Researchers have developed a new type of aerosol particle that can linger in the lungs for days, opening the way for improved drug therapy for asthma, cystic fibrosis and other lung disorders.
Tests of the large but lightweight particles on rats have found that medications attached to them stay active as much as 15 times longer than the longest-acting aerosol treatments currently known.Results of tests with the dry mist, developed by researchers at Pennsylvania State University and the Massachusetts Institute of Technology, are presented in the journal Science.
Human lungs generally do a terrific job of sweeping out foreign particles within minutes or hours of their being inhaled, either by sending material back up the throat or by being encapsulated and digested by janitor cells that work deep in the airways.
As a result, people taking inhaled medications have to take big doses and repeat them every few hours to maintain a steady dose. This chronic use, particularly in the case of bronchodilators used by asthmatics, tends to cause the lungs to become less responsive to the medicine over time, increasing the chance of a fatal asthma attack if a patient has an unusually severe shutdown of airways.
The new "large porous particles" are three to 10 times bigger than the ones now being used to deliver medication, but they weigh up to 90 percent less. That makes them less susceptible to being expelled or quickly gobbled up by the lung's defenses and able to stick around longer delivering medicine.
David Edwards, associate professor of chemical engineering at Penn State and lead author of the research team's report, describes the particles as somewhat "like a whiffle ball with medication inside."
When the particles are inhaled, the medicine slowly seeps out into the lungs to either act directly on lung tissue or enter the blood stream directly through the lung walls just as oxygen does.
Edwards first had the idea for porous particles while working in the lab of MIT chemical engineer Robert Langer. The two began researching the concept two years ago after Edwards joined the faculty at Penn State, and eventually enlisted help from colleagues at their institutions as well as Italy, France and Israel.
Edwards said if tests on humans work as well, patients in a few years might be able to use their inhalers once every day or two, and take lower doses each time.
The researchers started tests with medicines that were easiest to measure in rats, such as insulin and testosterone. Large porous insulin particles, for instance, stayed active in rats lungs for 96 hours, which is about 15 times longer than any previous particle was able to persist in the animals' lungs.
Other medications, including the leading fast-acting asthma reliever, albuterol, are now being tested with the new aerosol particles.
Edwards said the results so far indicate that the particles will be useful not only to deliver therapeutic payloads to the lungs but "also posses exciting potential as non-invasive delivery systems for medicines such as insulin to treat diabetes and interferon for cancer treatment."