Washington, Mar 26 : An Arizona State University researcher has developed a novel biosensing nanodevice that may do away with long lines at airport security checkpoints and revolutionize health screenings for diseases like anthrax, cancer and antibiotic resistant Staphylococcus aureus (MRSA).
This device has been developed by Wayne Frasch and its uniqueness lies in the fact that it is based on the world's tiniest rotary motor: a biological engine measured on the order of molecules.
Frasch worked with the enzyme F1-adenosine triphosphatase, or F1- ATPase, which though only 10 to 12 nanometers in diameter, has an axle that spins and produces torque.
F1- ATPase is part of a complex of proteins pivotal to creating energy in all living things, including photosynthesis in plants. It breaks down adenosine triphosphate (ATP) to adenosine diphospahte (ADP) for releasing energy.
Through his own detailed study of the rotational mechanism of the F1-ATPase, operating like a three-cylinder Mazda rotary motor, Frasch conceived of a way to take this tiny biological powerhouse and couple it with science applications outside of the human body.
For this the researcher showed that the enzyme can be armed with an optical probe (gold nanorod) and manipulated to emit a signal when it detects a single molecule of target DNA. This is achieved by affixing an inactive F1-ATPase motor to a surface.
Later, a single strand of a reference biotinylated DNA molecule is attached to its axle. The marker protein, biotin, on the DNA is known to bind specifically and tightly to the glycoprotein avidin, so an avidin-coated gold nanorod is then added. The avidin-nanorod attaches to the biotinylated DNA strand and forms a stable complex.
When a test solution containing a target piece of DNA is added, this DNA binds to the single complementary reference strand attached to the F1-ATPase. The DNA complex, suspended between the nanorod and the axle, forms a stiff bridge. Once ATP is added to the test solution, the F1-ATPase axle spins, and with it, the attached (now double-stranded) DNA and nanorod. The whirling nano-sized device emits a pulsing red signal that can then be detected with a microscope.
Frasch said that the rotation discriminates fully assembled nanodevices from nonspecifically bound nanorods, resulting in a sensitivity limit of one zeptomole (600 molecules), i.e. if it's not moving and flashing, it simply isn't relevant.
"Studies with the F1-ATPase in my laboratory show that since it can detect single DNA molecules, it far exceeds the detection limits of conventional PCR [polymerase chain reaction] technology," said Frasch.
A prototype of the DNA detector is already in development. It is roughly the size of a small tissue box. Sampling would be as simple as taking a swab from an infected wound or a piece of baggage, dissolving it in a solution and placing a drop on a slide bearing reference F1-ATPases and their nanorods. Once in the instrument, red blinking signals emitted by rotating nanorods would let a computer know there's trouble, literally, in a flash.
Frasch has also extended the method to do protein detection at the single molecule level and this is novel as, unlike DNA, proteins cannot be amplified artificially to improve the chances of detection.
An article detailing the findings: "Single-molecule detection of DNA via sequence-specific links between F1-ATPase motors and gold nanorod sensors" was recently published in the journal Lab on a Chip, and featured in the online journal Chemical Biology produced by the Royal Society of Chemistry.