Capsules containing mammalian cells

1. A microcapsule comprising:

a liquid core;

a stiff intermediate envelope comprising at least one biopolymer; and

at least one external envelope totally encapsulating the liquid core at its periphery,

said intermediate envelope being located between the liquid core and the external envelope,

said external envelope being able to retain the liquid core when the microcapsule is immersed in a gas and comprising at least one gelled polyelectrolyte and/or one stiffened biopolymer,

said microcapsule further comprising at least one eukaryotic mammalian cell, wherein the liquid core comprises at least one keratinocyte and the intermediate envelope comprises at least one fibroblast; and

said stiff intermediate envelope having an elastic modulus that is non-zero.

2. The microcapsule according to claim 1 , wherein the biopolymer of said intermediate envelope is selected from the group consisting of proteins of the extra-cellular matrix, proteoglycans, glycosaminoglycans, polysaccharides, and non-hydrolysed or partly hydrolysed form thereof.

3. The microcapsule according to claim 1 , wherein the microcapsule is obtained by a method comprising the following steps:

a) forming a multi-component liquid drop comprising:

a liquid core,

a liquid intermediate envelope formed with an aqueous composition comprising at least one biopolymer, totally encapsulating at its periphery the liquid core, and

a liquid external envelope formed with an aqueous composition, different from the intermediate composition, said aqueous composition comprising at least one polyelectrolyte and at least one surfactant, said liquid external envelope totally encapsulating at its periphery the intermediate envelope,

the liquid core and/or the liquid intermediate envelope comprising at least one eukaryotic mammalian cell as set forth in claim 1 ,

b) gelling by immersion of said multi-component liquid drop in a gelling solution containing a reagent capable of gelling the polyelectrolyte of the liquid external envelope, in order to obtain a gelled microcapsule comprising a gelled external envelope,

c) stiffening the intermediate composition of the liquid intermediate envelope, in order to obtain a gelled and stiffened microcapsule comprising a stiffened intermediate envelope, said stiffened intermediate envelope having an elastic modulus that is non-zero, and

d) recovering said gelled and stiffened microcapsules.

4. The microcapsule according to claim 3 , the method further comprising a step for dissolving the gelled external envelope.

5. A method for preparing the microcapsule according to claim 1 , the method comprising the following steps:

a) forming a multi-component liquid drop comprising:

a liquid core,

a liquid intermediate envelope formed with an aqueous composition comprising at least one biopolymer, totally encapsulating at its periphery the liquid core, and

a liquid external envelope formed with an aqueous composition, different from the intermediate composition, said aqueous composition comprising at least one polyelectrolyte and at least one surfactant, said liquid external envelope totally encapsulating at its periphery the intermediate envelope,

the liquid core and/or the liquid intermediate envelope comprising at least one eukaryotic mammalian cell as set forth in claim 1 ,

b) gelling by immersion of said multi-component liquid drop in a gelling solution containing a reagent capable of gelling the polyelectrolyte of the liquid external envelope, in order to obtain a gelled microcapsule comprising a gelled external envelope,

c) stiffening the intermediate composition of the liquid intermediate envelope, in order to obtain a gelled and stiffened microcapsule comprising a stiffened intermediate envelope, and

d) recovering said gelled and stiffened microcapsules.

6. The method according to claim 5 , wherein the method further comprises a step for dissolving the gelled external envelope.

7. An in vitro method for cultivating eukaryotic mammalian cells comprising:

a) cultivating a microcapsule under sufficient conditions for cell growth, said microcapsule comprising a liquid core, and at least one external envelope totally encapsulating the liquid core at its periphery,

said external envelope being able to retain the liquid core when the microcapsule is immersed in a gas and comprising at least one gelled polyelectrolyte and/or one stiffened biopolymer, said microcapsule further comprising at least one eukaryotic mammalian cell as set forth in the preparation method according to claim 5 ; and

b) harvesting said microcapsule.

8. A method for screening active ingredients comprising:

a) cultivating the microcapsule according to claim 1 in the presence and in the absence of a candidate substance,

b) detecting a phenotype of interest in the cells of the microcapsule cultivated in the presence of the candidate substance as compared with the cells of the microcapsule cultivated in the absence of the candidate substance, and

c) identifying the candidate substance as an active ingredient if a phenotype of interest has been detected.

9. The method according to claim 8 , wherein the active ingredient is a cosmetic active ingredient.

10. An in vitro method for cultivating eukaryotic mammalian cells comprising the following steps:

a) cultivating the microcapsule according to claim 1 under sufficient conditions for cell growth, and

b) harvesting said microcapsule.

11. The method according to claim 10 , wherein said eukaryotic mammalian cells are human cells.

12. The microcapsule of claim 1 , wherein the stiff intermediate envelope is obtained by a stiffening method selected from the group consisting of: polymerization, precipitation, colloidal aggregation, and a glassy transition caused by a variation in temperature.

13. The microcapsule of claim 1 , wherein the stiff intermediate envelope is obtained by coacervation of an intermediate composition of a liquid intermediate envelope formed with an aqueous composition comprising at least one biopolymer.