Immobilization of cells by electrostatic droplet generation: a model system for potential application in medicine

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Authors: V Manojlovic, J Djonlagic, B Obradovic, V Nedovic, B Bugarski

Published Date January 2006 Volume 2006:1(2) Pages 163 - 171

DOI: http://dx.doi.org/10.2147/IJN.S

V Manojlovic¹, J Djonlagic¹, B Obradovic¹, V Nedovic², B Bugarski¹

¹Faculty of Technology and Metallurgy, ²Faculty of Agriculture, University of Belgrade, Belgrade, Serbia and Montenegro

Abstract: The process of electrostatic extrusion as a method for cell immobilization was investigated that could be used for potential applications in medicine. An attempt was made to assess the effects of cell addition and polymer concentration on the overall entrapment procedure, ie, on each stage of immobilization: polymer–cell suspension rheological characteristics, electrostatic extrusion process, and the process of gelation. The findings should contribute to a better understanding of polymer–cell interactions, which could be crucial in possible medical treatments. Alginate–yeast was used as a model system for carrier-cells. The electrostatic extrusion was considered as a complex two-phase flow system and the effects of cell and alginate concentrations on the resulting microbead size and uniformity were assessed. Under investigated conditions, microbeads 50–600 µm in diameter were produced and the increase in both alginate and cell concentrations resulted in larger microbeads with higher standard deviations in size. We attempted to rationalize the findings by rheological characterization of the cell–alginate suspensions. 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 (5x10⁸ and 1x10⁹ cells/mL) did not significantly affect the rheological properties of Na-alginate solution. Lastly, we investigated the kinetics of alginate gelation with respect to the quantity of Ca²⁺ ions and cell presence. The gelation kinetics were examined under conditions of limited supply with Ca²⁺ ions, which can be essential for immobilization of highly sensitive mammalian cells that require minimal exposure to CaCl₂ solution. The molar ratio of G units to Ca²⁺ ions of 3.8:1 provided complete crosslinking, while the increase in alginate concentration resulted in prolonged gelation times but higher strength of the resulting gel. The cell presence decreased the rate of network formation as well as the strength of the obtained Ca-alginate hydrogel.

Keywords: alginate, electrostatic extrusion, rheology, yeast cells

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