Infection-on-a-Chip—Recreating the Biological Steps of Viral Infection on a Bioelectronic Platform to Profile Viral Variants of Concern

Viral infection begins when a virus particle breeches the host plasma membrane and successfully delivers its genome into that cell. Though these processes must occur for every viral pathogen that infects a host cell, the entry route can vary markedly depending on the viral pathogen, the host cell type, and the local microenvironmental conditions. Virus particles are responsive to their environment and use cues from it to adapt and successfully time the entry process into the host cell. Thus, it is a continual evolutionary battle between the host and the virus to thwart infection and disease. The best-known example of our time is SARS Coronavirus-2 (SARS-CoV-2), where viral mutation rates frequently outpace the development of technologies used to detect and identify emerging variants of concern (VOC). Given the continual emergence of VOC, there is a critical need to develop platforms that can identify the presence of a virus and readily identify its propensity for infection. We present an electronic biomembrane sensing platform that recreates the multifaceted and sequential biological cues that give rise to distinct SARS-CoV-2 virus host cell entry pathways and reports the progression of entry steps of these pathways as electrical signals. Within these electrical signals, two necessary entry processes mediated by the viral Spike protein, virus binding and membrane fusion, can be distinguished.<br/>Most infection 'on-chip' devices employ live cells, miniaturized cell cultures or organoid-like structures, which essentially replicate established virology assays in a smaller format. While these platforms have certain advantages, they do not significantly expedite the assay process, as cells still necessitate time to grow and respond, and typically rely on the delivery of an encapsulated reporter gene, making these systems somewhat cumbersome to operate. Consequently, they are too slow (taking days) for promptly evaluating emerging VOC and recommending timely action. Additionally, cell-based devices are not conducive to studying entry functions at the scale of the plasma membrane, where cell entry initiates. Our device, in contrast, focuses on the activities occurring at a single-cell membrane interface, which is a different “scale” of infection (the onset of entry). Our device has no living cells and can be performed without necessitating reporter-gene encapsulation. Unique to this work, our assay design faithfully replicates the biological cues governing virus response and the selection of distinct entry pathways, mirroring natural occurrences. We demonstrate that our device has this resolution for the fusion function, a critical step in infection that leads to the delivery of the viral genome across the host cell membrane barrier. Significantly, we have demonstrated functional assessment and used it to differentiate SARS-CoV-2 VOC (Wuhan-Hu-1, Omicron BA.1, and BA.4) – a milestone, to our knowledge, as it marks the first application of a cell-free, virus-free, and label-free system for this purpose. Remarkably, we find that these closely related VOC exhibit distinct fusion signatures that correlate with trends reported in cell-based infectivity assays, allowing us to report quantitative differences in fusion characteristics among them that inform their infectivity potentials. With this design and the electrical approach to interpreting responses, we can swiftly (in tens of minutes) assess and differentiate the functional traits of VOC. This speed is pivotal for determining societal responses as VOC continue to emerge.