Plastic pollution has been a growing global issue since the production and widespread consumption of plastic began more than 60 years ago. Over time, detrimental impacts on ter-restrial and aquatic organisms have been observed. Microplastics are plastic pieces or fibers (less than 5 mm) that contaminate aquatic systems and may impact zooplankton, aquatic ani-mals that naturally ingest phytoplankton and other food particles of a similar size. Zooplankton are consumed by fish, so organisms higher in the food web are expected to be impacted by zo-oplankton ingestion of microplastics as those plastics consumed by zooplankton are trans-ferred to the predatory fish and thus bioaccumulate through the trophic food web. This study investigated the potential of the model zooplankton, Daphnia magna, to ingest microplastic spheres and microfibers through concentration and extended exposure experiments. D. magna are a large species and were found to readily ingest polystyrene spheres 50µm in size. Since D. magna demonstrated an affinity for sphere ingestion, animals were exposed to the more com-mon contaminant, microfibers, to determine if ingestion occurred and if there were impacts on survival and reproduction. Despite a lack of fiber ingestion, Daphnia exposure to low levels of microfibers over twenty days showed a reduction in the number of eggs generated in a clutch, reduction in the viability of neonates that gestate to term, and reduction in the overall number of neonates. Microplastics may pose a harm not only to organisms such as D. magna but also to organisms higher in the trophic system through bioaccumulation and reduction in available zooplankton as a food source if reproductive success is decreased when exposed. Further stud-ies of native organisms are necessary to establish the effects of microplastic pollution on freshwater systems and the organisms that rely on them.

There is a critical need for cartilage regeneration therapies. Not only is cartilage necessary for proper joint function, as deterioration of cartilage leads to osteoarthritis, but it also serves important roles in other places in the body, like in the trachea. Specifically in the articular and tracheal niches, replacement cartilage should have adequate mechanical properties and specific geometries to restore native function. To address these needs, novel strategies to engineer high-density human mesenchymal stem cell (hMSC)-derived cartilage tissues are presented in this dissertation. Bioactive microspheres loaded with chondrogenic transforming growth factor beta 1 (TGF-ß1) were incorporated within some of these tissues for enhanced chondrogenesis. First, scaffold-free cartilage rings and tubes with controlled dimensions were successfully fabricated using custom-made culture wells and a ring-to-tube assembly approach, respectively. The use of TGF-ß1 microspheres in the hMSC rings and tubes significantly improved the quality and quantity of generated cartilage tissue. Next, localized TGF-ß1 presentation within cartilaginous tissues facilitated organized fusion and culture of cartilage tissue building blocks with engineered epithelial and prevascular tissues. Successful development and/or maintenance of tissue-specific phenotypes in this co-culture approach with localized presentation of cues guiding cell differentiation is a promising step toward engineering a functional replacement trachea. Next, extracellular matrix (ECM) scaffolds fabricated from high-density hMSC condensates with and without TGF-ß1 microspheres were shown to support chondrogenesis of re-seeded hMSCs. Importantly, addition of microspheres to hMSC condensates significantly enhanced ECM production and consequently yielded 50% more scaffolds. Additionally, ECM scaffolds were demonstrated to drive chondrogenesis when TGF-ß1 was loaded into them, which suggests improved potential for clinical translat (open full item for complete abstract)

This thesis presents the application of an empirical model of total internal reflection (TIR) we recently developed in conjunction with a home-built sensor to detect nanoaggregates in highly scattering opaque polystyrene colloidal suspensions. The nanoaggregates are detected directly without any sample dilution or special sample preparation. Additional results on nanoaggregate detection in gold nanoparticle suspensions are presented. Preliminary tests of our model and sensor in an absorbing dye solution are also presented.

In this study, the theoretical model for magnetophoretic mobility was further developed to include the contribution of intrinsic properties of particles or cells and the influence of the properties of the suspending fluid. Using these improvements, the dependence of the magnetophoretic mobility of unlabeled cells/microspheres and cells/microspheres labeled with colloidal magnetic labels on suspending fluid was used to determine the magnetic susceptibility of cells/microspheres and colloidal labels. The combination of these theoretical improvements, and the experimental studies, makes the methodology developed a universal characterization method. To explain the dependence of magnetophoretic mobility or fluorescence intensity on concentrations of the affinity labels, a binding model was proposed. Good agreement was found for lymphocytes labeled with anti CD3 antibody conjugates and the model. The data indicated that the conjugation of larger magnetic labels decreases the binding affinity of the antigen antibody interaction and the antibody binding capacity (ABC). A scale up model was then proposed, and experimentally verified on larger scale immunological labeling. This model assists in other projects in our lab focused on the efficient magnetic cell sorting at large scale. Restricted by high autofluorescence levels, alveolar macrophages, are difficult to analyze using flow cytometry. Immunomagnetically based CTV system was studied to evaluate if CTV can be used as an alternative of flow cytometry on quantitative cellular receptor study. A good agreement between CTV and FCM was found when monocytes were studied. CTV was then successfully used to analyze AM cells for basal receptor expression, and the expression kinetics when LPS was used for activation. CTV was used to determine if proteins can be immunomagnetically separated via the use of colloidal labels or molecular labels by measuring the magnetism of a labeled protein. Feasibility of the separation process was d (open full item for complete abstract)

There has been interest in applying intraperitoneal (IP) chemotherapy to treat malignant peritoneal-confined tumors where clinical trials have demonstrated a pharmacokinetic advantage, improved objective response, and prolonged survival using IP chemotherapy. However, treatment efficacy has been limited to microscopic residual disease (i.e. tumor diameter < 2 cm) presumably due to poor tumor penetration. For this reason, plus the high costs and potential complications associated with peritoneal catheters, IP treatment has not gained wide acceptance, despite its demonstrated survival advantage. The goal of this dissertation was to develop an approach to improve the utility of IP chemotherapy. Our laboratory has shown that at apoptosis-inducing concentrations, paclitaxel, which has shown significant activity against many types of human solid tumors, can enhance tumor porosity and consequently drug penetration in solid tumors. The FDA-approved formulation (TaxolO) uses Cremophor EL to solubilize paclitaxel. Cremophor causes potential life-threatening hypersensitivity reactions and Cremophor micelles sequester and reduce the free fraction of paclitaxel, thereby limiting drug uptake into tissues. Thus, we have developed paclitaxel-loaded PLGA microspheres that release the drug at specified rates to exploit the unique pharmacodynamic properties of paclitaxel and eliminate Cremophor-associated complications. We developed three paclitaxel microsphere formulations that release paclitaxel at different rates so that the fast-release microspheres would induce apoptosis, thereby enhancing the tumor penetration of the slow-release microspheres. Pharmacokinetic studies of IP administered paclitaxel microspheres showed a lower plasma AUC and higher drug concentrations in the peritoneal cavity, compared to the Cremophor formulation. The spatial distribution of paclitaxel microspheres after IP administration demonstrated a passive targeting advantage with localization of the microsph (open full item for complete abstract)

Leukocyte adhesion to the endothelium is an important component of the inflammatory response. The adhesion process is a multi-step cascade that is mediated by ligands expressed on leukocytes and complementary receptors expressed on endothelial cells. The ligand-receptor pairs involved in leukocyte adhesion to the endothelium can be classified into four main groups: selectins, immunoglobulin superfamily, integrins, and cadherins. It is known that leukocyte expressed Mac-1 (an α M β 2 integrin) plays an important role in this adhesion process, but the identification of the counter receptor for Mac-1 on the endothelium remains controversial. Several studies suggest that ICAM-1 is a counter receptor for Mac-1. There are data both supporting and refuting this conjecture. Previous studies in our lab using Mac-1 coated microspheres strongly suggest that ICAM-1 is not involved in Mac-1 microsphere adhesion to human umbilical vein endothelial cells (HUVEC). Therefore, we hypothesize that HUVEC express an as yet unidentified receptor for Mac-1. The goal of this thesis is to investigate the feasibility of using two different techniques to isolate this novel receptor for Mac-1: immunoprecipitation and Phosphatidylinositol Phospholipase C (PI-PLC) approach. The first approach would be to immuoprecipitate the novel receptor from HUVEC lysates using Mac-1 coated microspheres. In this approach, the surface proteins on the HUVEC would be biotinylated to help discriminate surface proteins from intercellular proteins and a detergent would be used to solubilize the membrane bound proteins. In the present study the conditions for optimal biotinylation of HUVEC were established and the maximal detergent level that can be used before the presence of the detergent desorbs proteins from microspheres was determined. The results indicate that incubation of HUVEC in Hanks Balanced Salt Solution containing biotin for 5 minutes at 4 °C results in significant biotinylation of the HUVEC while havi (open full item for complete abstract)

This study was done to enhance the compatibility between an acidic and basic drug when used in combination within the same dosage form by encapsulating the drugs within an ethyl cellulose microsphere. The drugs encapsulated include acidic (acetaminophen and aspirin) and basic (theophylline, and hydroxyzine) drugs. Microspheres were prepared by the solvent evaporation technique using methylene chloride and acetone as the dispersed phase and light mineral oil with span 80 as the continuous phase. Various drug to polymer ratios (1:1, 1:2, and 1:3) were chosen and evaluated to determine which microspheres resulted in the highest drug entrapment efficiency. The microspheres with highest drug entrapment were characterized by performing particle size analysis, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and in vitro drug release. Stability studies were performed with a (1:1) mixture of an encapsulated acidic and basic drug at 40 °C for three months. The 1:1 ratio had the highest entrapment for the drugs aspirin (32%) and hydroxyzine (41%), while the 1:3 ratio had the highest entrapment for acetaminophen (65%) and theophylline (52%). Spherical, uniform microspheres were collected and the average particle size was found for acetaminophen (91.17 µm), aspirin (193.36 µm), hydroxyzine (93.89 µm) and theophylline (264.56 µm). DSC thermograms for the drug loaded microspheres determined that the drug present exists in an amorphous phase in the polymeric matrix indicating no interaction between the drug and the polymer. The in vitro drug release studies showed that acetaminophen and hydroxyzine released in 15-30 minutes and aspirin and theophylline released in 180-240 minutes. The drug release data was fitted to various kinetic models which resulted in acetaminophen following first order release (R2 value of 0.9693), aspirin following zero order release (R2 value of 0.9925), hydroxyzine following firs (open full item for complete abstract)

Due to the prevalence of osteoarthritis in the United States and worldwide, there is a critical and growing need for replacement cartilage tissues. Motivated by this need, tissue engineering strategies combine principles of biology and engineering to generate living tissues for the repair and replacement of damaged or diseased cartilage. This thesis aimed to develop systems to direct stem cell chondrogenesis through investigation of the hypothesis that the chondrogenic potential of stem cells in high density culture can be guided through controlling growth factor presentation via incorporated TGF-β1 loaded biopolymer microspheres. The chondrogenic differentiation of human mesenchymal stem cells (hMSC) in aggregates incorporated with TGF-β1 releasing poly(lactide-co-glycolide) (PLGA) microspheres was regulated through varying the amounts of incorporated microspheres, and glycosaminoglycan (GAG) production after 3 weeks was comparable to that of traditional cell aggregates cultured in growth factor-containing medium. A system of genipin-crosslinked microspheres was also developed, enabling sustained TGF-β1 delivery via cell-mediated microsphere degradation at rates controlled by the level of hydrogel crosslinking. These gelatin microspheres were shown to regulate GAG production in hMSC aggregates from 3 different donors at levels dependent on the amount of incorporated microspheres, growth factor concentration, and microsphere degradation rates. This gelatin microsphere incorporated hMSC system was scaled up for the production of self-assembling microsphere incorporated cell sheets more appropriately sized for the treatment of clinical cartilage defects. The inclusion of fast- or slow-degrading microspheres with or without loaded TGF-β1 significantly increased sheet thickness and compressive equilibrium modulus, and enabled more uniform matrix deposition by comparison to cell-only sheets. Sheets incorporated with fast-degrading microspheres containing TGF-β1 produced (open full item for complete abstract)

Introduction: Adhesions following surgery represent a significant problem often resulting in pain, disability, and additional surgeries. Compounds are available for the prevention of postoperative adhesions, but effectiveness is difficult to assess; current models of adhesion comparison are limited to qualitative methods with much potential bias. Objectives: The objectives of the research performed were to create a quantitative model of adhesion strength assessment, to successfully encapsulate ketorolac tromethamine (KT) into poly(lactic-co-glycolic acid) microspheres, and to characterize of the microspheres for use in preventing adhesion formation. Quantitative Model Methods: The primary focus of this research was the creation of an adhesion complex that was suitable to quantitative testing using the Material Testing System (MTS™ System Corp, Eden Prairie, MN) machine platform. Following a midline infraumbilical laparotomy, bowel packing and retraction, and adequate exposure of the uterine horns and adjacent pelvic sidewall, a salpingostomy is made using electrocautery 1cm caudal the uterus-fallopian tube junction. A 7cm 8fr. latex urinary catheter, reinforced with a coaxial internal semi-rigid 5fr. polypropylene catheter, is inserted until it lies entirely within the lumen of the uterus. A 10cm segment of 6.35mm ID latex rubber drain tubing is secured to the dorsal aspect of the broad ligament medial the uterine horn; this is placed to prevent sidewall-broad ligament adhesion avoiding interference with the sidewall-uterus adhesion. The uterus and latex rubber drain are attached to the sidewall of the pelvis. The peritoneum lateral to the attached uterus is coagulated along the full length of the catheter insert at a setting of 6/10 (17W output) using a shielded electrocautery tip; cauterized area corresponds to the uterine horn lie and is limited to the peritoneum only. This injury is mirrored on the cannulated uterus to desiccate the superficial layer, (open full item for complete abstract)

Dialysis access graft failure is a major complication in providing care to patients on hemodialysis therapy. The failure rates have been reported as high as 80% at one year for this procedure. The major cause of failure is intimal hyperplasia. Intimal hyperplasia is an exaggeration of the normal vascular wall healing response to injury resulting from the migration and proliferation of medial smooth muscle cells. To mitigate this disease condition, we developed a perivascular polymeric controlled drug delivery device which we hypothesized when applied locally, would be effective in preventing intimal hyperplasia by enabling a sustained release of the therapeutic agent to the anastamotic site. This novel polymeric device, named PolyRing, is a composite system consisting of poly (DL-lactide-co-glycolide) microspheres embedded in a poly (ethylene glycol) hydrogel. The drug for the treatment of intimal hyperplasia is encapsulated within the poly (DL-lactide-co-glycolide) microspheres. The device is snapped into place around the vessel to deliver the drug. This work focuses on evaluating the feasibility of releasing the drug Simvastatin from the device to provide localized, site specific, sustained drug delivery for the prevention of intimal hyperplasia in vascular tissue. Simvastatin, obtained in a pro-drug form, when hydrolyzed to its active form, Simvastatin Acid, acts as a potent competitive inhibitor of the 3-Hydroxy-3-methylglutaryl coenzyme A reductase. The inhibition of this enzyme suppresses the mevalonate pathway and thereby prevents the proliferation of smooth muscle cells. As the focus is on controlled localized delivery, we hypothesize the need of using the active form as against the lactone form. Therefore, we fabricated Simvastatin and Simvastatin Acid loaded poly (DL-lactide-co-glycolide) microspheres using oil-water and water-oil-water techniques respectively. The oil-water emulsion resulted in smooth surfaced microspheres (determined by Scanning Electron (open full item for complete abstract)

The long-term clinical success of autologous vein and synthetic vascular grafts is limited due to the development of anastomotic intimal hyperplasia (IH). Previously published data suggests that cyclosporine (CyA) (an immunosuppressive drug) may reduce the development of IH in a canine model [1]. However, systemic administration of CyA could create serious adverse effects. Therefore, it is our long-term goal to test the hypothesis that the controlled local release of cyclosporine from a polymeric vascular wrap will prevent the development of IH. In order to test this hypothesis, we developed three controlled release polymeric devices that could be placed around vascular graft anastomotic sites to deliver therapeutic drugs locally. The first device is a poly(ethylene glycol) (PEG) hydrogel sheet. The second device is a composite device consisting of poly(DL-lactide-co-glycolide) (PLGA) microspheres dispersed in the PEG hydrogel sheet. The third device is in the form of a ring (referred to as PolyRing from here on) that can be slipped around the anastomotic sites. PolyRing is a composite polymeric device consisting of PLGA microspheres embedded in a PEG hydrogel. In-vitro studies were conducted on the three devices to evaluate the effects of different sterilization procedures on the properties of the device. It was determined that gamma sterilization was the preferred sterilization method of choice. In-vivo studies were conducted on a swine model to evaluate the biocompatibility, drug optimization and efficacy of PolyRing. The biocompatibility study utilized four (4) domestic swine with non-drug loaded PolyRings harvested at two (2) and four (4) week time points. PolyRings (ID 3-5 mm; OD 7-8 mm; Length 5 mm) were implanted in subcutaneous and muscular tissues and around jugular veins and carotid arteries. The histological findings of gamma sterilized PolyRing implants at two and four weeks demonstrated the biocompatibility of this device. A minimal foreign body reacti (open full item for complete abstract)

Polyimide foams have emerged as high performance cellular materials with great potential for applications in aerospace due to their excellent mechanical, chemical and electrical properties. A novel technology in the development of polyimide foams consists of solid precursors in the form of powders with embedded blowing agent that can be converted by simple thermal treatment into single polymeric spherical microstructures or inflated together to produce foams with varying ranges of density and properties. This technology is hereafter referred to as solid-state powder foaming. Solid-state foaming from poly(amic acid) precursor particles was studied by examining concurrent and competitive phenomena that determine the morphology and physical properties of resulting polyimide microstructures. Phenomenological analysis of morphological relations, as well as physicochemical processes provided a comprehensive understanding of the governing principles by which potential particle inflation is achieved. Resulting polyimide microstructures present morphologies that are the result of the combined effect of morphological features on the precursor particles, blowing agent concentration and processing conditions exerted on the powders during the inflation process. A strong interrelation was found between different controlling factors such as precursor morphology and processing conditions. The balance between local temperature and concentration inside the particles can be manipulated by these controlling factors in such a way that a particle under a certain set of conditions might experience multiple bubble growth, while under slightly different conditions might present single bubble inflation or no inflation at all. Results from the phenomenological analysis served as the basis of a numerical model and corresponding parametric study where the different parameters of the governing phenomena were evaluated and studied. This parametric study provided a comprehensive understanding of t (open full item for complete abstract)