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Master's Dissertation
DOI
https://doi.org/10.11606/D.75.2007.tde-14042008-092411
Document
Author
Full name
Claudia do Amaral Razzino
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 2007
Supervisor
Committee
Machado, Sergio Antonio Spinola (President)
Toledo, Renata Alves de
Yamanaka, Hideko
 
Title in Portuguese
Desenvolvimento, caracterização e utilização de um nanobiossensor enzimático para a determinação da carbaril
Keywords in Portuguese
acetilcolinesterase
biossensores
eletrodos modificados
nanotubos de carbono
pesticidas
Abstract in Portuguese
Desde a descoberta dos nanotubos de carbono, tem sido grande o interesse em explorar suas aplicações, e uma delas é a modificação de eletrodos. Muitos trabalhos ilustram as vantagens da aplicação de eletrodos de carbono vítreo modificados com nanotubos de carbono e enzimas. Estes sistemas apresentam resposta amperométrica elevada, com diminuição nos potencias de oxidação ou redução do substrato ou produto enzimático, eliminando a resposta de interferentes. Apresentam bons limites de detecção, melhoras na sensibilidade e estabilidade à medida que oferecem um microambiente favorável à atividade da enzima. Todas estas vantagens tornam interessante o emprego de tais biossensores no monitoramento de pesticidas. Diante da escassez de trabalhos que descrevem esta aplicação, neste trabalho, objetivou-se explorá-la, com ganho em sensibilidade pelo uso dos nanotubos de carbono e em seletividade pelo uso das enzimas. Neste trabalho foi desenvolvido um nanobiossensor para a determinação de carbaril em amostras de tomate. Para isto, os nanotubos de carbono utilizados foram tratados quimicamente e em seguida caracterizados por microscopia eletrônica de transmissão. O eletrodo de carbono vítreo modificado com nanotubos de carbono foi caracterizado eletroquimicamente e por microscopia eletrônica de varredura. A enzima acetilcolinesterase utilizada teve sua atividade catalítica enzimática determinada pelo método espectrofotométrico. O nanobiossensor teve seus parâmetros de operação otimizados e foi utilizado na determinação de carbaril em amostras de tomate. A avaliação de reprodutibilidade de preparação do nanobiossensor apresentou desvio padrão relativo de 4,02%. Os desvios padrão relativos para a repetibilidade e reprodutibilidade de medidas são, respectivamente, 1,18 e 3,27%. Duas amostras de tomate foram dopadas com 0,500 µmol L-1 e 6,00 µmol L-1 de carbaril, e as respectivas recuperações foram de 96,00 e 95,08%. Os limites de detecção e quantificação obtidos com o nanobiossensor foram LD = 8,96 nmol L-1 e LQ = 29,9 nmol L-1.
 
Title in English
Development, characterization and utilization of a enzymatic nanobiosensor for a carbaryl determination
Keywords in English
acetylcholinesterase
biosensors
carbon nanotubes
modified electrodes
pesticides
Abstract in English
Since the discovery of carbon nanotubes, a great interest in exploring their applications has raised, being one of those the modification of electrodes. Many works has shown the advantages of applying glassy carbon electrodes modified with carbon nanotubes and enzymes. These systems present elevated amperometric response with decreased potentials of oxidation or reduction of either the substract or the enzymatic product, eliminating the response of interferences as well. Moreover, these systems present good detection limits, as well as sensibility and stability improvements in consequence of a favorable microenvironment for the enzyme action. All these advantages make interesting the employment of such biosensors in pesticides monitoring. Due to the scarcity of works describing this kind of application, the aim of this work is its exploration, focusing on sensibility increasing caused by the use of carbon nanotubes, as well as selectivity increasing caused by the use of enzymes. In this work a nanobiosensor was developed to carbaryl determination in tomato samples. For this, the employed carbon nanotubes were chemically treated before their characterization by transmission electron microscopy. The glassy carbon electrode modified with carbon nanotubes was characterized both electrochemically and by scan electron microscopy. The employed acetylcholinesterase enzyme had its enzymatic activity measured by spectrophotometric means. The nanobiosensor had its operational parameters optimized and it was employed in the determination of carbaryl in tomato samples. The reproducibility of the nanobiosensor preparation was 4.02%. The relative standard deviation for the repeatability and reproducibility were, respectively, 1.18 and 3.27%. Two tomato samples were spiked with 0.500 µmol L-1 and 6.00 µmol L-1 of carbaryl, and their respective recoveries were 96.00 and 95.08%. The detection and quantitation limits obtained with the developed nanobiosensor were, respectively, 8.96 and 29.9 nmol L-1.
 
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ClaudiaARazzinoR.pdf (8.20 Mbytes)
Publishing Date
2008-04-15
 
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