Poster
Presentation 22:
Ultrasound-Triggered Drug Delivery with Contrast Imaging:
Effect of Microencapsulation Method
M.A. Wheatley1,2,
D. El-Sherif1, R.
Shimp2
1School of Biomedical Science Engineering and Health
Systems
2Chemical Engineering
Drexel University
Philadephia, PA 19104
dalia@io.ece.drexel.edu
(215) 895-5831
Medical ultrasound is a highly valuable diagnostic tool,
especially when compared with other imaging modalities. It is non-invasive,
real-time, portable, extremely safe compared to X-ray, and inexpensive
relative to MRI. Recently, ultrasound contrast agents have been developed
which when injected into the body, greatly enhance the
contrast of the acquired image.
We have developed a method for producing hollow microcapsules,
with diameters less then 10 microns so they can pass the pulmonary bed
after intravenous injection. We describe the use of these agents
for concomitant imaging and drug delivery. The drug-loaded contrast
is imaged as it passes through the region of interest. At the same
time drug release is triggered right at the insonated area. This
study investigates two parameters: The effect of encapsulation method (solvent
extraction and spray drying) on the drug payload by adsorption, and the
effect of insonation parameters (such as time, insonation frequency and
pressure) on the release profile. Hollow polylactide-co-glycolide microcapsules
were prepared by the above techniques. The freeze-dried capsules were filtered
and sized on a Horiba particle size analyzer. Zeta potential data
was recorded pre- and post drug loading. FITC-BSA was used as a model high
molecular weight bioactive drug. Release studies were performed in
vitro in a release chamber fitted with an acoustic window. Insonation
frequencies were in the medical range, at 5 and 10 MHz.
Drug release was measured by an increase in FITC fluorescence in the release
medium. The spray dried sample showed greater adsorption and drug
release. The most dramatic increase in release was after 5 minutes for
the 10 MHz low (1.25 MPa) pressure insonation, which showed 316% greater
release than control, a total of 1.89 mg.
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