Researchers at the University of North Carolina at Chapel Hill (UNC) have developed a way to use gold nanoparticles and laser light to measure the stickiness of the mucus that lines the airway. The new method could help doctors better monitor and treat lung diseases such as cystic fibrosis and chronic obstructive pulmonary disease (COPD).
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"People who are suffering from certain lung diseases have thickened mucus," explains Amy Oldenburg, a physicist at UNC whose research focuses on biomedical imaging systems. "In healthy adults, hair-like cell appendages called cilia line the airways and pull mucus out of the lungs and into the throat. But if the mucus is too viscous it can become trapped in the lungs, making breathing more difficult and also failing to remove pathogens that can cause chronic infections."
Doctors can prescribe mucus-thinning drugs, but have no good way to monitor how the drugs affect the viscosity of mucus at various spots inside the body. Recognizing this, the researchers placed coated gold nanorods on the surface of mucus samples and then tracked the rods' diffusion into the mucus by illuminating the samples with laser light and analyzing the way the light bounced off the nanoparticles. The slower the nanorods diffused, the thicker the mucus. The team found this imaging method worked even when the mucus was sliding over a layer of cells—an important finding since mucus inside the human body is usually in motion.
"The ability to monitor how well mucus-thinning treatments are working in real time may allow us to determine better treatments and tailor them for the individual," says Oldenburg.
It will likely take five to 10 more years before the team's mucus measuring method is tested on human patients, Oldenburg says. Gold is non-toxic, but for safety reasons the researchers would want to ensure that the gold nanorods would eventually be cleared from a patient's system.
The team is also working on several lines of ongoing study that will some day help bring their monitoring device to the clinic. They are developing delivery methods for the gold nanorods, studying how their imaging system might be adapted to enter a patient's airways, and further investigating how mucus flow properties differ throughout the body.
The research team will present their work at The Optical Society's (OSA) 98th Annual Meeting, Frontiers in Optics, to be held October 19-23, 2014, in Tucson, AZ (Presentation FTu5F.2, "Imaging Gold Nanorod Diffusion in Mucus Using Polarization Sensitive OCT," will take place Tuesday, Oct. 21, at 4:15 p.m. MST in the Tucson Ballroom, Salon A at the JW Marriott Tucson Starr Pass Resort).
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