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  • 1
    Electronic Resource
    Electronic Resource
    Highly hydrophobically modified polyelectrolytes: Field variables to control emulsion type (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 945-948 
    Details
    ISSN: 1435-1536
    Keywords: Key words Emulsion type ; amphiphilic polymer ; polyelectrolyte ; polymeric surfactant ; balanced copolymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Highly hydrophobically modified (with n-dodecylamide chain) linear poly(acrylic acid)s (HHMPAAH) and poly(sodium acrylate)s (HHMPAANa) with various degrees of grafting (τ) were synthesized and used as emulsifiers of the n-dodecane/water system. The type of emulsion, oil in water (O/W) or water in oil (W/O), was investigated as a function of the polymer chemical structure (τ, salt or acid form of the copolymer) and aqueous phase electrolyte concentration (NaNO3). Increasing τ and/or salt concentration was found to favor the formation of inverse emulsions. Direct liquid–liquid dispersions are more likely to form with poly(sodium acrylate)s than with poly(acrylic acid)s. Hence, field variables such as τ, pH and ionic strength are relevant parameters to control emulsion type. Moreover, a balanced polyelectrolyte neither soluble in oil nor in water was synthesized for the first time. With this original emulsifier, the dispersion type was found to change from O/W to W/O with polymer salting out. The work provides convenient model system for fundamental studies of polymer conformation at liquid–liquid interfaces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050332
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  • 2
    Electronic Resource
    Electronic Resource
    Highly hydrophobically modified polyelectrolytes stabilizing macroemulsions: relationship between copolymer structure and emulsion type (1999)
    Springer
    Colloid & polymer science 277 (1999), S. 89-94 
    Details
    ISSN: 1435-1536
    Keywords: Key words Emulsion type ; amphiphilic polymer ; polyelectrolyte ; polymeric surfactant ; balanced copolymers ; HLB scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The types of emulsions, oil (n-dodecane) in water (O/W) or water in oil (W/O), stabilized with highly hydrophobically grafted linear poly(sodium acrylate)s, were investigated as a function of polymer chemical architecture. Consequently, a large number of macroemulsifiers, covering a wide range of hydrophobicity, were synthesized by changing the degree of grafting (τ), length (n) and type (single- versus twin-tailed) of the hydrophobic moiety. Monovalent salt (NaNO3) concentration was used as a probe to adjust and hence to estimate the hydrophile-lipophile balance (HLB) of each copolymer. τ, n, type of graft and electrolyte concentration were identified as field parameters to control emulsion type. In general, decreasing either τ or n was found to favor the formation of direct emulsions. Inverse dispersions were preferentially formed with twin-tailed rather than single-tailed copolymers. Moreover, the types of emulsions stabilized with well-balanced polyelectrolytes can be flipped from O/W to W/O with increasing salt concentration. Finally, following the Davies concept, a HLB scale for polymers was created from a comparison with surfactants of nearly identical chemical structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050372
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  • 3
    Electronic Resource
    Electronic Resource
    Evaluation of the new serum-free medium (MDSS2) for the production of different biologicals: Use of various cell lines (1994)
    Springer
    Cytotechnology 14 (1994), S. 47-59 
    Details
    ISSN: 1573-0778
    Keywords: BHK ; BSR ; human recombinant IL-2 ; rabies virus ; recombinant BHK ; serum-free medium ; surface-attached growth ; suspension culture ; Vero
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The presence of serum in cell culture raises safety problems for the production of biologicals, thus a new serum-free medium (MDSS2) was developed. The evaluation of this medium for the growth of different cell lines (BHK-21 C13, BSR and Vero) has shown that cells grew in this medium similarly to standard serum-containing medium, independently of the culture system used: in static (as monolayer) as well as in agitated systems (in suspension in spinner and perfusion reactors). BHK-21 and BSR cells grew as aggregate cultures and could proliferate in both static and agitated culture systems. Vero cells stayed attached to a substrate and proliferated equally in static and in agitated microcarrier-culture systems. The cell densities obtained with BHK-21 cells depended only on the culture system used. They ranged from 2–3×106 to 6–12×106 cells per ml for static batch and perfusion reactor cultures respectively. The cell concentration was 3 to 6 times higher than in classical cultures performed in serum-containing medium. The cell densities obtained with Vero cells were indistinguishable from those obtained in serum-containing medium, whatever the cell culture system used. These cell lines have been used for the production of rabies virus. With respect to BHK-21 and BSR, similar production rates of rabies glycoprotein have been found as in the standard roller bottle process. The production of rabies virus and of viral glycoprotein by Vero cells cultivated in serum-free medium was augmented 1.5-fold and 2.5-fold, respectively, when compared to serum-containing medium. A recombinant BHK-21 cell line, producing human IL-2, can also proliferate in MDSS2, after addition of insulin. The specific IL-2 production rate was augmented 3–4 fold in comparison to serum-containing medium. For the cells tested, the MDSS2 serum-free medium is a good growth and production medium. Its use for cultivating other cell lines and/or for the production of other biologicals is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00772195
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  • 4
    Electronic Resource
    Electronic Resource
    The new medium MDSS2N, free of any animal protein supports cell growth and production of various viruses (1999)
    Springer
    Cytotechnology 30 (1999), S. 191-201 
    Details
    ISSN: 1573-0778
    Keywords: BHK-21/BRS ; MDCK ; non-animal-derived ; serum-free medium ; Vero ; virus-production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The development of media free of serum and animal or human proteins is of utmost importance for increasing the safety of biologicals produced for therapy and vaccination. In order to reduce the risk of contamination, we have modified the serum free medium MDSS2, a very efficient serum free medium for the production of various biologicals including experimental vaccines using different cell lines (Merten et al., 1994), by replacing the animal derived products by plant extracts. The new serum and animal protein free medium (MDSS2N) can be efficiently used for biomass production of various cell lines. These cells grow equally well or better in this new serum-free medium than in the old formulation (MDSS2): • BHK-21/BRS cells, adapted to MDSS2N, showed an overall specific growth rate of 0.0197 h-1 (μ_max = 0.0510±0.0058 h-1), whereas those cultivated in MDSS2 grew with an average specific growth rate of 0.0179 h-1 (μ_max = 0.0305±0.0177 h-1). • Vero cells grew with an average specific growth rate of 0.0159 h-1 and 0.0153 h-1 in MDSS2 and MDSS2N, respectively. Very similar growth rates were obtained in microcarrier cultures in stirred tank reactors: the specific growth rates were 0.0161 h-1 and 0.0166 h-1 for MDSS2 and MDSS2N cultures, respectively. • For MDCK cells, when cultured on microcarriers in bioreactors, a higher average specific growth rate was observed in MDSS2N than in MDSS2; values of 0.0248 h-1 and 0.0168 h-1, respectively, were obtained. The capacity of MDSS2N to support the production of different viruses was equally evaluated and it could be established that for certain viruses there are no or insignificant differences between MDSS2N and MDSS2 (influenza and polio virus), whereas, the production of rabies virus is somewhat reduced in MDSS2N when compared to MDSS2. The use of MDSS2N for cell culture and the production of various viruses is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008021317639
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