Label-free electrochemical DNA biosensor for zika virus identification

Seventy years after its discovery, the zika virus emerged in Brazil and spread rapidly throughout the Americas, bringing unusual complications such as microcephaly. The World Health Organization classifies zika as the most harmful viral disease today and considers the development of new diagnostic methods for zika and related diseases, such as dengue, urgent. Although there are tests to identify both infections, current diagnostic methods are slow, nonspecific, and costly. This study describes an impedimetric electrochemical DNA biosensor for label-free detection of zika virus. Disposable electrodes were fabricated by thermal evaporation on polyethylene terephthalate substrates covered with a nanometric gold layer manufactured in three-contact configurations. The disposable, evaporated electrodes were morphologically characterized by atomic force microscopy and scanning electron microscopy. The electrode surface was characterized by electroanalytical techniques. Genetic sequences of primers and complementary capture probes were designed based on analysis of the zika and dengue virus genomes. The biosensor used a three-contact electrode to identify DNA sequences in a drop of sample, and for detection of zika virus sequences, it allowed for direct reading of the hybridization event without labeling on disposable electrodes and with a 1.5 h response time. In this system, impedance measurements indicated a limit of detection of 25.0 ± 1.7 nM. The developed biosensors showed selectivity for zika in the synthetic DNA assays, and therefore, are promising for clinical analysis.