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making vaccine delivery systems that you could inject once and get really high antibody titers [measurements]. There are many other areas as well where the work in drug delivery could really improve medical treatments in the third world. It’s quite vast, what the future holds, in terms of drug delivery systems.
X: Doesn’t the perennial challenge with drug delivery come down to figuring out ways to fool the body’s immune response?
RL: That is a challenge. Of course, it’s not like an all-or-none challenge. Sometimes you will get encapsulation. But that encapsulation is not sufficient to stop molecules from getting out of the capsule. With nanoparticles and micro-capsules, the drugs do come out, and of course there are now many products on the market based on these things, both injectable systems like Risperdal Consta that Alkermes makes and Lupron Depot that Takeda makes. Many of these last for many months. Even some of these birth control systems, like Norplant, last for many years.
With nanoparticles, there what you’re trying to do is often have it circulate and go in the right place in the body. There are strategies there too. We’ve done work and others have too in decorating those nanoparticles with a substance like polyethylene glycol that it make it harder for problems to occur.
X: There’s a company in San Diego that’s dealing with both of your areas of expertise. It’s called Viacyte. They’ve been developing an artificial pancreas that uses pre-pancreatic stem cells in a packet that is implanted just beneath the skin. The device allows the encapsulated pancreatic cells to release insulin and related hormones into the bloodstream.
RL: Diabetes, of course, is a more complex situation in that you are responding to something like glucose, and you want the drug to come out, you want the timing of that to be very precise. That’s actually an area that we’ve been working on in our lab as well. We have a large grant from the Juvenile Diabetes Foundation to try to come up with what we call super bio-compatible materials. I think we’re all excited to see how Viacyte’s results turn out.
X: They developed a mesh that prevents the white blood cells from coming in and attacking the pancreatic cells, but still allows insulin and other hormones to come out of the packet and into the bloodstream.
RL: A lot of people have tried to do this over the years. The goal on the one hand is to create a mesh or a pore structure that has a size that allows insulin and glucose to get through, back and forth, but won’t allow antibodies or macrophages to get through…There really are three challenges: One is to encapsulate the cells in a way that doesn’t hurt them. Two is getting the pore structure just right. And three is the bio-compatibility issue.
X: Could you also give us your overview of where innovation is taking place in tissue engineering?
RL: There’s a lot. Tissue engineering has gotten to … Next Page »