Carbon nanotube device detects genetic mutations

University of Pittsburgh researcher Alexander Star, in collaboration with California-based company Nanomix, Inc., has developed devices made of carbon nanotubes that can detect mutated genes that may cause hereditary diseases.

This approach to detecting gene mutations increases the speed of detection in comparison to conventional techniques. It will also dramatically decrease the cost and inconvenience associated with this type of genetic detection.

“The development of this type of technology will enable label-free detection of mutated DNA sequences,” said Star, an assistant professor of chemistry at the University of Pittsburgh.

Carbon nanotubes are cylindrical carbon molecules with innovative properties that make them potentially useful in a wide variety of applications. These include nano-electronics, optics, and now, detection of genetic mutations, as shown by Star and colleagues. Carbon nanotubes are only a few nanometers wide — they span the width of a molecule of DNA. This makes them highly compatible with DNA, allowing sensitive detection. Carbon nanotubes exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat.

The carbon nanotube device works by using the nanotubes’ electrical properties to detect unusual mutations in DNA. The device is a network of single-walled carbon nanotubes (SWNTs) deposited onto interdigitated electrodes. They are used to make conductance measurements. DNA sequences bind to the surface of the SWNTs; hybridization — the matching of DNA to its complementary strands — is electronically measured by changes in conductivity. “Simply put, healthy DNA and mutated DNA will give different electronic responses when hybridization occurs,” Star said.

The nanotube device was used to find a particular mutation in hereditary hemochromatosis, an inherited disorder that increases the amount of iron that the body absorbs from the gut. The iron is then deposited in excess in a variety of organs. Most commonly, excess iron in the liver causes cirrhosis, which may develop into liver cancer. Iron deposits in the pancreas can result in diabetes.

The nanotube device will be able to detect many other kinds of disease-related genes. “This type of technology will help in the detection of any single-gene genetic disorder, for example cystic fibrosis,” Star said. Cystic fibrosis is the number-one genetic killer among children and young adults, affecting one out of every 3000 children born.

Star was able to verify that his new device worked by detecting signature electronic responses when testing DNA. Fluorescent microscopy was also used to determine if DNA had attached to the nanotube surfaces and was successfully matched to its complementary DNA. “Normal, healthy DNA was fluorescently tagged, and when it binds [to the nanotube] it can be seen with a fluorescent microscope,” said Star. The electronic signal of the normal and mutated DNA can be corroborated with the presence or absence of a fluorescent signal.

The development of this type of technology holds many promises. “This type of SWNT technology will enable the development of handheld devices that will enable home testing, which will eliminate the need for time-consuming visits to doctors requiring specialized equipment and techniques,” said Star.

Star’s research was supported in part by the National Science Foundation’s Small Business Innovation Research program.