Ordered alphabetically by student's last name
Kinetics and Thermodynamic Equilibria of Precipitation and Crystalization of Lysozyme Aaron Chockla, Yu-Chia Cheng, Abraham Lenhoff Department of Chemical Engineering The design and optimization of protein separation processes such as crystallization rely heavily on empirical methods to design and optimize. The general goal of this project is to characterize the phase behavior of proteins in concentrated salt solution. A specific objective is to characterize the dense amorphous protein phase that forms at high ionic strengths through measurements of dissolution rates of the precipitate. The initial data collected for this project follow the expected trends reasonably well, showing that with increasing ionic strength with constant initial protein concentration, both the induction time and final protein concentration is reduced. Also, as initial protein concentration increases at constant ionic strength, the induction time decreases while the final protein concentration remains constant. Given these results, the next course of action is to vary the precipitating agent, or salt used to control the ionic strength, pH and protein. This will help confirm or disprove the developing theories. Funded by the HHMI Undergraduate Science Education Program. |
Particle Separations in Microfluidic Channels Jonathan Edwards, Steven Kestel, and Eric M. Furst Department of Chemical Engineering Microfluidics
is an emerging field in both chemical and biological analysis, and in chemical
production. Commonly, microfluidic devices are characterized by tiny
channels which direct minute quantities of fluid. This project focused
on particle separations in microfluidic systems. Optical traps, or
“laser tweezers”, create a gradient force which is capable of holding a colloidal
particle in place. Arrays of optical traps were then used to conduct
sized-based separations of particles. For instance, when a solution
of one and three micron particles flows through the traps, the three micron
particles are trapped while the one micron particles pass through.
To construct the microfluidic channels, a rapid and inexpensive process called
soft lithography was employed. Next, to form the optical trap arrays,
a 1064 nm Nd: YAG laser was scanned from trap to trap. For this project,
hexagonal trap arrays were formed. Several parameters which govern
these separations were investigated, including laser power, fluid velocity,
trap array geometry, and particle size ratios. Also, the effect of particle
size on retention time and the collision interaction between particles was
characterized. Applications of microfluidic particle separations include
cell sorting and solid-phase bioassays.
|
In-vivo glucose sensor using Poly(vinyl alcohol)/Sodium Tetraborate Decahydrate (Borax) Network Nikki Ennis and Annette Shine Department of Chemical Engineering A
wireless in vivo glucose sensor would be very beneficial to diabetics, eliminating
the discomfort of constant pinpricks. A proposed sensor consists of a magnetic
strip surrounded by a polymer network, which has hydroxyl groups cross-linked
with borate ions. Disruption of these cross-links by glucose is are quantifiable
by measuring the rheology of the network via resonant frequency spectrum
of the implanted sensor. The goal of this research is to design the polymer
system that responds to glucose concentrations in the physiological range
by optimizing the members of hydroxyl and boronic acid groups. A model system
of poly (vinyl alcohol) (PVOH) and borax was used, which forms a gelled network.
Dynamic shear rheology measurements were taken on a modular compact rheometer
with a cone and plate fixture. Frequency sweeps were run from 0.1 to 100 1/s
at strains of 0.3%, which amplitude sweeps confirmed were in the linear range.
This low frequency range gave molecular insight about the polymer network.
The viscoelastic storage modulus, G’, and the loss modulus, G”, both increased
when the concentrations of PVOH and Borax were increased. In the presence
of 180.5mg/dL glucose, both G’ and G” decreased by about a factor of 2. The
frequency dependence of G’ and G” showed Maxwell-like behavior, with a relaxation
time of about .3s (1.8wt%PVOH gel). This indicates that network elasticity,
rather than viscosity, would dominate at the higher resonant frequency of
the magnetic sensor. Funded by the HHMI Undergraduate Science
Education Program.
|
|
Tracer Particle Interactions
with a Beta-Hairpin Hydrogel
Becky Gable, Cecile Veerman and Eric M. Furst Chemical Engineering, University of Delaware Hydrogels have promising applications in tissue engineering and drug delivery. MAX1 is an amphiphilic peptide which self-assembles into a hydrogel network upon changes in the solution conditions, such as pH or ionic strength. Knowledge of the interactions between hydrogels and embedded particles with unique sizes and surface chemistries is crucial in understanding and optimizing hydrogel functionality. Interactions between MAX1 and fluorescent tracer particles were characterized through multiple particle tracking, isothermal titration calorimetry (ITC), and bulk rheological measurements. Multiple particle tracking was used to monitor the MAX1 hydrogel self-assembly process over time. Tracer particle movement decreased with increasing time after the initiation of self-assembly. However, peptide adsorption to the tracer particles was indicated by anomalous mean-squared displacements versus lag time curves which did not fall on a master curve for polystyrene and carboxylated polystyrene particles of various sizes. ITC confirmed differences in peptide adsorption for polystyrene, carboxylated polystyrene, amine-modified polystyrene, and polyethylene glycol (PEG) coated polystyrene particles due to unique surface chemistries. However, similar gel strengths for MAX1 with and without the various particles were observed using dynamic bulk rheological measurements. A proposed model hypothesizes that surface chemistry differences affect the particle stability within the MAX1 medium through its interactions with the hydrogel network. From these characterizations of the interactions between MAX1 and various tracer particle sizes and surface chemistries, MAX1’s potential in tissue engineering and drug delivery applications proves promising. Funded by the HHMI Undergraduate Science Education Program. |
Kinetics and Thermodynamics of Recombinant Bovine Granulocyte Colony Stimulating Factor (bG-CSF) Aggregation Justin Quon, Jennifer Andrews, Professor Christopher Roberts Department of Chemical Engineering Abstract withheld by request Funded by the HHMI Undergraduate Science Education Program. |
