Biological functionalization of single-wall carbon nanotubes
Date
2005
Authors
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Publisher
University of Delaware
Abstract
Specific interaction of carbon nanotubes (CNT) with biologically relevant materials is now compounding its scope of research in modern day science. Functionalization of carbon nanotubes with proteins is being widely studied since such an effect can promote their specific interaction with corresponding compounds or in the case of biological sciences, certain types of cells. Research on bio-chemical and biological sensors can find immense application of sensing elements such as carbon nanotubes due to their exceptional electronic and chemical properties. This work has studied the functionalization of carbon nanotubes with antibodies that are specific to the surface receptors in cancer cells. Antibody functionalized carbon nanotubes could potentially be used to identify and adhere to breast cancer cells and can be used for targeted detection and drug delivery upon further research. This research has covered a new aspect of studying this interaction through confocal microscopy which uses fluorescence to observe a specimen that is conjugated to a fluorescing molecule. Through confocal microscopy we were able to quantify the interaction between fluorescently labeled carbon nanotubes and antibodies. CNTs were conjugated to Dihexaoxacarbocyanine iodide, a substance which emits green light when excited at a wavelength of 488nm. The CNTs were observed alongside with antibodies conjugated to a fluorescent dye which responded to an excitation wavelength of 543 nm. The main advantage of confocal microscopy are a) the ability to use two different sources of light; and b) the ability to quantify the interaction of the two light components to give us a measure of the interaction between the two species (components). The Weighted Colocalization Coefficient gives us the relation between total colocalized light intensity and the total intensity of each individual wavelength. It has been observed that the WCC increases with the time of interaction allowed between CNTs and antibodies, varying from 0.67 at ≈5min to 0.89 at ≈2 hours. ☐ A study on the effect of this functionalization on the electronic properties of carbon nanotubes has also been conducted by utilizing a carbon nanotube field effect transistor device. A decrease in the conductivity of the device has been observed when exposed to antibodies. This effect is attributed to electron donation from antibodies to nanotubes. As a result of this charge transfer on a nanotube bundle, a change in resistance of the device has been observed from ≈84kΩ to ≈312kΩ. This experimental device could be exploited in future research in the design of novel new bio-sensing devices with high sensitivity and specificity of a carbon nanotube-based device, which will be a revolution in terms of speed and sample size of detection and diagnostic techniques.