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Photopolymerization is the basis of several multi-million dollar industries including films and coating, inks, adhesives, fiber optics, and biomaterials. The fundamentals of the photopolymerization process, however, are not well understood. As a result, spatial variations of photopolymerization impose significant limitations on applications in which a high spatial resolution is required. To address these issues, microrheology was implemented to study the spatial and temporal effects of free-radical photopolymerization. In this work a photosensitive, acrylate resin was exposed to ultraviolet light, while the Brownian motion of micron sized, inert fluorescent tracer particles was tracked using optical videomicroscopy. Statistical analysis of particle motion yielded data that could then be used to extract rheological information about the embedding medium as a function of time and space, thereby relating UV exposure to the polymerization and gelation of monomeric resins. The effects of varying depth, initiator concentration, inhibitor concentration, composition of the monomer, and light intensity on the gelation process were studied. The most striking result is the measured difference in gelation time observed as a function of UV penetration depth. The observed trend was found to be independent of UV light intensity and monomer composition. The intensity results were used to test the accuracy of energy threshold model, which is used to empirically predict photo-induced polymerization. The results of this research affirm the ability of microrheology to provide the high spatial and temporal resolution necessary to accurately monitor the photopolymerization process. The experimental data provide a better understanding of the photo-induced polymerization, which could lead to expanded use and improved industrial process optimization. The use of microrheology to monitor photopolymerization can also aid in the development of predictive models and offer the ability to perform in-situ quality control of the process.

In controlled release applications a drug is molecularly dispersed in a polymer phase. In the presence of a thermodynamically compatible solvent, swelling occurs and the polymer releases its content to the surrounding medium. The rate of the drug release can be controlled by interfering with the swelling rate of the beads or by influencing diffusion through the viscosity of the polymer. Beads that contain chitosan were prepared through the ionotropic gelation method where tripolyphosphate (TPP) was used as the crosslinking agent. Beads that consisted of 3% w/v isoniazid (lNH) and 5% w/v chitosan were prepared in a 5% w/v TPP solution (pH 8.7) as the primary beads. To improve the drug loading of chitosan isoniazid beads (ClB) the TPP concentration, pH of the TPP solution and the INH concentrations were altered for maximum drug loading. To increase the porosity of the beads of chitosan beads Explotab® (EXPL), Ac-Di-Sol® (ADS) and Vitamin C (VC) were added individually to chitosan solutions at concentrations of 0.1, 0.25 and 0.5% w/v before adding the mixture to the TPP solution. Morphology, swelling and drug loading studies were used to evaluate the different formulations. After these excipients were added individually they were also added in combinations of two excipients respectively and characterised. From the results of the drug loading studies the beads that contained only chitosan and isoniazid showed a percentage drug loading of (43.92%) which is the best of all the beads that were analyzed. The multi excipient combination of Ac-Di-Sol® and Explotab® showed the best swelling capability at both pH levels. Dissolution studies were conducted on all the formu lations over a period of 6 hours (360 minutes) at pH 5.6 and pH 7.4. From the dissolution results it were clear that no chitosan dissolved at both pH values. The dissolution of single pharmaceutical excipient (SPE) and multi pharmaceutical excipient (MPE) formulations can be arranged in the following order: VC/ADS < VC < ADS/EXPL < ADS < VC/EXPL < CIB < EXPL. Explotab® is a potential excipient for enhanced drug release over a wide pH range. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2007.

Controlled release systems aim at achieving a predictable and reproducible drug release profile over a desired time period. These controlled release formulations offer many advantages over conventional dosage forms. These advantages include: reduced dosing intervals, constant drug levels in the blood, increased patient compliance and decreased adverse effects. Complex controlled release formulations such as those with sustained release properties, often require additional steps during the production phase. The cost and economic impact associated with these complex controlled release dosage formulations often outweigh the short term benefits. Thus the development of an economic method to produce controlled release particles is of great importance especially in third world countries. In controlled release formulations the drug is often equally dispersed throughout a polymer matrix. In the presence of a thermodynamically compatible solvent, swelling occurs and the polymer releases its content to the surrounding medium. The rate of drug release can be controlled by interfering with the amount of swelling and rate of diffusion by manipulating the viscosity of the polymer matrix. Chitosan is an ideal candidate for controlled drug delivery through matrix release systems. It is a biodegradable polymer with absorption-enhancing properties. Cross-linking chitosan with different cross-linking agents allow the preparation of beads. Beads are frequently used in controlled release dosage forms as they are very flexible in dosage form development and show various advantages over single unit dosage forms. Because beads disperse freely in the gastrointestinal tract they maximize drug absorption, reduce fluctuation in peak plasma, and minimize potential side effects without lowering drug bio-availability. Chitosan beads and excipient containing chitosan beads were prepared and investigated as possible controlled release formulations. Pyrazinamide was chosen as the model drug. Chitosan beads and excipient containing chitosan beads were prepared by ionotropic gelation in tripolyphosphate. In this study chitosan/pyrazinamide beads containing pharmaceutical excipients (Ascorbic acid, Explotab and Ac-Di-Sol) were produced. The excipients were added individually and in combinations to the chitosadpyrazinamide dispersion and the beads were characterized on the basis of their morphology, solubility, fiability, drug loading capacity and swelling behaviour, as well as drug release (dissolution properties). The drug loading of the pyrazinarnide loaded chitosan beads, was 52.26 % 0.57%. It was noted that the inclusion of excipients in the beads resulted in an increase in drug loading with the combination of Ascorbic acid and Ac-Di-Sol giving the highest drug loading of 67.09 ± 0.22%. It was expected that the addition of the pharmaceutical excipients would lead to a sustained release of pyrazinamide. Dissolutions studies, however, revealed a burst release in both phosphate buffer solution (PBS) pH 5.60 and 7.40 over the first 15 minutes and the curve reached a plateau after 30 minutes. Thus, apparently the inclusion of the pharmaceutical excipients did not contribute to a sustained release of pyrazinamide over the tested period of six hours. In future studies the dissolution time can possibly be extended to a period of 24 hours. It might be possible for the remaining drug (approximately 40%) in the beads to be released over the extended period. Other polymers can also be investigated to control the release of pyrazinamide. Further studies are, however, necessary to investigate this possibility in the future. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2007.

Low molecular weight gelators (LMWGs) are small molecules that are capable of entrapping solvents to form a gel in organic solvents or aqueous solution. These compounds rely solely on noncovalent forces to form the fibrous networks necessary to entrap a variety of solvents. The organogels and hydrogels thus formed could have applications in a variety of fields from environmental to biological to medicinal. Carbohydrates are ideal starting materials to synthesize LMWGs, because of their natural abundance, dense chirality, and biocompatibility. D-Glucose is the most common monosaccharide and D-glucosamine is isolated from natural sources, such as crab shells. Several series of compounds were synthesized using compounds 1-3 as the starting materials. These include esters, carbamates, amides, and ureas. The structure and gelation relationship was analyzed to obtain guidelines for designing new LMWGs. Compound 1 is a simple derivative of D-glucose and its terminal alkynyl esters and saturated carbamates are effective gelators. Compound 2 is a simple derivative of D-glucosamine and its amide and urea derivatives are also effective gelators. Compound 3 is formed from the deoxygenation of D-glucose. 1OOHOOCH3OHOPh2OOHOOCH3NH2OPh3OOHOOHOPh The design, synthesis and gelation properties of several classes of sugar based low molecular organo/hydrogelators will be discussed in this thesis in chapters 2, 3, and 4. After obtaining highly effective organo/hydrogelators, potential applications of these novel molecular systems can be explored. Some preliminary study on using one of the gelator in enzyme assay has shown that it is possible to utilize the hydrogels to immobilize enzymes. However, future research can explore further on the applications of these gelators.

O amido de milho é uma importante fonte de energia para os seres humanos, além de ser um polímero natural utilizado nas indústrias químicas, farmacêuticas e de alimentos. O amido possui grande capacidade de retenção de água e gelatinizam na presença de água e em elevadas temperaturas. Nestas condições, suas propriedades reológicas e mecânicas se modificam e fazem com que seja interessante o uso na fabricação de diversos materiais. Os processos de aglomeração e recobrimento de partículas, em combinação com outros métodos, podem proporcionar o aprimoramento de ingredientes alimentícios em pó, por meio da alteração do tamanho e forma das partículas. Além disso, o processo de aglomeração também permite alterar o índice de compactação, incorporar aditivos às partículas e aplicar películas de revestimento. Assim, este trabalho teve como objetivo realizar o estudo do tamanho e forma de partículas de amido de milho aglomeradas com alginato de sódio, produzidas por meio de formação de gotas a partir de suspensão de amido-alginato de sódio, e posterior gelificação iônica em cloreto de cálcio. Os processos de aglomeração e recobrimento foram estudados por meio dos métodos de gotejamento e método de dispersão em óleo. O método de gotejamento, ou dripping, consistiu no gotejamento da suspensão de amido-alginato em solução de cloreto de cálcio. O método de agitação em líquidos imiscíveis consistiu na gelificação iônica da suspensão sob agitação continua, em que o óleo de soja é a fase contínua e a suspensão de amido-alginato é a fase dispersa. Após a secagem em estufa a 60 °C, as partículas foram caracterizadas pelas análises de tamanho e forma. As alterações na microestrutura dos grânulos e investigação da resistência foram observadas por ensaios de calorimetria diferencial de varredura. As partículas também foram caracterizadas por análises de imagem de tamanho e forma. Os grânulos de amido foram produzidos utilizando-se a partir de suspensões de amido-alginato, e resultaram em frações de amido iguais a (50, 60, 70, 80 e 90)%. O aumento da concentração de amido de milho na suspensão de alginato resultou no aumento da viscosidade e também grânulos secos com maior tamanho. Para o método de dispersão em óleo, o aumento da frequência de agitação de 4 Hz para 11 Hz produziu menores tamanho de gota e, consequentemente, em grânulos secos com menores tamanhos. A aplicação destas técnicas de aglomeração por formação de gotas pode ser uma ferramenta útil para a produção de microcápsulas ou agregação de sistemas particulados contento dois ou mais ingredientes com distribuições de tamanho distintas. / Cornstarch is an important source of energy for humans, as well as being a natural polymer seen in the chemical, pharmaceutical and food industries. Starch has a high retention capacity of water and gelatin in the presence of water and in heat. Under these conditions, its rheological and mechanical properties change and make it interesting to use as a material medium. Agglomeration and particle coating processes, in combination with other methods, can provide the enhancement of powdered food ingredients by altering the size and shape of the particles; agglomeration process can also replace, adopt applications and apply coating films. The aim of this work is to study the size and shape of particles of agglomerated particles with sodium alginate produced by the formation of droplets from the suspension of sodium starch alginate and subsequent ionic gelation in calcium chloride. The agglomeration and recoating processes were studied by means of the drip methods and oil dispersion method. The dripping method consisted of the drip of the starch-alginate suspension in to calcium chloride solution. The method of stirring in immiscible liquids consisted of ionic gelation of the suspension under continuous stirring, wherein the soybean oil is the continuous phase and the starch-alginate suspension is the dispersed phase. After oven drying at 60 ° C, the particles were characterized by size and shape analyzes. Changes in microstructure and resistance of the beads investigation were observed by differential scanning calorimetry assays. Particles were also characterized by size and shape image analyzes. The starch granules were produced using starch-alginate suspensions, and resulted in starch fractions equal to (50, 60, 70, 80 and 90%). Increasing the concentration of corn starch in the alginate suspension resulted in increased viscosity and also larger dried granules. For the oil dispersion method, increasing the stirring frequency from 4 Hz to 11 Hz produced smaller droplet size and consequently smaller dried granules. The application of these agglomeration techniques by droplet formation can be a useful tool for the production of microcapsules or aggregation of particulate systems containing two or more ingredients of different size distribution.

by Wang Guo-Xin. / "April 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (p. 184-194). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

The heat-induced gelation properties of ultrafiltered (UF) whole milk concentrate were studied under different physical and chemical conditions. total solids concentration, homogenization pressures, heating temperatures, and heating times were found to have a positive correlation with gel strength. The addition of calcium chloride, sodium chloride, or trisodium citrate produced gels of higher strengths and textural properties than the gels obtained with non-salt-treated concentrate. Calcium chloride produced the strongest gels with a cheese-like texture and poor spreadability. Sodium chloride produced gels of intermediate strength with a firm, elastic texture and poor spreadability. Trisodium citrate produced the softest gels with a smooth, creamy texture and good spreadability. A shelf stable 40% total solids UF concentrate was manufactured using ultra-high temperature (UHT) processing by direct steam injection. The pourable concentrate had a shelf life of 75 to 90 days at 23°C and did not have the ability to produce heat-induced gels after a second heating. Addition of calcium chloride, sodium chloride, or trisodium citrate restored the heat-induced gelation of the retentate. However, the gels were weaker and presented different characteristics than did the gels from non-UHT-treated concentrate. Transmission electron microscopy (TEM) studies revealed a relationship between gel firmness and gel ultrastructure of the heat-induced gels. The gels consisted of a network of casein micelles connected with strands of a less dense protein material. The tighter the network the stronger the gel strength. High heating temperatures and calcium chloride addition caused fusion of the casein micelles int he network. Sensory evaluation of two prototype gelled desserts by a general consumer population showed a good potential for the use of the heat-induced gelation property of UF-concentrated whole milk in the development of new gelled dessert applications.

Les enjeux de santé publique et de développement durable conduisent à intensifier l’utilisation de protéines végétales notamment dans les secteurs de biens de consommation comme l’industrie pharmaceutique,l’agro-alimentaire et les cosmétiques. La levée récente de certains verrous technologique permet aujourd’hui la purification industrielle de protéines végétales issus de tourteaux provenant de la production d’huiles végétales. Ces protéines sont valorisables comme substituts aux graisses saturées dans la structuration d’huiles à destination de la consommation humaine. Le manque de texture d’huiles végétales insaturées peut être compensé par ces protéines jouant le rôle de stabilisants et de gélifiants dans les émulsions. Nous nous intéressons aux propriétés fonctionnelles des protéines de blé, de tournesol et de colza, en volume et aux interfaces. Nous avons montré que des gels de protéines de tournesol avec des élasticités modulables sont obtenus par dénaturation thermique. La dynamique de formation de films protéique aux interfaces fluides a été étudiée en combinant des mesures de tensiométrie, de viscoélasticité dilatationnelle et d’ellipsométrie. Les mesures sur plusieurs ordres de grandeurs en concentrations et en temps mettent en évidence différents régimes de structuration associés à différentes dynamiques d’adsorption pour les trois protéines de blé, de tournesol et de colza étudiées. Nous discutons également le rôle de la flexibilité des protéines dans ces différents régimes de structuration. / Challenges of public health and sustainable development trend to intensify the use of vegetables proteins, particularly in consumer goods sectors such as pharmaceutical, food and cosmetics industries. The recent overcome of technical limitation allows the industrial purification of vegetables proteins derived from meal made by vegetable oils production. These proteins are valuable as substitutes for saturated fats in structuring oils for human consumption. The lack of unsaturated vegetable oil texture can be reduced by these proteins acting as stabilizers and gelling agents in emulsions. We are interested in the functional properties of wheat, sunflower and rapeseed proteins, by volume and at interfaces. We have shown that sunflower protein gels with modulable elasticities are obtained by thermal denaturation. In addition, we studied the dynamics of protein film formation at fluid interfaces by combining measurements of tensiometry, dilatational viscoelasticity and ellipsometry. We highlight different structuring regimes and discuss the role of protein flexibility in this structuring.