Recently, researchers from California have developed a totally new nanofiber device that is almost 100 times thinner than a human hair. Moreover, the nano-sized optical fiber is highly sensitive and is able to determine forces down to 160 femtonewtons that are ten trillion times smaller than a newton.
Thus, the researchers put the optical fibers in a solution with live Helicobacter pylori bacteria. And they discovered on the example of beating heart muscle cells from mice that the nano-sized optical fiber system allows detecting sound waves down to -30 decibels that are 1.000 times below than human ear can hear.
The nano-optical fiber is made from a highly thin fiber of tin dioxide, coated with a thin layer of polyethylene glycol and studded with gold nanoparticles. The principle of work includes placing the nano-optical fiber system into a solution of live cells, then the researchers send a light beam down the fiber and analyze the light signals it sends out.
While light goes down the optical fiber, it cooperates with the gold nanoparticles which diffuse the light as signals that is possible to see with a traditional microscope. Herewith, the more live-cells in which the optical fiber bundle placed, the more changes in the intensity of the light signals. And this signal intensity shows the level of force or sound that the fiber is getting from the surrounding cells.
Also, forces and sound waves from the live cells influence the gold nanoparticles, pushing the nanoparticles into the polymer layer that separates them from the optical fiber‘s surface. In this case, the researchers adjust the device so the intensity of the signals could correspond to various levels of force or sound waves.
The main option of the nano-sized optical fiber system is not only picking up the tiny forces and sounds but the nanomechanical probing of high resolution. Moreover, the polymer layer of the device can be adjusted. For example, for large forces measurement, a stiffer coating is ideal, a softer polymer such as a hydrogel is ideally fit for increased sensitivity.
According to the researchers, the main advantage of the optical nanofiber is that it is about ten times more sensitive than an atomic force microscope. Also, the one more difference is the compact size, because the nano-optical fiber is only several hundred nanometers in diameter.
The researchers confirm that their device is a compact AFM with the sensitivity of an optical tweezer. The field of the device future applications include detecting the presence and activity of a single bacterium; monitoring bonds forming and breaking; sensing changes in a cell’s mechanical behavior that might signal it becoming cancerous or being attacked by a virus, or as a mini stethoscope to monitor cellular acoustics in vivo.
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