Amperometric Biosensor Based On a High Resolution Photopolymer

G Model TAL-11168; No. of Pages 7

ARTICLE IN PRESS
Talanta xxx (2010) xxx–xxx

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Talanta
journal homepage: www.elsevier.com/locate/talanta

Amperometric biosensor based on a high resolution photopolymer deposited onto a screen-printed electrode for phenolic compounds monitoring in tea infusions
Pedro Ibarra-Escutia a , Jorge Juarez Gómez a ,Carole Calas-Blanchard b , Jean Louis Marty b , María Teresa Ramírez-Silva a,∗
a Departamento de Química, Área de Química Analítica, Universidad Autónoma Metropolitana-Iztapalapa, San Rafael Atlixco 186, Col. Vicentina, Del. Iztapalapa, C.P. 09340 Mexico, DF, Mexico b Université de Perpignan Via Domitia, Centre de Phytopharmacie, IMAGES EA 4218, 52 Av. Paul Alduy, 66860 Perpignan Cedex, France

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An amperometric biosensor based on laccase, from Trametes versicolor (LTV), was developed and optimized for monitoring the phenolic compounds content in tea infusions. The fungal enzyme was immobilized by entrapment within polyvinyl alcohol photopolymer PVA-AWP (azide-unit pendant water-soluble photopolymer) onto disposable graphite screen-printedelectrodes (SPE). Sensitivity optimization in terms of pH, temperature and applied potential was carried out. The linear range, detection limit, operational and storage stabilities were also determined. The laccase biosensor (LTV-SPE) was calibrated for o-, m- and p-diphenol as well as caffeic acid. The highest response was found at 0.1 M acetate buffer pH 4.7, though it must be added the goodreproducibility and operational stability were also obtained. The useful lifetime of the biosensor is estimated to be greater than 6 months. LTV-SPE was used for the determination of the equivalent phenol content (EPC) in tea infusions by the direct addition into the electrochemical cell: the results were compared with those from the Folin–Ciocalteu spectrophotometric method. The amperometric detectionexhibits some interesting advantages such as high simplicity, minimal sample preparation and shorter response time. A stable and sensitive amperometric response was obtained toward standard diphenolic compounds and herbal infusions. These biosensors are useful for easy and fast monitoring of EPC that can be related to the antioxidant capacity of natural extracts. © 2010 Elsevier B.V. All rightsreserved.

Article history: Received 30 November 2009 Received in revised form 4 March 2010 Accepted 9 March 2010 Available online xxx Keywords: Biosensor Phenolic compounds Antioxidant Tea Laccase

1. Introduction In the last three decades, numerous studies on free radicals are largely found in the clinical and nutritional literature. Free radicals are highly unstable molecules, generated in vivoduring metabolic processes that can be neutralized by certain compounds known as antioxidants, naturally produced by the human body. However, some factors like pollution, sunlight exposure, cigarette smoking or simply a malfunction of the antioxidant production may lead to a free radical excess which induces oxidative damage in cell constituents and promote numerous degenerative diseases andaging. That is why cellular antioxidants play an important role in pre-

∗ Corresponding author. Tel.: +52 55 58 04 46 70; fax: +52 55 58 04 46 66. E-mail addresses: mtrs218@xanum.uam.mx, mtrs218@yahoo.com (M.T. Ramírez-Silva). 0039-9140/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.talanta.2010.03.017

venting the formation and opposing the cellular oxidants action[1–4]. In this way, countless dietary compounds have been purportedly and intensely marketed as being important supplementary antioxidants, among the most frequently mentioned ones are: vitamins C and E, carotenoids, tocopherols, etc. [5–7]. The polyphenols, known to have antioxidant properties, form an extensive group of compounds commonly found in legumes, cereals, fruits and medicinal plants...