Researchers at Purdue have developed a method of monitoring both metallic and semiconducting nanotubes within cells and blood plasma without using any kind of marking or dying labels. The method, called transient absorption, uses two near-infrared lasers to energize and detect the shining nanotubes.
The method should be useful for monitoring the effects of nano-based treatments during laboratory and clinical development.
The nanotubes have a diameter of about 1 nanometer, or roughly the length of 10 hydrogen atoms strung together, making them far too small to be seen with a conventional light microscope. One challenge in using the transient absorption imaging system for living cells was to eliminate the interference caused by the background glow of red blood cells, which is brighter than the nanotubes.
The researchers solved this problem by separating the signals from red blood cells and nanotubes in two separate “channels.” Light from the red blood cells is slightly delayed compared to light emitted by the nanotubes. The two types of signals are “phase separated” by restricting them to different channels based on this delay.
Researchers used the technique to see nanotubes circulating in the blood vessels of mice earlobes.
The researchers also have taken images of nanotubes in the liver and other organs to study their distribution in mice, and they are using the imaging technique to study other nanomaterials such as graphene.
Abstract in Nature Nanotechnology: Label-free imaging of semiconducting and metallic carbon nanotubes in cells and mice using transient absorption microscopy