School of Biomedical Engineering, Science & Health Systems
MICROENCAPSULATION RESEARCH
Contrast Agents for Diagnostic Ultrasound Imaging : Surfactant Stabilized (Next
Generation)
Surfactant stabilized microbubbles increase the contrast of a medical ultrasound
image to allow physicians to diagnose microscopic cancerous lesions in soft
tissue. Current research focuses on attaching antibodies to the bubbles to target
specific sites, such as tumors and atherosclerotic plaque.
In Vivo Post Injection, Kidney
ST68-air
ST44-C4F10
Surfactant-Stabilized Agent
• Incorporation of targeting ligands
• Harmonic and subharmonic imaging
• Triggered drug delivery
ST68-SF6
Contrast Agents for Diagnostic Ultrasound Imaging : Polymeric Microcapsules
Polymer-Coated Agent
• New methods of preparation
• Triggered drug delivery
• Site-specific targeting
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Like the surfactant stabilized microbubbles above,
bubbles coated with a biocompatible polymer also
increase the contrast of a medical ultrasound image.
We are also developing the polymer coated bubbles
to act as drug carriers, which will release their drugs
directly at the imaged site when triggered by
ultrasound.
Ex-vivo Gene Therapy for Spinal Cord Injury Repair
Currently, we are microencapsulating genetically engineered cells that contain a gene
that codes for human brain-derived neurotrophic factor (BDNF). The microencapsulated
cells are implanted in the spinal cord at the injury site where they produce BDNF, which
promotes axon growth for reconnecting the spinal tissue. The capsules are designed to
allow free passage of the BDNF, but prevent factors from the host immune system from
accessing the cells. This design allows use of the cells without the need for immune
suppression. Current efforts also focus on coating the capsules with growth-permissive
substrates, such as laminin.
Programmable Drug Delivery
Microencapsulation of liposomes provides a means
of producing a highly versatile drug delivery system
with multiple control points and of overcoming the
problem of rapid elimination and destruction in vivo.
The release of FITC-BSA from microencapsulated
liposomes was studied in order to evaluate the
properties of this dual component system for
controlled drug delivery.
Faculty/Contact: Margaret Wheatley, Ph.D., Drexel University.
E-mail: wheatley@coe.drexel.edu
WWW.BIOMED.DREXEL.EDU/ResearchPortfolio/
V 3.0 SD [020403]
School of Biomedical Engineering, Science & Health Systems
CONTRAST AGENTS FOR DIAGNOSTIC ULTRASOUND IMAGING:
SURFACTANT STABILIZED (NEXT GENERATION)
Surfactant stabilized microbubbles increase
the contrast of a medical ultrasound image
to allow physicians to diagnose microscopic
cancerous lesions in soft tissue. Current
research focuses on attaching antibodies to
the bubbles to target specific sites, such as
tumors and atherosclerotic plaque.
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In Vivo Pre Injection
ST68-air
ST44-C4F10
ST68-SF6
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Color Doppler Imaging:
ST68-PFC and ST44-PFC, ~1 x 10*9 microbubbles/mL
Injected in right jugular vein of NZ white rabbit
(Siemens Elegra Imaging, right kidney)
In Vivo Post Injection
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3-D Harmonic Image of Kidney
Surfactant-Stabilized Agent
• Incorporation of targeting ligands
• Harmonic and subharmonic imaging
• Triggered drug delivery
In vivo Harmonic Imaging ST44-PFC
Pre-injection MI 0.3
Post-injection of 0.1 ml/kg
ST68-air
ST44-C4F10
ST68-SF6
Color Doppler Imaging
Pre-injection
Post-injection
CAI ST68 0.1 mL/Kg ; MI 0.4, 3.3/6.6 MHz (2nd)
Faculty/Contact: Margaret Wheatley, Ph.D., Drexel University.
E-mail: wheatley@coe.drexel.edu
Collaborating Researchers: F. Forsberg, Ph.D., Thomas Jefferson University; B. Goldberg, Ph.D., Thomas Jefferson University.
Funding: NIH
Laboratories: Calhoun Laboratories at Drexel University.
WWW.BIOMED.DREXEL.EDU/ResearchPortfolio/
V 3.0 SD [020403]
School of Biomedical Engineering, Science & Health Systems
CONTRAST AGENTS FOR DIAGNOSTIC ULTRASOUND IMAGING:
POLYMERIC MICROCAPSULES
Bubbles coated
with a biocompatible
polymer increase the
contrast of a medical
ultrasound image to
allow physicians to
diagnose microscopic cancerous
lesions in soft
tissue.
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In Vivo Power
Doppler Imaging
Pre-injection
Scanning elecron micrograph
of capsules
Post-injection
 Drug Delivery (Therapeutic) Contrast Agents
We are also developing the polymer coated bubbles to act as drug carriers, which will release their
drugs directly at the imaged site when triggered by ultrasound.
Protein Released with Time
Protein Released (mg)
2.19
Stirred
1.99
F=5MHz and P=2.07 MPa
1.79
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F=10MHz and P=1.25 MPa
1.59
F=10MHz and P=2.63 MPa
1.39
F=5MHz and P=0.838 MPa
1.19
0
Time (min)
5
10
15
 Targeted Contrast Agents
Current research focuses on
attaching antibodies to the
bubbles to target specific
sites, such as tumors and
atherosclerotic plaque.
Attachment of PLGA
Contrast Agents to Cells
after 6 Hours of Incubation
Control 1- Cells without
capsules
Control 2 - PLGA
capsules attached without peptide
Experimental- PLGA
capsules attached with
peptide
Faculty/Contact: Margaret Wheatley, Ph.D., Drexel University.
E-mail: wheatley@coe.drexel.edu
Collaborating Researchers: F. Forsberg, Ph.D., Thomas Jefferson University; B. Goldberg, Ph.D., Thomas Jefferson University.
Funding: NIH
Laboratories: Calhoun Laboratories at Drexel University.
WWW.BIOMED.DREXEL.EDU/ResearchPortfolio/
V 3.0 SD [020403]
School of Biomedical Engineering, Science & Health Systems
EX-VIVO GENE THERAPY FOR SPINAL CORD INJURY REPAIR
Currently, we are microencapsulating genetically engineered
cells that contain a gene that codes for human brain-derived
neurotrophic factor (BDNF). The microencapsulated cells are
implanted in the spinal cord at the injury site where they
produce BDNF, which promotes axon growth for reconnecting
the spinal tissue. The capsules are designed to allow free
passage of the BDNF, but prevent factors from the host
immune system from accessing the cells. This design allows
use of the cells without the need for immune suppression.
Current efforts also focus on coating the capsules with growthpermissive substrates, such as laminin.
In vitro cell growth in microcapsules
Transplantation of encapsulated cells in vivo
a
b
a
a. Microcapsules inside the
spinal cord of a rat.
b
Cells encapsulated at high concentration
a
b. BDNF producing fibroblasts encapsulated with
cresol violet inside the
microcapsules.
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Day 3
Day 5
Section of spinal cord stained
with RT97, which stains neurofilament, a cytoskeletal protein
of neurons. The red color shows
growth of neurons around the
microcapsule.
Day 7
Section of spinal cord stained
with CGRP, which stains a
neurotransmitter. The green
color provides evidence of
sprouting of neurons.
Day 12
At day 5, some of the capsules were broken open
by treatment with EDTA, and the released cells
were allowed to grow in culture
Immediately after
release from capsules
2 days post-release
Cross-section of implant area: the green stain
represents neuronal growth on the periphery of the
implanted capsule (the arrow indicates the genetically
engineered cell aggregate inside the capsule).
Faculty/Contact: Margaret Wheatley, Ph.D., Drexel University.
E-mail: wheatley@coe.drexel.edu
Collaborating Researchers: I. Fischer, Ph.D., MCP Hahnemann University; M. Murray, Ph.D., MCP Hahnemann University.
Funding: NIH
Laboratories: Calhoun Laboratories at Drexel University.
WWW.BIOMED.DREXEL.EDU/ResearchPortfolio/
V 3.0 SD [020403]
School of Biomedical Engineering, Science & Health Systems
PROGRAMMABLE DRUG DELIVERY
Microencapsulation of liposomes provides a means of producing a highly versatile drug
delivery system with multiple control points and of overcoming the problem of rapid elimination
and destruction in vivo. The release of FITC-BSA from microencapsulated liposomes was
studied in order to evaluate the properties of this dual component system for controlled drug
delivery. Alginate was used as the encapsulating polymer due to the mild conditions of the
encapsulation process. Liposomes composed of phosphatidylcholine (PC) and cholesterol
(Chol) in the molar ratio 7:3 and of phosphatidylcholine, phosphatidylglycerol (PG) and
cholesterol in the ratio 6:1:3 were encapsulated in alginate crosslinked with Ca2+ (Ca-Alg), Al3+
(Al-Alg) and Ba2+ (Ba-Alg). A rapid initial burst of protein release was observed from liposomes
that were encapsulated in Ca-Alg and Al-Alg. The extent of the burst was slightly different in
liposomes encapsulated in Ca-Alg and Al-Alg and no burst was observed in those
encapsulated in Ba-Alg indicating that the crosslinking ions could significantly affect the
release of entrapped protein. Also, release of FITC-BSA from liposomes encapsulated in CaAlg varied significantly with liposome composition. Release studies indicated that cholesterol
containing liposomes were leakier after encapsulation in Ca-Alg compared to those without
cholesterol. In all cases, the release from microencapsulated liposomes was much faster than
that from free liposomes suggesting an interaction between the liposomes and the alginate.
Differential scanning calorimetry suggested that alginate was inserted into the lipid bilayer
resulting in a rapid release of protein from microencapsulated liposomes. Also, it was
observed that the degree of interaction between liposomes and alginate had a strong
dependence on liposome composition.
Immediately after encapsulation
Ten days after start of delivery
Alginate-encapsulated liposomes. Over time, the lipsomes discharge the drug. Sustained release can last up
to 30 days.
Faculty/Contact: Margaret Wheatley, Ph.D., Drexel University.
E-mail: wheatley@coe.drexel.edu
Collaborating Researchers: H. Shaw, Ph.D., NASA.
Funding: NASA
Laboratories: Calhoun Laboratories at Drexel University.
WWW.BIOMED.DREXEL.EDU/ResearchPortfolio/
V 3.0 SD [020403]
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