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JARROD HANSON | Ph.D. Candidate
Biomedical Engineering
Nanoscale Double Emulsions Stabilized by Amphiphilic Diblock Copolypeptides
We have created amphiphilic block copolypeptides that have the ability to form stable nanoscale double emulsions. The combination of both encapsulated oil and water phases make them ideal for simultaneous delivery of hydrophobic and hydrophilic cargo. Amphiphilic block copolypeptides were synthesized using transition metal mediated ring opening polymerization of α-amino acid N-carboxyanhydrides. Block copolypeptides (poly-(L-lysine)x-b-poly-(L-leucine)y, KxLy containing α-helical hydrophobic segments formed stable oil in water (OW) emulsions. However, when (poly-(L-lysine)x-b-poly-(D/L-leucine)y, Kx(rac-L)y block copolypeptides were emulsified they produced stable water in oil in water double (WOW) emulsions. We will discuss how the conformation of the hydrophobic block greatly affects emulsion nanostructure. Double emulsions can also be formed with block copolypeptides containing a variety of hydrophilic and hydrophobic chain lengths and functionality. Encapsulation of fluorescent hydrophilic and hydrophobic cargos shows that the double emulsions can act as dual carriers.
Jarrod Hanson is a polymer chemist interested in researching polymeric materials for biomedical applications. He graduated magna cum laude with a B.S. in Chemistry from the University of Massachusetts, Amherst in 2001. In the fall of 2001, Jarrod enrolled in the Chemistry Department at the University of California, Santa Barbara where he began his graduate research in Professor Timothy J. Deming’s laboratory. In 2004, he moved, along with Professor Deming, to the department of Biomedical Engineering at the University of California, Los Angeles. Jarrod expects to graduate in 2008 with his Ph.D. in Biomedical Engineering.
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VICTOR SUN | Ph.D. Candidate
Bioengineering
Block Copolypeptide Vesicles for Drug Delivery
Drug delivery vehicles have been investigated for several years because of the several challenges associated with administering a naked drug. These challenges include enzymatic and proteolytic degradation, catabolism in the liver, clearance by the kidneys, recognition by the immune system, inability to cross the cell membrane, solubility issues, and nonspecific toxic effects on normal cells. Encapsulation of the drug is an approach that may address these challenges, and therefore, we have been investigating novel vesicles comprised of polyarginine and polyleucine segments as potential drug carriers. Specifically, we have previously shown in vitro that these vesicles can transport dye-labeled dextran into both epithelial and endothelial cells without being toxic. These vesicles were also shown to be stable in serum-free media, be processed to different sizes, and be prepared in large quantities. This presentation will discuss our recent efforts in further investigating these vesicles. Specifically, we have examined their stability in serum-containing media, as well as monitored leakage of their contents by loading a fluorescent dye along with a quencher into the aqueous core. We have also performed cellular uptake experiments in the presence of different drugs to identify the mode of cellular entry for the vesicles. Lastly, we have performed immunostaining to elucidate the intracellular trafficking pathway for these vesicles, which will enable us to engineer the next generation vesicles that are more effective in delivering drugs.
Victor Sun is currently a graduate student in the laboratory of Professor Daniel Kamei in the Department of Bioengineering at UCLA. His thesis focuses on improving the half-lives of therapeutics in the body using protein-based and polypeptide-based drug delivery systems. Victor conducted his undergraduate studies at UC Riverside, where he graduated with a BS in Biochemistry. He also has an MS from the Department of Bioengineering at UCLA.
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TAE-JOON JEON | Ph.D. Graduate
Chemical and Biomolecular Engineering
Bringing Lipid Bilayer Technologies from Benchtop to Marketplace
Lipid bilayers and their biomimetic analogs are used in a variety of scientific applications and have also been explored as a platform for highly sensitive and rapid single molecule sensing. However, these uses are inhibited by the fragility and short lifetime of the membrane supporting the protein. To achieve increased stability we have devised a hydrogel encapsulation technique where the lipid bilayers were encapsulated in situ within a PEG-DMA hydrogel (HEM). The lifetime and mechanical stability were significantly enhanced, and the hydrogel is permeable to both ions and biomolecules, making it ideal for sensor applications. Alpha-hemolysin was incorporated and continuously measured in an HEM for 5 days. To further stabilize HEM, the membrane was conjugated to the hydrogel (cgHEM), resulting in an extremely long lived membrane that remained stable for over 11 days. The effort to stabilize a membrane was further extended to developing a storable and shippable platform. A lipid bilayer membrane was created in which the process of membrane self-assembly was halted by including a high freezing point solvent phase. Upon thawing, the membrane formation process resumed and a functional bilayer was formed. The solidification of the membrane precursor allowed for transport and indefinite storage. To further reduce the complexity of the membrane experiment, channel proteins can be introduced either in aqueous phase or in MP before freezing it. The broad usability of this membrane platform represents a significant advance in the field of science and engineering, industry, and education.
Tae-Joon Jeon is a recent Ph.D. graduate of the Department of Chemical and Biomolecular Engineering at UCLA. He received his Bachelor’s degree from Seoul National University in Korea. After a year of industrial experience at IBM Korea, he began his graduate studies at UCLA. His dissertation advised by Jacob Schmidt, a professor of Bioengineering, focused on the development of novel biomimetic membrane technologies for protein based sensors and electrophysiological studies. He has made significant progress with successful approaches toward creating a robust biomimetic membrane platform. As a result, articles describing new methods to create membranes and their characteristic properties have been published in several peer-reviewed journals including PNAS, JACS, and Advanced Materials. He is a member of the American Chemical Society and Biophysics Society. |
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RICHARD FAN | M.S. and Ph.D. Candidate
Biomedical Engineering
A Pneumatic Haptic Feedback System to Assist Rehabilitation After Lower Limb
Amputation
A haptic feedback system has been developed to provide sensory information to patients with lower-limb prostheses or peripheral neuropathy. In my research, piezoresistive force sensors were mounted against four critical contact points of the foot to collect and relay force information to a system controller, which, in turn, drives four corresponding pneumatically controlled balloon actuators. The silicone-based balloon actuators were mounted on a cuff worn on the middle thigh, with skin contacts on the posterior, anterior, medial, and lateral surfaces of the thigh. Actuator characterization and human perceptual testing were performed to determine the effectiveness of the system in providing tactile stimuli. The actuators were determined to have a monotonic input pressure-vertical deflection response. Six normal subjects wearing the actuator cuff were able to differentiate inflation patterns, directional stimuli and discriminate between three force levels with 99.0%, 94.8% and 94.4% accuracy, respectively. With force sensors attached to a shoe in-sole worn by an operator, subjects were able to correctly indicate the movements of the operator with 95.8% accuracy. These results suggest that the pneumatic haptic feedback system design is a viable method to provide sensory feedback for the lower limbs.
Richard E. Fan received his B.S. degree in Electrical Engineering from the University of Arizona in 2005, his M.S. degree in Electrical Engineering from the University of California, Los Angeles in 2006, and is currently pursuing his M.S. and Ph.D. degrees in Biomedical Engineering at UCLA. He works as a Graduate Student Researcher at the UCLA Center for Advanced Surgical and Interventional Technology (CASIT), Los Angeles, CA. His current research interests include haptic feedback and rehabilitation engineering. |
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MARTY CULJAT | Engineering Research Director
Center for Advanced Surgical and Interventional Technology (CASIT)
Flexible conformal ultrasound transducers for imaging of soft and hard tissues
Current medical ultrasound techniques require scanning with rigid multi-element arrays to obtain images over curved surfaces of the body. An ultrasound imaging system that does not require mechanical scanning can potentially expand the use of ultrasound to medical personnel with limited ultrasound training, including point of care physicians and those in remote or emergency settings. A flexible, conformal ultrasound transducer array and imaging system is currently being developed that can be wrapped around extremities and curved surfaces of the body. By wrapping the transducer around an object and obtaining image data with the transducer fixed, mechanical scanning is eliminated. Additional advantages are that this configuration provides multiple unique “looks” around internal objects and can allow for high resolution volumetric images in real time. The device is intended for use both in a partially wrapped configuration (i.e., around the abdomen), or fully wrapped around an object (i.e., around a leg or finger). The development of a flexible, conformal transducer prototype and preliminary results are described.
Martin Culjat, Ph.D., is Engineering Research Director at UCLA's Center for Advanced Surgical and Interventional Technology (CASIT), Assistant Researcher in the UCLA Department of Surgery, and Adjunct Assistant Professor in the UCSB Department of Electrical and Computer Engineering. He has a biomedical engineering background and expertise in medical imaging, and sensor and system design, fabrication, and integration. He is currently focused on ultrasound and terahertz (THz) medical imaging, robotic surgery, minimally invasive surgery, ophthalmologic surgery, prosthetics, and haptic feedback. |
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