Filtering by
- All Subjects: chemical engineering
- All Subjects: Drug Delivery
- Creators: Holloway, Julianne
- Member of: Theses and Dissertations
The first technique involves imbedding sorbent particles inside the fibers: forming particle-embedded fibers. It is demonstrated that particles will spontaneously coat themselves in the fibers at dilute loadings, but at higher loadings some get trapped on the fiber surface. A mathematical model is used to show that when these particles are embedded, the polymeric coating provided by the fibers may be designed to increase the kinetic selectivity and/or stability of the embedded sorbents. Two proof-of-concept studies are performed to validate this model including the increased selectivity of carbon dioxide over nitrogen when the MOF ZIF-8 is embedded in a poly(ethylene oxide) and Matrimid polymer blend; and that increased hydrothermal stability is realized when the water-sensitive MOF HKUST-1 is embedded in polystyrene fibers relative to pure HKUST-1 powder.
The second technique involves the creation of a pore network throughout the fiber to increase accessibility of embedded sorbent particles. It is demonstrated that the removal of a blended highly soluble polymer additive from the spun particle-containing fibers leaves a pore network behind without removing the embedded sorbent. The increased accessibility of embedded sorbents is validated by embedding a known direct air capture sorbent in porous electrospun fibers, and demonstrating that they have the fastest kinetic uptake of any direct air capture sorbent reported in literature to date, along with over 90% sorbent accessibility.
In this thesis, a novel series of grafted siloxanes have been explored for their probable application in the healthcare industry. The siloxanes are grafted with poly(ethylene glycol) (PEG) and quaternary ammonium salt (QUAT). The effects of varying 1) molar ratios of QUAT to PEG and 2) PEG chain length on contact angle, surface tension, critical micelle concentration (CMC), and micelle assembly properties were studied. In contact angle experiments, the hydrophilicity of grafted siloxanes increased by grafting PEG and QUAT. The amphiphilicity increases and CMC decreases as the PEG chain length shortens. Adding QUAT also reduces CMC. These trends were observed in surface tension and Isothermal Titration Calorimetry experiments. A change in self-assembly behaviour was also observed in Dynamic Light Scattering experiments upon increasing the PEG chain length and its ratio relative to the quaternary ammonium in the siloxane polymer.
These polymers have also been studied for their probable application as a sensitive 1H NMR spectroscopy indicator of tissue oxygenation (pO2) based on spectroscopic spin-lattice relaxometry. The proton imaging of siloxanes to map tissue oxygenation levels (PISTOL) technique is used to map T1 of siloxane polymer, which is correlated to dynamic changes in tissue pO2 at various locations by a linear relationship between pO2 and 1/T1. The T1-weighted echo spin signals were observed in an initial study of siloxanes using the PISTOL technique.
The change in the ratio of QUAT to PEG and the varying chain length of PEG have a significant effect on the physical property characteristics of siloxane graft copolymers. The conclusions and observations of the present work serve as a benchmark study for further development of adaptive polymers and for the creation of integrated “nanoscale” probes for PISTOL oximetry and drug delivery.
This research utilizes infrared imaging to investigate the effects of fill level and rotation rate on the particle bed hydrodynamics and the average wall-particle heat transfer coefficient. 3 mm silica beads and a stainless steel rotary drum with a diameter of 6 in and a length of 3 in were used at fill levels of 10 %, 17.5 %, and 25 %, and rotation rates of 2 rpm, 6 rpm, and 10 rpm. Two full factorial designs of experiments were completed to understand the effects of these factors in the presence of conduction only (Case 1) and conduction with forced convection (Case 2). Particle-particle friction caused the particle bed to stagnate at elevated temperatures in Case 1, while the inlet air velocity in Case 2 dominated the particle friction effects to maintain the flow profile. The maximum heat transfer coefficient was achieved at a high rotation rate and low fill level in Case 1, and at a high rotation rate and high fill level in Case 2. Heat losses from the system were dominated by natural convection between the hot air in the drum and the external surroundings.
Traumatic brain injury (TBI), a neurological condition that negatively affects neural capabilities, occurs when a blunt trauma impacts the head. Following the initial injury that immediately impacts neural cell function and survival, a series of secondary injury events lead to substantial sustained inflammation for weeks to years post-injury. To develop TBI treatments that may stimulate regenerative processes, a novel drug delivery system that efficiently delivers the appropriate drug/payload to injured tissue is crucial. Hyaluronic acid (HA) hydrogels are attractive when developing a biomaterial for tissue reparation and regeneration. HA is a natural polymer with physicochemical properties that can be tuned to match the properties of the extracellular matrix (ECM) of the many tissues including the central nervous system (CNS). Here, the project objective was to develop a HA hydrogel system for local delivery of a biological payload; this objective was completed by employing a composite system with two parts. The first part is an injectable, shear-thinning bulk hydrogel, and the second is microgels for loading biological payloads. The bulk hydrogel was composed of cyclodextrin modified HA (Cd-HA) and adamantane modified HA (Ad-HA) that give rise to guest-host interactions that facilitate physical crosslinking. The microgel, composed of norbornene-HA (Nor-HA) and sulfated-HA, crosslink via chemical crosslinks upon activation of a UV photoinitiator. The sulfated-HA microgels facilitate loading of biological payloads by mimicking heparin binding sites via the conjugated sulfated group. Neuregulin I, an epidermal growth factor with neuroprotective properties, is one such protein with a heparin binding domain that may be retained in the sulfated-HA microgels. Specifically, the project focused on mechanical testing of this composite microgel/hydrogel system and also developing protein affinity assays.