Common plastics -- known to scientists as polymers -- are all around us. They are used to make garbage bags, milk jugs and coated paper, as well as car bumpers, carpet fibers and soft drink containers. Other types of polymers can be found in paints, coatings and adhesives. Some polymers occur naturally, such as cellulose, starch, and spider silk.
Polymers "flow" under heat and pressure, allowing them to be molded into useful products. But polymers can also be used to coat the surface of other objects, or as carriers for designer drug molecules.
How can polymers help deliver drugs to the body? When you take any kind of drug, including aspirin, the drug molecules don't just travel to the site of pain or disease. Instead, the drug is dispersed throughout the body via the bloodstream. In the case of the toxic chemotherapy drugs used in cancer treatments, this means a lot of healthy cells can be killed by the drugs, not just the cancerous ones. Scientists have made great strides in developing drug molecules that only target unhealthy cells at a specific site. This is called targeted drug delivery.
However, it's much easier to target individual cells in a Petri dish in the laboratory; the process is much more complicated in the human body. Any injected molecule must avoid a complex network of blood proteins, cells lining blood vessel walls, and other cells that interact with the blood in the liver. Unhealthy levels of the drug can build up in this and other organs, causing damage. Any interaction with these normal cells will dilute the potency of the drug molecule before it reaches the tumor site, making it ineffective.
That's where polymers become so useful. There are only limited ways that polymers can link to each other, as well as to other cells and molecules. This means that linking them to an anticancer drug, for example, allows for the control of where and when the drug is released. That's because the polymer-drug linkages are so strong that they will only be broken after they are absorbed by a cell. The cell's enzymes catalyze and break the linkage, releasing the drug. And scientists have found that tumor cells absorb such molecules more easily than healthy cells.
For more information see:
Depomed, Inc. -- the company that invented the Swell Pill
Kos Pharmaceuticals, Inc. -- find out which drugs are delivered by the Swell Pill.
The Biophysical Society contributed to the information contained in the TV portion of this report.