Detta är ett uppsatsförslag hämtat från Nationella Exjobb-poolen. Klicka här för att komma tillbaka till samtliga exjobbsförslag.
The effects of different additives on amorphous freeze- and spray dried disaccharide formulations
Sensitive drugs (e.g. proteins and peptides) and living cells (e.g. lactic acid bacteria) are able to keep high activity following a drying process if proper additives are used. Mono- and disaccharides, such as trehalose and sucrose, are commonly used as protectants.
It is assumed, that the protective effect is caused by the ability of the protectant to replace water during drying, and add stability by preferential hydration mechanisms. A prerequisite for this is that the protectant is present in its amorphous (molecularly disordered) form. A common way to prepare amorphous formulations is by freeze- or spray drying.
However, amorphous solids are less stable than their crystalline counterparts and they tend to transform when subjected to heat or moisture during storage. Therefore, these formulations need to be stored in protective atmospheres and low temperatures to maintain function and structural integrity. Several additives, mostly polymers, have been studied and are known to provide stability to amorphous systems.
Area of interest and scientific questions
Stabilization of amorphous solid system are of interest in both drug and food formulation and in future use of living cells for various biological products. However, when it comes to preservation of lactic acid bacteria by freeze-drying, the fundamental aspects of the physical stability of the protectant are not yet fully understood. For instance, how do additives (polymers, surfactants, cell supernatants, peptones) affect the amorphous stability of the protective disaccharides? Do these additives affect survival of lactic acid bacteria in the dry state? What is the influence of concentration of different additives on stability?
This master thesis project involves working with aspects of bacteria formulation, with issues also relevant for industrial processes. Fermentation, formulation, drying, and dry state stability will be examined. Powder characterization will be performed with calorimetry (differential scanning and isothermal calorimetry) and cell activity/viability with plate count assays. The water content after drying will be analyzed with Karl-fisher titration and water activity. Storage studies at different temperatures and relative humidity will be studied.
Two exam projects will be done as a collaborative effort both at the department of pharmacy, UU and at the department of microbiology, SLU.
Informationen om uppsatsförslag är hämtad från Nationella Exjobb-poolen.