Abstract
Within this thesis, many building blocks that are necessary to fabricate nano-scale biotechnology devices are examined. In this rapidly expanding field, carbon nanotubes (CNTs) have been identified as a key component. In particular, the biomedical applications of CNTs functionalised with DNA or RNA, utilising dielectrophoresis as a nano-manipulating tool, is investigated. The use of RNA and RNase A to generate chemically unmodified and pure single walled CNTs in a simple two step procedure is described. RNA is shown to efficiently wrap and solubilise CNTs while RNase effectively strips the RNA from the CNT, providing a convenient purification technique. The mechanism of binding of DNA to carbon nanotubes (CNTs) is shown to be much more efficient when the DNA is single-stranded rather than a double-stranded helix, while parameters (e.g. pH) are optimised for the most efficient CNT solubilisation with RNA. The compatibility of RNA-CNT composites with mammalian cells in tissue culture is also investigated. Flow cytometry and confocal microscopy show it is highly likely that RNA-CNTs composites are internalised into mammalian cells, while laser heating did not effectively kill cells. This is presumably because the power was too low or not enough CNTs were internalised in the cells. DNA-CNT composites are used to electrically sense the binding of biomolecules which have been trapped between micro-electrodes by dielectrophoresis. In a fluid cell, it is shown that solutions affect the flow of current through the CNTs, as an ionic solution increases the resistance in relation to deionised water, whereas with no CNTs, the opposite is true. Moreover, a rise in the resistance is also seen as proteins bind to CNTs. The nano-manipulation of DNA was studied with dielectrophoresis. It is shown that poly(dG)-poly(dC) (GC) collects at higher frequencies than poly(dA)-poly(dT) (AT) indicating that GC is a better conductor than AT. It was also found that different lengths of DNA polarise at about the same frequency, while shorter lengths need a higher field intensity to trap them.