RESUMO
The brewers' spent grain is a by-product generated during brewery process and is a potential source for arabinoxylans (AX) extraction. In the present work, the extraction and characterization of an arabinoxylan-rich fraction from brewers' spent grain (BSG-AX) were performed, and BSG-AX was evaluated as release matrix for caffeine. The BSG-AX showed an AX content of 72% (w/w), a ferulic acid content of 3.52⯵g/mg BSG-AX, an Ara/Xyl ratio of 0.89, an intrinsic viscosity of 41.18â¯mLâ¯g-1, and a molecular weight of 43.80â¯kDa. The studied BSG-AX showed a good antioxidant capacity compared with other polysaccharide gums and was estimated by DPPH (114.41⯵M Trolox equivalent/g BSG-AX) and FRAP (49.01⯵mol Fe2+/g BSG-AX) assays. The partial specific volume (0.63â¯cm3â¯g-1), loss on drying (10.68%), swelling (10.87%), solubility (80.93%) and electrostatic interactions (by zeta potential, -3.44 to -9.17â¯mV) were determined and used to evaluate the application of the BSG-AX as release matrix. A film containing the BSG-AX, glycerol (as plasticizer) and caffeine (target drug) was prepared as release matrix. Glycerol promoted an increase in the extensibility and the surface smoothness of the BSG-AX-caffeine film. The drug was released (≈98%) in about 7â¯h. These results are promising to concern the design and use of BSG-AX based biofilms for the controlled release of bioactive compounds.
Assuntos
Cafeína/química , Estimulantes do Sistema Nervoso Central/química , Portadores de Fármacos , Grão Comestível/microbiologia , Fermentação , Hordeum/microbiologia , Resíduos/análise , Xilanos/química , Preparações de Ação Retardada , Liberação Controlada de Fármacos , Microbiologia de Alimentos , Glicerol/química , Cinética , Plastificantes/química , Solubilidade , Viscosidade , Xilanos/isolamento & purificaçãoRESUMO
The manufacture and evaluation of a novel sensor built with a composite material, highly selective to nitrate ions using doped polypyrrole as a recognition agent, are presented. When the ratio of recognition agent to graphite was optimized at 1:1, and the sensitivities found closely approached nernstian behavior. The stability times attained were less than 14 min with response times also below 20 s. Batch characterization of the sensor displayed a sensitivity of 57.1 mV/decade of nitrate ion activity (alphaNO3-) and a detection limit of 5.37 x 10(-5) M, which are comparable to those reported for commercial sensors. Evaluation of the selectivity coefficients showed high affinity to nitrate ion, superior to that of commercial sensors and others reported in the literature. The composite material gives the sensor a prolonged service life with the added capability of allowing the regeneration of its active surface. Coupling the sensor and a solid state, composite-type, reference electrode to a flow injection analysis system (FIA) permitted to achieve an effective overall assessment of the system. A nitrate determination test was conducted on real samples. A comparison of the results obtained, either with stationary measurements or with FIA, indicated that there were no significant differences from the values from manufacturer's specifications.
Assuntos
Nitratos/análise , Nitratos/química , Polímeros/química , Pirróis/química , Calibragem , Concentração de Íons de Hidrogênio , Dinitrato de Isossorbida/análogos & derivados , Dinitrato de Isossorbida/química , Sensibilidade e EspecificidadeRESUMO
An amperometric tubular cell involving composite biosensors for the determination of beta-d-glucose in a flow injection analysis (FIA) system is proposed. Diverse configurations and parameters are evaluated to improve the system's response. The configuration producing less noise resulted when the biosensor was located closer to the auxiliary electrode, which also required coupling both electrodes within the system under a continuous flow regime. Further, we report on the influence of the active area of the biosensor and of the flow rate used. Statistical analyses of the data revealed two regions with a linear response range for the determination of beta-d-glucose, with a detection limit of 4.7 x 10(-4) M and in the low concentration region a sensitivity of 17.46 +/- 0.12 microAM(-1). At the beta-d-glucose concentrations studied there was no evidence of enzymatic saturation. An increment on the ionic strength of the sample and carrier passing through the analysis system decreases its sensitivity. The reproducibility of the analytical system in terms of its standard deviation was 2.9% with a 95% confidence level, having a lifetime that lasted at least 100 days. beta-d-Glucose was determined in different commercial medical glucose-containing solutions, the experimental results are in good agreement with those reported by the manufacturer.