Last updated on March 15, 2014 at 9:21 EDT

Invention Could Improve Cancer Drug Delivery, Lessen Harmful Effects Of Chemotherapy

December 23, 2010





Chemotherapeutic drugs are sometimes encased in small capsules called liposomes, which are made of organic lipids that are already present in human cells. The lipid encasing keeps the body’s immune system from attacking the foreign molecule before it can deliver the drug.


The highly toxic drugs used for chemotherapy destroy cancer cells, but with no way to discriminate between cell types, they can also damage healthy cells. This damage to the body’s normal, healthy cells leads to the side effects normally associated with chemotherapy treatments: anemia, hair loss, vomiting ““ as cells that make up stomach lining are destroyed ““ and nausea, among others.

Keys in a lock


“It all depends on the disease that we’re targeting, but in the case of tumor cells, they over-express certain receptors for several reasons. One is tumor cells are proliferating very quickly, and so they’re over-expressing a lot of nutrient receptors because they want to divide faster,” said Xenia Kachur, a third-year graduate student in the Biomedical Engineering Graduate Interdisciplinary Program, or GIDP. The extra receptors make the liposomes more likely to latch onto and get inside tumor cells than normal cells.

As they degrade, liposomes release drugs bit-by-bit in an uncontrolled fashion, which may not effectively destroy tumor cells. Said Sarah Leung, a fourth-year graduate student in the biomedical engineering GIDP who also is in the Romanowski lab: “There’s a particular concentration at which you have optimal results, so below that you don’t have enough of the drug to get a good response, and above that it might be even more toxic.”


Drugs coated in gold

“A property of gold is that it can convert near infrared light into heat,” said Kachur. “By putting gold on the surface of these liposomes, we can then put in a stimulus such as near-infrared light. The gold converts the light into heat, the heat causes the liposome to become leaky, and then whatever’s really concentrated inside can diffuse out through the leaky liposome.”



“By using more or less light, you can release more or less of the drug and time the responses as well, so when you trigger light, some drug will leak, you can trigger it again and have more drug leak, or you can wait a little while, let the drug disperse, do its thing, then trigger it again. It allows for a lot more freedom with the release process,” said Leung. “By having this very triggered response you can hit that therapeutic window.”




The invention has another bonus: “The gold-coated liposome is biodegradable, which is one of the best parts of our system,” said Leung. Currently there are no approved chemotherapeutic treatments that allow the gold nanostructures to be eliminated from the body by the body’s own mechanisms, said Leung.

Kidneys, the organs that normally filter waste molecules out of the blood, have a limit as to the size of molecule they can filter. “Because of the size it degrades into, our system should be clearable via the kidney, which is really unique,” said Leung.

There still are many steps to take to test the invention before it could be used in cancer therapy. But if successful, gold-coated liposomes could provide a method to target chemotherapeutic drugs to cancer cells, non-invasively trigger the drugs’ release using infrared light and provide a way for the body naturally to filter the drug from the bloodstream.


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