Nanowire
A nanowire is a nanostructure that has a thickness or diameter constrained to tens of nanometers or less and an unconstrained length in which quantum mechanical effects are important. Many different types of nanowires exist, including metallic (e.g., Ni, Pt, Au), semi conducting (e.g., Si, InP, GaN, etc.), and insulating (e.g., SiO2, TiO2). Molecular nanowires are composed of repeating molecular units either organic (e.g. DNA) or inorganic (e.g. Mo6S9-xIx). The nanowires could be used to link tiny components into extremely small circuits created out of chemical compounds.
Nanowires probe
Researchers at the Lawrence Berkeley National Lab in the US have made their device by attaching a tin oxide nanowire waveguide to the tapered end of an optical fibre. Light traveling along the fibre can be effectively coupled into the nanowire. This robust nanowire probe can be used as a non-invasive endoscope to image the inside of living cells. It can also be used to transport tiny "cargo", in medical applications to deliver genes, proteins and therapeutic drugs into biological cells.
Principle
According to the researchers by combining the advantages of nanowire waveguides and fibre-optic fluorescence imaging, we can manipulate light at the nanoscale inside living cells for studying biological processes within single living cells with high spatial and temporal resolution. Advances in nanophotonics have made it possible to overcome the diffraction limitations of current techniques and the fluorescence sensing techniques use sub-micron tapered optical fibres which can image sub-cellular components only by rupturing cell membranes.
But the developed device can provide high-resolution optical images of the inside of a single living cell when the tip is inserted into the cell and light is passed. The nanowire can be re-used many times because it is flexible and can be repeatedly bent and buckled. The light emitted from the endoscope was closely confined to the nanowire tip and can provide highly directional and localized illumination.
The endoscope is also non-invasive because it can be safely inserted into a cell cytoplasm without causing any damage to the cell. The blue light emitted by the nanoprobe is not dangerous as the volume illuminated is very small in the order of picolitres.
Applications
Although single-cell delivery systems based on carbon and boron nitride nanotubes already exist, such devices have relatively long delivery times of up to 30 minutes. The new nanowire probes are much quicker and release quantum dot cargo into the target cells in just one minute.
This nanowire endoscope can be used to do point-delivery of genes, proteins, therapeutic drugs or other cargo with high spatial resolution and may also be used to electrically or optically stimulate a living cell with a simultaneous high-solution optical signal being output from the same nanowire probe.

For more about the research of Peidong Yang and his group, visit the Website at http://www.cchem.berkeley.edu/pdygrp/main.html