RESUMO
The aim of this study was to develop an assay to analyze the serum profile of Mannose-binding lectin (MBL) through a simple and "in-house" method (called "dot-N-man"). Furthermore, the study attempted to associate molecular masses of MBL to the profile of MBL gene polymorphisms in patients with hepatitis C. Heterogeneity in molecular masses of MBL is due to the impairment of oligomers formation, which is linked to genetic polymorphisms in the MBL gene. Individuals with AA genotype (wild-type) produce high-molecular-mass proteins, whereas AO and OO individuals produce intermediate and low-molecular-mass proteins, respectively. Sera of thirty patients carrying the hepatitis C virus (HCV) were investigated using MBL binding assay with mannan-coated nitrocellulose (dot-N-man). Purified MBL was evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting. Dot-N-Man assay yielded MBL with molecular masses ranging between 55 and 320â¯kDa, comparable to low and high molecular mass forms of MBL. Nonreducing SDS-PAGE showed high molecular mass bands in all AA individuals while bands of 270 and 205â¯kDa were observed in sera for a number of patients with AO and OO genotypes, respectively. Immunoblotting confirmed the MBL samples obtained from the dot-N-man. These results provide new insights to understand the MBL molecular forms profile in patients infected with HCV- which could be useful in future investigations on the influence of the MBL structure/genotype on both the progression of infection and the response to hepatitis C therapy.
Assuntos
Hepacivirus/imunologia , Hepatite C , Immunoblotting/métodos , Lectina de Ligação a Manose , Polimorfismo Genético , Colódio/química , Feminino , Hepatite C/genética , Hepatite C/imunologia , Humanos , Masculino , Mananas/química , Lectina de Ligação a Manose/genética , Lectina de Ligação a Manose/imunologiaRESUMO
Label-free immunosensor based on amine-functionalized carbon nanotubes screen-printed electrode is described for detection of the cardiac troponin T, an important marker of acute myocardial infarction. The disposable sensor was fabricated by tightly squeezing an adhesive carbon ink containing carbon nanotubes onto a polyethylene terephthalate substrate forming a thin film. The use of carbon nanotubes increased the reproducibility and stability of the sensor, and the amine groups permitted nonrandom immobilization of antibodies against cardiac troponin T. Amperometric responses were obtained by differential pulse voltammetry in presence of a ferrocyanide/ferricyanide redox probe after troponin T incubation. The calibration curve indicated a linear response of troponin T between 0.0025 ng mL(-1) and 0.5 ng mL(-1), with a good correlation coefficient (r=0.995; p<0.0001, n=7). The limit of detection (0.0035 ng mL(-1) cardiac troponin T) was lower than any previously described by immunosensors and was comparable with conventional analytical methods. The high reproducibility and clinical range obtained using this immunosensor support its utility as a potential tool for point-of-care acute myocardial infarction diagnostic testing.
Assuntos
Técnicas Biossensoriais , Infarto do Miocárdio/sangue , Nanotubos de Carbono/química , Polietilenotereftalatos/química , Troponina T/sangue , Animais , Anticorpos Imobilizados/química , Anticorpos Imobilizados/isolamento & purificação , Calibragem , Técnicas Eletroquímicas , Eletrodos , Ferricianetos/química , Ferrocianetos/química , Humanos , Limite de Detecção , Camundongos , Infarto do Miocárdio/diagnóstico , Infarto do Miocárdio/patologia , Miocárdio/química , Miocárdio/metabolismo , Miocárdio/patologia , Impressão , Reprodutibilidade dos Testes , Troponina T/isolamento & purificaçãoRESUMO
Screen-printed electrodes (SPE) have been widely used in the design of disposable sensors bringing advances in the use of electrochemical immunosensors for in field-clinical analysis. In this work, streptavidin polystyrene microspheres were incorporated to the electrode surface of SPEs in order to increase the analytical response of the cardiac troponin T (cTnT), a specific biomarker for the acute myocardial infarction diagnosis. The precise calculation of the stoichiometric streptavidin-biotin ratio [1:4] allowed the increase of sensitivity and stability of the immunosensor response to the cTnT analyte. The surface of the immunosensor was characterized by scanning electron microscopy and cyclic voltammetry. It was observed that the use of streptavidin microspheres significantly increased the analytical sensitivity of the electrode in 8.5 times, showing a curve with a linear response range between 0.1 and 10 ngmL(-1) of cTnT and a detection limit of 0.2 ngmL(-1). The proposed SPE showed ease preparation and high sensitivity allowing the detection of cTnT in the range of clinical levels. The new device coupled with a portable electrochemical analyzer shows great promise for point-of-care quantitative testing of necrosis cardiac proteins.