Preparação, caracterização e aplicação da plataforma baseada em óxido de grafeno reduzido e polifácido 3-hidroxifenilacético) para diagnóstico do vírus da dengue

Abstract

Dengue is an acute infectious disease transmitted by the sting of the infected mosquito Aedes aegypti. It is considered one of the main public health problem worldwide. The evolution of dengue is fast and the symptoms are unspecific and can be mistaken with other infectious illness. In this case, clinical diagnosis is difficult, making necessary a medical laboratory. Biosensors are an interesting alternative due to the possibility of producing low-cost, sensitive, miniaturized and simple devices for decentralized diagnosis. This work was explored a platform based on reduced graphene oxide (OG- r) and poly (3-hydroxyphenylacetic acid), for diagnosis of dengue virus type 3 by differential pulse voltammetry. Graphene oxide (OG) and OG-r were obtained from the oxidation of graphite by the Hummers method and chemical reduction with hydrazine, respectively. The chemical modifications of the materials were confirmed by Infrared Spectroscopy. Images of atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed that the OG has a thickness of 1.27 nm and that the OG- r has a wrinkled structure. Cyclic voltammetry (VC) and electrochemical impedance spectroscopy (EIS) showed that the OG-r presents electrochemical properties superior to the OG and the gold electrode without modification. The electrode modified with OG- r provides the formation of a polymeric nanocomposite with superior electrochemical properties, in comparison to the electrode without modification. The platform presented good electrochemical stability after a storage time of 120 days. In addition, it exhibited high efficiency for immobilization and oligonucleotide hybridization by both direct electrochemical oxidation of guanine and indirect oxidation using the electroactive intercalator (ethidium bromide). These results showed that the platform can be applied to the development of genosensors. The mimetic peptide was immobilized covalently on the platform and this process was confirmed by Cv, EIE and AFM. The biosensor recognized IgM antibodies present in serum samples from patients infected with dengue virus at high dilutions (1:1000 and 1:10000), evidencing the high sensitivity of the system. In addition, it was able to qualitatively discriminate serum samples from dengue patients from healthy controls by different detection techniques. The biosensor remained functional after 40 days of storage, maintaining 90.1% of its initial capacity. Thus, due to the high sensitivity of the system and the use of real samples, this biosensor becomes promising for specific clinical diagnoses, can be used in the critical phase of the disease and in real time.