Biossensores baseados em filmes de Langmuir-Blodgett e Langmuir-Schaefer de lipídios, bisftalocianina de lutécio e tirosinase.
Carregando...
Data
2019-08-16
Autores
Pereira, Matheus Santos
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
O presente trabalho descreve o estudo da interação entre o lipídio AA (ácido araquídico), os fosfolipídios DPPC (1,2-dipalmitoil-sn-glicero-3-fosfatidilcolina) e DPPG (1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol) com a enzima Ty (tirosinase). Através da interação monocamada lipídica/enzima foi desenvolvido um biossensor para a detecção de polifenóis. O estudo de interação foi realizado via filmes de Langmuir, ou seja, monocamadas lipídicas dispostas na interface ar/água que mimetizaram modelos de membranas biológicas, sendo estes analisados através de isotermas (π-A) e do módulo de compressibilidade. Além disso, foram realizadas medidas de PM-IRRAS (do inglês - Polarization Modulation - Infrared Reflection-Adsorption Spectroscopy) que auxiliaram no estudo da interação membrana/enzima em nível molecular. Por meio desses estudos foi possível observar uma maior interação e incorporação da enzima nas monocamadas de DPPC/Ty. Então, os filmes de Langmuir foram depositados em ITO (substrato eletrocondutor de vidro recoberto com óxido de estanho dopado com índio) utilizando a técnica de Langmuir-Blodgett (LB). Os filmes foram avaliados como biossensores para detecção de polifenóis em amostras padrões de catecol por voltametria cíclica. Nessa etapa, foram avaliados os efeitos das matrizes lipídicas, número de camadas e concentração do eletrólito de suporte no processo eletrocatalítico de redução do catecol. Além disso, foi avaliado o efeito da incorporação do mediador eletrônico LuPc2 (bisftalocianina de Lutécio) à matriz lipídica. Os estudos eletroquímicos indicaram que os filmes de DPPC/Ty e de DPPC:LuPc2/Ty, ambos contendo 3 camadas LB, apresentaram resultados promissores para a aplicação sensorial, porem valores de limites de detecção (7.59 vs. 7,08 µmol L-1) e , intervalo linear de reposta (10,0 a 400 µmol L-1 vs. 8,00 a 400 µmol L-1) demonstram que o uso da LuPc2 mediador eletrônico não é tão vantajoso como o esperado. A partir disso, filmes LS de DPPC/Ty que apresentaram propriedades similares aos filmes LB foram testados em amostras reais de chá, sendo os valores de concentração encontrados compatíveis aos do método padrão de “Folin-Ciocalteu”.
This work describes the study of interaction between lipid AA (arachidic acid), phospholipids DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine) and DPPG (1,2-dipalmitoyl-snglycero-3-phosphoglycerol) with the enzyme Ty (tyrosinase). A biosensor for the detection of polyphenols was developed through the interaction of lipid monolayer/enzyme. The study of interaction was performed in Langmuir films, in other words, lipids monolayer organized at the air/water interface simulated biological membrane models, using the isotherms (π-A) and the compressibility module. In addition, measurements of PM-IRRAS (Polarization Modulation - Infrared Reflection-adsorption Spectroscopy) were performed to study of membrane/enzyme interaction at the molecular level. In these studies, it was possible to observe a strong interaction and incorporation of the enzyme in DPPC monolayer. Thus, the films were grown on ITO (indium doped tin oxide glass substrate) using the Langmuir-Blodgett (LB) technique. The films were evaluated as biosensors for detection of polyphenols in standard catechol samples using cyclic voltammetry. At this stage, the effects of lipid matrices, number of layers and support electrolyte concentration on the electrocatalytic catechol reduction process were evaluated. After that, the effect of the incorporation of the electron mediator LuPc2 (Lutetium bisphthalocyanine) into the lipid matrix was evaluated. Electrochemical studies indicated that DPPC/Ty and DPPC:LuPc2/Ty films, both containing 3 LB layers, showed promising results for sensory application, but the limits of detection (7.59 vs. 7.08 µmol L-1 ) and the linear ranges (10.0 at 400 µmol L-1 and 8.00 at 400 µmol L-1 ) demonstrate that the use of electron mediator LuPc2 is not as advantageous as expected. From this, LS films of DPPC/Ty were tested on real tea samples, and the concentration values found were compatible with the standard “FolinCiocalteu” method.
This work describes the study of interaction between lipid AA (arachidic acid), phospholipids DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine) and DPPG (1,2-dipalmitoyl-snglycero-3-phosphoglycerol) with the enzyme Ty (tyrosinase). A biosensor for the detection of polyphenols was developed through the interaction of lipid monolayer/enzyme. The study of interaction was performed in Langmuir films, in other words, lipids monolayer organized at the air/water interface simulated biological membrane models, using the isotherms (π-A) and the compressibility module. In addition, measurements of PM-IRRAS (Polarization Modulation - Infrared Reflection-adsorption Spectroscopy) were performed to study of membrane/enzyme interaction at the molecular level. In these studies, it was possible to observe a strong interaction and incorporation of the enzyme in DPPC monolayer. Thus, the films were grown on ITO (indium doped tin oxide glass substrate) using the Langmuir-Blodgett (LB) technique. The films were evaluated as biosensors for detection of polyphenols in standard catechol samples using cyclic voltammetry. At this stage, the effects of lipid matrices, number of layers and support electrolyte concentration on the electrocatalytic catechol reduction process were evaluated. After that, the effect of the incorporation of the electron mediator LuPc2 (Lutetium bisphthalocyanine) into the lipid matrix was evaluated. Electrochemical studies indicated that DPPC/Ty and DPPC:LuPc2/Ty films, both containing 3 LB layers, showed promising results for sensory application, but the limits of detection (7.59 vs. 7.08 µmol L-1 ) and the linear ranges (10.0 at 400 µmol L-1 and 8.00 at 400 µmol L-1 ) demonstrate that the use of electron mediator LuPc2 is not as advantageous as expected. From this, LS films of DPPC/Ty were tested on real tea samples, and the concentration values found were compatible with the standard “FolinCiocalteu” method.
Descrição
Palavras-chave
Biossensores, Polifenóis, Filmes de Langmuir, Chá Mate