Organic Electrochemical Transistor (OECT) for Real Time, Electrical quantification of SARS CoV 2 neutralizing antibodies

Since the outbreak of the Covid-19 pandemic, researchers have refocused their efforts on viral neutralization assays and neutralizing antibody quantifications for vaccination pre-clinical studies and long-term efficacy. Nowadays, the gold standard to assess antibody titer is the plaque reduction neutralization test (PRNT), an end-point assay which evaluates the highest serum antibody dilution that neutralizes viral replication, by inspecting the cytopathic effect (CPE) induced on cell cultures. Here, we have designed and implemented an accurate real-time technique for quantitative serum neutralization assay, employing poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (Pedot:Pss)-based Organic Electrochemical Transistors (OECT) for the automated evaluation of the CPE induced by Sars-Cov-2 on Vero E6 cells, using a customized prototype for in-vitro measurements inside the incubator. Transistors seeded with viral proliferating cell cultures reported faster time responses during the experiment, caused by the disruption of the cell layer grown onto the active area of our devices. On the contrary, when neutralizing antibodies stopped the viral infection, OECT data superimposed with standard control growth. The device reliability was proved using optical imaging (cell layer evaluation), Quantitative Reverse Transcription Polymerase Chain Reaction (investigating viral proliferation) and standard PRNT assays, obtaining robust matching. We noted that OECTs allowed to extract the neutralizing test outcome in less than 48h, earlier than the usual 72-hour required for PRNT screening, without the need of cell staining or fixing at the end of the experiment. Furthermore, the devices can be revitalized and re-used for up to three consecutive experiments, reducing plastic waste and their effective cost/experiment Our low-cost and scalable devices have the potential to speed-up large-scale viral neutralization screening without the need for cancerous staining or highly specialized operators. Finally, owing to the versatile nature of the proposed assay and the possibility to optimize the device geometry/dimensions to match the cell lines under test, the technology could be easily transferred to assess neutralizing antibody response towards different viruses in their permissive cell substrates.