Porous microcarrier

D matrices, such as gels, sponges and porous microcarriers... 

Anchorage-dependent cells are grown in suspension culture by growing the cells attached to small microcarrier beads (100-300 pm) suspended in the culture medium by agitation. There are two types of microcarriers available (Chapter 5, sections 5.8 and 5.9 Griffiths, 1990) the non-porous microcarriers whereby cells are growing only on the outer surface of the beads, and porous microcarriers whereby cells are growing predominantly in the internal porous structure of the microcarrier beads. 

There is no substantial literature on direct sparging of non-porous microcarrier cultures. As is discussed in section 4.6, the difficulty is that the presence of bubbles induces bead flotation, i.e. attachment of beads to bubbles, and the formation of large bead-bubble aggregates that tend to rise and accumulate at the surface of the culture vessel, which is a highly undesirable characteristic. Nevertheless, it is possible slowly to sparge microcarrier cultures without undue cellular injury if suitable surfactants/antifoams (e.g. Pluronic F-68 or Medical Emulsion AF see section 4.6) are used. 

For non-sparged cultures of non-porous microcarriers, cellular injury is likely to be the result of three distinct mechanisms (Papoutsakis, 1991a) interactions... 

High-density (1 x 10 mH) scaleable systems (to 2001) based on porous microcarriers. 

Microcarrier culture has most of the advantages of both suspension and anchorage-dependent systems and this is a particularly valuable asset for porous microcarrier culture (Looby Griffiths, 1990). 

An alternative commercial system that is now available is the Cytopilot (Pharmacia) (Reiter et al, 1990, 1991), which is a 25-1 system using polyethylene carriers (Cytoline) that supports up to 1.2 x 10 CHO K1 cells mH carrier. The range of porous microcarriers available is given in Table 5.9.3. 

The preparation of novel solid materials is a huge field for applications such as microfiltration, separation membranes or their supports, microstructured polymer blends, and porous microcarriers for the culture of living cells and enzymes. The considerable progress accomplished over the last four years makes it possible to envision many future developments. Some attempts for specific applications have already been made as shown below. 

Lee, D.W., Gregory, D., Haddow, D.J., Piret, M.J., and Kilbum, D.G., High density BHK culture using porous microcarriers, in Animal Cell Technology Developments, Processes and Products, Spier, R.E., Griffiths, J.B., and MacDonald, C., Eds., Butterworth-Heinemann, Oxford, 1992, pp. 480-486. 

There is a range of porous microcarriers available (Table 3), which allow one to design their own fluidized system, or alternative some of the carriers are designed for stirred cultures. 

Many microporous beads are available, as are systems such as the Pharmacia Cytopilot using Cytoline porous microcarriers. There is a preference for microporous microcarriers that could be used in stirred, rather than fluidized, bioreactors, and these are now available (Cellsnow and ImmobaSil). ImmobaSil is of particular value as it is extremely permeable to oxygen, is a non-animal product safe from bovine contaminants, is robust, and can be used in all culture modes. 

Production The production culture may be a batch of several hundred roller bottles, 30 to 50 cell factories, or a single bioreactor for suspension (100 to 10,000 L) or microcarrier (50 to 500 L) ceUs. Although batch-type production is still the most common process, continuous processes where the product is harvested daily over a long period (20 to 100 d) are being increasingly used. Culture systems based on hollow fibers, porous microcarriers, or other immobilization techniques are used for continuous perfusion processes. During the production phase, the virus seed or a promoter (e.g., for interferon) may be added. 

The potential applications of such a polymerization technique for preparing novel polymeric materials include microfiltration, separation membranes, polymer blends with a unique microstructural morphology, and porous microcarriers for cultures of living cells and enzymes [7]. Some other interesting ideas about the preparation of novel materials include the conductive composite film [95] and microporous silica gel [96]. 

Porous polymeric membranes derived from microemulsion polymerization have found significant use in the field of bio- and medical technology. Thus, in a number of biochemical operations, these porous membranes have been found to perform the function of a porous microcarrier for culturing living cells and enzymes. The... 

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