The present invention relates to coated silk films. Further, the present invention relates to pharmaceutical or cosmetic compositions comprising the coated silk films. Furthermore, the present invention relates to coated silk films or pharmaceutical compositions comprising the coated silk films for use in medicine. In addition, the present invention relates to methods of producing the coated silk films.

BACKGROUND OF THE INVENTION

In the past years, sophisticated drug depot systems for controlled delivery of drugs have been developed, for example to achieve constant drug levels during therapy. These systems have the advantage of reducing toxic side effects so that the number of drug administrations can be decreased, while at the same time improving cellular uptake and bioavailability. There is also an ongoing quest to design depot systems which facilitate controlled delivery of substances other than pharmaceutical compounds such as cosmetic compounds. In general, the material employed as a carrier for controlled delivery of a substance should offer control of structure, morphology and function, while also exhibiting good mechanical stability. For example, biodegradable and biocompatible polymers are preferred because of their ability to retain their properties for a limited period of time before gradually decomposing into soluble nontoxic degradation products which can be excreted from the body. Many synthetic polymers (e.g. polyester or polyurethane) and biopolymers (e.g. polysaccharides or proteins) have been employed to produce drug depot systems for encapsulation, incorporation, or binding of active compounds. In particular, the use of silk as biopolymer for drug depot systems, especially because of its biocompatibility, non-toxicity and biodegradability, has been investigated in the art. For example, silk films have been tested for their ability to deliver drugs and other substances. Especially, silk derived from spiders or insects has been used.

The inventors of the present invention studied silk films as drug release systems. Without wishing to be bound to any theory, they surprisingly found that drugs released faster through the side surfaces than through the upper and lower surfaces of silk films, thus, resulting in a(n) (initial) burst drug release profile. However, in many applications it is desirable to release the loaded drug over an extended period of time controllably, constantly, and sustainably. The inventors of the present invention surprisingly found that a controlled, constant, and sustained drug release profile can be achieved with silk films which comprise at least at their side surfaces a coating layer in order to reduce the rapid diffusion of compounds through said side surfaces. The favourable release profile of the coated silk films renders them eminently suitable for controlled, constant, and sustained delivery of pharmaceutical as well as cosmetic compounds. The compounds can be small molecular weight compounds such as drugs and/or proteins. Due to their stability and biocompatibility under physiological conditions, the coated silk films are especially suitable for in vivo applications. The casting of silk films from an aqueous solution avoids the use of organic solvents.

SUMMARY OF THE INVENTION

In a first aspect, the present invention relates to a coated silk film comprising(i) an active agent release sheet which comprises one or more first silk film layers comprising at least one active agent, and(ii) one or more release modifying layers covering at least the side surface(s) of the active agent release sheet.

In a second aspect, the present invention relates to a pharmaceutical composition comprising the coated silk film according to the first aspect, wherein the active agent is a pharmaceutical agent.

In a third aspect, the present invention relates to a cosmetic composition comprising the coated silk film according to the first aspect, wherein the active agent is a cosmetic agent.

In a fourth aspect, the present invention relates to a coated silk film according to the first aspect or pharmaceutical composition according to the second aspect for use in medicine.

In a fifth aspect, the present invention relates to a coated silk film according to the first aspect or pharmaceutical composition according to the second aspect for controlled and sustained release of at least one pharmaceutical agent.

In a sixth aspect, the present invention relates to a coated silk film according to the first aspect or pharmaceutical composition according to the second aspect for the treatment of wounds, skin diseases, or skin defects.

In a seventh aspect, the present invention relates to the use of the coated silk film according to the first aspect or cosmetic composition according to the third aspect for controlled and sustained release of at least one cosmetic agent.

In an eight aspect, the present invention relates to a method of producing a coated silk film comprising the steps of:(i) providing an active agent release sheet which comprises one or more first silk film layers comprising at least one active agent, and(ii) covering at least the side surface(s) of the active agent release sheet with one or more release modifying layers.

The following figures are merely illustrative of the present invention and should not be construed to limit the scope of the invention as indicated by the appended claims in any way.

