetonitrile/water mixtures. In acetonitrile-rich mixtures, up to chi(water) <= 0.12, we found a slow ESPT process on the order of nanoseconds. At Xwater chi(water) approximate to 0.15, the RO- fluorescence band intensity is at the minimum, whereas at chi(water) approximate to 0.030, it is at the maximum. The steady-state fluorescence spectra of these mixtures show that the intensity of the RO- fluorescence band at chi(water) approximate to 0.030 is about 0.24 of that of the ROH band. We explain this unusual phenomenon by the presence of water clusters that exist in the acetonitrile-rich CH3CN/H2O mixtures. We propose that a water bridge forms between the 2-OH and 8-sulfonate by preferential solvation of 2N8S, and this enables the ESPT process between the two sites of the molecular structure of 2N8S. In mixtures of chi(water) >= 0.25, the ESPT process takes place to water clusters in the bulk mixture. The higher the chi(water) in the mixture, the greater the ESPT rate constant. In neat water, the rate constant is rather small, 4.5 X 10(9) s(-1). TD-DFT calculations show that a single water molecule can bridge between 2-OH and 8-sulfonate in the excited state. The activation energy for the ESPT reaction is about 9 kcal/mol, and the RO-(S-1) species is energetically above the ROH(S-1) species by about 1.6 kcal/mol.

Abstract Foodborne microbial diseases are still considered a growing public health problem worldwide despite the global continuous efforts to ensure food safety. The traditional chemical and thermal-based procedures applied for microbial growth control in the food industry can change the food matrix and lead to antimicrobial resistance. Moreover, currently applied disinfectants have limited efficiency against biofilms. Therefore, antimicrobial photodynamic therapy (aPDT) has become a novel alternative for controlling foodborne pathogenic bacteria in both planktonic and sessile states. The use of aPDT in the food sector is attractive as it is less likely to cause antimicrobial resistance and it does not promote undesirable nutritional and sensory changes in the food matrix. In this review, aspects on the antimicrobial photodynamic technology applied against foodborne pathogenic bacteria and studied in recent years are presented. The application of photodynamic inactivation as an antibiofilm strategy is also reviewed.

Abstract A procedure for the physical vapor deposition (PVD), in high-vacuum conditions, for high purity and crystalline methylammonium lead halide perovskite thin films is described. This procedure and methodology can be used to fabricate high-performance hybrid organic-inorganic materials that have recently emerged as the next-generation photovoltaic technology. PVD of methylammonium iodide and lead iodide to produce lead halide perovskite thin films was optimized according to the equilibrium vapor pressures of corresponding precursors evaporated from Knudsen effusion cells. Optical properties of perovskite thin films were characterized by UV-Vis-NIR and fluorescence spectroscopy. The high crystallinity of vapor-deposited thin films on glass, indium fin oxide, fluorine-doped fin oxide, and TiO2 surfaces was proved by scanning electron microscopy and X-ray diffraction. This vapor deposition approach leads to the production of very pure, crystalline and high stable perovskite thin films.

Abstract Anthocyanins are potential food colorants due to their color, low toxicity and biological properties. However, the low chemical stability of anthocyanins has limited their use. In this work, the thermal stability of cyanidin-3-O-glucoside (cy3glc) (major blackberry anthocyanin) and blackberry purees through molecular inclusion with beta-cyclodextrin (beta-CD) was assessed. Complexation with beta-CD showed a thermal stabilization of cy3glc, resulting on a decrease of the degradation rate constant (k) and in several alterations in the cy3glc-beta-CD DSC thermogram. To assess the bioaccessibility of blackberry anthocyanins, the stability of blackberry purees through simulated in vitro digestion was also studied. Despite the rapid degradation of anthocyanins observed within the first minutes of simulated intestinal digestion, complexation with beta-CD allowed anthocyanins degradation to be slowed down. The results obtained demonstrate the ability of beta-CD to increase blackberry anthocyanins thermal stability and also to decrease the rate of degradation of these pigments under simulated gastrointestinal conditions.