Doctors might soon diagnose you by feeding a lab-on-a-fiber straight into your veins

• By Ryan Whitwam on March 21, 2014 at 12:23 pm

The backbone of the modern internet is based on fiber optic cables strung across the globe, but these optical fibers could be used to carry more than just data. Researchers around the world are tantalizingly close to using the same glass fibers found in telecom equipment to house a new generation of chemical sensors. The hunt for the so called “lab-on-a-fiber” has the potential to reduce healthcare costs dramatically and make your next checkup a bit less of a hassle.

Today’s laboratory technologies require rooms full of pricey instruments and temperature controlled reagents — all this just to check your blood sample for cholesterol or evidence of an infection. It’s not feasible to have this kind of facility everywhere, so samples are shipped off and you have to wait days or weeks for results. In some areas of the world, these tests aren’t even available. Shouldn’t there be a way to use all this fabulous modern technology to make everything faster and easier? Well, scientists have been working on that for decades.

The idea of a lab-on-a-fiber is similar to a lab-on-a-chip, which already exists. The main problem with using an integrated electronic chip in human health is that we’re very wet and goopy inside. A lab-on-a-chip is made largely of metal semiconductors that corrode under such conditions, but a glass optical cable doesn’t have that problem. These chips are also too large to be implanted in the body, but fiber optics could be threaded directly into the blood vessels for real time monitoring.

Making a photonic cable system capable of analyzing chemical signatures is, in some ways, very similar to making it work in telecommunications. The inner surface of a standard fiber optic cable is coated with tiny amounts of germanium oxide, making it more reflective. When light is sent down the cable, it bounces off the inner surface and remains confined to the core. That’s why fiber optic cables can transmit data so far with little to no signal loss. The most promising approach to building a lab-on-a-fiber relies on this property of optical fibers to control when and how light leaves the core to detect target molecules.

Imagine these specialized fiber probes as long, flexible tunnels. As the light passes from one end to the other, it encounters a series of tilted gratings that act like small mirrors. These disruptions in the cable bounce certain wavelengths of the light out of the core where they can come in contact with the outer layer where a carefully chosen coating can bind the target molecule, for example protein markers for a disease. The remaining light is bounced back to the starting point with a gold mirror and everything is read with a standard spectrometer.

Early tests on these labs-on-a-fiber are very promising — some versions can detect target molecules with concentrations as low as 2 nanograms per liter. That’s roughly the same as a dash of salt in a 25-meter pool. The small size and sensitivity of this technology could make getting tests done quite a bit faster, but would also expand medical technology to more areas of the world — regular optical cables are the basis for this tech, and they cost mere pennies. A device the size of a tablet could house all the hardware needed to operate a lab-on-a-fiber, and power requirements would be minimal as only a small amount of light is needed.

Before we see human applications of this technology, labs-on-a-fiber could show up in industrial scenarios. Long optical fibers could be fed down waterways to monitor for chemical contamination from manufacturing facilities, waste runoff, or pesticides. When we begin feeding such probes into humans, the possibilities for understanding drug metabolism and interactions could accelerate the pace of pharmaceutical innovation and make disease treatment more precise. All it takes is a little light.