Hydrogels: FedEx for Cancer Drugs

The most exciting phrase to hear in science, the one that heralds new discoveries, is not 'Eureka!' (I've found it!), but 'That's funny…’

-Isaac Asimov

Whether by accident or on purpose, the discovery of hydrogels has proven to be a very useful tool in the scientific world.  Researchers employ hydrogels in a variety of circumstances ranging from developing contact lenses, tissue-engineering applications and even towards the simultaneous detection and removal of toxins from water.  As Courtney and Anne have previously mentioned, Gabriella Tamasi demonstrated that hydrogels are also beneficial for drug delivery.  But you may be asking yourself, how do they work? I know I did.   And here’s what I found out…

Hydrogels are a network of hydrophilic, or water-loving, polymers.  Acting as a sponge, they can absorb up to thousands of times their weight in water.  However, they remain insoluble in aqueous environments because of their physical or chemical cross-links, which permit them to transport drugs throughout the body.  Drugs are loaded into the hydrogel in two different ways.  One of the ways entails mixing the drug with the hydrogel monomer (the subunit of the polymer chain) and then allowing the polymer to grow, trapping the drug inside.  The other involves “swelling” the hydrogel, which makes its pores larger, in a solution of the drug.  The drug travels through the pores via diffusion and then the hydrogel is dried, returning it to its’ initial size and again the drug is trapped inside the molecule.  So once the drug is inside, how is it released?

Scientists can tailor the composition of the gel and thus its’ ability to respond to different stimuli, like a change in pH or temperature.  These external cues can trigger the hydrogel to swell, increasing the size of its’ openings and therefore allowing the drug to escape through the porous interface.  Other systems for releasing drugs involve disrupting the cross-linking between the hydrogel’s monomers, causing it to dissolve and free the drug.

Recent research has looked at the ability of hydrogels to deliver drugs to very specific targets, as is necessary for fighting cancer.  This process utilizes aptamers, or short polymers, that bind to a target molecule.  In this case, they bind to known surface antigens, or proteins, of cancer cells that can be described as cancer biomarkers.  This technology will not only help to decrease the dosage of drugs, but also decrease the unfavorable side effects that come with most cancer therapies.

Clearly, hydrogels have enormous potential in the scientific realm, but even greater implications for medicine.  Who knows what they’ll discover hydrogels can do next.

For more info visit these sites:

http://www.springerlink.com/content/u25220521v262358/fulltext.pdf

http://www.nature.com/nchem/reshigh/2008/0508/full/nchem.7.html