Roselayne Ferro Furtado

Electrochemical immunosensors for Salmonella detection in food

Pathogen detection is a critical point for the identification and the prevention of problems related to food safety. Failures at detecting contaminations in food may cause outbreaks with drastic consequences to public health. In spite of the real need for obtaining analytical results in the shortest time possible, conventional methods may take several days to produce a diagnosis. Salmonella spp. is the major cause of foodborne diseases worldwide and its absence is a requirement of the health authorities. Biosensors are bioelectronic devices, comprising bioreceptor molecules and transducer elements, able to detect analytes (chemical and/or biological species) rapidly and quantitatively. Electrochemical immunosensors use antibody molecules as bioreceptors and an electrochemical transducer. These devices have been widely used for pathogen detection at low cost. There are four main techniques for electrochemical immunosensors: amperometric, impedimetric, conductometric, and potentiometric. Almost all types of immunosensors are applicable to Salmonella detection. This article reviews the developments and the applications of electrochemical immunosensors for Salmonella detection, particularly the advantages of each specific technique. Immunosensors serve as exciting alternatives to conventional methods, allowing “real-time” and multiple analyses that are essential characteristics for pathogen detection and much desired in health and safety control in the food industry.

A novel xyloglucan film-based biosensor for toxicity assessment of ricin in castor seed meal.

Oil from the seed of the castor plant (Ricinus communis L.) is an important commodity for a number of industries, ranging from pharmaceuticals to renewable energy resources. However, the seed and subsequent seed meal contain ricin (RCA60), a potent cytotoxin, making it an unusable product for animal feed. In order to investigate the efficiency of reducing the toxicity of the seed meal, a biosensor is proposed by exploring the lectin-carbohydrate binding. A gold electrode was assembled with a film of Xyloglucan (XG) extracted from Hymenaea courbaril L. The analytical response to RCA60 was obtained using a polyclonal antibody against RCA60 conjugated to peroxidase. The current responses were generated by reaction with H2O2 and amplified with hydroquinone as chemical mediator. Voltammetric studies showed that the XG film was tightly bound to the gold electrode. This biosensor allows discriminate lectins in native and denatured forms. The limit of detection of native RCA60 was 2.1 μg mL(-1). This proposed biosensor showed to be a potential and accurate method for toxicity assessment of the ricin in castor seed meal by simple polysaccharide film-electrode strategy.

Novel polyurethanes from xylan and TDI: Preparation and characterization

ABSTRACT Xylan is a hemicellulose, which is found abundantly in nature. In this work, a novel polyurethane was developed involving xylan and tolylene-2,4-diisocyanate (TDI). Polymer synthesis was achieved through conventional heat or microwave-assisted reaction in dimethyl sulfoxide. Because xylan has multiple OH groups on each polymer chain, the TDI/xylan molar ratio had to be adjusted to produce a soluble polymeric product. The reaction products were characterized by 13C NMR, FTIR, thermogravimetric analysis, and differential scanning calorimetry. The xylan polyurethane was shown to exhibit improved thermal stability over xylan.

BIOSSENSOR AMPEROMÉTRICO PARA DETERMINAÇÃO DE PERÓXIDO DE HIDROGÊNIO EM LEITE

An amperometric biosensor was developed for detection of hydrogen peroxide in milk samples. The biosensor was constructed from the immobilization of peroxidase on printed carbon electrode. Optimization parameters were evaluated in order to obtain better performance of the biosensor. The biosensor showed linearity in the range 5.0 to 40.0 µ mol L-1H2O2 in phosphate buffer. Milk samples without dilution reported the detection limit for H2O2 of 0.42 µmol L-1 and quantification of 1.39 µmol L-1.The biosensor could be a sensitive and inexpensive alternative for the detection of H2O2 in adulterated milk samples.

Practical use of immobilized lysozyme for the remediation process of Escherichia coli in aqueous solution

The lysozyme enzyme was immobilized on vitreous surface (fragments with diameters of 0.3 and 1.0 mm) for remediation of the microorganism Escherichia coli JM 109 into fresh water and saline solutions with 0.9% NaCl (w/v). Characterization of enzymatic film was carried out by infrared spectroscopy and atomic force microscopy techniques. Bactericide activity of the enzyme was evaluated by spectrophotometric analysis. It was verified that the enzymatic film was strongly coupled with the vitreous surface. The topographic analysis demonstrated that the deposited film was uniform and homogeneous. It was observed bactericide activity of film deposited on vitreous surface with 0.3 mm in fresh and saline solutions. This fact was not verified to vitreous fragments with 1.0 mm of diameter.

Derivatives of Cardanol through the Ene Reaction with Diethyl Azodicarboxylate

Cardanol is an alkyl/alkenyl phenolic material obtained from cashew nut shell liquid (CNSL), which is a byproduct of cashew nut processing. In an effort to develop new uses, cardanol was derivatized for the first time with diethyl azodicarboxylate (DEAD) through the ene reaction. The reaction was facile and required only the application of heat without a catalyst. Both conventional heating and microwave heating were shown to be effective; the latter entailed much shorter reaction time and substantial energy savings. The reaction product (a hydrazino-ester derivative of cardanol) was characterized by nuclear magnetic resonance (NMR). The product increased in viscosity with time and may be useful as a viscosifier in oil-based commercial formulations and as a synthon for further organic reactions.

Synthesis of a cardanol-amine derivative using an ionic liquid catalyst

Cardanol is a biobased raw material derived from cashew nut shell liquid. In order to extend its utility, new derivatives and additional applications are useful. In this work cardanol was first epoxidized, and a novel aniline derivative prepared from it under mild reaction conditions with the help of an ionic liquid catalyst. The reaction chemistry was studied by using nuclear magnetic resonance. The resulting aminohydrin adduct showed antioxidant property and should also be a useful synthon for further reactions. As an example, the aminohydrin was shown to undergo a condensation reaction with formaldehyde to form a prepolymer, which could be further reacted to form thermosetting resins.

Morphological and Electrochemical Characteristics of Electrosynthesized PPy/CD Composite

Neste trabalho, a eletrodeposicao do composito polipirrol/cardanol (PPy/CD) foi realizada visando boa caracteristica eletroquimica e melhoria de propriedade mecânica do filme. Compositos de PPy/CD foram crescidos em superficie de ouro potenciodinamicamente e potenciostaticamente, em diferentes concentracoes de Py e CD em meio de acetonitrila. A caracterizacao do composito foi seguida com o uso de tecnicas de espectroscopia de infravermelho, microscopia eletronica de varredura, microscopia de forca atomica e voltametria ciclica. O composito apresentou a incorporacao do CD no PPy com morfologia globular e tambem na forma de nodulos, com graos de 1-2 nm. Os compositos crescidos por voltametria ciclica e cronoamperometria apresentaram cargas anodicas de aproximadamente 2,9 e 5,7 mC, respectivamente.