Capsules release medicine on cue

By Madeline Keleher

Temperature-sensitive capsules can release drugs on command, according to a study by a University professor that was published last week in the journal of Physical Review Letters.

The capsules are an unprecedented application of mechanics to drug delivery, a field dominated by pharmacologists and chemical engineers, said Sahraoui Chaieb, scientist and professor of mechanical engineering at the University. Chaieb has developed liposome capsules capable of releasing drugs at different rates depending on the temperature. This could be used to more efficiently and painlessly deliver drugs for diseases such as cancer and diabetes.

The discovery originated from Chaieb’s work with membrane wrinkling. Membranes wrinkle similarly to the way a piece of paper does when you crumple it in your hand, Chaieb said.

“(Membranes) can be greatly compressed and they get progressively stronger as they are compressed,” said Tom Witten, researcher and professor of physics at the University of Chicago.

Membranes called liposomes crumple and strengthen like this when they are partially polymerized and then cooled. The particles in the membranes are polymerized, or sewn together, using ultra violet light.

“When liposomes cool down, usually there is a phase change, but this is hindered by the UV,” Chaieb said.

Instead, the polymerized liposomes wrinkle. The degree of wrinkling depends on the degree of polymerization, meaning the more sewn together a membrane is, the more it wrinkles.

The capsules are created from these membranes at high temperatures and are made to contain a specific drug. Cooling the temperature by about 5 or 10 degrees causes the capsule to crumple, releasing the drug that was stored inside, Chaieb said.

Temperature change can be facilitated by small particles called nanoparticles. Nanoparticles can cool things by being exposed to an oscillating magnetic field, Chaieb said.

Currently the capsules are being studied as treatments for many diseases, such as cancer and diabetes. There is hope that they can be manipulated to deliver Doxil, a cancer drug, or insulin at exactly the right moment.

“There’s no injection, no heating, nothing-just a magnetic field,” Chaieb said.

Chaieb said his capsules, unlike conventional medicines such as Advil, do not rely on time-release degradation — instead, they deliver on demand.

“(With membrane wrinkling) not only can we control when the drug comes out, but how much of it comes out,” Chaieb said.

This opens up a wide range of possibilities for the improvement of drug-delivery. Chaieb said he is currently testing his new method on breast cancer cells.