Influence of starch botanical source on aqueous two-phase system phase behavior and starch microspheres preparation

Abstract: Background: Starch is a well-studied material, produced by plants in granules to store energy. Starch finds a lot of applications in day-to-day life, in the food and pharmaceutical industry. This project was focusing on the utilization of starch retrogradation and the ability to form aqueous two-phase systems to prepare microspheres from the starch of different botanical sources and characterize them. Materials and Methods: Three different starches were used: potato, corn, and barley, all waxy, meaning they have higher amylopectin compared to normal starches. Modification of raw native starch was needed, as the untreated starch could not be used for microsphere preparation. The behavior of an aqueous two-phase system comprising starch and polyethylene glycol was investigated, and acquired microspheres were characterized using microscopic evaluation, enzymatic degradation kinetics data and differential scanning calorimetry to assess the crystallinity of formed structures, aka microspheres. Results and discussion: Modification of the starches was generally successful; two out of three samples had the same profile as the reference and were assessed by doing a rheology investigation. Phase characterization followed the results achieved during rheology studies, providing information about the content of the phases and their distribution. Microscopic evaluation showed that microspheres received from different botanical sources of starch have different properties, such as porosity, surface and inner structure, shape and size. Enzymatic digestion and differential scanning calorimetry results have proven the same outcomes, as starch microspheres had different degradation kinetics and melting peaks. Conclusion and future work: Due to various constraints and time limitations, it was not possible to fulfil all the goals that were set during the planning stage of the project. Nevertheless, native waxy starches were successfully hydrolyzed, their phase behavior was studied, and their thermal properties have been investigated. Though, there is still a room for a vast amount of experiments: consequent phase behavior studies are required to further understand how microspheres are prepared, a potential study of rapidly dissolving potato starch microspheres based on the enzymatic degradation result, a study of microsphere preparation in presence of excipients and investigation of possible encapsulation of API in microspheres