The primary objective of my thesis was to investigate the effect of crimp-like fibrous scaffolds on bovine fibroblasts and to develop a scaffold for anterior cruciate ligament (ACL) tissue engineering. To achieve this objective, fibrous biodegradable polymeric scaffolds were fabricated, which upon relaxation developed a crimp-like structure, which resembled the crimp seen in native collagen. The understanding of the crimp mechanism allowed for controlling crimp-like patterns in various polymer fibre systems, and was determined to be due to residual stress coupled with an operating temperature (Top) above the glass transition temperature of the polymer (Tg). The benefit of crimp was evaluated by seeding fibroblasts on crimp-like fibres that were subjected to dynamic mechanical loading. The results showed a significant increase in extracellular matrix (ECM) accumulation by fibroblasts that experienced crimp unfolding. In addition, fibroblasts seeded on mechanically stimulated crimp-like fibrous scaffolds formed ECM bundles that resembled collagen fibre fascicles. Two separate studies were conducted to fabricate fibrous scaffolds with high modulus: one on thermoplastic polyesters and the other on a photocrosslinkable polyester. Of the thermoplastic polyesters investigated, poly(L-lactide-co-D,L-lactide) P(LLA-DLLA) exhibited the highest modulus, and was the most resistant to hydrolytic degradation. These fibres were placed in a heated aqueous environment to exhibit a crimp-like pattern similar to that of native collagen. Bovine fibroblasts were shown to attach, proliferate and deposit ECM on the surface of the P(LLA-DLLA) fibrous scaffolds. In addition, the deposited ECM appeared to be organized in distinctive bundles that resembled fascicles found in native ACL. However, upon crimp unfolding the crimp was not completely recovered. Photocrosslinkable poly(L-lactide-co-trimethylene carbonate cinnamate) P(LLA-TMC cinnamate) fibres in addition to supporting cell proliferation and ECM accumulation, completely recovered their crimp-like pattern, via [2 + 2] cycloaddition of the cinnamate groups. The recovery of crimp upon unfolding is a novel design feature incorporated into electrospun fibres as it innately mimics the function of collagen fibres found in the ACL. From the results obtained it is evident that crimp and its unfolding are key design features/conditioning techniques that need to be incorporated into fibrous scaffolds that possess high modulus, intended for ligament tissue engineering. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2012-01-05 14:11:25.965

Poly-γ-glutamic acid (γ-PGA) is a naturally occurring biopolymer made up of repeating units of glutamic acid and can be potentially used for multiple applications. This study compared the production of γ-PGA by eight bacteria (B. subtilis 23856, B. subtilis 23857, B. subtilis 23858 B. subtilis 23859, B. subtilis natto, B. licheniformis 1525, B. licheniformis 6816 and B. licheniformis 9945a) in GS and E media. B. subtilis natto and B. licheniformis 9945a have been investigated extensively for γ-PGA production, however, the remaining six have not previously been used. Using the eight bacteria, yields of up to 22.3 g/l were achieved in shake flasks. On characterization, it was observed that γ-PGA with different properties (crystallinity, acid/salt form and molecular weights ranging from 3,000 Da to 871,000 Da) was produced. Production of γ-PGA by B. subtilis natto in GS medium was scaled up using a fermenter and was tested for novel probiotic applications. The survival of probiotics during freeze drying, storage and ingestion was improved by combining them with a γ-PGA matrix. For L. paracasei, 10% γ-PGA protected the cells significantly better (P < 0.05) than 10% sucrose during freeze drying, whereas for B. longum and B. breve, it showed comparable cryoprotectant activity (P > 0.05) to 10% sucrose. This study also demonstrated the potential use of a non-dairy foodstuff (orange juice) for delivery of probiotics. Two Bifidobacteria strains protected with γ-PGA survived significantly better (P < 0.05) in orange juice for 39 days, with a log reduction in viability of less than 2.99 CFU/ml, when compared to unprotected cells, which showed complete loss in viability by day 20. In addition, γ-PGA protection improved survival of Bifidobacteria in a solution mimicking the environment of the stomach. γ-PGA-protected Bifidobacteria showed little (< 0.47 log CFU/ml) or no loss in viability when stored in simulated gastric juice (pH 2.0) for four hours, whereas unprotected cells died within two hours.

A field study evaluating the sustainability of four organic vegetable production systems was conducted in Lexington, Kentucky in 2006 and 2007. The four systems included no-till, raised beds covered with biodegradable black mulch, bare ground with shallow cultivation, and bare ground with shallow cultivation and wood chip mulch. The two-year study compared yield, weed control, labor, and costs associated with each system, as well as physical, chemical, and microbiological soil characteristics. In 2006, tomatoes (Lycopersicon esculentum Mill.) were grown in the four systems, with no significant difference in yield. Summer squash (Cucurbita pepo L.) was grown in the four systems in 2007. The no-till system had significantly lower yields than other systems. The bare ground with cultivation and mulch system had the best weed control in both years.

The food packaging industry is a £300bn global industry growing at a rate of 12% per year and increasingly favouring polymer or polymer-based materials. This generates 58m tonnes of "plastic" packaging waste annually in the EU and poses significant challenges for management given existing legislative constraints and increasing concerns surrounding the environmental impacts. The government, consumers, food retailers and pressure groups are all driving the demand for biodegradable packaging from renewable resources that can be disposed of with reduced impacts to the environment. Green Peace has devised a pyramid classification system of "Poisonous Plastics", which ranks plastics in terms of their harmfulness to the environment. They are campaigning against the use of oil-based materials and advocating the take up of biodegradable materials. The market for biodegradable food packaging is expanding rapidly but is still in its early stages of development and has not reached a critical mass to achieve significant market penetration. This is predominantly due to a lack of suitable materials that meet all environmental, functional and economical requirements. Whilst the long-term solution requires continued efforts in materials research and development, in the shorter term, changing working practices can abate the environmental impact of the industry. This research project tackled the challenge of environmental packaging from several directions: A novel starch-based material was developed that would fill the current gap in the food packaging market and facilitate recovery of the used materials by home composting. Using the sponsoring organisation as a case study, it was proved that by changing working practices by increasing rework and re-processing waste material for use in lower grade applications, both manufacturing costs and environmental impact can be reduced, thus benefiting both industry and the environment. A Life Cycle Assessment of selected biopolymers and oil-based polymers confirmed Green Peace's damning view of PVC and highlighted the need to develop biopolymers further. A domestic composting study of a range of commercially available "biodegradable" polymer materials revealed that a number of biodegradable packaging materials may typically biodegrade well in industrial high-temperature composting systems but fail to biodegrade under a low-temperature home composting environment and thus alerted the potential pitfall in waste management of some biodegradable polymers.

This study aimed at guiding osteoblast cells on biodegradable polymer carriers with well-defined surface microtopography and chemistry, and investigating the effect of cell alignment on osteoblast phenotype expression. A blend of two different polyesters, one being natural in origin (PHBV) and the other synthetic (P(L/DL)LA), was used to form a film with parallel macro- (250 &micro / m wide) or microgrooves (27 &micro / m wide) on its surface, by solvent casting on patterned templates. The micropatterned Si template was produced by photolithography, while the Teflo macropatterned template was lathe cut. Fibrinogen (Fb) was adsorbed or immobilized via epichlorohydrin spacer/crosslinker on the film surfaces to enhance cell attachment by increasing the surface hydrophilicity and by providing RGD amino acid sequence for integrin binding. Surface hydrophilicity was assessed by water contact angle measurements. Adsorption of Fb caused an increase in hydrophilicity, while the opposite was achieved with its covalent immobilization. Fb was homogeneously immobilized throughout the whole micropatterned film surface with amount of 153.1 &plusmn / 42.4 g Fb/cm2, determined with the Bradford assay, while it was adsorbed within the grooves of the micropattern. Surface characteristics of the films were studied with Scanning Electron (SEM) and Light microscopy. Osteoblast cells derived from rat bone marrow were seeded on the polymeric films with different surface topography and chemistry and were grown for one and three weeks. Osteoblast proliferation on the films was determined with Cell Titer 96 TM Non-Radioactive Cell Proliferation (MTS) test. Alkaline Phosphatase (ALP) assay and tetracycline labelling of mineralized matrix were carried out to determine osteoblast phenotype expression on different surfaces. SEM and fluorescence microscopy were used to evaluate the cell alignment. Osteoblasts on the micropatterned films with adsorbed Fb aligned along the groove axis with a mean deviation angle of 13.1o, while on the unpatterned films deviation from horizontal axis was 63.2o and cells were randomly distributed. Cell alignment did not affect cell proliferation. However, the highest ALP specific activity and the most homogeneous mineral distribution were obtained on the Fb adsorbed micropatterned films.

ABSTRACT CORNEA ENGINEERING ON BIODEGRADABLE POLYESTERS Zorlutuna, Pinar M. Sc., Department of Biotechnology Supervisor: Prof. Vasif Hasirci Co-Supervisor: Asst. Prof. AySen Tezcaner January 2005, 66 pages Cornea is the outermost layer of the eye and has an important role in vision. Damage of cornea due to injuries or infections could lead to blindness lowering the quality of life of the patient severely. In such cases, transplantation or artificial corneas have been used for treatment but both had drawbacks. The novel approach for corneal replacements is the tissue engineering of the cornea, a promising method which would be free of these drawbacks, if successful. In this study, carriers for tissue engineering of the cornea were designed and tested in vitro. Blends of biodegradable and biocompatible polyesters of natural (PHBV8) and synthetic (PLLA) origin were used to construct these carriers. For the epithelial layer of the cornea, PLLA-PHBV8 micropatterned films were prepared with solvent casting and seeded with D407 (retinal pigment epithelial) cells. In order to achieve proper cell growth, the films were coated with fibronectin. For the stromal layer of the cornea, highly porous foams of PLLA-PHBV8 were prepared by lyophilization and seeded with 3T3 cells (fibroblasts). A new approach was developed to create a combination of the film and the foam to obtain a surface patterned, 3 dimensional cell carrier. These carriers were seeded with Saos-2 cells (osteosarcoma cells) in the preliminary optimization studies and with D407 and 3T3 cells in further studies. The cell numbers on the carriers were quantified by using MTS assay (non-radioactive cell proliferation assay) and the cell proliferation on polymeric carriers was significantly higher than that of control (Tissue culture polystyrene) by the day 14. Characterization of these cells and the carrier was done using a variety of microscopic methods. The micrographs showed that the foam had a highly porous structure and the pores were interconnected. 3T3 cells were found to be distributed quite homogeneously at the seeding site, but due to the high thickness of the foam, the cells could not sufficiently populate the core (central parts of the foam) during the given incubation time. The micropatterned film allowed multilayer formation of D407 cells. The functionality of the cells seeded on the carriers was examined by immunohistochemistry. These analyses proved that the cells retained their phenotype during culturing. D407 cells formed tight junctions characteristic of epithelial cells, and 3T3 cells deposited collagen type I into the foams. Based on the results, it can be concluded that the 3-D PLLA-PHBV8 construct with surface patterns have a serious potential for use as a tissue engineering carrier for the reconstruction of the cornea. Key words: Tissue engineering, cornea, polymeric carrier, biodegradable, polyester.

Xylan was extracted from cotton waste, characterized by DSC and TGA analysis and used in biodegradable film production. Pure cotton waste xylan did not form film. The presence of an unknown compound, as an impurity, yielded composite films. The unknown compound was determined as a phenolic compound, and most probably lignin, by using DSC and TGA analysis and Folin-Ciocalteau method. The effects of xylan concentration of the film forming solutions, glycerol (plasticizer) and gluten additions on thickness, mechanical properties, solubility, water vapor transfer rate, color and microstructure of the films were investigated. Films were formed within the concentration range of 8-14%. Below 8%, film forming solutions did not produce films, whereas xylan concentrations above 14% was not used because of high viscosity problems. The average tensile strength, strain at break, water vapor transfer rate and water solubility of the cotton waste xylan films were determined as about 1.3 MPa, 10%, 250 g/m2.24h and 99%, respectively. The addition of glycerol as the plasticizer resulted in a decrease in the tensile strength and an increase in strain at break. The change in water solubility due to the addition of glycerol was very small. In addition, water vapor transfer rate and the deviation of the color from the reference color for the plasticized films were found to be higher than the unplasticized films. The effect of addition of wheat gluten in cotton waste xylan film forming solutions on film formation was investigated at different concentration ratios. However, the incorporation of wheat gluten worsen the film quality.

The Bryan/College Station (B/CS) region has been reported to have elevated concentrations of dissolved organic carbon (DOC) in surface water. Increased DOC concentrations are worrisome as DOC has been shown to be an energy source for the recovery and regrowth of E. coli and many watersheds are impaired by high bacteria levels. To examine the sources and fates of DOC in rural and urban regions to better understand DOC movement though the environment, seven watersheds were studied. To investigate source, streams were analyzed using diffuse reflectance near infrared spectroscopy (DR-NIR) and carbon isotopes. Fate of DOC was determined through monthly streams samples, gathered between March 2011 and February 2012, which were incubated for biodegradable DOC (BDOC). Soil in the region was sampled based on land use categories. Soil was analyzed for DOC and BDOC as well as DOC adsorption, the other major fate of DOC. Above ground vegetation was sampled in conjunction with soil and analyzed for BDOC. Data indicated that fecal matter from cliff swallows provided considerable organic material to streams in the B/CS region as shown through DR-NIR. Carbon isotope values in streams ranged from -23.5 +/- 0.7% to -26.8 +/- 0.5%. Stream spectra may be able to predict carbon isotope values in streams (Adj. R2 = 0.88). Mean annual stream DOC concentrations ranged from 11 +/- 3 mg/L to 31 +/- 12 mg/L, which represents a significant decrease in DOC between 2007 and 2011. Concurrent increases in pH and conductivity were also recorded. The decrease in DOC and the increases in pH and conductivity may be due to impacts of high sodium irrigation tap water. Biodegradable DOC was low in streams, which is likely due to DOC being present in streams in refractory forms that are resistant to microbial breakdown. Soil chemistry, including soil adsorption, was greatly influenced by sodium. The elevated adsorption coefficients and release values seen in highly developed and urban open areas can be attributed to frequent exposure to high sodium irrigation water. The results indicate that sodium is a major driver of DOC in the system. Sound management decisions concerning irrigation water chemistry and urban development might eventually emerge to protect water quality as a result of this research.

In 2007 the production of expanded polystyrene (EPS) in the world was over 4 million tonnes and is expected to grow at 6 percent per year. With the increased concern about environmental protection, alternative biodegradable materials from renewable resources are of interest. The present doctoral thesis work successfully demonstrates that starch-based foams with mechanical properties similar to EPS can be obtained by reinforcing the cell-walls in the foams with cellulose nanofibers (MFC). High cellulose nanofiber content nanocomposites with a highly plasticized (50/50) glycerol-amylopectin starch matrix are successfully prepared by solvent-casting due to the high compatibility between starch and MFC. At 70 wt% MFC, the nanocomposites show a remarkable combination of high tensile strength, modulus and strain to failure, and consequently very high work to fracture. The interesting combination of properties are due to good dispersion of nanofibers, the MFC network, nanofiber and matrix properties and favorable nanofiber-matrix interaction. The moisture sorption kinetics (30% RH) in glycerol plasticized and pure amylopectin film reinforced with cellulose nanofibers must be modeled using a moisture concentration-dependent diffusivity in most cases. The presence of cellulose nanofibers has a strong reducing effect on the moisture diffusivity. The decrease in zero-concentration diffusivity with increasing nanofiber content could be due to geometrical impedance, strong starch-MFC molecular interaction and constrained swelling due to the cellulose nanofiber network present. Novel biomimetic starch-based nanocomposite foams with MFC contents up to 40 wt% are successfully prepared by freeze-drying. The hierarchically structured nanocomposite foams show significant increase in mechanical properties in compression compared to neat starch foam. Still, better control of the cell structure could further improve the mechanical properties. The effect of cell wall composition, freeze-drying temperature and freezing temperature on the resulting cell structure are therefore investigated. The freeze-drying temperature is critical in order to avoid cell structure collapse. By changing the starch content, the cell size, anisotropy ratio and ratio between open and closed cells can be altered. A decrease in freezing temperature decreases the cell size and increases the anisotropy ratio. Finally, mechanical properties obtained in compression for a 30 wt% MFC foam prepared by freeze-drying demonstrates comparable properties (Young's modulus and yield strength) to expanded polystyrene at 50% RH and similar relative density. This is due to the reinforcing cellulose nanofiber network within the cell walls. / QC 20100913

The goal of this project was to develop a non-toxic amphiphilic diblock copolymer nanoparticulate drug delivery system that will solubilize paclitaxel (PTX) and retain the drug in plasma. Methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) (MePEG-b-PCL) diblock copolymers loaded with PTX were characterized and their physicochemical properties were correlated with their performance as nanoparticulate drug delivery systems. A series of MePEG-b-PCL was synthesized with PCL blocks ranging from 2-104 repeat units and MePEG blocks of 17, 44 or 114 repeat units. All copolymers were water soluble and formed micelles except MePEG₁₁₄-b-PCL₁₀₄, which was water insoluble and formed nanospheres. Investigation of the effects of block length on the physicochemical properties of the nanoparticles was used to select appropriate copolymers for development as PTX nanoparticles. The critical micelle concentration, pyrene partition coefficient and diameter of nanoparticles were found to be dependent on the PCL block length. Copolymers based on a MePEG molecular weight of 750 g/mol were found to have temperature dependent phase behavior. Relationships between the concentration of micellized drug and the compatibility between the drug and core-forming block, as determined by the Flory-Huggins interaction parameter, and PCL block length were developed. Increases in the compatibility between PCL and the drug, as well as longer PCL block lengths resulted in increased drug solubilization. The physicochemical properties and drug delivery performance characteristics of MePEG₁₁₄-b-PCL₁₉ micelles and MePEG₁₁₄-b-PCL₁₀₄ nanospheres were compared. Nanospheres were larger, had a more viscous core, solubilized more PTX and released it slower, compared to micelles. No difference was seen in the hemocompatibility of the nanoparticles as assessed by plasma coagulation time and erythrocyte hemolysis. Micellar PTX had an in vitro plasma distribution similar to free drug. The majority of micellar PTX associated with the lipoprotein deficient plasma fraction (LPDP). In contrast, nanospheres were capable of retaining more of the encapsulated drug with significantly less PTX partitioning into the LPDP fraction. In conclusion, although both micelles and nanospheres were capable of solubilizing PTX and were hemocompatible, PTX nanospheres may offer the advantage of prolonged blood circulation, based on the in vitro plasma distribution data, which showed that nanospheres retained PTX more effectively.