Nanosys, Inc. announced
today the results of their initial studies using a novel silicon nanowire mucous
membrane drug delivery device. These devices have a nano-structured surface
that relies on adhesive properties known in physics as van der Waals forces
of adhesion. Results of initial studies published this week in the American
Chemical Society's Nano Letters, outline the device's ability to significantly
improve drug delivery to mucous membranes such as those in the nose, intestine,
eyes, vagina and mouth.
Mucous membranes have long been a target for drug delivery due to their large
surface area and rich blood supply. However, nature has designed these membranes
to also be efficient barriers to foreign substance penetration, such as drugs.
Mucus, which is constantly produced by these tissues, is moved across the surface
by tiny beating hair-like structures called cilia. Removal of a substance floating
in the mucus of the nasal cavity can be as fast as ten minutes, for example.
Previous attempts at overcoming this barrier function relied on chemical modification
of the delivery vehicle to better adhere to binding elements within the mucus.
Nanosys's silicon nanowires will adhere instead to the cells underneath the
mucus, the actual targets for drug delivery. This critical feature allows for
a longer residence time, improved local concentrations and better absorption
of target drugs by the tissues.
The team, led by Hugh Daniels at Nanosys and Tejal Desai and Kayte Fischer
at the University of California, San Francisco, also quantified the amount of
mucosal shear force the silicon nanowire-based devices could withstand before
being eliminated, and demonstrated it to be at least 100-fold better than a
non-silicon nanowire device.
"In the near term, there are a lot of chronic conditions of the nose,
sinuses and other tissues that could immediately benefit from more efficient
delivery of currently available drugs using our silicon nanowire drug delivery
technology. We are also excited about the longer term potential of delivery
of systemic drugs such as insulin via the mucous membrane route," said
Dr. Daniels. In addition, silicon nanowires are inexpensive to make and are
biocompatible. Nanosys expects to develop the technology further in partnership
with drug manufacturers whose drugs could be made more effective through this