Targeted Drug Delivery That Hits the Mark
One of the challenges with current cancer treatments is how to deliver drugs to tumors without causing debilitating side effects. By delivering drugs in a more targeted way, some of those side effects can be reduced. There are several companies and universities developing targeted drug delivery using nanoparticles. One method being developed by researchers at MIT and University of California at San Diego and Santa Barbara looks interesting. They have divided the task between two nanoparticles in order to increase the targeting effectiveness.
The approach involves several steps. First, they inject gold nanorods into the blood stream. The gold nanorods stay in the healthy blood vessels but exit the leaky blood vessels found at the site of tumors. The gold nanorods then accumulate in the tumor and an infrared laser is used to heat the gold nanorods, thereby heating the tumor.
The heating of a tumor increases the level of a stress related protein (called p32) on the surface of the tumor. Because an amino acid (called LyP-1) binds to the p32 protein,they developed a process to attach LyP-1 to spherical nanoparticles called liposomes. They then insert molecules of a chemotherapy drug inside the liposome.
When the drug packed liposome is injected into the bloodstream the amino acids on the nanoparticles
attach to the proteins the heat has pushed to the surface of the tumor and more
of the drug is delivered to the tumor.
Nanorods Work Better Than Nanospheres
Several methods in use today use spherical gold nanoparticles for drug delivery, so why did this group choose nanorods instead? It turns out that nanorods of different lengths absorb different frequencies of infrared radiation. The company making the nanorods, NanopartzTM, has shown that gold nanorods absorb infrared much more efficiently than spherical gold nanoparticles. Therefore gold nanorods do a better job of absorbing infrared light and heating up the tumor than spherical nanoparticles do.
It’s interesting to see this concept of using a combination of different nanoparticles doing different parts of the task to develop a system to deliver chemotherapy drugs to cancer tumors. It will be very interesting to see which of the several methods of targeted drug delivery under development is put into widespread use.
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spherical gold nanoparticles.
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