Effects of starch filler on the physical properties of lyophilized calciumalginate beads and the viability of encapsulated cells

• Main Author: Wong Sze Ling
• Format: Thesis
• Language: English; English
• Published: 2011
• Subjects: TP1-1185 Chemical technology
• Online Access: https://eprints.ums.edu.my/id/eprint/39144/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/39144/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/39144/

Calcium-alginate hydrogel is commonly used to encapsulate live cells. However, the qualities of lyophilized alginate beads could be undesirable for various reasons which may include reduction in encapsulation performance during storage. The objectives of this work were to improve the qualities of the lyophilized beads and to establish evidence if the bead qualities had significant influence on the stability of encapsulated cells. The bead qualities were manipulated by incorporating corn starch as the solid filler at various concentrations and produced using simple extrusion technique and subsequently lyophilized. The degree of shrinkage of SFAB during lyophilization was found to be dependent on the filler concentration with the control beads shrunk the most, by about 40% whereas the shrinkage reduced where beads shrunk from 18% to 9% with additional of starch filler. Sphericity of SFAB was also improved with Aspect Ratio of between 1.1 and unity. The relative porosity reduced from 71% (control sample) to 21.7% (SFAB 60%) in a near linear trend and SFAB was found to have ink bottle pore shape. With incorporation of starch fillers, SFAB with higher starch concentration had greater mechanical strength but its mechanical behaviour changed from spongy to brittle with a breakage point observed in the stress strain curve of starch concentration above 40%. Less hygroscopic behaviour was also observed from the lower EMC, range from 15% to 25% of SFAB with additional of starch compared to the control beads of EMC above 30%. Probiotic cells encapsulated within the alginate-starch beads were significantly more stable during freeze-drying process and storage, exposed to temperature, humidity and oxygen stresses in comparison to the cells encapsulated within the control beads. It is believed that with the incorporation of starch granules, stabilization on cells could occur in three possible mechanisms which are 1) shielding effect by the physical packing of starch granules 2) maintaining of particle sphericity through the presence of starch granules and 3) alteration of particle hygroscopic nature with starch granules. In conclusion, the qualities of the alginate beads were improved by incorporating starch filler and the bead qualities were found to have significant influence on the cell stability.