Bioengineering Seminar Schedule
Spring, 2005 (For prior semesters, click here: Fall
1999, Spring 2000 , Fall
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Friday, January 14, 12:00 - 1:00, Room 210 Hallowell
Aman Haque
Assistant Professor, Mechanical and Nuclear Engineering, Penn State University
"Single Cell Opto-Electro-Mechanical Probing: A Feasibility Study"
Abstract
Mechanical, electrical and chemical signals from the environment direct influence the physiological activities
and health of a cell. While the existing trend is to study these signals separately in their respective domains,
they are actually inherently coupled. Here we explore the feasibility and merits of a new instrument that can measure,
for the first time, externally applied (or internally generated) forces and electrical impedance of a single cell
in real time. The pico-Newton resolution micro-instrument (1 mm x 1mm in size) will be readily compatible with
conventional optical/fluorescence techniques for opto-electro-mechanical probing. Force sensing operation is unaffected
by the electrical and chemical nature of cell environment and the bio-impedance measurement scheme can automatically
compensate for any non-cell specific sources of error. Studies on the effects of mechanical, electrical and chemical
signals with real-time opto-electro-mechanical cell characterization will impact diagnosis and cure for various
diseases of the heart, skin, intestines, nerves, oncology, bones, lung - to name a few. Long-term contributions
would be novel lab-on-a-chip type diagnostic/therapeutic/drug discovery tools to monitor the bio-impedance of a
single cell with respect to external stimuli (toxin, drug).
Friday, January 21, 12:00 - 1:00, Room 210 Hallowell
Zhiwen Liu
Electrical Engineering, Penn State University
"Spatially Coherent Temporally Incoherent Optical Information Systems"
Abstract:
Coherence plays an important role in optical information systems. In this talk I will discuss spatially coherent
but temporally incoherent systems implemented by using ultrashort white light supercontinuum generated from highly
nonlinear photonic crystal fibers. Such systems have unprecedented parallelism and can open new possibilities in
imaging, spectroscopy, and optical communication. I will focus on two specific examples: chromatic confocal microscope
and ultrashort supercontinuum tweezers which have integrated functionalities of imaging, spectroscopy, and micro-manipulation.
Friday, January 28, 12:00 - 1:00, Room 210 Hallowell
David Francischelli
Medtronic, Inc.
"Research And Development At A Large Medical Device Company; The Surgical Ablation
Program as a Case Study"
Abstract
Medical device development is by its very nature, very regulated and arduous. Although slightly different for
every company, a typical product development cycle will have a number of phases, which include feasibility, gathering
of customer requirements, product definition, design, verification/scale-up and release. Each phase has a series
of deliverables, checks and balances. Although minimum requirements are set by various government regulatory bodies,
companies often have much more stringent requirements to mitigate potential risks. These additional requirements
are generally proportional to the size of the company - the larger the organization, the greater the potential
risk and the more extensive the quality standards. Although assuring a higher quality product, this can often lead
to frustratingly long development times.
Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia. It's prevalence increases with age and
affects about 10% of octogenarians. Hemodynamic impairment and thromboembolic events result in significant morbidity,
mortality and cost to the healthcare system. The surgical maze procedure has been shown to cure long-standing AF
in upwards of 90% of patients. However, technical complexity and the need for open-heart surgery have hampered
widespread adoption.
Although not first in the market, Medtronic has in just a few short years emerged as a leader in surgical therapies
for AF. The Cardioblate family of devices safely replicates the surgical scars of the maze procedure. To date,
over 25,000 patients have been treated with this irrigated RF-based system.
Friday, February 4, 12:00 - 1:15, Room 210 Hallowell
Gavin Robertson
Hershey
"Regulation of the Development of Blood Channels in Cutaneous Melanomas by Chromosome
10 p15.3"
Abstract
The development of a tumor-lined vascular system that is an adjunct to the endothelial-lined vasculature could
provide significant growth advantages to primary or metastatic tumors. The formation of structures that might perform
these functions are poorly understood even though structural components that could comprise this system have been
morphologically identified for many years. We observed that metastases obtained from 45% (10/22) of melanoma patients
contained blood channels without an endothelial lining and of these 60% had extensive interconnecting networks.
To ascertain the relevance of these structures to tumor growth, we established a model in which the development
of tumor-lined channels could be regulated. The establishment of an endothelial-lined vasculature in the tumors
preceded the formation of the tumor-lined channels, with the channels developing and becoming extensive during
the exponential phase of tumor growth through connections to leaky simple endothelial lined vessels. The formation
of the tumor-lined channels could be blocked by introduction of the chromosome 10p15.3 region and was accompanied
by a significant reduction in tumor growth. Thus, tumor lined vascular channels might provide melanoma tumors with
a growth advantage over that of an endothelial lined vasculature alone. These studies may now open this process
to a genetic dissection of its mechanistic underpinnings.
Friday, February 11, 12:00 - 1:00, Room 210 Hallowell
Axel Bergmann
Becker & Hick1
"Fluorescence Lifetime Images and Correlation Spectra Obtained by
Multi-Dimensional TCSPC"
Abstract
Multi-dimensional time-correlated single photon counting (TCSPC) is based on the excitation of the sample by
a high-repetition rate laser and the detection of single photons of the fluorescence signal
in several spectral detection channels. Each photon is characterized by its time in the laser period, its detection
channel number, and several additional variables such as the coordinates in an image
area, or the time from the start of the experiment. Combined with a confocal or two-photon laser scanning microscope,
multi-dimensional TCSPC makes a fluorescence lifetime technique with
multi-wavelength capability, near-ideal counting efficiency, and a time-resolution down to a few 10 ps. We show
that the same technique and the same hardware can be used to record fluorescence
decay functions and fluorescence correlation curves in selected spots of a sample. The decay curves are obtained
by building up histograms of the detection times in the laser pulse period. Correlation
functions are calculated by correlating the absolute detection times of the photons.
Friday, February 18, 12:00 - 1:00, Room 210 Hallowell
Student Presentations:
"Controlling Role of Water in Protein Adsorption"
by: Anandi Krishnan
Abstract
Interfacial energetics of protein adsorption from aqueous-buffer solutions to hydrophobic methyl-terminated
SAM surfaces are strikingly similar to the interfacial energetics of protein adsorption to
the hydrophobic air-water surface. Spreading pressure () isotherms exhibited a ‘Traube-rule-like’ progression in
similar to the ordering observed at the LV surface wherein molar
concentration required to reach a specified spreading pressure decreased with increasing MW. Collective results
from the observed ‘Traube-rule-like’ progression in interfacial-tension reduction,
an invariant partition coefficient , and a constant Gibbs’ surface excess (as a measure of amount of protein adsorbed)
for globular proteins spanning 3 decades in all imply that water controls the
energetics of the adsorption process. Hence, protein adsorption to hydrophobic surfaces has more to do with water
than the proteins themselves. A relatively straightforward theory of protein adsorption
predicated on the interfacial packing of hydrated spherical molecules with dimensions scaling as a function of
accounts for the essential physical chemistry of protein adsorption and rationalizes
significant experimental observations. From this theory it is evident that displacement of interfacial water by
hydrated proteins adsorbing from solution places an energetic cap on protein adsorption to
hydrophobic surfaces. This phenomenon is generic to all proteins. Hence, protein adsorption is not found to significantly
vary among diverse protein types. Variations from this general trend may
reflect deviations in protein geometry from simple spheres and/or tendency of some proteins to adopt a more spread/compact
configuration in the adsorbed state.
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"On-Chip Microdialysis System with In-Line Sensing Capabilities"
by: Yi-Cheng Hsieh
Abstract
An on-chip microdialysis system with in-line sensing electrodes is presented here. The design of this system
is based on membrane bonding onto microfluidic channels, having a high surface to volume ratio to promote efficient
dialysis and in-situ integration with biosensors for continuous monitoring. In diabetes treatment, microdialysis
probes have been used as sampling systems coupled to a glucose biosensor but struggle to obtain high recoveries
of analytes while the sampling housing, probes, and glucose sensors are fabricated as separate pieces and then
assembled resulting in a large dead volume. The problems can be solved by an in-situ combination of a microdialysis
probe and biosensor. As a first step towards greater biosensor integration with a miniaturized microdialysis system,
in-line sensing electrodes were used to determine fluid impedance from a dialyzed phosphate buffered saline (PBS)
solution, which characterizes solution conductivity as a function of PBS concentration. Impedance sensing electrodes
were fabricated using a patterned sputtered gold film with an electrode spacing of 40 mm and integrated with SU-8
microchannels. A polycarbonate track etch membrane (100 or 15 nm pore sizes) was applied on top of the SU-8, followed
by a lamination bond. This bonding procedure has resulted in a reproducible, non leaking bond. High recovery glucose
dialysis (100 nm pore size membrane) has been demonstrated using this system with a Therasense Free Style Glucose
Monitor to determine the glucose concentration in the exiting fluid. The permeability for glucose has been determined
to be 2.53 µm/s (std: 0.372 µm/s). Next, the response time of the microdialysis system was characterized.
Within 2 minutes of a reservoir concentration change, the outlet concentration of the dialysate has reached steady
state at a perfusion flow rate of 2 µl/min. Finally, PBS is dialyzed using DI water as a perfusion fluid
and the recovery is characterized (15 nm pore size membrane). The permeability of salt ions is determined to be
2.74 µm/s. For time domain results a 99% recovery is obtained at a perfusion flow rate of 0.5 ml/min and
the systems is able to reach steady state within 200 seconds of a reservoir salt concentration change. This work
represents the first step towards better integration of a miniaturized microdialysis system with in-line biosensors
for high frequency continuous medical monitoring. The integration of a biosensor directly with the microdialysis
system allows high recovery of analytes with a smaller diffusional surface area and lower flow rates resulting
in a less invasive, more precise microdialysis probe.
Friday, February 25, 12:00 - 1:00, Room 210 Hallowell
Ki H. Chon (CANCELED DUE TO WEATHER)
SUNY
"Development of a Cardiovascular Monitor and Sensor: from Hardware to Software"
Abstract
The cardiac autonomic nervous system is responsible for maintaining proper homeostasis, or balance, of the cardiovascular system. One of our major areas of research is to detect, quantify, and interpret differences in dynamic characteristics of the cardiac autonomic nervous system between normal and diseased subjects, in an attempt to find a marker for increased risk of sudden cardiac death. Identifying and quantifying differences in the dynamic characteristics of autonomic function between normal and diseased conditions may lead to a better understanding of the role of autonomic function imbalance in diseased conditions, and should have important clinical diagnostic and prognostic applications. Another active research area is the development of computational modeling approaches to understand differences in dynamics of renal autoregulatory mechanisms between normotensive and hypertensive conditions. Both hardware implementations and novel software data analysis techniques which we are using to achieve these research objectives will be presented. For the hardware development, a personal digital assistant device to obtain on-line and real-time data acquisition of ECG signals will be demonstrated. For software development, novel linear and nonlinear time-varying signal processing techniques that can be successfully applied to cardiovascular and renal data to differentiate between normal and diseased conditions will be demonstrated.
Friday, March 4, 12:00 - 1:00, Room 210 Hallowell
Student Presentations
"Understanding Mechanical Heart Valve Cavitation"
by: Luke Herbertson
Abstract
Mechanical heart valves (MHVs) are known to induce cavitation during closure and rebound. Cavitation may lead
to blood element damage and stable bubble formation, with the latter possibly introducing emboli into cranial circulation
and increasing the risk of stroke. Previous research has revealed that carbon dioxide is the primary blood gas
involved in stable bubble growth. The first objective of this study is to determine the role that carbon dioxide
plays in MHV cavitation bubble formation. This study applies wavelet transforms to acoustic signals associated
with cavitation bubble collapse. Second, laser Doppler velocimetry was implemented to examine the flow structures
associated with cavitation formation.
The cavitation events have been visualized using high-speed videography for the 29 mm Bjork-Shiley Monostrut (BSM)
and Medtronic-Hall MHVs in the mitral position. The experimental parameters were adjusted to provide dp/dt values
of 500, 2500 and 4500 mmHg/s. The degassed water (5 ppm) contained dissolved carbon dioxide pressures of 0, 40
and 100 mmHg. The collapse of cavitation bubbles produces high-frequency pressure fluctuations that are detected
using a hydrophone.
Root-mean squared (RMS) values were calculated to quantify the cavitation intensity over a frequency range of 35
- 300 kHz. The results of the carbon dioxide study reveal no statistical difference between the cavitation intensities
produced by the MHVs in degassed water containing 0, 40 or 100 mmHg CO2. The results from the wavelet study display
a marked improvement in the quantity and quality of information that can be extracted from acoustic cavitation
signals using the wavelet technique compared to conventional analysis techniques. The flow studies suggest vortical
structures play a role in the formation of cavitation bubbles in the BSM valve.
==================================================================================================
"Quantitative Analysis of Biomolecular Concentration in Living Cells with High Spatial Resolution"
by: Ronn Walvick
Abstract
The concentration of intrinsic biomolecules, such as proteins and cofactors, can be used as a reporter for health
and disease diagnoses. Biochemistry on lysed cells is a common experimental technique for these measurements. In
contrast, two-photon (2P) fluorescence is a noninvasive approach for imaging of these biomolecules in intact living
cells. While the fluorescence intensity depends linearly on the fluorophore concentration, it also depends on the
fluorescence quantum yield (i.e., lifetime) which is very sensitive to the cellular environment and molecular structure.
As a result, accurate and quantitative estimate of molecular concentration requires an in-depth understanding of
the cellular microenvironment's effect on the fluorescence properties of these molecules. Here we present a fluorescence-based
method for accurate estimation of the molecular concentration using a unique combination of steady-state and time-resolved
2P-fluorescence imaging for quantitative analysis of biomolecules in their native environment with high spatial
resolution. As proof of this concept, we present results on Hs578T human breast cancer cells, as a model system,
stained with a mitochondrial marker Rhodamine 123. The ratio of lifetime decays between the fluorophore in vivo
and in solution is used as a correction factor for constructing a two dimensional concentration map from an intensity
image. These preliminary results will be used to monitor energy metabolism using native biomolecules such as NADH.
===================================================================================================
"Heterogeneous Strain Fields and Focal Adhesion Stresses in a 3-D Continuum Elastic Model
of Sheared Endothelial Cells"
by: Michael Ferko
Abstract
Flow induced mechanotransduction is known to be heterogeneously distributed in endothelial cells. Thus, models for stress distribution are useful in interpreting the correlation between force and cell signaling. We developed a finite element mechanical model coupled with computational fluid dynamics and experimentally determined focal adhesions to map the distribution of stresses in the cell cytoplasm and in individual focal adhesions, thought to be sites of mechanoactivation. To compute the applied force distribution and resultant internal cellular stresses we have developed a process of rapidly creating a finite element model of a single cell or portion of a confluent monolayer of cultured endothelial cells. This process includes 3-D rendering of membrane-stained endothelial cells, a 2-D representation of the cells focal adhesion complexes acquired with total internal reflection fluorescence microscopy (TIRFM), and a coupled computational fluid and solid mechanics model of the rendered cell. Our preliminary results show that the inclusion of focal adhesions as cell attachment points in a continuum elastic model predicts heterogeneous strain distributions within the cell.
Friday, March 11, 12:00 - 1:00, Room 210 Hallowell
SPRING BREAK NO CLASSES
Friday, March 18, 12:00 - 1:00, Room 210 Hallowell
Joel Stiles
Carnegie Mellon University
"Counter-Intuitive Insights from Monte Carlo Simulations of Synaptic Transmission"
Abstract
Physiological function depends on the spatial and temporal dynamics of specific genes, proteins, signaling molecules,
and/or metabolites within and between cells. Realistic physiological simulations present an enormous challenge
because of the wide range of underlying space and time scales, as well as the widely disparate organization and
properties of different systems. In short, a major challenge is to develop modeling and simulation methods that
allow integration of mechanisms, kinetics, and stochastic behaviors at the molecular level with structural organization
and function at the cellular level.
Synaptic transmission exemplifies 3-D reaction-diffusion systems in which stochastic behaviors and spatial complexity
can be very important. Using examples from current research, I will describe our methods for Monte Carlo simulation
of synaptic microphysiology, and illustrate counter-intuitive results obtained from spatially realistic models
of the vertebrate neuromuscular junction. Particular examples will focus on presynaptic calcium dynamics and neurotransmitter
release, postsynaptic membrane topology and quantal current amplitude, and synaptic acetylcholinesterase distribution
and quantal current decay time.
Friday, March 25, 12:00 - 1:00, Room 210 Hallowell
Daryl Kipke
University of Michigan
""
Abstract
Friday, April 1, 12:00 - 1:00, Room 210 Hallowell
Gerald Miller (CANCELLED DUE TO ILLNESS)
Virginia Commonwealth University
"Classification and Recognition of Adverse Dysarthric (Cerebral Palsy) Speech Using
Hidden Markov Models (HMMs) and Artificial Neural Networks (ANNs)"
Abstract
Dysarthria is the most common acquired speech disorder affecting 170 per 100,000 in the United States. In its
severest form dysarthric speech is unintelligible to others and may take the form of producing vocal utterances,
rather than words recognizable to unfamiliar communication partners. Some people with dysarthric speech (like cerebral
palsied individuals) are also severely motor-impaired with limited or no control of their local environment. The
combination of speech and general physical disability can make it particularly problematic for them to interact
in their environment and limits independence. Positive intervention/rehabilitation using modern research technology
like Automatic Speech Recognition (ASR) would hence be very desirable. This presentation will examine the use of
Hidden Markov Models (HMMs) and Artificial Neural Networks (ANNs) for development of a front end speech recognition
platform to interface top standard commercially available speech recognition systems.
Friday, April 8, 12:00 - 1:00, Room 210 Hallowell
Marc Rigas
Scientific Review Administrator, NIH
Guest Speaker
""
Abstract
Friday, April 15, 12:00 - 1:00, Room 210 Hallowell
Cara Williams
Wyeth
"cPLA2a Antagonists are
Potent Inhibitors of Asthma Pathophysiology"
Abstract
cPLA2a antagonism represents a novel therapeutic approach for the treatment of inflammatory
disorders including asthma since it catalyzes the release of arachidonic acid from phospholipid membranes to initiate
the generation of prostaglandins, leukotrienes and platelet-activating factor (PAF). At sites of inflammation,
cPLA2a may be responsible for the production of multiple lipid mediators that potentate
cellular inflammation as well as bronchoconstriction, edema, mucus secretion, and pain. For these reasons cPLA2a antagonism may provide a clinical advantage over existing agents in the treatment of asthma
and other chronic inflammatory disorders such as OA or RA. Potent, non steroidal anti inflammatory cPLA2a
antagonists that are specific and orally active have been developed and tested in both rodent and sheep models
of asthma. In a rat model of antigen induced pulmonary inflammation administration of a cPLA2a
antagonist, (10 mg/kg PO) inhibited pulmonary eosinophilic inflammation. Efficacy was significantly improved with
a multiple dosing paradigm. The activity of this compound (10 mg/kg PO ) was also evaluated in a rat model of Sephadex-induced
pulmonary inflammation. Administration of the cPLA2a antagonist was shown to consistently
block both pulmonary eosinophilia and total inflammatory cell influx into the bronchoalveolar cavity. In a murine
model of OVA-induced pulmonary inflammation and in OVA-induced AHR, administration of the compound (10mg/kg ip)
inhibited BAL and tissue eosinophilia and airway hyperresponsiveness (AHR) to aerosolized methacholine.
In a sheep model of asthma, oral administration of the cPLA2a antagonist (10 mg/kg,
24 hours, 12 hours and 2 hours prior to challenge) completely blocked the increase in airway resistance associated
with a late asthmatic reaction. When a fourth dose of the compound (10mg/kg) was administered directly following
the late phase reaction, AHR to aerosolized carbachol that was measured the following day was completely inhibited.
In a multiple dosing paradigm, administration of the antagonist (3 mg/kg PO, bid) to sheep for 4 days prior to
antigen challenge, inhibited the early asthmatic response by approximately 62% and completely blocked the late
phase response and AHR. These results show that cPLA2a represents a novel therapeutic
target for the treatment of asthma. To our knowledge, these data are the first to demonstrate in vivo efficacy
in multiple asthma models with a potent orally active small molecule antagonist directed towards cPLA2a.
Friday, April 22, 12:00 - 1:00, Room 210 Hallowell
Student Presentations
"Comparative Study of Long-Term Osteoblast Growth Dynamics in a Compartmentalized Bioreactor"
by Xiaomei Liu
Abstract
Long-term in vitro osteoblast growth dynamics in a compartmentalized bioreactor relative to conventional tissue
culture (TCPS) is studied herein using a judicious combination of assays sensitive to different stages of cell
culture. The compartmentalized bioreactor is applied with simultaneous cell-growth-and-dialysis principle without
perturbing the pericellular environment by continuous perfusion or punctuated refeeding in the long-term cell culture.
Human fetal osteoblastic (hFOB 1.19, ATCC, CRL-11372) cell adhesion, proliferation, differentiation, morphology,
and extracellular matrix (ECM) mineralization were evaluated for 15- and 30-day culture periods in both the bioreactor
and TCPS. As observed by SEM and TEM, hFOB formed confluent, interconnecting multilayer at tissue-like density
in the bioreactor (relative to TCPS), with lower degree of apoptosis (assayed by TUNEL). This possibly correlates
with the stable insoluble ECM production in the bioreactor, which was lost in TCPS. In addition, hFOB exhibited
significantly higher alkaline phosphatase level at day 15 and Ca deposition at day 30 in the bioreactor, which
potentially indicate increased rates in cell differentiation and ECM mineralization. Preliminary studies show that
hFOB can sustain long-term in vitro culture up to 30 days in the bioreactor with superior cell performance relative
to conventional tissue culture.
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"Fluorescence Studies of EGFP-Tagged KIF3A/B Motors"
by Yangrong Zhang
Abstract
KIF3A/B is a kinesin family motor involved in ciliagenesis, intraflagellar trafficking and Golgi transport.
KIF3A/B is especially intriguing because, instead of the two identical heads found in most dimeric kinesins, it
contains two different head domains. Our previous motility data showed that KIF3A/B is processive, which means
that a single motor molecule can walk hundreds of steps before detaching from the microtubule. We also found that
the two heads of KIF3A/B move at different velocities, leading us to hypothesize the two heads have other distinct
functional properties, such as processivity and microtubule binding affinity. In order to study these properties
with higher resolution techniques, we made fluorescence labeled KIF3A/B motors by replacing the tail domains with
EGFP fusion proteins. Firstly, the run length and dwelling time of motors running on microtubules is being characterized
by total internal reflection fluorescence microscopy (TIRF) at single molecule level. Secondly, the structural
flexibility of the EGFP-tagged motor is being investigated using a novel time-resolved fluorescence and anisotropy
approach. Thirdly, the motor-microtubule binding affinity is being quantified by Fluorescence Correlation Spectroscopy
(FCS). The information provided here should prove beneficial for investigating the correlation between the fast
molecular dynamics, binding, and biological function of KIF3 motors.
=================================================================================================================
"Molecular Recognition Imaging of Dual Component Protein Films by Atomic Force Microscopy"
by Aashiish Agnihotri
Abstract
During blood-material interaction, plasma proteins rapidly adsorb to the surface. An important component of
this adsorbed protein layer is fibrinogen, which interacts with circulating platelets and facilitates platelet
adhesion, activation and aggregation, eventually leading to surface-induced-thrombosis.
Fibrinogen-surface interactions have been studied extensively by many techniques including high-resolution atomic
force microscopy (AFM), which allows direct observation of protein/surface interactions in a physiologically relevant
environment at the molecular level. We have previously studied fibrinogen surface interactions in sub-monolayer
distributions utilizing pure protein solutions on ultra smooth surfaces. As the AFM probe does not have any direct
chemical or biological sensitivity, identification of a protein is entirely dependent on the structural details
observed in the topographic images. In order to use AFM in studies of more complex protein solutions that better
represent blood, new techniques capable of differentiating between different protein types are necessary. We have
developed an adhesion-mapping mode of AFM with functionalized probes for molecular recognition imaging in dual
component protein films composed of fibrinogen and bovine serum albumin (BSA) adsorbed on mica. Adhesion mapping
mode of AFM was used to generate both topographic images and adhesion maps that highlight the spatial distribution
of the two different proteins. The efficacy of the functionalized probes was first established by performing adhesion
mapping on patterned dual component protein films and then extended to random dual component protein films generated
by sequential adsorption of submonolayer amounts of fibrinogen followed by backfilling with BSA.
========================================================================================================================================
"Biological Fluid Separation in Microfluidic Channels using Flow Rate Control"
by Sung Yang
Abstract
Most biological cell analyses require the ability either to remove cells from a biological fluid, such as the removal of blood cells from whole blood to leave blood plasma, or to concentrate the cells for downstream processing. Typically in medical laboratories, to separate plasma, or collect cells from an initial biological sample for clinical analysis, a centrifugation technique is used in which 4600g/6000rpm is required as a gravitational force, rotational speed, respectively depending on rotor types for centrifugation. In miniaturized total analysis systems (ì-TAS), it is difficult to utilize the centrifugation technique in small devices because it relies on body forces. In this work, a blood plasma separation microdevice is presented, which may be integrated with downstream plasma analysis device.
Friday, April 29, 12:00 - 1:00, Room 210 Hallowell
Student Presentations
"Compatibility of Liquid Crystals with Kinesin and Microtubules for Different Applications"
by Dinesh Baskar
Abstract
Kinesin are intracellular transporters that move on protein tracks called microtubules. The molecular motors
are involved in chromosomal transport during cell division and axonal transport in nerve cells. Kinesins can be
used micro scale transport in vitro in lithographically fabricated channels providing an alternative to micro fluidics.
Our long term goal is to create micro scale sensors for detection of biomolecules and viruses. Liquid crystals
provide sensitive detectors for low concentration of analytes because small perturbation can exert long range disorder
in liquid crystal. These changes can be easily detected by the changes in birefringence but these systems suffer
from mass transport problems reducing their applicability. Our approach is to combine micro scale transport properties
of microtubule - kinesin system with detection abilities of liquid crystals. We have identified liquid crystals
that are both birefringent and compatible with kinesin and microtubules. Current studies are aimed at putting together
a biosensor to sense the analytes.
===============================================================================================================================
"Development of a CFD Tool to Explore the Interactions Between Cancer Cells and Leukocytes"
by Meghan Henty
Abstract
Experiments have shown that in the presence of flow, melanoma cells adhere to and migrate through an endothelium
more efficiently when neutrophils are present. These results led to the hypothesis that melanoma cells adhere to
neutrophils first, which brings them close enough to the endothelium to either bind or migrate. Parallel plate
flow chamber experiments have determined the binding efficiency of melanoma cells to neutrophils on a model endothelium
is affected by altering the fluid dynamics of the system. To explore how the fluid affects these interactions,
a computational fluid dynamics (CFD) tool is being developed to model the parallel plate flow chamber experiment.
Some initial steps in the development of this CFD tool will be presented, including the creation of a model cell
and the determination of adhesion kinetics parameters.
==================================================================================================================================
"Characterization of Cylindrical Polymer Actuators"
by Elizabeth Eaton
Abstract
Mechanical and electromechanical actuators have provided means for achieving design requirements in a variety
of applications over the last decades and centuries. As the technology improves and society moves towards ever-more
sophisticated solutions at lower costs, however, actuators that can do more complex tasks with smaller expenditures
are coming into high demand. Electroactive materials are those that experience a change in shape when a voltage
is applied across their thickness. Although there are many different materials within this broader category, electroactive
polymers (EAPs) are of particular interest due to their relatively superior fracture toughness, flexible size and
shape, and high strain capacity. EAPs such as 3M's polyacrylate VHB tape will expand in one direction while contracting
in another, provided a flexible electrode has been applied to the two surfaces. In order to expand in one direction,
the material must shrink in an orthogonal direction, by conservation of volume. In assuming incompressibility for
these materials, it is accepted that the thickness is dependent on only a corresponding dimensional change in a
perpendicular direction. This research characterizes the relationships
between strain and force for specific dielectric electroactive polymers in the single-layer tubular geometry under
distinct conditional classifications. The most basic of these is the relationship of length to force applied in
an open, passive construction. Additional configurations include open and closed (filled) tubes under activation.
==============================================================================================================================
"A Study of the Optimization of Window Parameters (Length and Shape) of a Short-Time Fourier
Transform (STFT) Employed in a Micro-Emboli Detection Algorithm for Increased Detection Accuracy"
by Sowmya Ballakur
Abstract
An algorithm has been developed for the automatic detection of microemboli based on measurements of the distribution of spectral energy in the blood background signal of a Doppler Ultrasound blood velocity signal. The effect of window length and shape in the Short-time Fourier Transform has been investigated with the goal of maximizing the difference between the peak intensity values produced by the emboli and the background signal. The study used a 10 MHz continuous wave probe, a pulsatile flow phantom, blood mimicking fluid and 500 micron diameter polystyrene microspheres as simulated emboli. Three embolic events of duration approximately 0.7, 3.0 and 12 ms, with sufficient background signals, were isolated into individual data segments. Background distributions were estimated from segments (100 ms long) obtained from the same data sets. Three parameters-- the maximum peak intensity of the embolic distribution (Epeak) and the 95th percentile value of the background distribution (B95) and the Embolic to Blood ratio (EBR) were evaluated for each set of embolic and non-embolic data as a function of window length for the five selected window types (shapes)- rectangular, bartlett, gaussian, flattop and the kaiser window. The study is designed to investigate whether matching the window - in time duration and/ or mainlobe bandwidth - to that of the embolus, would significantly improve these parameters from which detection accuracy is determined.
Tuesday, June 1, 2005, Room 210 Hallowell Building
Gaurav Girdhar
"Simultaneous Tether Extraction from Endothelial Cells and Leukocytes and Its Implication in Leukocyte Rolling"
Abstract
The stability of neutrophil rolling on the endothelium is vital for the ensuing integrin-mediated firm adhesion
and extravasation to sites of infection. Several potential mechanisms that include multiple bond formation and
cellular mechanical properties have been proposed for this enhanced stabilization. The mechanism of tether (membrane
nanotube) extraction from one (single) or both (simultaneous) of the interacting cells and its potential to instantaneously
and dramatically decrease the force on the receptor-ligand tether bond has been investigated in the present study.
Employing the micropipette aspiration technique and florescence microscopy, two tethers (one each from the two
interacting cells with the adhesive bond in the middle) are shown to be extracted when the cells are separated
after a brief contact. The constitutive relationship for extraction of the above simultaneous tether with a passive
neutrophil or T-cell as the force transducer is determined. In addition, the above relationship has been shown
to have excellent agreement with that deduced theoretically by simultaneously solving constitutive equations for
single tether extraction from either cell alone. Utilizing the constitutive relations determined above in a model
of cell rolling it is shown that simultaneous tether extraction from the neutrophil and endothelium greatly enhances
the stability of neutrophil rolling.
Friday, June 17, 2005, Room 210 Hallowell Building, CG623 Hershey
Anandi Krishnan
Final Defense
"Protein Adsorption to Hydrophobic Surfaces"
Abstract
Adsorption energetics of diverse purified proteins as well as whole-blood plasma and serum (aqueous-buffer)
solutions were remarkably similar at two hydrophobic surfaces - water-air (liquid, vapor, LV) and solid-water (solid-liquid,
SL). A 'Traube-rule-like' progression (molar concentration required to reach a specified spreading pressure decreases
with increasing MW ) was observed at both hydrophobic surfaces (LV and SL) for globular proteins spanning three-orders-of-magnitude
in molecular weight (MW). Collective results from the observed 'Traube-rule-like' progression in interfacial-tension
reduction, an invariant partition coefficient, and a constant Gibbs' surface excess (as a measure of amount of
protein adsorbed) all imply that water controls the energetics of the protein adsorption process. Hence, protein
adsorption to hydrophobic surfaces has more to do with water than the proteins themselves. A relatively straightforward
theory of protein adsorption predicated on the interfacial packing of hydrated spherical molecules with dimensions
scaling as a function of MW accounts for the essential physical chemistry of protein adsorption and rationalizes
significant experimental observations. From this theory, it is evident that displacement of interfacial water by
hydrated proteins adsorbing from solution places an energetic cap on protein adsorption to hydrophobic surfaces.
This phenomenon is generic to all proteins. As a consequence, protein adsorption is not found to vary significantly
among diverse protein types. Variations from this general trend may reflect deviations in protein geometry from
simple spheres and/or tendency of some proteins to adopt a more spread/compact configuration in the adsorbed state.
Thursday, July 28, 2005, Room 210 Hallowell Building, CG623 Hershey
Aashiish Agnihotri
Final Defense
"Molecular Level Interactions Between Blood-Components and Model Biomaterials Studied by
Atomic Force Microscopy"
Abstract
Fibrinogen is a key plasma protein involved in initiation of thrombosis on synthetic surfaces, and its adsorption
to the biomaterial surface and subsequent interactions with the blood platelets are of fundamental interest in
biomaterials development. In this work the influence of surface properties on the adsorption and activity of fibrinogen
has been investigated at the single molecule scale using atomic force microscopy (AFM). Tapping mode AFM was used
to study the time-dependent changes in the structure of fibrinogen under aqueous conditions following adsorption
on two model surfaces:
hydrophobic graphite and hydrophilic mica. Spreading kinetics of fibrinogen on the two surfaces was determined
by measuring the heights of the D and E domains of individual molecules over a time-period of ~2 hours. With the
objective of relating the observed post-adsorption structural changes to the surface availability of active epitopes
and extending AFM imaging studies to complex multicomponent protein films, the adhesion mapping mode of AFM was
developed for biologically sensitive imaging. The successful application was demonstrated by performing fibrinogen
recognition imaging in patterned dual-component protein films and randomly distributed dual-component protein films.
The effect of surface properties on the activity of fibrinogen was studied by measuring the interactions between
the platelet membrane integrin GPIIbIIIa and fibrinogen adsorbed to model hydrophilic and hydrophobic surfaces
by using the force mode of AFM. Taken together, this work adds to the current knowledge of surface thrombogenesis
by improving understanding of the molecular events that occur during blood-material interactions.
For additional information, contact Ms. Doretta Garvey, Dept
of Bioengineering, Tel: 814.865.1407 or E-Mail: bioe@engr.Professor, Biomedical Engineering
psu.edu