Stimulus-responsive colloidosomes which completely dissolve upon a mild pH change are developed. pH-Responsive nanoparticles that dissolve upon a mild pH increase are synthesized by a nanoprecipitation method and are used as stabilizers for a double water-in-oil-in-water Pickering emulsion. These emulsions serve as templates for the production of pH-responsive colloidosomes. Removal of the middle oil phase produces water-core colloidosomes that have a shell made of pH-responsive nanoparticles, which rapidly dissolve above pH 7. The permeability of these capsules is assessed by FRAP, whereby the diffusion of a fluorescent tracer through the capsule shell is monitored. Three methods for tuning the permeability of the pH-responsive colloidosomes were developed: ethanol consolidation, layer-by-layer assembly and the generation of PLGA-pH-responsive nanoparticle hybrid colloidosomes. The resulting colloidosomes have different responses to the pH stimulus, as well as different pre-release permeability values. Additionally, fundamental studies regarding the role of particle surface roughness on Pickering emulsification are also shown. The pH-responsive nanoparticles were used as a coating for larger silica particles, producing rough raspberry-like particles. Partial dissolution of the nanoparticle coating allows tuning of the substrate surface roughness while retaining the same surface chemistry. The results obtained show that surface roughness increases the emulsion stability of decane-water systems (to almost twice), but only up to a certain point, where extremely rough particles produced less stable emulsions presumably due to a Cassie-Baxter wetting regime. Additionally, in an octanol-water system, surface roughness was shown to affect the type of emulsion generated. These results are of exceptional importance since they are the first controlled experimental evidence regarding the role of particle surface roughness on Pickering emulsification, thus clarifying some conflicting ideas that exist regarding this issue.

ABSTRACT ENCAPSULATION OF WHEAT GERM OIL Yazicioglu, Basak M.Sc., Department of Food Engineering Supervisor: Prof. Dr. Serpil Sahin Co- Supervisor: Prof. Dr. G&uuml / l&uuml / m Sumnu February 2013, 82 pages Wheat germ oil is a rich source of omega 3 and omega 6, octacosanol and tocopherol which has vitamin E activity. Due to these properties it is beneficial for health but it is prone to oxidation in free form. The aim of this study was to encapsulate wheat germ oil in micron size and determine the best encapsulation conditions by analysing encapsulation efficiency, particle size distribution and surface morphology of the capsules. The effects of core to coating ratio, coating materials ratio and ultrasonication time on encapsulation of wheat germ oil were investigated. Maltodextrin (MD) and whey protein concentrate (WPC) at different ratios (3:1, 2:2, 1:3) were used as coating materials. Total solid content of all samples was 40% (w/w). Five different core to coating ratios (1:8, 1:4, 2:4, 3:4, 4:4) were experimented. Ultrasound was used at 320 W and 20 kHz frequency for three different times (2, 5, 10 min). Prepared emulsions were frozen and then freeze dried for 48 hours to obtain microcapsules. Encapsulation efficiency analysis, particle size analysis and scanning electron microscopy (SEM) analysis were performed. Increasing WPC content in coating led to an increase in encapsulation efficiency. Microcapsules prepared with MD:WPC ratio of 1:3 were found to have higher encapsulation efficiencies (65.62%-89.62%) than the other ratios. Increase in oil load led to decrease in encapsulation efficiency thus 1:8 core to coating ratio gave better results. The best conditions for microcapsules were determined as ultrasonication time 10 min, core to coating ratio of 1:8 and MD:WPC ratio 1:3.

Precipitation with a Compressed Fluid Antisolvent (PCA) and Rapid Expansion from Supercritical Solution (RESS) are two processes based on supercritical fluids that are capable of producing submicron particles. Novel variations of these basic processes have been examined to produce stable particles of various pharmaceutical compounds. PCA is an antisolvent precipitation technique where an organic solution of drug + polymer in solvent is atomized (sprayed) into supercritical (SC) CO₂. Upon liquid mixing, the solute materials precipitate to form microparticles. A Vapor-over-Liquid technique has been used to produce larger, uniform particle sizes of biodegradable polymers. By suspending a protein in the solvent phase, the protein can be encapsulated/coated by the precipitating polymer. RESS is a process by which a homogeneous solution at supercritical conditions is sprayed through an expansion nozzle to atmospheric conditions. The resultant change in phase leads to the precipitation of the solute materials. The production of extremely small particles (<50 nm) have been predicted but rarely demonstrated. Typically, particle growth occurs to form larger (~1 μm) particles. A novel adaptation was developed, dubbed RESAS (Rapid Expansion from Supercritical to Aqueous Solution), wherein the expansion is conducted within an aqueous environment. The aqueous phase can contain surfactant or lipid stabilizers to capture and preserve submicron particles of water-insoluble drug actives in the form of a suspension. / text

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Triple fortification of salt with vitamin A, iron, and iodine has been investigated in the past to reduce micronutrient deficiencies in the developing world. The objective is to develop integrated nutrient delivery technology by microencapsulating a self-emulsifying drug delivery system (SEDDS) made of surfactants and a bioactive compound, retinyl palmitate. The SEDDS is used to enhance absorption of the vitamin A through food systems and to achieve targeted release of the active ingredient. Encapsulating vitamin A was difficult when using the spray dryer and the enteric coating, Aquacoat®. Losses of the micronutrient after a three month storage period ranged from 50-99% at both 25°C/20% RH and 45°C/60% RH. The result of a matrix encapsulation and poor coating formation contributed to the high losses. Further investigation of coating systems with the aim of stabilizing all three samples for a six month storage period such as using other encapsulating methods is recommended.

Triple fortification of salt with vitamin A, iron, and iodine has been investigated in the past to reduce micronutrient deficiencies in the developing world. The objective is to develop integrated nutrient delivery technology by microencapsulating a self-emulsifying drug delivery system (SEDDS) made of surfactants and a bioactive compound, retinyl palmitate. The SEDDS is used to enhance absorption of the vitamin A through food systems and to achieve targeted release of the active ingredient. Encapsulating vitamin A was difficult when using the spray dryer and the enteric coating, Aquacoat®. Losses of the micronutrient after a three month storage period ranged from 50-99% at both 25°C/20% RH and 45°C/60% RH. The result of a matrix encapsulation and poor coating formation contributed to the high losses. Further investigation of coating systems with the aim of stabilizing all three samples for a six month storage period such as using other encapsulating methods is recommended.

Barley protein based microcapsules (1-5µm) incorporating fish oil/β-carotene were successfully prepared. Well suspended solid microcapsules, rather than emulsions, were able to form after high pressure emulsifying process. These wet-status microcapsules could be turned into dry powder by a spray drying process. The microcapsules demonstrated spherical shape and high loading capacity. Oxidative stability tests under accelerated conditions and in food formulations suggest barley proteins are effective microencapsulation materials to protect fish oil against oxidation. Microcapsule degradation and bioactive compound release behaviors were studied in the simulated gastro-intestinal tract. The data revealed that nano-encapsulations (20-30nm) were formed as a result of enzymatic degradation of microcapsule bulk matrix in the simulated gastric tract. These nano-encapsulations delivered β-carotene to a simulated human intestinal tract intact, where they were degraded by pancreatic enzymes and steadily released the β-carotene. These uniquely structured microcapsules may provide a new strategy to develop target delivery systems for nutraceuticals / Food Science and Technology

Thesis (Ph. D.)--Biomedical Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Nie, Shuming; Committee Member: Bao, Gang; Committee Member: Chung, Leland; Committee Member: Murthy, Niren; Committee Member: Prausnitz, Mark.

Thesis (PhD) -- University of Western Sydney, 2007. / A thesis submitted to the University of Western Sydney, College of Health and Science, School of Natural Sciences, as a requirement for the degree of Doctor of Philosophy. Includes bibliography.

Thèse (Ph. D.)--Université Laval, 2008. / Bibliogr.: f. 128-162. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.