Síntese e caracterização de materiais zeolíticos e sua aplicação como agentes de contraste para exames de imagem por ressonância magnética
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2020-12-10
Autores
Contro, Janine
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Universidade Estadual Paulista (Unesp)
Resumo
O objetivo do presente trabalho é a síntese e caracterização de materiais zeolíticos com potencial de serem aplicados como agentes de contraste em exames de Imagem por Ressonância Magnética (MRI). Os materiais estudados foram a zeólita Faujasita (FAU), Zeólita A (LTA), zeólita Beta (BEA), Zeólita ZSM-5 (MFI) e zeólita Mordenita (MOR), estes materiais foram trocados ionicamente com metais lantanídeos, como o gadolínio Gd3+. Os materiais foram caracterizados por difração de raios-x (DRX) e então foram submetidos a estudos relaxométricos, nos quais foram calculados os tempos de relaxação T1 e T2 utilizando técnicas como inverse recovery e saturation recovery. Estes estudos foram realizados na Universidade do Texas – Health Science Center em Houston sob a orientação do Prof. Dr. Ponnada A. Narayana. Os estudos in vivo também foram realizados na Universidade do Texas, para isso os potenciais novos agentes de contraste foram administrados a ratos Sprague Dawley, que foram então submetidos ao exame de Imagem por Ressonância Magnética de seu cérebro e abdômen. Estudos comparativos de desempenho das zeólitas e dos agentes de contraste comerciais foram realizados utilizando o Gd-DOTA (ácido gadotérico – Dotarem). A zeólita Faujasita apresentou valores de relaxividade muito maiores que o Dotarem chegando a apresentar valores de relaxividade 10x maiores. Nos testes preliminares as imagens utilizando a mFAU-1 apresentaram muito mais detalhes que as imagens utilizando o Dotarem. Porém no estudo comparativo o mesmo não foi observado, provavelmente por causa da sobreposição do efeito de T2 sobre T1 nas concentrações utilizadas. Os agentes de contraste a base de zeólitas se mantém mais tempo na corrente sanguínea possibilitando exames dependentes de contraste mais longos. Mas ainda assim, em dois dias, como é o caso do Dotarem, todo o contraste já foi expelido pelo corpo do animal. Os resultados obtidos até o momento são muito iniciais para o desenvolvimento de um novo agente de contraste, porém se mostram promissores. Possivelmente um ajuste na concentração de contraste a ser administrada ao objeto de estudo pode melhorar o contraste nas imagens obtidas por Ressonância Magnética.
The objective of the present work is the synthesis and characterization of zeolitic materials with potential of being applied as contrast agents for magnetic resonance imaging (MRI). The materials are the zeolites Faujasite (FAU), zeolites A (LTA), zeolite Beta (BEA), zeolite ZSM-5 (MFI) and zeolite Mordenite (MOR) ion exchanged with lanthanides metals, such as Gadolinium Gd3+. The zeolites ion exchanged with Gadolinium were characterized by x-ray powder diffraction (XRD). Relaxometry studies (relaxation times T1 and T2) of the zeolitic materials were performed using the inverse recovery technique and saturation recovery and their variations. The relaxometry studies were performed in collaboration with Prof. Dr. Ponnada A. Narayana from The University of Texas – Health Science Center at Houston. In vivo studies were also performed at The University of Texas injecting the potential new contrast agents in Sprague Dawley rats and scanning their brain and abdomen. Comparative performance studies of the zeolites and commercial contrast agents were done using the Gd-DOTA (gadoteric acid – Dotarem). The Faujasite zeolite showed relaxivity results much higher than the Dotarem, some materials had the relaxivity 10x higher than the Dotarem. In the preliminary tests, the images using the mFAU-1 as contrast showed more details than tha images using Dotarem as contrast agent. However on the comparative studies the result was not the same, it may happen because of the sobreposition of the effect of T2 over T1 at these concentrations. The contrast agents based on zeolites maintained in the blood stream for longer periods of time than Dotarem, which makes possible longer exams that rely on the contrast agent. On the other hand, in two days, such as the Dotarem, the clearance is complete, in other words, all contrast is cleared from the animal body. The results obtained up until now are just the beginning of a long study to the development of a new contrast, yet they are promising. Perhaps the adjustment of the concentration of contrast agent to be administered can improve the contrast of the images obtained by MRI.
The objective of the present work is the synthesis and characterization of zeolitic materials with potential of being applied as contrast agents for magnetic resonance imaging (MRI). The materials are the zeolites Faujasite (FAU), zeolites A (LTA), zeolite Beta (BEA), zeolite ZSM-5 (MFI) and zeolite Mordenite (MOR) ion exchanged with lanthanides metals, such as Gadolinium Gd3+. The zeolites ion exchanged with Gadolinium were characterized by x-ray powder diffraction (XRD). Relaxometry studies (relaxation times T1 and T2) of the zeolitic materials were performed using the inverse recovery technique and saturation recovery and their variations. The relaxometry studies were performed in collaboration with Prof. Dr. Ponnada A. Narayana from The University of Texas – Health Science Center at Houston. In vivo studies were also performed at The University of Texas injecting the potential new contrast agents in Sprague Dawley rats and scanning their brain and abdomen. Comparative performance studies of the zeolites and commercial contrast agents were done using the Gd-DOTA (gadoteric acid – Dotarem). The Faujasite zeolite showed relaxivity results much higher than the Dotarem, some materials had the relaxivity 10x higher than the Dotarem. In the preliminary tests, the images using the mFAU-1 as contrast showed more details than tha images using Dotarem as contrast agent. However on the comparative studies the result was not the same, it may happen because of the sobreposition of the effect of T2 over T1 at these concentrations. The contrast agents based on zeolites maintained in the blood stream for longer periods of time than Dotarem, which makes possible longer exams that rely on the contrast agent. On the other hand, in two days, such as the Dotarem, the clearance is complete, in other words, all contrast is cleared from the animal body. The results obtained up until now are just the beginning of a long study to the development of a new contrast, yet they are promising. Perhaps the adjustment of the concentration of contrast agent to be administered can improve the contrast of the images obtained by MRI.
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Palavras-chave
Zeólita, Imagem por ressonância magnética, Agente de contraste, Gadolínio, Zeolite, Magnetic resonance imaging, Contrast agent, Gadolinium