Phospholipid vesicles are biocompatible, and have potential for intracellular applications, but minimal membrane integrity limits their use in membrane-rich environments. Stabilized membranes overcome this limitation while maintaining biocompatible surface structures. Additionally, the modularity of phospholipid bilayer makes them ideal components when designing biologically inspired sensors. Membrane composition can be tailored to specific applications, transmembrane proteins can provide added functionalities, and the isolated interior can prevent cytotoxic and interfering detection chemistries from altering the cellular environment. This work has focused on expanding the capabilities of stabilized phospholipid membranes, and determining which formulations hold promise in developing stabilized phospholipid vesicle nanosensors.Current membrane stabilization methods suffer from either incomplete stabilization, or irreversible stabilization limiting the applications of vesicle nanosensors. Therefore, a facile method to prepare robust phospholipid vesicles using commonly available phospholipids stabilized via the formation of an interpenetrating, acid-labile, cross-linked polymer network that imparts controlled polymer destabilization and subsequent vesicle degradation was developed. Upon exposure to acidic conditions, the highly cross-linked polymer network was converted to linear polymers, substantially reducing vesicle stability upon exposure to chemical and physical insults. The resultant transiently stabilized vesicles have potential for enhanced drug delivery and chemical sensing applications requiring minimal membrane defects, and allow for improved physiological clearance.Some vesicle nanosensor schemes may require the passive diffusion of low molecular weight species across the membrane in addition to controllable degradation. Therefore, the acid-degradable, polymer-stabilized, phospholipid vesicle production method was extended to bis-SorbPC membranes by simultaneously polymerizing the vesicle with an acetal-containing cross-linker. The vesicles display prolonged stability under physiological conditions, and significant additional stability compared to vesicles composed of naturally occurring phospholipids. The vesicles demonstrated potential utility for sensing and therapeutic applications.Phospholipid vesicles can also serve as labels to observe movement in macromolecular biological assemblies, but a dearth of caged fluorescent labels limits design and function. Therefore, the first caged fluorescent thiol was synthesized, shown to label amines rapidly, and demonstrated the required photolytic properties. The caged fluorescent thiol has potential as a label in observing the movement of macromolecular biological assemblies and as a fluorescent probe for observing endosomal trafficking and release.

The impact of lactate producing direct-fed microbial (DFM) on growth performance and rumen fermentation in beef cattle was explored in four studies. Experiment 1 studied the interaction between DFM and degradable intake protein (DIP) supply in receiving cattle. No differences (P≥0.06) in intake, morbidity, or immune response were observed; however, during the first 28 d gain and efficiency responses to DFM were dependent on DIP (DIP×DFM P≤0.05). Experiment 2 showed that in vitro gas production and select endpoint metabolites differed (P≤0.04) with DFM application. Experiment 3 compared lactate producing DFM to a lactate producing/utilizing DFM in finishing cattle. No differences (P≥0.14) in intake, gain, efficiency, or carcass characteristics were observed between control and lactate DFM; however, gain and growth efficiency differed (P≤0.05) between the lactate producing and lactate producing/utilizing DFM during the later portions of feeding. Experiment 4 studied the impact of DFM on ruminal fermentation, lactate utilization, and total tract digestibility. Ruminal pH and molar proportions of acetate were increased (P≤0.05) with DFM; however, lactate utilization and total tract digestibility did not differ (P≥0.33). The studies suggest that DFM improve growth performance during receiving and responses are at least partly mediated through differences in ruminal fermentation.

A degradable/polar/hydrophobic/ionic (D-PHI) polyurethane with properties intended to promote tissue regeneration in a small diameter peripheral artery vascular graft was evaluated for cell biocompatibility and growth. Films were cast in polypropylene 96 well plates for monocyte/endothelial cell (EC) co-culture in vitro studies and porous scaffold discs were implanted in an in vivo subcutaneous mouse model. After 7 days in culture the co-culture demonstrated cell adhesion and growth, low esterase activity (a measure of degradative potential and cell activation), no detectable release of pro-inflammatory cytokine (tumour necrosis factor -α) but measurable anti-inflammatory interleukin (IL)-10. The EC and the co-culture expressed the EC biomarker CD31, whereas the monocyte monoculture did not. Cytokine array analysis of the in vivo characterization of D-PH supported an anti-inflammatory phenotype of cells at the site of the implant. Levels of IL-6 significantly decreased over time while IL-10 was significantly higher at 6 weeks post implant. TNF-α levels did not change significantly from 24 hours onwards, however the trend was towards lesser amounts following the initial time point. Histological analysis of the explanted scaffolds showed excellent tissue ingrowth and vascularization. A live/dead stain showed that the cells infiltrating the scaffolds were viable. Both the in vitro and in vivo results of this thesis indicate that D-PHI is a good candidate material for tissue engineering a peripheral artery vascular graft.

A degradable/polar/hydrophobic/ionic (D-PHI) polyurethane with properties intended to promote tissue regeneration in a small diameter peripheral artery vascular graft was evaluated for cell biocompatibility and growth. Films were cast in polypropylene 96 well plates for monocyte/endothelial cell (EC) co-culture in vitro studies and porous scaffold discs were implanted in an in vivo subcutaneous mouse model. After 7 days in culture the co-culture demonstrated cell adhesion and growth, low esterase activity (a measure of degradative potential and cell activation), no detectable release of pro-inflammatory cytokine (tumour necrosis factor -α) but measurable anti-inflammatory interleukin (IL)-10. The EC and the co-culture expressed the EC biomarker CD31, whereas the monocyte monoculture did not. Cytokine array analysis of the in vivo characterization of D-PH supported an anti-inflammatory phenotype of cells at the site of the implant. Levels of IL-6 significantly decreased over time while IL-10 was significantly higher at 6 weeks post implant. TNF-α levels did not change significantly from 24 hours onwards, however the trend was towards lesser amounts following the initial time point. Histological analysis of the explanted scaffolds showed excellent tissue ingrowth and vascularization. A live/dead stain showed that the cells infiltrating the scaffolds were viable. Both the in vitro and in vivo results of this thesis indicate that D-PHI is a good candidate material for tissue engineering a peripheral artery vascular graft.

Se pretende obtener un material semibiodegradable basado en ácido hialurónico químicamente enlazado a cadenas de polímeros acrílicos. Los hidrogeles de ácido hialurónico presentan en general buenas características para su utilización en regeneración del sistema nervioso central: es biodegradable, es un componente importante del tejido neural, sus propiedades mecánicas son semejantes a las del tejido cerebral, promueve la formación de nuevos capilares (angiogénesis), y limita la inflamación. Con este nuevo material se pretende mejorar el excesivo grado de hinchado en medio fisiológico, su rápida degradación, mejorar la adhesión celular, además la matriz permanente de las cadenas acrílicas pueden actuar como un soporte permanente durante el proceso regenerativo sin que se produzca una pérdida brusca de propiedades mecánicas y estructurales. El trabajo consiste en caracterizar este nuevo material así como los productos intermedios necesarios para su obtención final, comparándolo con las propiedades de un hidrogel de ácido hialurónico sin incorporar cadenas acrílicas. Los estudios celulares se llevaran a cabo in vitro, como fase preliminar para futuros implantes en el cortex cerebral, estudiando la capacidad de diferenciación de precursores neurales y de generación de nuevos capilares con el fenotipo típico de la barrera hematoencefálica, mediante el estudio de cocultivos de precursores neurales y células endoteliales. / Perez Garnes, M. (2015). Structures based on semi-degradable biomaterials for neural regeneration in the central nervous system [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48799 / TESIS

Adhesives are widespread. They hold together the furniture, cars and electronics that we use on a daily basis. The majority of commercially available glues are sourced from petroleum-based monomers and are not degradable in any practical way. The permanent nature of these adhesive materials makes disassembly for recycling difficult. Current bio-based glues such as hide and starch glue are not strong enough to compete with commercial glues. Inspiration from nature is helping us to tackle this problem. Marine mussels achieve strong bonding to underwater surfaces through the use of adhesive plaques containing the uncommon amino acid 3,4-dihydroxyphenylalanine. Incorporating this chemistry into a degradable polylactic acid backbone allows for the development of strong bonding biodegradable glue. Throughout this work, the synthesis of these materials is discussed as well as methods to improve the bonding of these materials to compete with commercial glues. The degradation of these materials as well as their cytocompatibility is discussed.

Quartz Crystal Microbalance (QCM) is a sensitive and effective technique to analyze mass changes at the interface between a solid material and a liquid environment. In this Master thesis, QCM was employed for evaluating the interactions between selected degradable polymers and nanodiamond particles (nDP), fibronectin and the growth factor BMP-2.   Many parameters must be adapted to allow QCM measurements involving degradable polymers. These parameters were then tailored to allow QCM measurements with PLA, poly(LLA-co-CL), poly(TMC-D-LA) and PS.   Moreover, QCM provides quantitative measurements of protein adsorption on degradable polymers. The behavior of PLA and poly(LLA-co-CL) was further evaluated and compared with respect to protein adsorption. This behavior was demonstrated to be different for the two polymers considered and to be dependent on protein concentration in solution.   Eventually, exploiting QCM it was also possible to assess the relationship between nDP and the adsorption of fibronectin and BMP-2 onto PLA and poly(LLA-co-CL).

No description available.

Current treatment for posterior segment ocular diseases requires intravitreal injections administered every 4-6 weeks. The potential for siRNA to be used to treat these diseases is extremely attractive due to the specificity of these molecules and their potential for making long term changes to the expression patterns of the cells. Due to physiological recognition, however siRNA undergoes rapid degradation upon application. The development of cationic nanogels using polymeric “smart” biomaterials with degradable components to transport siRNA is described. pH – sensitive N, N dimethylaminoethyl methacrylate (DMAEMA) was crosslinked with thermo-sensitive diethylene glycol methacrylate (DEGMA), by free radical emulsion-precipitation polymerization. Size, charge and morphology were analyzed to assess potential as a nanovehicle. Through modification of the particle composition, cationic nanogels, determined by zeta potential, with sizes of approximately 160 nm confirmed with dynamic light scattering (DLS), were synthesized. A composition of 55:45 (DEGMA:DMAEMA); a size and charge ideal for cellular uptake. These particles had minimal impact on cell proliferation and exhibited spherical morphology when imaged by TEM at physiological pH. The structure was maintained between pH 3.5-9. Sensitivity to pH was shown by DLS through swelling at physiological pH, which may be useful can be taken advantage of in future studies for loading and release. Degradation with a reducing agent was shown using gel permeation chromatography, DLS and turbidity analysis. The results suggest this formula will undergo degradation in the cell. Reducing environments mimicking intracellular conditions that promoted degradation of the crosslinker showed enhanced release of dexamethasone phosphate as a model drug. Ongoing work is focused on examining gene silencing using these formulations. / Thesis / Master of Applied Science (MASc)

No description available.