Serum Substitutes

Any new formulation may be evaluated against the properties of a serum-substituted medium for growth and productivity. As well as growth promotion, a serum supplement in medium may also lead to a reduction in cell death by apoptosis and this allows extended culture longevity. This can enable a substantial increase in recombinant protein productivity. 

In summary, advances in our understanding of the nutritional and hormonal requirements of cells in culture and of the role played by attachment factors and transport proteins have led to the possibility that any cell can be cultured in the absence of serum. The type of serum substitute used and the means of achieving a serum-free culture system should be determined by the ultimate purpose that the culture system is to serve. The advantages of serum-free culture are manifest both in the practical realm of providing an inexpensive and simple starting material for the purification of cell-secreted proteins, such as antibodies, and for providing a more precise definition of the in vitro environment in order to model more... 

The cells can then be adapted through growth in a series of progressively lower serum concentrations. To achieve the final step to serum-free condition, one of three methods can be used addition of commercial serum substitutes, addition of defined proteins or addition of only amino acids, trace elements and other small molecules to provide a protein-free medium. The last of these alternatives is the most difficult to achieve however, it may ultimately prove to be the most useful. 

There are three categories of serum-free media totally protein free, those containing complex serum substitutes and those containing defined proteins and other additives. 

This discussion provides an overview of the methods for selecting a serum lot and balanced nutrient medium as starting points for adapting a cultured cell line to serum-free conditions. The ultimate stringency of serum-free medium attained (containing serum substitutes, defined additives or protein-free) depends on the needs of the researcher and the characteristics of the cell line. Serum provides many different functions for the cell and there are many different types of cells, each of which requires a medium derived to meet its particular needs. The information provided here should enable the development of a serum-free medium appropriate for each particular case. 

Table 1 Serum substitutes and supplements for serum-free media...

The N3 supplement is used as a serum substitute to avoid retinoids m serum triggering the response of reporter cells N3, however, can be arduous and expensive to prepare (see Table 1). Given the short-term nature of this assay, it may be advisable first to try the assay in serum-contaimng medium or in medium using serum that has been stripped of retinoids by treatment with charcoal followed by sterile filtration Alternatively, serum-free medium supplement containing insulin, transferrin, and selenite can be obtained from Boehnnger Mannheim (Indianapolis, IN) Whichever medium or serum treatment is chosen, it is important that the viability of both the tissue explant and reporter cell monolayer is ensured over the duration of the assay... 

A hybridoma can live indefinitely in a growth medium that includes salts, glucose, glutamine, certain amino acids, and bovine serum that provides essential components that have not been identified. Serum is expensive, and its cost largely determines the economic feasibihty of a particular ciilture system. Only recently have substitutes or partial replacements for serum been found. Antibiotics are often included to prevent infection of the culture. The pH, temperature and dissolved oxygen, and carbon dioxide concentration must be closely controlled. The salt determines the osmotic pressure to preserve the integrity of the fragile cell. 

Much higher asymmetric induction was observed in the two-phase oxidation of simple alkyl aryl and diaryl sulphides296, substituted alkyl aryl sulphides297 and dithioacetals of formaldehyde298 by sodium metaperiodate in the presence of proteins such as bovine serum y-globulin and egg albumin. Optical purities of the sulphoxides so formed ranged between 20 and 85%. 

Note The reaction is very specific for N-substituted imidazole derivatives. In serum investigations the detection limit was 50 ng clotrimazole per milliliter serum. The reagent can be employed on silica gel, kieselguhr and Si 50000 layers. 

SI (le Systeme International d UniUs) units are used in many countries to express clinical laboratory and serum drug concentration data. Instead of employing units of mass (such as micrograms), the SI system uses moles (mol) to represent the amount of a substance. A molar solution contains 1 mol (the molecular weight of the substance in grams) of the solute in 1 L of solution. The following formula is used to convert units of mass to moles (mcg/mL to pmol/L or, by substitution of terms, mg/mL to mmol/L or ng/mL to nmol/L). 

We found that the negatively charged surfactant, sodium laurel sulfate, can be successfully substituted for the serum proteins used previously. In low ionic strength solutions, the cmc of the surfactant is 8.1 mM [577]. We explored the use of both sub-CMC (data not shown) and micelle-level concentrations. Saturated micelle solutions are most often used at pION. 

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