Portable reduced graphene oxide biosensor for detection of rabies virus in bats using nasopharyngeal swab samples

Rabies is a lethal zoonotic disease caused by rabies virus (RABV) that affects human health and the economy. RABV is transmitted mainly by bats in Brazil, and surveillance in remote areas is hampered by the difficulty of properly collecting samples during fieldwork and the diagnosis is performed in laboratory conditions. Here, we report a portable electrochemical biosensor based on nucleic acid interactions for RABV detection in nasopha-ryngeal swab samples. The working electrode of the biosensor is composed of reduced graphene oxide (rGO) thin-film immobilized with cDNA through pi-pi stacking to enhance virus detection and specificity. Sensor performance was determined using RNA, and swab samples from bats. RNA detection shows good selectivity, and quantification presents a highly linear calibration curve (R2 = 0.990) using a concentration range of 0.145-25.39 ng/mu L. A LOD of 0.104 ng/mu L was reached with a sensitivity of 0.321 mu A (ng/mu L)-1. RABV detection in naso-pharyngeal swab samples showed a good difference of positive sample from negative with a response time in seconds, ultra-fast detection compared to known techniques. Three biosensor groups were identified and named after physic-chemical surface characterization as: GO-1, GO-2, and rGO; with best performance for rGO group due to its sp2 hybridized network. Thus, we have successfully fabricated a promising electrochemical biosensor for fast in-situ detection of the RABV in swab samples, which can be expanded to other enveloped viruses that have RNA.