Porous Alginate-Poly(ethylene glycol) Entrapment System for the Cultivation of Mammalian Cells

Abstract

A novel gel entrapment method has been developed where macropores are created within alginate beads to provide an environment for high-density growth of mammalian cells. The method takes advantage of an interaction between poly(ethylene glycol) (PEG) and alginate to provide a network of pores within the bead for growth while the surrounding alginate matrix retains the integrity of the bead and minimizes cell leakage. Hybridomas were grown to a density approaching 10(8) cells/mL of beads in this system, while conventional alginate restricted growth to a maximum of 2 x 10(7) cells/mL of beads. In addition, cell leakage was minimal even at high cell densities, which was not the case with the conventional alginate system. Study of the conventional system determined that cell growth was limited by the alginate matrix; increasing the alginate concentrations resulted in lower final cell densities. In contrast, the PEG-alginate system permits growth in pores so the alginate matrix serves only as a structural matrix for cells. The pore size can be varied as a function of PEG concentration (10-20 wt % PEG) to provide radially defined areas for cell growth and radial diffusion pathways for nutrients/products in the adjacent alginate matrix. Because the PEG-alginate entrapment process does not require additional chemical reactions or temperature changes, the system offers a simple alternative to attain high cell densities in an immobilized bead system. As an illustration of the concept, cells entrapped in this system were grown to high density in both batch and perfusion modes for the production of monoclonal antibodies. Using the suspension batch culture as the base case, the specific monoclonal antibody production rate increased 1.6-fold for the slower growing batch-immobilized culture and 3-fold for the immobilized perfusion culture.

Endoluminal hydrogel films made of alginate and polyethylene glycol: Physical characteristics and drug‐eluting properties

“…Even though the addition of PEG is primarily for its drug delivery potential, its presence can evidently alter the properties of the composite hydrogel. 17,18 Our data indicate that the addition of PEG to the alginate network increases the compliance of the film relative to the pure alginate (Fig. 2) and thus may reduce the long-term risk of fatigue failure, particularly in those regions of the film that are not physically supported by the stent struts.…”

A novel alginate hollow fiber bioreactor process for cellular therapy applications

“…During culture, exit of up to 20% of the cells from the alginate slabs into suspension was observed, which is common for cell lines cultured in alginate. 24 It was difficult to distinguish the rate of slab exit from the rate of cell division in suspension. Therefore, total cell numbers, including cells in the supernatant, were used to calculate the growth rates in alginate slabs.…”

CHO immobilization in alginate/poly-l-lysine microcapsules: an understanding of potential and limitations

“…An advantage of this system is that much higher cell densities may be attained in the bioreactor, greater than 10 7 cell mL reactor -1 , simply by increasing the volume of microcapsules in the bioreactor. This assumes that there are no medium limitations, such as through perfusion operation (Seifert and Phillips 1997). Furthermore the SC productivity could be increased three-fold despite the reduced specific growth rate.…”

“…Several types of microcapsules have been used for mammalian cells cultures (Scheirer et al 1984;King et al 1987;Miller et al 1988;Al-Rubeai et al 1990;Yoshioka et al 1990;Uludag et al 1993;Heald et al 1994;Seifert and Phillips 1997;Cruise et al 1998;Park et al 1998). However, it has yet to be demonstrated whether such systems offer advantages over classical suspension cultures in terms of specific growth rate or specific productivity.…”