Viruses are tiny little things, but the tiniest of them are so small that only an electron microscope can measure them effectively. This is a major problem because electron microscopy can be a time consuming process, not to mention the expense.
Scientists at Polytechnic Institute of New York University (NYU-Poly) have developed a new method that has been used to set a record for the smallest virus detected in solution, the bacteriophage MS2 weighing in at only 6 attograms (6.0 × 10-18 grams). The team hopes that this technology will find its way into clinical point-of-care devices that could be used to rapidly detect just about any infectious disease.
More about the technology and what inspired it:
[L]ight from a tunable laser is guided down a fiber optic cable, where its intensity is measured by a detector on the far end. A small glass sphere is brought into contact with the fiber, diverting the light’s path and causing it to orbit within the sphere. This change is recorded as a resonant dip in the transmission through the fiber. When a viral particle makes contact with the sphere, it changes the sphere’s properties, resulting in a detectable shift in resonance frequency.
Arnold and his co-researchers achieved this by attaching gold nano-receptors to the resonant microsphere. These receptors are plasmonic, and thus enhance the electric field nearby, making even small disturbances easier to detect. Each gold “hot spot” is treated with specific molecules to which proteins or viruses are attracted and bind.
Arnold explained that the inspiration for this breakthrough technique came to him during a concert by violinist Itzhak Perlman: “I was watching Perlman play, and suddenly I wondered what would happen if a particle of dust landed on one of the strings. The frequency would change slightly, but the shift would be imperceptible. Then I wondered what if something sticky was on the string that would only respond to certain kinds of dust?”
The sensor itself, called a Whispering Gallery-Mode Biosensor, is unique to Arnold’s work. Its name derives from the famous Whispering Gallery in the dome of St. Paul’s Cathedral in London. Much the way its unique acoustics allow a whisper to be heard anywhere within the circular gallery, light traveling within the glass sphere of the biosensor orbits many times, ensuring nothing on the surface is missed.
Study abstract in Applied Physics Letters: Taking whispering gallery-mode single virus detection and sizing to the limit