Single virus sensing strikes gold
A hybrid whispering gallery mode/plasmonic biosensor can detect and size the smallest known virus, so that no viral particle can evade detection.
The ability to detect and characterize invasive biological particles, such as viruses, within the body is critical to providing early treatment for disease. Once infected, the body serves as an incubator, allowing viral loads to build and eventually overload the immune system, leading to the manifestation of disease. The best-case scenario is a short-lived illness, while the worst case can result in death. Due to the broad variability in outcomes (influenza infection, for example, can result in varying degrees of severity) it is important to administer treatment at the earliest stage possible, but this requires the ability to detect and characterize trace quantities of unknown viral load.
In order to detect bioparticles, we considered resonant systems, which have long proven sensitive to changes in their local environment. For instance, a guitar's tone alters when its strings are tightened, and bells sound different on cold days. However, these macroscopic phenomena are not suitable for bioparticle detection. Instead, we envisioned a micro-scale system. Born of an idea conceived for telecommunications applications,1 the whispering gallery mode (WGM) biosensor uses micro-optical structures, such as glass spheres, to confine light at specific frequencies (that is, resonances or whispering gallery modes). The light typically comes from a narrow-band tunable laser source operating in the near-IR spectral regime.