Diagnostic Nano-sensors Using Nanowire
Nanotech researchers are investigating a number of nanomaterials, including nanowires, quantum dots, and iron oxide, to create nano-sensors designed to detect disease. Functionalized nanowires have been used in the lab to detect disease indicators, cancer cells, and measure blood chemistry.
Nanotechnology can make the process of diagnosing diseases faster and more efficient by enhancing the capability of sensors to identify specific diseases. Researchers have created sensors by bonding antibodies to nanowires.
When biological molecules that indicate the presence of a particular disease attach to matching antibodies, they change the resistance of the nanowire. Because a nanowire is so small, with a diameter of about 10 nanometers, even a small change like bonding an additional molecule to the nanowire can make a noticeable change in its electrical properties.
Using several nanowires in an array with each nanowire functionalized with a different antibody, allows each nanowire to be used to detect a different type of disease.
When you apply a voltage to each nanowire, you drive a current through it. When the resistance of the nanowire changes because the wire has bonded with a virus or protein, the electrical current also changes. This change lets the doctor know which virus or protein is present in the blood sample.
This method is useful when trying to figure out what might be causing certain symptoms in a patient. But a more sensitive test is needed if a disease is in a very early stage, or if a doctor needs to detect any remnants of a particular disease in the patient after therapy is complete.
More sensitive diagnostic sensors also use nanowires and antibodies, but these sensors look only for cells carrying that particular disease. To increase sensitivity, you simply use a larger number of those antibodies to increase the chance of detection.
Researchers at MIT and Harvard have developed a sensor using billions of carbon nanotubes that they functionalized with antibodies to attach to cancer cells. They’ve designed this device to be sensitive enough to indicate if even a single cancer cell is trapped on a carbon nanotube.
This test would alert doctors that cancer cells are in the bloodstream before the cells can form new tumors. This method could be used, for example, on a patient with a cancer tumor to determine whether the cancer is isolated to that one tumor or is spreading throughout the bloodstream, or to detect HIV being carried in the blood.
Another way to make use of these nanomaterial-based sensors is to determine the level of a particular substance, such as glucose molecules, in a patient. Various researchers are working with either nanowires or nanotubes to make implantable glucose sensors.
After the development, testing, and regulatory approvals are complete, patients may be able to wear an unobtrusive patch containing a small insulin reservoir and pump controlled by these nanosensors. This system could automatically inject a diabetic patient with insulin to control the person’s blood sugar level.
This method might be useful also for patients with life-threatening allergies to detect an allergic reaction and administer the necessary medicine to halt its progress.