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Master's Dissertation
DOI
10.11606/D.46.2019.tde-23012019-092804
Document
Author
Full name
Pablo Alejandro Fiorito
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2001
Supervisor
Committee
Torresi, Susana Ines Cordoba de (President)
Biaggio, Sonia Regina
Serrano, Silvia Helena Pires
Title in Portuguese
Construção de biossensores utilizando polímeros condutores eletrônicos
Keywords in Portuguese
Biossensores
Eletroquímica
Polímeros condutores
Abstract in Portuguese
Neste trabalho são elaborados biossensores para a detecção amperométrica de glicose. Para isso, imobilizou-se a enzima glicose oxidase em matrizes de polímeros condutores. Foram construídos sensores utilizando-se poli(pirrol) e poli(N-metilpirrol). Com o objetivo de substituir o oxigênio molecular na etapa de transdução do sinal, o ferroceno foi incorporado dentro do polímero condutor. Para isso, os polímeros foram elaborados utilizando misturas água-etanol como meio de polimerização. A inclusão do ferroceno no sensor resulta em maior sensibilidad à glicose (4,33 µA Mm-1 cm-2 para o biossensor preparado a partir da mistura água-etanol contendo o ferroceno e de 0,23 µA mM-1 cm-2 para o sensor sem ferroceno ). Por outro lado, permite o funcionamento do sensor a potenciais menores que no caso do sensor sem ferroceno (0,4 V para o sensor com ferroceno vs. 0,65 V para o caso sem ferroceno). O deslocamento do potencial de detecção para valores menos positivos não foi suficiente para evitar as interferências causadas pelos íons ascorbato e ureato. Para isto, mostrou-se 100% efetivo o recobrimento dos sensores com uma película de Nafion®. A sobreoxidação do poli(pirrol) também mostrou potencialidade para a eliminação de interferentes, embora o processo resulte na perda de sensibilidade, provavelmente causada pela desnaturação da enzima. Quando usado o poli(N-metilpirrol) como suporte para a enzima, obtiveram se melhores respostas, causadas pela possibilidade de se preparar filmes mais espessos, consequentemente de imobilizar maior quantidade de enzima, sem observar perda de resposta causada por problemas difusionais.
Title in English
Construction of biosensors using electronic conductive polymers
Keywords in English
Biosensors
Conductive polymers
Electrochemistry
Abstract in English
The present work describes the elaboration of a biosensor for glucose detection. The enzyme, glucose oxidase, was immobilized in different conducting polymers. Two different polymers were used: polypyrrole and poly(N-methilpyrrole ). With the aim of replacing the molecular oxygen in the transduction step, ferrocene has been immobilized within the conducting polymer. Once the ferrocenium was insoluble in water, in order to develop a different route, the electropolymerization was carried out in a mixture of water and ethanol (1:1). This procedure leads to a polymer with a poor electroactivity, detected by Raman experiments. The ferrocene addition in the sensor increases the sensitivity to the glucose determination (4,33 µA mM-1 cm-2 for the biosensor with ferroecene and 0,23 µA mM-1 cm-2 for the sensor without ferrocene). Alternatively, the sensor containing ferrocene allows to operate at less positive potentials than that one without ferrocene (+ 0,40 V and + 0,65 V, respectively). This potential shift was not enough to inhibit the interference caused by ascorbate and ureate ions. One method to avoid the interference problem was to recover the sensor with a very thin layer of Nafion. Also poly(pyrrole) overoxidation is a very efficient method to eliminate this interference, but this process leads to a sensitivity decrease dueto enzyme denaturation. A better response was observed for sensor assembled using the poly(Nmethyl-pyrrole) as the support for enzyme immobilization. This behavior was provoked by the thicker of polymer film formed leading to higher amount of immobilized enzyme. Even though, no diminution in the response was caused by diffusion problems.
 
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Publishing Date
2019-01-23
 
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