Lens-Free Holographic Imaging, AI For Rapid Quantification Of Viral Plaque

The gold-standard technique for determining the quantity of replication-competent lytic virions, the plaque assay, necessitates staining and typically takes longer than 48 hours to complete. Researchers have demonstrated how deep learning and lens-free holographic imaging may be used to speed up and automate the test. The small imaging device measures the amount of infected tissue and the number of plaque-forming units while simultaneously capturing phase information label-free at a rate of about 0.32 gigapixels per hour per well. It also covers an area of about 30 × 30 mm2 and has a 10-fold wider dynamic range of virus concentration than conventional assays.

In less than 20 hours, the automated plaque test for the vesicular stomatitis virus recognized plaque-forming units at rates greater than 90% with 100% specificity. It also detected the initial cell-lysing events from viral replication as early as 5 hours after incubation. Additionally, it decreased the incubation times of the encephalomyocarditis virus by about 20 h and the herpes simplex virus type 1 by about 48 h. The stain-free test should suit clinical diagnostics, vaccine development, and virology research.

Researchers present a small, label-free, cost-effective live plaque assay that can automatically deliver a quantitative plaque-forming unit (PFU) readout significantly faster than conventional viral-plaque assays without staining. To image the spatiotemporal properties of the target PFUs during their incubation, they constructed a small lens-free holographic imaging prototype; the total cost of the parts for this imaging system, excluding a typical laptop computer, is less than US$880.

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