A Novel Impedance Platform Based on Printed Polymer Electrodes for Automated Virus Neutralization Assays

Abstract

Cell-based neutralization assays are of central importance for the development of new vaccine candidates as well as quality assurance of already approved vaccines. Suppression of viral infection by neutralizing antibodies present in serum of vaccinated individuals serves as an indicator for efficacy of a vaccine. Established readouts used to date are hardly automated, provide no time resolution and require expensive reagents. These shortcomings are limiting factors in vaccine development. In contrast, when virus-compatible host cells are grown on multi-electrode arrays, the cellular infection state and the associated cell response are assessable by impedance measurements. Unlike endpoint assays, the host cell response is followed continuously in real time, label-free and noninvasively. Here, a sensor platform comprising hardware, software and disposable electrode arrays is described suitable for fully automated cell-based neutralization assays tailored for high throughput screening campaigns. To develop cost-effective, disposable electrode arrays for impedance measurements, we screen printed film electrodes made from conducting polymers on the bottom of multi-well plates. The polymer electrodes were characterized for their host cell compatibility and readout performance in comparison to established gold-film electrodes. Hard- and software were tailored for robust and routine use in virological assays. Virus titration, virus neutralization as well as antiviral drug (Efavirenz) intervention studies were conducted using vesicular stomatitis virus (VSV) pseudotypes or the Env HIV-1 infectious molecular clones Ce1176 and X1632 as viral model systems. The assays showed very similar analytical performance in terms of titration curves and dose–response relationships for polymer electrodes compared to commercial gold-film electrode arrays and reporter-based endpoint assays. Considering their technical advantages over established assays, impedance readings based on low-cost polymer electrode arrays may become an attractive alternative to conventional assays using luminescent or colorimetric readouts.