One of the hopes of nanoparticle technology is for drug delivery. And the field is having some success. A paper in Nature, published today for example has shown how siRNAs can be delivered directly to tumours using nanoparticles.
Eugene Zubarev from Rice University spoke at the ACS meeting this morning about some other successes in using nanoparticles, made from gold, for treating cancer. And it’s pretty neat stuff. Zubarev has been finding ways to make the well-used cancer drug paclitaxel, or more commonly known as taxol, more efficient, and less toxic.
He did this by attaching taxol to gold nanoparticles. Each nanoparticle had phenol groups, up to 100 of them, stuck to it, and these phenols could grab hold of the taxol molecules. This worked with 70% success so that each nanoparticle was carrying 70 taxol molecules.
To make the taxol less toxic to healthy tissue, Zubarev included in the linking group between the nanoparticle and the drug a linker group, a hydrazone. In this linker there sits a chemical site that can be cut, severing the link between the nanoparticle and the drug. This linker cutting is a reaction called a hydrolysis, and proceeds best at pH 5 to 6. This is important because normal, healthy cells have pH of around 6.5, so wouldn’t help with this release of the taxol. Cancer cells, however, have a lower pH of around 5.
This means that the drug will be released much more efficiently in the cancer cells.
Zubarev has tested his delivery system on rats and shown that tumours being treated with his nanoparticle treatment shrink at least as quickly as those treated with taxol, and in many cases they shrink faster. The survival rates for these rats was higher in those treated with simply taxol.
Zubarev doesn’t’ have proof that this effect is because of better drug delivery to the infected tissue, but hopes that this is the cause.