An understanding of potential and limitations of alginate/PLL microcapsules as a cell retention system for perfusion cultures

Abstract

Microcapsules for high cell density culture of mammalian cells have found an increasing interest, however, the poor stability of the microcapsules and the lack of characterisation methods led to few quantitative results. Alginate-poly-L-lysine (PLL) microcapsules have been studied in detail in order to form a basis for comparison of capsules made from different polymers. Since the microcapsules can be easily retained in the bioreactor without the need for a cell separation device, high cell densities were achieved with a maximum of 4 × 10⁷ cell/ml_{microcapsules}, corresponding to a colonisation of 5% of the internal capsule volume. Measurement of microcapsule integrity and mechanical resistance showed that alginate-PLL microcapsules are not suitable for perfusion cultures since they are very sensitive to media composition, mainly the presence of non-gelling ions that have a higher affinity for alginate than PLL and Ca²⁺, leading to the leakage of PLL and Ca²⁺, and to microcapsule rupture.

Keywords:

• Cell microencapsulation
• CHO-DP12
• alginate
• animal cell culture
• mechanical resistance
• perfusion culture

This work was funded by the Irish Research Council (IRC) and the National Institute of Biotechnology Research and Training (NIBRT). Confocal analyses were possible through the help of the Programme for Research in Third-Level Institutions (PRTLI) Cycle 4. The PRTLI is co-funded through the European Regional Development Fund (ERDF), part of the European Union Structural Funds Programme 2007–2013. The authors declare that they have no conflict of interest with respect to the work reported here.