October 23, 2012
Lung Mucus Gel Prevents Nanoparticles From Getting Through
Joint press release by the Saarland University and the Helmholtz Centre for Infection Research
Mucus coats our airways' internal surfaces. The viscous gel humidifies the lungs and prevents viruses and other small particles like diesel soot from entering the body unchecked. Previously unclear was the extent to which such nanoparticles are able to move through the lungs' mucus. Here, the research evidence was contradictory. Scientists could not explain why, in inhaled medication development, drug nanoparticles often simply got stuck in the mucus never making it to their target destination inside the lung cells.
"Our results are helping us to better understand the etiology of infectious diseases of the airways and how to treat them more effectively. In particular, they represent an important basis for the continued development of new inhaled medications," explains Professor Lehr. The newly gained insights show that it is important to consider how drugs overcome the mucus gel scaffold. Mucolytic techniques can be used where, essentially, the rods are melted such that they dissolve before the nanoparticle and, once the particle has passed, they fuse again.
One of the research tools Professor Christian Wagner and his team of experimental physicists at the Saarland University use to support their assumptions are optical tweezers: Bundled laser beams are used to grab and move the smallest particles just like you would use a regular pair of tweezers. "We can use the optical tweezers' laser beams to measure the force that is required to move a particle within the gel. This allows us to make conclusions about the medium that the bead is moved through," explains Professor Wagner. "We were able to pull the bead through the liquid inside the pore at a constant force — just as we would if we were dealing with a normal gel. However, whenever the bead hits the pore's wall, in other words the mucus's gel rods, the laser beam is unable to move it any further," explains Wagner. Experiments using an atomic force microscope as well as other tests are further supporting their hypothesis: As such, iron nanoparticles were able to penetrate the "normal" reference gel but not the lung mucus without any difficulties under the influence of a magnetic field. Structural analyses of the mucus were performed by scientists at Fresenius Medical Care Germany using a cryo-electron microscope.
The researchers expect that insights into the special structure of lung mucus will help guiding the development of a new generation of drugs to treat diseases of the airways.
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