Investigations of cell immobilization in alginate: rheological and electrostatic extrusion studies

Abstract

In this study, the process of electrostatic extrusion as a method for cell immobilization was investigated. We have assessed the effects of concentrations of yeast cells (as a model cell type) and Na alginate on the size of the resulting microbeads and attempted to rationalize the obtained findings by rheological characterization of the cell-alginate suspensions. Under the investigated conditions, microbeads, 50-600 mu m in diameter, were produced and the increase in both alginate and cell concentrations resulted in larger microbeads with their sizes having higher standard deviations. Rheological characterization revealed non-Newtonian, pseudoplastic behavior of cell-alginate suspensions with higher viscosities at higher alginate concentrations. However, the presence of cells even at high concentrations (5 x 10(8) and 1 x 10(9) cells mL(-1)) did not significantly affect the rheological properties of the Na alginate solution. Finally, we have investigated the kinetics of alginate gelation with respect to the quantity of Ca2+ ions and the presence of cells. The molar ratio of alpha-L-guluronic acid units to Ca2+ ions of 4:1 provided complete crosslinking. The presence of cells decreased the rate of network formation as well as the strength of the obtained Ca alginate hydrogel.