Imunossensor Impedimétrico Para Detecção De Igg Anti-Febre Maculosa Em Plasma Sanguíneo

Abstract

Introduction: Brazilian Spotted Fever (BSF) is a serious and medically important disease due to its rapid progression and high mortality rate. Treatment efficacy depends primarily on rapid diagnosis, currently performed through indirect immunofluorescence and PCR tests, which are costly and require extensive laboratory support. Objective: To develop a label-free impedimetric immunosensor based on IgY antibody immobilization for the detection of antiBrazilian Spotted Fever IgG in capybara blood plasma samples. Methods: To propose an alternative methodology, an impedimetric immunosensor (IM) was developed based on the immobilization of IgY antibodies specific for anti-Rickettsia rickettsii IgG using capybara (Hydrochoerus hydrochaeris) blood plasma for characterization, validation, and applications of a ready-made IM, esing a glassy carbon electrode as a surface, which was first activated by chronoamperometry for 10 minutes, with Cyclic Voltammetry and Electrochemical Impedance Spectroscopy readings between steps, followed by IgY immobilization by drop casting, blocking of the remaining surface with casein, and analysis of the purified samples and antibodies. Results and Discussion: The selectivity of the IM was observed when comparing the readings of capybara-reactive IgG (IgGcr) with nonreactive IgG (IgGnr). A reagent IgG calibration curve was obtained, from which the Limits of Detection (LOD) and Quantification (LOQ) of 1.3 ng.mL-1 and 4.4 ng.mL-1, respectively, were calculated. Accuracy tests showed that different concentrations of IgGcr presented a maximum deviation of 20.0%, with CI between 90.00% and 95.00%. Intermediate precision tests showed a relative standard deviation of 2.09% for researcher 1 and 2.61% for researcher 2, and the F test showed no significant difference between the recovery values found by the two analysts, since Fcal 1.56 < 5.05 and P-value 0.48 > 0.05. Conclusion: Therefore, an impedimetric immunosensor was developed to detect anti-BSF IgG in capybara blood plasma, which significantly contributes to improving diagnostic tests, reducing costs, and facilitating performance.