Microcarriers Manufacturers

Microcarrier Manufacturer Material Diameter (microns) Culture mode... 

Batch latex manufacturing, 14 721 Batch membrane system, 21 638 Batch microcarrier cell culture systems, 5 350, 352-354... 

In a batch configuration, host cells that contain an expression vector for the recombinant product are added to a predetermined volume of growth medium (Figure 4.12A). The cells are allowed to grow until the nutrients in the medium are depleted or the excreted by-products reach inhibitory levels. At that time, the cells are harvested, and recombinant protein, found in inclusion bodies, cell-membrane fractions, or cytoplasm, are isolated after disruption of the harvested cells. Because the host cells are destroyed at the end of each run, they must be replaced every three to seven days for fermentation or every two weeks for roller-bottle or microcarrier-support production of adherent cells. To ensure uniformity and reproducibility, the FDA requires manufacturers of recombinant proteins to establish and validate a seed stock of recombinant host cells that are validated to contain the characterized expression vector and to be free of contaminants. 

There are several manufacturers of microcarriers for animal cell culture, providing products with different chemical composition, size, form, and density. Table 9.2 shows a list of common commercially available microcarriers and their manufacturers. 

Table 9.2 Commercially available microcarriers and their manufacturers ...

Swell the dry beads made of cross-linked dextran, polyacrylamide or gelatin in PBS-A or Hepes buffered saline as described by the manufacturer. The cross-linked dextran beads require 2-3 h to swell at room temperature. Avoid stirring with a simple bar magnet as this may grind the beads. Addition of non-ionic detergent (e.g. Tween 80) to 0.1% may help initial wetting of the microcarrier. 

Proper alignment of the system is of course necessary. Differences in systems from various manufacturers are not so much in the technique itself but more in the user-friendliness of the system. The main fields of CLSM applications in bioengineering concern bacteria growing in soils [16,17], on non-transparent supports such as leaves [18], in biofilms [19-21], in particular for wastewater treatment or biofouling studies [22], and mammalian cells growing on microcarriers [23,24] or in aggregates [25,26]. 

Another area that has seen considerable advances is that of the physical environment for cell growth. Glassware has almost entirely disappeared from most tissue culture laboratories, to be replaced by an enormous, and expensive, range of plasticware. This has enabled the scientist to derive more sophisticated culture vessels and has led to the manufacture of three-dimensional culture systems and microcarriers. An added benefit has been the reliability and reproducibility of culture systems and, as a result, the avoidance of variability and contamination... 

Gelatin microcarriers are manufactured from denatured porcine collagen (gelatin) obtained from processing pig skin from certified slaughterhouses and from stock certified to be free of transmittal disease. After denaturation under harsh thermal... 

Microcarrier culture Microcarriers are small particles, usually spheres 100 to 300 fim in diameter that are suspended in stirred culture medium. The technique was initiated in 1967 but required considerable developmental work to produce a range of suitable microcarriers (e.g., the Cytodex series by Pharmacia). The first industrial process based on microcarriers was for FMDV. Subsequently, a wide range of microcarriers based on gelatin, collagen, polystyrene, glass, cellulose, polyacrylamide, and silica have been manufactured to meet all situations. The key criteria in the design of effective microcarriers were to make the surface chemically and electrostatically correct... 

Microcarrier culture has proven to be the most effective scale-up method for ADC, despite its limitations (critical procedures, low surface area-to-volume ratio of a sphere). To increase the surface area porous particles were developed. The initial particle was the Verax microsphere which was 500 fim in diameter and manufactured from bovine collagen. The interconnecting channels of 20- to 40- u.m diameter provided an internal open volume of 80% of the sphere. The spheres were fluidized at 75 cm/min upward flow, and cell densities in excess of 10 /mL intrasphere volume were achieved (equivalent to 4 x 10 /mL in the bioreactor). The sphere matrix provided a huge surface... 

Figure 6.16 Flowsheet for the manufacture of three different types of solid lipid microcarriers for controlled nutrient or drug delivery using membrane homogenization approach. The dashed area represents the temperatnre-controlled operations carried out at 80°C (above the melting point of oil).

As stated earlier (Section 3.1.1)), it has always been a calorimetric problem to study the metabolism of cells adherent to a substratum. The obvious solution these days is to use beads in a bioreactor-type vessel. An early application of such a technique was the use of solid Cytodex 1 microcarriers (Pharmacia) to measure the heat production of anchorage-dependent green monkey kidney (Vero) cells [38] in a Thermometric stirred perfusion vessel [95]. As seen in Figure 39, the heat production was proportional to the number of cells assessed by counting in a Biirker chamber the number of nuclei released from cells and stained with a hypotonic solution of citrate containing crystal violet [38]. In recent years, different kinds of microcarriers have been manufactured that are optimised for specific cell types. 

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