A scanning electron micrograph below shows solid polymer microspheres
designed for timed drug release. The horizontal bar is a 10 micron size reference. As the microspheres dissolve in the body, they continuously release the drug contained within them. This provides sustained levels of the drug at all times. By releasing the drug locally, the amount of the drug required is reduced, as well as possible systemic side effects.
A 10 micron diameter polymer wall microcapsule to provide pulsed drug release
is shown below in an optical photomicrograph. The microcapsule is filled with a
red dye for clarity. Microcapsules made with different polymer formulations that
dissolve at different rates may be used to provide burst release of the drug at
specific intervals. This mimics the pattern of conventional booster doses,and it
makes possible both injectable and oral single dose vaccines.
Tests of a 3-stage, single dose vaccine prepared at Whalen Biomedical
Laboratories to protect against exposure to botulinum toxin at lethal levels
were conducted by the U.S. Army. Approximately 80% of the vaccine
treated animals survived, while 100% of the controls did not.