Browsing by Author "Freitas, Victor de"
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- Molecular Imprinting of Complex Matrices at Localized Surface Plasmon Resonance Biosensors for Screening of Global Interactions of Polyphenols and ProteinsPublication . Guerreiro, Joana Rafaela Lara; Bochenkov, Vladimir E.; Runager, Kasper; Aslan, Hüsnü; Dong, Mingdong; Enghild, Jan J.; Freitas, Victor de; Sales, M. Goreti F.; Sutherland, Duncan S.Molecular imprinting polymers (MIP) have been applied to capture and stabilize complex protein matrices at plasmonic sensor surfaces. Ultrathin MIP layers at the surface of gold nanodisks enable the label free quantification of global interactions of polyphenols with protein mixtures. Separate polyphenols (catechin, procyanidin B3- catechin dimer, and PGG-pentagalloyl glucose) give specific and different binding levels to the MIP supported saliva plasmonic sensor. The demonstrated biosensor has application to study bioavailability of polyphenols or evaluation of local retention of small drug molecules.
- Wine astringent compounds monitored by an electrochemical biosensorPublication . Costa, Joana J.; Moreira, Felismina; Soares, Susana; Brandão, Elsa; Mateus, Nuno; Freitas, Victor de; Sales, GoretiAn innovative approach for monitoring astringent polyphenols in beverages (wines) is described, consisting of an electrochemical biosensor constructed by adsorbing salivary α-amylase or proline-rich protein (PRP) onto amined gold screen-printed electrodes. Interaction with polyphenols was tested using pentagalloyl glucose (PGG) as a standard, an important representative element for astringency. The analytical properties of the resulting biosensors were evaluated by electrochemical impedance spectroscopy at different pHs. The PRP-biosensor was able to bind to PGG with higher sensitivity, displaying lower limit of the linear range of 0.6 μM. Wine samples were tested to prove the concept and the concentrations obtained ranged from 0.17 to 4.7 μM, as expressed in PGG units. The effects of side-compounds on PRP and on α-amylase binding to PGG were tested (gallic acid, catechin, ethanol, glucose, fructose and glycerol) and considered negligible. Overall, concentrations > 1.0 μM in PGG units are signaling electrochemical impedance, providing a quantitative monitoring of astringent compounds.