November 21, 2009
Nanoparticles For Gene Therapy

An MIT press release about the use of nanoparticles to deliver gene therapy contains an interesting statistic about the size of the overall effort to develop clinically useful gene therapies: In the United States alone almost 1000 gene therapy clinical trials are underway. That's a surprisingly large number. Is it true? Seems too high to be possible.

There are nearly 1,000 clinical trials under way in the United States involving gene therapy, for diseases including cancer, cardiovascular disease and neurological disorders. However, no gene therapy treatments have been approved in the United States.

This is an example of why it is hard to predict the future. It is hard to predict the success rate of those many attempts. Once some succeed we also do not know how much of the successful techniques for a particular disease target will be reusable against other diseases. Gene therapy researchers in the early 1990s sounded pretty optimistic. But their high hopes were repeatedly dashed in failed experiments. Is success just around the corner or another 15 years away? For some of us (though we mostly do not know it yet personally) the answer is a matter of life and death.

Gene therapy has huge potential because it delivers instructions. Most diseased cells could be restored to a non-diseased state if they could only be sent enough instructions on how to repair themselves. Cell therapies get more press in part because of the ethical debate about embryonic stem cells. But gene therapies are crucial for rejuvenation because of the need to repair damaged brain cells. Lots of organs will some day just be replaced by organs grown in special vats. But the brain replacement is effectively person replacement. You have get your brain repaired in order to save your identity from death by aging.

The MIT press release on nanoparticles for gene therapy delivery sounds promising because these researchers at MIT and U Wisc have automated the process of searching the potential solution space by making large numbers of nanoparticle variations,

Anderson and chemist David Lynn, then a postdoctoral fellow in Langer’s lab and now a professor at the University of Wisconsin, developed a large collection of different biodegradable polymers (large molecules composed of repeating subunits) known as poly(beta-amino esters).

When these synthetic polymers are mixed with DNA, they spontaneously assemble to form nanoparticles. These nanoparticles can travel through the body to the target cells, where they are taken up by a process known as endocytosis, the equivalent of cellular eating. Once “eaten” by the cells, the nanoparticles release their DNA payload inside of the cell, where it can then be activated by the cellular machinery. In some ways, these polymer-DNA nanoparticles can act like an artificial virus, delivering functional DNA when injected into or near the targeted tissue.

There are infinite possible sequences for such polymers, and small variations can make a polymer more or less efficient at delivering DNA. Anderson and Langer's group have developed a way to automate both the production of vast numbers of particles with slight variations and the screening techniques used to determine the particles’ effectiveness.

“Instead of trying to make one perfect polymer, we make thousands,” says Anderson. That increases the odds that the researchers will hit on a nanoparticle that does what they want.

Will they succeed in developing useful gene therapy delivery vehicles? I hope so.

Share |      Randall Parker, 2009 November 21 05:21 AM  Biotech Gene Therapy

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