Publications

Abstract The indiscriminate use of antibiotics in food-producing animals has received increasing attention as a contributory factor in the international emergence of antibiotic-resistant bacteria (Woodward in Pesticide, veterinary and other residues in food, CRC Press, Boca Raton, 2004). Numerous analytical methods for quantifying antibacterial residues in edible animal products have been developed over years (Woodward in Pesticide, veterinary and other residues in food, CRC Press, Boca Raton, 2004; Botsoglou and Fletouris in Handbook of food analysis, residues and other food component analysis, Marcel Dekker, Ghent, 2004). Being Amoxicillin (AMOX) one of those critical veterinary drugs, efforts have been made to develop simple and expeditious methods for its control in food samples. In literature, only one AMOX-selective electrode has been reported so far. In that work, phosphotungstate: amoxycillinium ion exchanger was used as electroactive material (Shoukry et al. in Electroanalysis 6:914-917, 1994). Designing new materials based on molecularly imprinted polymers (MIPs) which are complementary to the size and charge of AMOX could lead to very selective interactions, thus enhancing the selectivity of the sensing unit. AMOX-selective electrodes used imprinted polymers as electroactive materials having AMOX as target molecule to design a biomimetic imprinted cavity. Poly(vinyl chloride), sensors of methacrylic acid displayed Nernstian slopes (60.7 mV/decade) and low detection limits (2.9 x 10(-5) mol/L). The potentiometric responses were not affected by pH within 4-5 and showed good selectivity. The electrodes were applied successfully to the analysis of real samples.

Abstract This work proposes a new biomimetic sensor material for trimethoprim. It is prepared by means of radical polymerization, having trimethylolpropane trimethacrylate as cross-linker, benzoyl peroxide as radicalar iniciator, chloroform as porogenic solvent, and methacrylic acid and 2-vinyl pyridine as monomers. Different percentages of sensor in a range between 1 and 6% were studied. Their behavior was compared to that obtained with ion-exchanger quaternary ammonium salt (additive tetrakis(p-chlorophenyl)borate or tetraphenylborate). The effect of an anionic additive in the sensing membrane was also tested. Trimethoprim sensors with 1% of imprinted particles from methacrylic acid monomers showed the best response in terms of slope (59.7 mV/decade) and detection limit (4.01 x 10(-7) mol/L). These electrodes displayed also a good selectivity towards nickel, manganese aluminium. ammonium, lead, potassium, sodium, iron, chromium, sulfadiazine, alanine, cysteine, tryptophan, valine and glycine. The sensors were not affected by pH changes from 2 to 6. They were successfully applied to the analysis of water from aquaculture.

Abstract Enrofloxacin (ENR) is an antimicrobial used both in humans and in food producing species. Its control is required in farmed species and their surroundings in order to reduce the prevalence of antibiotic resistant bacteria. Thus, a new biomimetic sensor enrofloxacin is presented. An artificial host was imprinted in specific polymers. These were dispersed in 2-nitrophenyloctyl ether and entrapped in a poly(vinyl chloride) matrix. The potentiometric sensors exhibited a near-Nernstian response. Slopes expressing mV/Delta log([ENR]/M) varied within 48-63. The detection limits ranged from 0.28 to 1.01 mu g mL(-1). Sensors were independent from the pH of test solutions within 4-7. Good selectivity was observed toward potassium, calcium, barium, magnesium, glycine, ascorbic acid, creatinine, norfloxacin, ciprofloxacin, and tetracycline. In flowing media, the biomimetic sensors presented good reproducibility (RSD of +/-0.7%), fast response, good sensitivity (47 mV/Delta log([ENR]/M), wide linear range (1.0 x 10(-5)-1.0 x 10(-3) M), low detection limit (0.9 mu g mL(-1)), and a stable baseline for a 5 x 10(-2) M acetate buffer (pH 4.7) carrier. The sensors were used to analyze fish samples. The method offered the advantages of simplicity, accuracy, and automation feasibility. The sensing membrane may contribute to the development of small devices allowing in vivo measurements of enrofloxacin or parent-drugs.

Abstract The observation of a micellar cubic phase is reported for a mixture of an antimicrobial peptide from the Lactoferrin family, LFampin 265-284, and a model membrane system of dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol (3:1), as derived from small-angle x-ray diffraction (SAXD) measurements. The system shows remarkable thermotropic polymorphism: the peptide disrupts the lipid bilayer, forming a cubic phase of the space group Pm 3n (t < 28 degrees C), and as the temperature increases it shows a complex phase behavior (not fully clarified by SAXD). The onset, volume fraction of each phase, and phase parameters are seen to vary with peptide/lipid ratio and temperature. The obtained SAXD data represent the first experimental evidence, to our knowledge, of a micellar cubic phase in the context of antimicrobial peptide/membrane interaction. We propose that the micellization of the membrane according to the carpet model, for long proposed as a possible mechanism of action, can go through the formation of a cubic micellar phase.

Abstract Food-grade galacto-oligosaccharides (GOS) are commercially available as transparent syrups or dried powders Food powders can be found in an amorphous metastable state which is very sensitive to changes in temperature and moisture content In this work the impact of water content on thermal behavior and relative humidity on water sorption behavior of amorphous GOS powders were studied Results from differential scanning calorimetry (DSC) and sorption Isotherms suggest that GOS mixture studied with high content of oligosaccharides has low ability to crystallize A dramatic decrease in the stability of GOS powders occurred above critical water content (12-14 g/100g) and corresponding critical water activity (0 55-0 62) Above these conditions GOS powder lost its amorphous character collapsed and shrank as the powder became a transparent solution-like material The knowledge about the physicochemical changes acquired during the present study should be used to a proper control of processing and storage conditions to achieve and maintain optimum powder quality with desired properties

Abstract The standard massic energy of combustion, in oxygen, of the crystalline 9-anthracenecarboxylic acid was measured, at T=298.15 K, by static-bomb combustion calorimetry, from which the standard molar enthalpy of formation, in the condensed phase, was calculated as Delta(f)H degrees(m)(cr) = -(267.3 +/- 3.4) kJ . mol(-1). The standard molar enthalpy of sublimation of this acid, at T=298.15K, Delta(g)(cr)H degrees(m) = (139.4 +/- 0.9) kJ . mol(-1), was determined from the temperature-vapour pressure dependence, obtained by the Knudsen mass-loss effusion method. From the data presented above, the standard molar enthalpy of formation, in the gaseous phase, at T = 298.15 K, was derived, Delta(f)H degrees(m)(g) = -(127.9 +/- 3.5) kJ . mol(-1). The experimental result is interpreted in terms of enthalpic increments, molecular structure and compared with structurally similar compounds.

Abstract In the title compound, C42H29Br, the dihedral angles between the central benzene ring and the three attached benzene rings are very similar, lying in the range 52.65 (6)-57.20 (7)degrees. Of the dihedral angles between the rings of the o-biphenyl substituents, two are similar [46.34 (7) and 47.35 (7)degrees], while the other differs significantly [64.17 (7)degrees]. In the crystal, molecules are linked into centrosymmetric dimers by two weak C-H center dot center dot center dot pi interactions.

Abstract Swimming pool water requires disinfection in order to protect swimmers frompathogenic microorganisms. However, disinfection has also unintended consequences.Chlorine, the most commonly used disinfectant, reacts with the organic matter (natural,human and synthetic) present in the pool water producing disinfection by-products(DBPs) which are of primary concern. Currently, more than one hundred DBPs havebeen identified in swimming pools including, trihalomethanes, haloacids, halonitriles,haloaldeydes, haloketones, halonitromethanes, haloamines, haloamides, haloalcohols andhalogenated UV filters. Some of these DBPs have been detected in the blood, alveolar airand urine of swimming pool attendants. Exposure to DBPs has been linked to adversehealth effects, like increased risk of asthma and other respiratory diseases as well asbladder cancer. Very recently, the genotoxicity and mutagenicity of swimming poolwater have been assessed. It has been found that the mutagenicity of pool waters wassimilar to that of typical drinking water, indicating that the levels of mutagenic DBPs aresimilar in both waters.

Abstract Tamoxifen is a nonsteroidal antiestrogen that is currently and widely used in the treatment of breast cancer in all of its stages, in adjuvant therapy as a long-term suppressant of tumor recurrence and also as a chemopreventive agent in women that are in high risk of developing this type of estrogen-dependent cancer. From a toxicological and (bio)analytical point of view the knowledge of the metabolic pathways of a drug is found to be extremely important. So, in the present work the most important tamoxifen biotransformation steps were reviewed in the light of recent pharmacological data. This overview also includes the current controversy concerning tamoxifen DNA-damaging (genotoxic) versus non-genotoxic mechanisms. A special focus will be given to the putative application of electrochemical methods as a modern and reliable analytical tool for determination of tamoxifen and its metabolites. Moreover, the potential of DNA electrochemical sensors for detection of structural damage to DNA as a basis for toxicity screening is highlighted. Future prospects looking for the importance of developing new analytical methodologies are also discussed.