Quantificação do fator de crescimento semelhante a insulina I (IGF-I) em plasma bovino por ELISA
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Data
2016-02-01
Autores
Maioli, Marcos Antonio [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Esse estudo teve como objetivo a padronização de um ensaio imunoenzimático (ELISA) para a determinação das concentrações plasmáticas de IGF-I total, utilizando o sistema de amplificação biotina-estreptavidina peroxidase em um ensaio competitivo. O IGF-I foi extraído da IGFBP, utilizando o tampão glicina acidificado seguido de neutralização do pH com hidróxido de sódio. As microplacas foram sensibilizadas com anti IgG de coelho, e as dosagens realizadas utilizando duas abordagens, um método sem competição (incubação prévia das amostras com o anticorpo anti-h-IGF-I) e outro com competição (adição simultânea de IGF-I biotilinado e amostra). Os melhores resultados foram obtidos utilizando o método competitivo, com a sensibilização da placa com 0,25 μg/poço de IgG anti-coelho, o anticorpo específico na diluição 1:250.000 e 0,06 ng/poço de IGF-I biotinilado. O ensaio in house apresentou, um limite inferior de detecção de 50 ng/mL, uma correlação de 0.945 entre doses quando comparado à uma metodologia comercial. Além disso, após 33 ensaios (1114 amostras) a metodologia apresentou uma boa precisão, com coeficientes de variação inter-ensaio de 12,94% (345,8 ng/mL) para os controles alto e 20,71% (131,6 ng/mL) para o baixo. Dessa forma, conclui-se que a metodologia imunoenzimática para quantificação de IGF-I total utilizando o sistema de amplificação biotina-estreptavidina peroxidase em um ensaio competitivo está estabelecida e apresenta-se como uma ferramenta útil para estudos que visem o monitoramento das concentrações de IGF-I.
This study aimed to standardize an enzyme-linked immunosorbent assay (ELISA) to determine plasma concentrations of total IGF-I using the amplification biotin-streptavidin peroxidase system in a competitive assay. The IGF-I was extracted from IGFBPs using the acidified glycine buffer followed by the pH neutralization with sodium hydroxide. The microplates were coated with anti-rabbit IgG, thereafter the measurements were carried out using two approaches, one without competition (prior incubation of samples with the anti-hIGF-I antibody) and another with competition (simultaneous addition of IGF-I and biotinylated sample). The best results were obtained using the competitive method, with the following combination of reagents: microplates were coated with 0.25 µg/well of anti-rabbit IgG, the specific antibody at a dilution of 1:250.000 and 0.06 ng/well of biotinylated IGF-I. The in house methodology showed sensitivity of detection limit of 50 ng/ml, a correlation between doses of 0.945 when compared to a commercial method. In addition, after 33 assays (quantification of 1114 samples) the proposed methodology presented a good precision, with interassay variation coefficients of 12.94% and 20.71% for the high and low controls, respectively. Finally, we concluded that ELISA method for the quantification of total IGF-I using the system biotin-streptavidin-peroxidase amplification in a competitive assay is established and is presented as a useful tool for studies aimed at monitoring the IGF-I concentrations.
This study aimed to standardize an enzyme-linked immunosorbent assay (ELISA) to determine plasma concentrations of total IGF-I using the amplification biotin-streptavidin peroxidase system in a competitive assay. The IGF-I was extracted from IGFBPs using the acidified glycine buffer followed by the pH neutralization with sodium hydroxide. The microplates were coated with anti-rabbit IgG, thereafter the measurements were carried out using two approaches, one without competition (prior incubation of samples with the anti-hIGF-I antibody) and another with competition (simultaneous addition of IGF-I and biotinylated sample). The best results were obtained using the competitive method, with the following combination of reagents: microplates were coated with 0.25 µg/well of anti-rabbit IgG, the specific antibody at a dilution of 1:250.000 and 0.06 ng/well of biotinylated IGF-I. The in house methodology showed sensitivity of detection limit of 50 ng/ml, a correlation between doses of 0.945 when compared to a commercial method. In addition, after 33 assays (quantification of 1114 samples) the proposed methodology presented a good precision, with interassay variation coefficients of 12.94% and 20.71% for the high and low controls, respectively. Finally, we concluded that ELISA method for the quantification of total IGF-I using the system biotin-streptavidin-peroxidase amplification in a competitive assay is established and is presented as a useful tool for studies aimed at monitoring the IGF-I concentrations.
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Método, Hormônio, Validação, Imunoensaio, Methods, Hormone, Validation, Immunoassay