Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1995-07-20
1997-06-03
Nutter, Nathan M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
536 3, 536 187, 536 20, 536 58, 536 63, 536107, 536110, 536115, 536119, 5361231, 424489, 424490, 424491, 424492, 424493, 424494, 424495, 424496, 424497, 424499, 424501, 427212, 4272133, 42721331, 42721332, 42721333, 42721335, 42721336, 264 41, 264 43, 264 433, 264 47, B01J 1314
Patent
active
056356099
DESCRIPTION:
BRIEF SUMMARY
The present invention relates essentially to the use of a transacylation reaction with formation of covalent amide bonds between an esterified polysaccharide and a polyamine to form a stable membrane, in aqueous medium, at least at the surface of gelled particles, to the particles thus produced, to processes for their manufacture and to the compositions containing them.
More precisely, the present invention essentially relates to the use of a transacylation reaction between, on the one hand, a polysaccharide bearing esterified carboxylic groups, and, on the other hand, a polyamine, in order to form, in aqueous medium, a stable membrane at least at the surface of gelled particles, to the modified particles thus produced, to the processes used to form such modified particles, and to compositions containing the particles thus obtained, such as cosmetic, pharmaceutical, therapeutic, agrifood, enzymatic, biotechnological, reagent or diagnostic compositions.
TECHNOLOGICAL BACKGROUND
It is well known that spheres may be prepared very readily, for example from sodium alginate, by using the property of alginate solutions to gel in the presence of cations such as, for example, calcium ions. The material to be encapsulated in the spheres is first dispersed in the aqueous alginate solution. This solution is added dropwise to an aqueous solution of a calcium salt. There is immediate gelation, which produces spheres of gelled alginate. The surface of the spheres may then be stabilized by immersion in a solution of a polycationic polymer such as poly-L-lysine or polyethyleneimine (Lim, F., U.S. Pat. No. 4,352,883, 1982). A membrane forms at the periphery, resulting from ionic association between the alginate and the polycation. This membrane allows small molecules to pass through while retaining large molecules and cells. It is then possible to liquefy the inner gel by immersing the alginate spheres, stabilized by the polycationic polymer, in a citrate solution, so as to chelate the calcium in the spheres (Lim, F., U.S. Pat. No. 4,352,883, 1982). The material incorporated then remains contained within the membrane.
This process has the great advantage of being carried out entirely in aqueous medium and of retaining excellent viability with respect to encapsulated living cells, which may multiply within the capsule. Hence, it is widely used for the inclusion of living tissues, cells and microorganisms. Thus, alginate spheres containing microorganisms are used in the food industry in order to carry out fermentations (fermentation of dairy products, beer, champagne, etc.). These techniques are applied to plant or animal cells or organs with the aim of cryoprotecting or producing metabolites, to animal cells or tissues (islets of Langerhans, hepatocytes, etc.) for implantation in human or veterinary medicine (cell therapy), or for carrying out toxicology tests in vitro. Cells are also cultured in such spheres for the production of biological substances such as the monoclonal antibodies developed by hybridomas, which accumulate in the spheres and are thus easily harvested after opening the membranes.
However, the process has drawbacks associated with the nature of the membrane. As it involves no covalent bonds but only ionic bonds between the alginate and a polycation, it is of limited stability (Dupuy et al., J. Biomed. Mat. Res., 1988, 22, 1061-1070). The polymers have a tendency to pass into solution over time. Moreover, if the pressure increases within the capsule under the effect of cell multiplication, the membrane cannot resist the pressure and cells are released into the medium. It is thus often necessary to apply successively alternate layers of alginate and then of polycation ("sandwiches") in order to obtain a solid membrane which does not allow the contents to diffuse out (Wong H. and Chang T. M. S. Biomat. Art. Cells & Immob. Biotech., 1991, 19, 675-686).
French Application Document No. 9,210,173 (1992) describes the use of a transacylation reaction between a polysaccharide ester, such as propylene glycol algi
REFERENCES:
patent: 3503769 (1970-03-01), McDowell
patent: 4352883 (1982-10-01), Lim
patent: 5132242 (1992-07-01), Cheung
patent: 5194300 (1993-03-01), Cheung
patent: 5298410 (1994-03-01), Phillips et al.
Edwards-Levy Florence
Levy Marie-Christine
Orly Isabelle
Coletica
Nutter Nathan M.
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