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Authors
Advisor(s)
Abstract(s)
A presente dissertação tem com objetivo o desenvolvimento de um biossensor com
base nos polímeros de impressão molecular para a deteção de uma molécula alvo, o
ácido glutâmico que é convertido em glutamina pela glutamina sintetase, recorrendo à
potenciometria. Nas células neoplásicas a glutamina não é sintetizada podendo-se
considerar que o ácido glutâmico é um potencial agente anti-cancro.
A técnica de impressão molécular utilizada foi a polimerização em bulk,
combinando a acrilamida e a bis acrilamida com o ácido glutâmico. Para se verificar se
a resposta potenciométrica obtida era de facto da molécula alvo foram preparados em
paralelo com os sensores, materiais de controlo, ou seja, moléculas sem impressão
molécular (NIP). Para se controlar a constituíção química dos vários sensores
nomeadamente, do NIP e do polímero de impressão molecular (MIP) antes e após a
remoção bem como a molécula foram realizados estudos de Espetroscopia de
Infravermelhos de Transformada de Fourier (FTIR), Scanning electron microscope
(SEM) e Espetroscopia de Raios X por dispersão em energia (EDS).
Os materiais desenvolvidos foram aplicados em várias membranas que diferiam
umas das outras, sendo seletivas ao ião. A avaliação das características gerais das
membranas baseou-se na análise das curvas de calibração, conseguidas em meios com
pHs diferentes, comparando os vários elétrodos. O pH 5 foi o que apresentou melhor
resultado, associado a uma membrana que continha um aditivo, o p-tetra-octilphenol, e
com o sensor com percentagem de 3%.
Posto isto, testou-se em material biológico, urina, com as melhores características
quer em termos de sensibilidade (18,32mV/década) quer em termos de linearidade
(1,6x10-6 a 1,48x10-3 mol/L). Verificou-se ainda que aplicando iões interferentes na
solução, estes não interferem nesta, podendo ser aplicados na amostra sem que haja
alteração na resposta potenciométrica. O elétrodo é capaz de distinguir o ácido
glutâmico dos restantes iões presentes na solução.
The aim of this work is the development of biosensor based on molecularly imprinted polymer for detecting a target molecule, glutamic acid that is converted into glutamine by glutamine synthetase, using potentiometry. In neoplastic cells glutamine isn’t synthesized so glutamic acid can be considered a potential anticancer agent. The molecular imprinting technique used was the polymerization in bulk by combining acrylamide and bis acrylamide with glutamic acid. To verify that the potentiometric response obtained was indeed the target molecule were prepared in parallel with the sensors, control materials, with non molecular imprinting polymers (NIP). To control the chemical constitution of the various sensors, NIP and the molecularly imprinted polymer (MIP) before and after remotion of the molecule were performed by spectroscopy studies of Fourier Transform Infrared (FTIR), Scanning Electron Microscope ( SEM) and Spectroscopy and X-Ray energy dispersive (EDS). The developed materials have been applied in various membranes differing from each other with the selective ion. A review of the general characteristics of the membranes was based on an analysis of the calibration curves obtained in media with different pH values, by comparing the various electrodes. The pH 5 showed the best result associated to a membrane containing an additive, p-tetra-octilphenol, and the sensor percentage of 3%. It was tested in biological material, urine, with the best characteristics in terms of sensitivity (± 18,32mV / decade) in terms of linearity (1,6x10-6 to 1,48x10-3 moles / L) . It was also found that by applying interfering ions in solution, they do not interfere with this and may be applied to the sample without changing the potentiometric response. The probe is capable of distinguishing the rest of glutamic acid ions present in the solution.
The aim of this work is the development of biosensor based on molecularly imprinted polymer for detecting a target molecule, glutamic acid that is converted into glutamine by glutamine synthetase, using potentiometry. In neoplastic cells glutamine isn’t synthesized so glutamic acid can be considered a potential anticancer agent. The molecular imprinting technique used was the polymerization in bulk by combining acrylamide and bis acrylamide with glutamic acid. To verify that the potentiometric response obtained was indeed the target molecule were prepared in parallel with the sensors, control materials, with non molecular imprinting polymers (NIP). To control the chemical constitution of the various sensors, NIP and the molecularly imprinted polymer (MIP) before and after remotion of the molecule were performed by spectroscopy studies of Fourier Transform Infrared (FTIR), Scanning Electron Microscope ( SEM) and Spectroscopy and X-Ray energy dispersive (EDS). The developed materials have been applied in various membranes differing from each other with the selective ion. A review of the general characteristics of the membranes was based on an analysis of the calibration curves obtained in media with different pH values, by comparing the various electrodes. The pH 5 showed the best result associated to a membrane containing an additive, p-tetra-octilphenol, and the sensor percentage of 3%. It was tested in biological material, urine, with the best characteristics in terms of sensitivity (± 18,32mV / decade) in terms of linearity (1,6x10-6 to 1,48x10-3 moles / L) . It was also found that by applying interfering ions in solution, they do not interfere with this and may be applied to the sample without changing the potentiometric response. The probe is capable of distinguishing the rest of glutamic acid ions present in the solution.
Description
Keywords
Polímero de impressão molecular Ácido glutâmico Potenciometria Polimerização em bulk Elétrodos seletivos Molecular Imprinting Polymer Glutamic acid Potentiometry Polymerization in bulk Selective electrodes