Advancement in SARS-CoV-2 diagnosis: A new and stable electrochemical biosensor for genomic RNA detection.

Coronavirus disease (COVID-19) is caused by infection with the SARS-CoV-2 virus, having already caused more than seven million deaths worldwide. Conventional techniques for SARS-CoV-2 detection have limitations, as high cost, low specificity, and longer analysis time, among others. Biosensors emerge as a necessary alternative to overcome the difficulties of current diagnostics. This paper reports a sensor platform where silver-doped zinc oxide nanomaterial (Ag:ZnONp) was used onto carbon screen-printed electrode and ethidium bromide as indicator for development of a specific electrochemical genosensor for COVID-19. This genosensor demonstrated good linearity between the concentrations of 5.62 × 104-5.62 copies/mL and a detection limit of 5 copies/mL with gRNA in patient's samples, with a response time within 30 min. Molecular modeling and morphological analysis are in agreement with obtained electrochemical results. Additional techniques such as AFM, SEM, and EIS were conducted to characterize the morphological and electrochemical properties of the biosensor's surface. The biosensor was also capable of detecting the target presence in spiked samples and demonstrated a stability of 60 days, higher than other similar biosensors for SARS-CoV-2.

Fentogram electrochemical detection of HIV RNA based on graphene quantum dots and gold nanoparticles.

This work reports the construction of an HIV-specific genosensor through the modification of carbon screen-printed electrodes (CSPE) with graphene quantum dots decorated with L-cysteine and gold nanoparticles (cys-GQDs/AuNps). Cys-GQDs were characterized by FT-IR and UV-vis spectra and electronic properties of the modified electrodes were evaluated by cyclic voltammetry and electrochemical impedance spectroscopy. The modification of the electrode surface with cys-GQDs and AuNps increased the electrochemical performance of the electrode, improving the electron transfer of the anionic redox probe [Fe(CN)6]3-/4- on the electrochemical platform. When compared to the bare surface, the modified electrode showed a 1.7 times increase in effective electrode area and a 29 times decrease in charge transfer resistance. The genosensor response was performed by differential pulse voltammetry, monitoring the current response of the anionic redox probe, confirmed with real genomic RNA samples, making it possible to detect 1 fg/mL. In addition, the genosensor maintained its response for 60 days at room temperature. This new genosensor platform for early detection of HIV, based on the modification of the electrode surface with cys-GQDs and AuNps, discriminates between HIV-negative and positive samples, showing a low detection limit, as well as good specificity and stability, which are relevant properties for commercial application of biosensors.