research review
CdSe QDs target neural activation A new technique holds promise for better understanding of brain disorders.
Researchers at the University of Washington (UW) have developed a new way to stimulate neurons in the brain using quantum dots. Being able to switch neurons on and off and monitor how they communicate with one another is crucial for understanding and treating a host of brain disorders.
Recently a team of Stanford University researchers altered mammalian nerve cells to carry light-sensitive proteins from single- celled algae, allowing the scientists to rapidly flip the cells on and off, just with flashes of light. The problem with this process, however, is that the light- controlled cells must be genetically altered
to perform this trick. An alternative, says the UW team, led by electrical engineer Lih Y. Lin and biophysicist Fred Rieke, is to use CdSe quantum dots—tiny semiconductor particles, just a few billionths of a metre across, that confine electrons within three spatial dimensions.
When these otherwise trapped electrons are excited by electricity, they emit light, but at very precise wavelengths, determined both by the size of the quantum dot and the material from which it is made. Because of this, quantum dots are being explored for a variety of applications.
Lin, Rieke and colleagues have extended the use of quantum dots to the targeted activation of cells. In laboratory experiments, the researchers cultured cells on quantum dot films, so that the cell membranes were in close proximity to the quantum-dot coated surfaces.
The electrical behaviour of individual cells was then measured as the cells were exposed to flashes of light of various wavelengths; the light excited electrons within the quantum dots, generating electrical fields that triggered spiking in the cells.
The experiments, says Lin, show that “it is possible to excite neurons and other cells and control their activities remotely using light. This non-invasive method can provide flexibility in probing and controlling cells at different locations while minimising undesirable effects.”
So far, the technique has only been applied to cells cultured outside the body; to gain insight into disease processes and be clinically useful, it would need to be performed within living tissue. To do so, Lin says, “we need to modify the surface of the quantum dots so that they can target specific cells when injected into live animals.”
Further details of this work have been published in the paper, “Remote switching of cellular activity and cell signalling using light in conjunction with quantum dots,” by K. Lugo et al, Biomedical Optics Express, Vol. 3, Issue 3, pp. 447-454 (2012).
http://dx.doi.org/ 10.1364/BOE.3.000447 52
www.compoundsemiconductor.net March 2012
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