Carbendazim e modelos de biomembrana via filmes de Langmuir e Layer-by-Layer: mecanismos de interação e desenvolvimento de sensores
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Data
2016-02-25
Autores
Furini, Leonardo Negri [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Nesta tese filmes de Langmuir foram empregados para estudar a interação entre lipídios e um fungicida denominado carbendazim (MBC) e espectroscopia de impedância e espalhamento Raman amplificado em superfície (SERS, do inglês surface-enhanced Raman scattering) empregados na detecção deste fungicida. Os lipídios utilizados para formar os filmes de Langmuir foram brometo de dioctadecildimetilamônio (DODAB), brometo de didodecildimetilamônio (DDAB), 1,2-dipalmitoil-sn-3-glicerofosfatidilcolina (DPPC) e 1,2-dipalmitoil-sn-3-glicero-[fosfo-rac-(1-glicerol)] (DPPG) e o estudo da interação foi realizado com e sem MBC na subfase aquosa.Os resultados mostraram que o MBC interage fortemente com o DODAB e DDAB, moderadamente com o DPPC e fracamente com o DPPG, indicando que a interação é de origem eletrostática. Unidades sensoriais compostas por eletrodos interdigitados recobertos com filmes LbL de DODAB/NiTsPc e perileno/DPPG compuseram uma língua eletrônica capaz de distinguir diferentes concentrações de MBC em solução via espectroscopia de impedância. Analisando individualmente cada unidade sensorial, a composta pelo filme LbL de DODAB/NiTsPc foi a que apresentou melhor desempenho frente ao MBC. Os estudos SERS foram realizados em três etapas. Na primeira, várias morfologias de nanopartículas foram sintetizadas e avaliadas quais apresentam melhor sinal SERS do MBC. Deste estudo ficou determinado que as nanopartículas esféricas de prata apresentaramo melhor sinal SERS do MBC. A interação do MBC com a superfície destas nanopartículas foi realizada a partir de espectros SERS do MBC em vários pHs. Cálculos teóricos foram utilizados para atribuição dos modos vibracionais do MBC e assim ajudar na interpretação dos resultados experimentais. De principal relevância, das espécies de MBC as formas neutra (MBC0 ) e desprotonada (MBC- ) apresentam afinidade pela superfície de prata, originando assim sinal SERS. Por fim, o limite de detecção do MBC foi determinado via SERS utilizando um procedimento que garante a reprodutibilidade das medidas, uma vez que a técnica SERS não é, ainda, uma técnica analítica de rotina.
This work Langmuir films were employed to study the interaction between lipids and a fungicide called carbendazim (MBC), impedance spectroscopy and surface-enhanced Raman scattering (SERS) were used in the detection of this fungicide.The lipids employed to Langmuir films were dioctadecyldimethylammonium bromide (DODAB), didodecyldimethylammonium bromide (DDAB), 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG) with and without MBC in the subphase. The results show that the MBC interacts strongly with DODAB and DDAB, moderately with DPPC and weakly to DPPG, indicating that it is electrostatic interaction. Sensor units composed of interdigitated electrodes coated with LbL films DODAB/NiTsPc and perilene/DPPG composed an electronic tongue able to distinguish different MBC concentrations in solution, via impedance spectroscopy. Analyzing each sensory unit, the composed with LbL film DODAB/NiTsPc showed the best performance. The SERS studies were performed in three stages. The first one, several morphologies of nanoparticles were synthesized and evaluated which have better SERS signal of MBC. From this study it was concluded that the spherical nanoparticles of silver have better SERS signal of MBC and the subsequent results were obtained only with this nanoparticle. The interaction between MBC and surface of these nanoparticles was carried out by SERS spectra of MBC at several pHs. Here, theoretical calculations were used for assignment of vibrational modes of the MBC and thus help in the interpretation of experimental results. According to experimental and theoretical results neutrally (MBC0 ) and deprotonated (MBC- ) species have affinity for the silver surface and then show SERS signal. Finally, the MBC limit of detection was determined via SERS using a procedure which ensures the reproducibility of the measurements, since SERS technique is not, yet, a routine analytical technique.
This work Langmuir films were employed to study the interaction between lipids and a fungicide called carbendazim (MBC), impedance spectroscopy and surface-enhanced Raman scattering (SERS) were used in the detection of this fungicide.The lipids employed to Langmuir films were dioctadecyldimethylammonium bromide (DODAB), didodecyldimethylammonium bromide (DDAB), 1,2-dipalmitoyl-sn-glycero-3- phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG) with and without MBC in the subphase. The results show that the MBC interacts strongly with DODAB and DDAB, moderately with DPPC and weakly to DPPG, indicating that it is electrostatic interaction. Sensor units composed of interdigitated electrodes coated with LbL films DODAB/NiTsPc and perilene/DPPG composed an electronic tongue able to distinguish different MBC concentrations in solution, via impedance spectroscopy. Analyzing each sensory unit, the composed with LbL film DODAB/NiTsPc showed the best performance. The SERS studies were performed in three stages. The first one, several morphologies of nanoparticles were synthesized and evaluated which have better SERS signal of MBC. From this study it was concluded that the spherical nanoparticles of silver have better SERS signal of MBC and the subsequent results were obtained only with this nanoparticle. The interaction between MBC and surface of these nanoparticles was carried out by SERS spectra of MBC at several pHs. Here, theoretical calculations were used for assignment of vibrational modes of the MBC and thus help in the interpretation of experimental results. According to experimental and theoretical results neutrally (MBC0 ) and deprotonated (MBC- ) species have affinity for the silver surface and then show SERS signal. Finally, the MBC limit of detection was determined via SERS using a procedure which ensures the reproducibility of the measurements, since SERS technique is not, yet, a routine analytical technique.
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Palavras-chave
Fungicida, Filmes de Langmuir, SERS