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Development and evaluation of enzymatically-degradable hydrogel microparticles for pulmonary delivery of nanoparticles and biologics
textThe emerging class of biologic drugs, including proteins, peptides, and gene therapies, are widely administered by injection, despite potential systemic side effects. Rational design of targeted carriers that can be delivered non-invasively, with reduced side effects, is essential for the success of these therapies, as well as for the improvement of patient compliance and quality of life.
One potential approach is to take advantage of specific physiological cues, such as enzymes, which would trigger drug release from a drug carrier. Enzymatic cleavage is highly specific and could be tailored for certain diseased tissues where specific enzymes are up regulated. Enzymatically-degradable hydrogels, which incorporate an enzyme- cleavable peptide into the network structure, have been extensively reported for releasing drugs for tissue engineering applications. These studies showed that a rapid response and corresponding drug release occurs upon enzyme exposure, whereas minimal degradation occurs without enzyme. Recently, Michael addition reactions have been developed for the synthesis of such enzymatically-degradable hydrogels. Michael addition reactions occur under mild physiological conditions, making them ideally suited for polymerizing hydrogels with encapsulated biologic drugs without affecting its bioactivity, as in
traditional polymerization and particle synthesis. The focus of my research was to create enzymatically-degradable hydrogel microparticles, using Michael addition chemistry, to evaluate for use as an inhalable, disease-responsive delivery system for biologic drugs and nanoparticles.
In this dissertation, I utilize bioconjugation and Michael addition chemistries in the design and development of enzymatically-degradable hydrogels, which may be tailored to a multitude of disease applications. I then introduce a new method of hydrogel microparticle, or microgel, synthesis known as the Michael Addition During Emulsion (MADE) method. These microgel carriers were evaluated in vitro, and found to exhibit triggered release of encapsulated biologic drugs in response to enzyme, no significant cytotoxic effects, and the ability the avoid rapid clearance by macrophages. Lastly, in vivo studies in mice were conducted, and microgels were found to exhibit successful delivery to the deep lung, as well as prolonged pulmonary retention after intratracheal aerosol delivery. In conclusion, a new class of enzymatically-degradable microgels were successfully developed and characterized as a versatile and promising new system for pulmonary, disease-responsive delivery of biologic drugs.Biomedical Engineerin
Thermodynamic Properties of Block Copolymer Electrolytes Containing Imidazolium and Lithium Salts
We report on the thermal properties, phase behavior, and thermodynamics of a series of polystyrene-block-poly(ethylene oxide) copolymers (SEO) mixed with the ionic species Li[N(SO_(2)CF_3)_2] (LiTFSI), imidazolium TFSI (ImTFSI), and an equimolar mixture of LiTFSI and ImTFSI (Mix). Differential scanning calorimetric scans reveal similar thermal behavior of SEO/LiTFSI and SEO/ImTFSI at the same salt concentrations. Phase behavior and thermodynamics were determined using a combination of small-angle X-ray scattering and birefringence. The thermodynamics of our mixtures can be mapped on to the theory of neat block copolymer phase behavior provided the Flory−Huggins interaction parameter, χ, between the blocks is replaced by an effective χ (χ_(eff)) that increases linearly with salt concentration. The phase behavior and the value of m, the slope of the χ_(eff) versus salt concentration data, were similar for SEO/LiTFSI, SEO/ImTFSI, and SEO/Mix blends. The theory developed by Wang [ J. Phys. Chem. B. 2008, 41, 16205] provides a basis for understanding the fundamental underpinnings of the measured value of m. We compare our experimental results with the predictions of this theory with no adjustable parameters
Evaluation of impacts of future climate change and water use scenarios on regional hydrology
General circulation models (GCMs) have been widely used to simulate current
and future climate at the global scale. However, the development of
frameworks to apply GCMs to assess potential climate change impacts on
regional hydrologic systems, ability to meet future water demand, and
compliance with water resource regulations is more recent. In this study
eight GCMs were bias-corrected and downscaled using the bias correction and
stochastic analog (BCSA) downscaling method and then used, together with
three ET0 methods and eight different water use scenarios, to drive an
integrated hydrologic model previously developed for the Tampa Bay region in
western central Florida. Variance-based sensitivity analysis showed that
changes in projected streamflow were very sensitive to GCM selection, but
relatively insensitive to ET0 method or water use scenario. Changes in
projections of groundwater level were sensitive to both GCM and water use
scenario, but relatively insensitive to ET0 method. Five of eight GCMs
projected a decrease in streamflow and groundwater availability in the future
regardless of water use scenario or ET method. For the business as usual
water use scenario all eight GCMs indicated that, even with active water
conservation programs, increases in public water demand projected for 2045
could not be met from ground and surface water supplies while achieving
current groundwater level and surface water flow regulations. With adoption
of 40 % wastewater reuse for public supply and active conservation four
of the eight GCMs indicate that 2045 public water demand could be met while
achieving current environmental regulations; however, drier climates would
require a switch from groundwater to surface water use. These results
indicate a high probability of a reduction in future freshwater supply in the
Tampa Bay region if environmental regulations intended to protect current
aquatic ecosystems do not adapt to the changing climate. Broad interpretation
of the results of this study may be limited by the fact that all future water
use scenarios assumed that increases in water demand would be the result of
intensification of water use on existing agricultural, industrial, and urban
lands. Future work should evaluate the impacts of a range of potential land
use change scenarios, with associated water use change projections, over a
larger number of GCMs.</p
Salt-doped block copolymers: ion distribution, domain spacing and effective χ parameter
Phase Behavior of a Block Copolymer/Salt Mixture through the Order-to-Disorder Transition
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