DNA exists in cells as two individual strands intertwined together by a process called DNA hybridization. These strands partially separate, or dehybridize, to copy itself into RNA and form proteins. The hybridization of DNA within cells is thought to occur very rapidly, on the order of nanoseconds, making it very hard to study. Traditional methods of studying DNA hybridization involved transmission genetics—the study of crossing organisms to produce offspring traits that are then studied for inheritance mechanisms—the study of cell reproduction through cytology, and current biomolecular genetics techniques.
Biomolecular genetics techniques used today include optical techniques such as Fluorescence Correlation Spectroscopy (FCS). This process involves analyzing the optical fluorescence of single strands of DNA as they hybridize. Scientists separate, cut, and label the DNA strands to be studied with fluorescent reporter molecules. When hybridization is induced by optical excitation of the DNA solution, the strands give off a fluorescent yellow glow. If no hybridization occurs, the color is the same as the original reporter molecule. This can be disadvantageous for studying cellular kinetics due to the fact that the DNA must be labeled with fluorescent molecules and the emission bandwidth is limited by the small number of photons emitted over a very short period of time.
Columbia University researchers from the school's physics, chemistry, and engineering departments have discovered a novel process for studying DNA hybridization and biomolecular kinetics that involves using nanoscale field-effect transistors. These transistors are used specifically to study the hybridization of two halves of a DNA double helix. DNA strands are attached to the inner walls of CNTs, where they then bind with other strands to form DNA double helixes. The CNT transistors amplify and detect the inherent bioelectrical charge given off by these biomolecules with enough sensitivity to detect the hybridization of a single DNA molecule. The researchers are hoping to incorporate these nanoelectronics into instrumentation applications similar to FCS DNA sequencing or protein microassays.
- . Hybridization kinetics is different inside cells. Proceedings of the National Academy of Sciences [Internet]. 2009 ;106(51):21649 - 21654. Available from: http://www.nasw.org/users/mslong/2009/2009_12/KineticsInCells.htm
- . Label-free single-molecule detection of DNA-hybridization kinetics with a carbon nanotube field-effect transistor. Nature Nanotechnology [Internet]. 2011 ;6(2):126 - 132. Available from: http://engineering.columbia.edu/researchers-find-new-use-nanoscale-transistors
This technology is a generational enhancement on traditional biomolecular sensing and DNA sequencing technologies.
This technology has potential benefits for human health and security by allowing for the advanced study of biomolecular processes, DNA kinetics, and environmental sensing.
There are two types of risk inherent to this technology. There are the environmental and human health risks associated with the manufacture of CNTs. CNTs have been shown to be cytotoxic and can pierce cell walls. They can also causes respiratory damage similar to other nanoparticles. More importantly, this technology poses significant moral and ethical risks. One might argue that the advancement of technologies such as synthetic biology and DNA sequencing are dependent on the institutional capacity to handle the fast pace of development in these technologies, or the lack thereof. For this reason, the social and ethical risks associated with using nanoscale transistors for faster, cheaper, and more reliable DNA sequencing are unknown to ambiguous at best. These risks are dependent on the intended use of the technology, and the institutional controls to regulate the technology.