Process for the production of a hybrid structure consisting of coupled silk fibroin microfibers and nanofibers, hybrid structure thus obtained and its use as implantable medical device

An implantable medical device comprising:

• a hybrid structure comprising coupled microfibers and nanofibers of silk fibroin, said hybrid structure obtained according to the process comprising:
• a) preparing of one or more parts made of microfibrous fibroin;
• b) preparing of one or more parts made of nanofibrous fibroin;
• c) treating of said one or more parts of nanofibrous fibroin and of said one or more parts of microfibrous fibroin, separately or after coupling, with a solvent for fibroin and/or with a solution comprising fibroin dissolved in the solvent;
• c′) if in step c) the nanofibrous and microfibrous parts have been treated separately with a solvent for fibroin and/or with a solution comprising fibroin dissolved in a solvent, coupling of said parts;
• d) consolidating the hybrid microfibrous/nanofibrous structure obtained in step c) or in step c′) by thermal treatment at a temperature between 10° C. and 150° C., for a time between 1 minute and 24 hours;
• e) removing the solvent by washing with water or a water-alcohol mixture at a temperature between 10° C. and 100° C., or by evaporation at a temperature between 10° C. and 100° C.,
• wherein the solvent for fibroin or the solvent of the solution comprising fibroin used in step c) is selected from:
• (i) formic acid, 1,1,1,3,3,3-hexafluoro-2-propanol, trifluoroacetic acid, hexafluoroacetone, N-methylmorpholine N-oxide, ionic liquids, and mixtures thereof, wherein said solvents are pure or in mixture with water;
• (ii) calcium chloride-ethanol-water mixtures, calcium nitrate-methanol-water mixtures, aqueous solutions of lithium salts and;
• (iii) mixtures among the solvents of (i) and (ii).