Microcarrier preparation

Table 18.1 compares the relationship between cell culture surface area and bioreactor volume in many different culture systems usually used with adherent cells. For microcarriers, this coefficient might reach 60 cm2/ml of medium for culture area prepared with 10 mg of microcarriers per milliliter. For Roux bottles, this coefficient is around 3 cm2/ml. In cultures initiated with 2 mg of microcarriers per milliliter of medium, high cell densities of even 3 X 106 cells/ml are often reached, compared with smaller cell densities from 2 to 3 X 105 cells/ml usually observed in Roux bottle systems. Another great advantage of the use of microcarrier culture systems is the possibility of preparing cell cultures with hundreds or even thousands of liters (Montagnon et al., 1984). 

Mendon a RZ, Ioshimoto LM, Mendon a RMZ, De Franco M, Valentini EJG, Be ak W, Pereira CA (1993), Preparation of human rabies vaccine in VERO cell culture using a microcarrier system, Braz. J. Med. Biol. Res. 26 1305-1317. 

Only a small fraction of the cells in a preparation obtained from a tissue will go on to divide. For this reason, seeding levels are often high and microcarriers are not very suitable initially as many may remain without a dividing cell attached. 

One bead one sequence" approach allows the preparation of simultaneously millions of physically separate individual compounds on solid microcarriers (beads)... 

Figure 5.7.3 The expected results and time frames when following a microcarrier or Nunc multiplate (MP) culture path. The microcarrier culture system requires one more extra day of equipment preparation compared with the MP pathway. One should also note that WI-38 will require an additional 24-h growth period in order to achieve comparable yields to that of MRC-5.

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. 

The class I FruA isolated from rabbit muscle ( RAMA ) is the aldolase used for preparative synthesis in the videst sense, because of its commercial availability and useful specific activity of 20 U mg. Its operating stability in solution is limiting, but recently more robust homologous enzymes have been cloned, e.g. from Staphylococcus camosus [152] or from the extremophilic Thcrmus aquaticus [153], vhich promise to be unusually stable in synthetic applications [154]. Attempts at catalyst immobilization have been performed vith rabbit muscle FruA, vhich has been covalently attached to microcarrier beads [58], cross-linked in enzyme crystals (CLEG) [59], or enclosed in a dialysis membrane [73]. It vas recently sho vn that... 

Although Heng s work [113] achieved feeder layer-free and xeno-free cultures of hESCs in chemically defined medium, the researchers only verified a few ES cell lines (HES-3 and H7). It is not clear whether the microcarriers and cell culture protocol used by Heng et al. could support all hESC and hiPSC lines. It is preferable to prepare or synthesize microcarriers composed of other types of biomaterials and to develop and design optimal microcarriers for hPSC culture in feeder layer-free and xeno-free culture conditions by referencing Heng s work [113]. 

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]. 

A solid microcarrier for encapsulating flavor-enhancing ingredients such as 5 -ribonucleotide was prepared from W/O/W emulsion using cacao butter as a melted lipid phase (Kukizaki et al., 2001). This microcarrier was used in Japan as a supplement in miso paste. The W/O emulsion with a mean particle size of 0.48 tm was produced at 40°C using a rotor-stator homogenizer. This W/O... 

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