RESUMO
An electrochemical impedimetric immunosensor was developed for ultrasensitive determination of insulin-like growth factor-1 (IGF-1) based on immobilization of a specific monoclonal antibody on gold nanoparticles (GNPs) modified gold electrode. Self-assembly of colloidal gold nanoparticles on the gold electrode was conducted through the thiol groups of 1,6-hexanedithiol (HDT) monolayer as a cross linker. The redox reactions of [Fe(CN)(6)](4-)/[Fe(CN)(6)](3-) on the electrode surface was probed for studying the immobilization and determination processes, using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The interaction of antigen with grafted antibody recognition layer was carried out by soaking the modified electrode into antigen solution at 37°C for 3 h. The immunosensor showed linearity over 1.0-180.0 pg mL(-1) and the limit of detection was 0.15 pg mL(-1). The association constant between IGF-1 and immobilized antibody was calculated to be 9.17×10(11) M(-1). The proposed method is a useful tool for screening picogram amounts of IGF-1 in clinical laboratory as a diagnostic test.
Assuntos
Anticorpos Monoclonais/química , Técnicas Biossensoriais/instrumentação , Condutometria/instrumentação , Imunoensaio/instrumentação , Fator de Crescimento Insulin-Like I/análise , Nanoestruturas/química , Nanotecnologia/instrumentação , Anticorpos Monoclonais/imunologia , Eletrodos , Desenho de Equipamento , Análise de Falha de Equipamento , Ouro/química , Fator de Crescimento Insulin-Like I/química , Fator de Crescimento Insulin-Like I/imunologia , Nanoestruturas/ultraestruturaRESUMO
A selective and sensitive electrochemical impedance immunosensor based on immobilization of a specific monoclonal antibody on Au nanoparticles modified gold electrode was developed for determination of human growth hormone (hGH). Colloidal gold nanoparticles were coated on the gold electrode through the thiol groups of 1,6-hexanedithiol monolayer as a cross-linker. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were utilized for characterization of various coating layers. The relative charge transfer resistance of the hGH antibody/Au-colloid/1,6-hexanedithiol modified gold electrode changes linearly with the concentration of the human growth hormone (hGH) solutions. The limit of detection (LOD) was about 0.64 pgmL(-1) and the linear dynamic range was obtained from 3 to 100 pgmL(-1). The affinity of hGH toward immobilized antibody was calculated to be 4.1 x 10(11)M(-1) by the slope of the calibration curve. The proposed immunosensor might be used as an accurate and applicable tool for specific diagnosis and evaluation in paraclinical tests, replacing the routine invasive and hazardous radio-immunoassay (RIA) method.
Assuntos
Anticorpos Monoclonais/química , Técnicas Biossensoriais/instrumentação , Eletroquímica/instrumentação , Ouro/química , Hormônio do Crescimento Humano/análise , Nanopartículas/química , Nanotecnologia/instrumentação , Adsorção , Anticorpos Monoclonais/imunologia , Impedância Elétrica , Eletrodos , Desenho de Equipamento , Hormônio do Crescimento Humano/química , Hormônio do Crescimento Humano/imunologia , Imunoensaio/instrumentação , Nanopartículas/ultraestrutura , Análise Espectral/instrumentaçãoRESUMO
A new simple, selective, high sensitive and rapid method has been developed for spectrophotometric determination of ultra trace amounts of ruthenium based on its catalytic effect on the oxidation of pyronin B by periodate at lambdamax=555 nm. The described method is able to quantify ruthenium in the range of 0.1-100 ng ml-1 (r=0.9973), with a detection limit (S/N=3) of 0.036 ng ml-1. Under optimum conditions, this procedure has been successfully applied to determine the trace levels of ruthenium in the environmental and biological samples. The precision, expressed as relative standard deviation of three measurements, is better than 2.44%.
