Professor of bioengineering and therapeutic sciences
University of California, San Francisco
All creatures struggle with a common problem: they must let in nutrients and vent wastes while also keeping pathogens and poisons out. At a cellular level, humans and other vertebrates safeguard their bodies using “tight junctions,” watertight bonds between adjacent cells. Tight junctions are in almost all our tissues and even help waterproof our skin. But they also make it very difficult for drugs to get into the body’s tissues from the outside world.
Nanoscale and microscale drug-delivery devices as small as a few atoms or as large as the width of a human hair can interact with tight junctions and other cellular features to more effectively administer drugs to patients. For example, we have developed a tiny film with nanoscale wire-shaped features that cells like to grab onto. The film activates certain chemical pathways in the cells that alter cell membrane structure and prop open the tight junctions. That allows doctors to use reduced, less dangerous doses of highly toxic anticancer drugs or to get more of a drug to a certain part of the body. For example, particles to treat diabetes could stick to the intestinal wall and release insulin over time rather than quickly flushing out of the body.
One device we are developing is for age-related macular degeneration, which causes blindness if left untreated. Right now patients go to the doctor and have a needle poked into their eye once a month to deliver the drug. Our nanoscale device can be delivered in a single injection, and it lasts from six months to a year. It would sit in the back of the eye and deliver the drug over time through microscopic pores, then dissolve away once it is emptied.
In the future, we will see particles with nanoscale parts that can not only target specific sites but also improve a drug’s absorption within the body by prying open tight junction barriers.