NMP 2008
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JEANETTE POLKINGHORNE |
Boston
Scientific and |
PROBING THE DRUG RELEASE PROFILE OF A DRUG-ELUTING MEDICAL DEVICE
Jeannette Polkinghorne
Boston Scientific
Jinping Dong (Characterization Facility), Dean Poppe (CEMS)
Cardiac leads, which connect
medical devices such as pacemakers and defibrillators to the heart, are used
to monitor the heart’s rhythm and provide
therapy when needed. A drug delivery system is incorporated onto the end
of cardiac leads to reduce inflammation and fibrosis at the lead-tissue
interface and enables optimal lead performance. In this research, confocal
Raman microscopy is used to capture images of the drug delivery system
at different time points and in different elution media.
Raman scattering provides chemical fingerprints of a material irradiated
by a laser. Combing high resolution confocal optical microscopy and Raman
spectroscopy, a 3-D chemical map can be obtained from a material with the
ultimate resolution of 2-300 nm laterally and ~500 nm vertically. The Raman
images show that the drug (dexamethasone acetate) forms 1-3um sized particles
in the silicone matrix of the lead collar. Upon being immersed in a methanol
solution for 1 hour, a majority of the drug was eluted to a depth extending
to tens of microns. Holes were left within the silicone matrix; the number
and size of the holes do not match with the drug domains before elution which
suggests a potential complex drug release process. This research provides
insight into the mechanism of release to help guide design of refined devices
for human use.