Desenvolvimento de magneto-imunoensaios para detecção de anticorpos em amostras de plasma e aplicação no diagnóstico da COVID-19 e da COVID longa

Abstract

In 2019, the virus known as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) caused a global surprise due to its high transmissibility, leading the World Health Organization (WHO) to declare the COVID-19 pandemic. The diagnosis of the disease is predominantly performed by RT-PCR and rapid tests, both of which have certain limitations. Antibody detection is an effective strategy for diagnosis and prognosis, contributing to the reduction of the transmission rate. This study proposes a diagnostic method to detect IgM antibodies, indicative of recent or active infection, and IgG antibodies for post-vaccination monitoring. The proposed immunoassay involves using magnetic particles (MPs) functionalized and modified with the Spike (S) and Nucleocapsid (N) proteins of SARS-CoV-2, which recognize antibodies in the plasma sample. The developed method employed a disposable electrochemical microfluidic device containing eight screen-printed carbon electrodes, allowing for eight simultaneous analyses. The method achieved an ultra-low detection limit of 7.13 ag mL-1 for anti-S IgG antibodies, 55.4 ag mL-1 for anti-S IgM, and 51 ag mL-1 for anti-N IgG. The method was tested on plasma samples from healthy individuals and patients diagnosed with COVID-19 by RT-PCR. The validation of the magneto-immunoassay, evaluated by ROC curve and scatter plot, demonstrated high specificity and sensitivity. Thus, the proposed electrochemical immunoassay proved to be highly specific and sensitive for the detection of IgG and IgM antibodies, making it a useful and rapid tool for the diagnosis of COVID-19 and long COVID.