Porous tissue scaffoldings for the repair or regeneration of tissue

Abstract

The present patent describes a three-dimensional interconnected open cell porous foams that have a gradient in composition and / or microstructure through one or more directions. These foams can be made from a blend of absorbable and biocompatible polymers that are formed into foams having a compositional gradient transitioning from predominately one polymeric material to predominately a second polymeric material. These gradient foams are particularly well suited to tissue engineering applications and can be designed to mimic tissue transition or interface zones.

Description

[0001] The present invention relates generally to the field of tissue repair and regeneration. More particularly the present invention relates to porous biocompatible bioabsorbable foams that have a gradient in composition and / or microstructure that serve as a template for tissue regeneration, repair or augmentation.[0002] Open cell porous biocompatible foams have been recognized to have significant potential for use in the repair and regeneration of tissue. Early efforts in tissue repair focused on the use of amorphous biocompatible foam as porous plugs to fill voids in bone. Brekke, et al. (U.S. Pat. No. 4,186,448) described the use of porous mesh plugs composed of polyhydroxy acid polymers such as polylactide for healing bone voids. Several attempts have been made in the recent past to make TE scaffolds using different methods, for example U.S. Pat. No. 5,522,895 (Mikos) and 5,514,378 (Mikos, et al.) using leachables; U.S. Pat. No. 5,755,792 (Brekke) and U.S. Pat. No. 5,133,755 (...

AI Technical Summary

Benefits of technology

[0009] The present invention provides a biocompatible gradient foam that has a substantially continuous transition in at least one characteristic selected from the group consisting of composition, stiffness, flexibility, bioabsorption rate pore architecture and / or microstructure. This gradient foam can be made from a blend of absorbable polymers that form compositional gradient transitions from one polymeric material to a second polymeric material. In situations where a single chemical composition is sufficient for the application, the invention provides a biocompatible foam that may have microstructural variations in the structure across one or more dimensions that may mimic the anatomical features of the tissue (e.g. cartilage, skin, bone etc.).

[0012] The present invention also provides a method for the repair or regeneration of tissue contacting a first tissue with a gradient foam at a location on the foam that has appropriate properties to facilitate the growth of said tissue. The concept of a continuous transition in physical properties, chemical composition and / or microstructural features in the porous scaffold (foam) can facilitate the growth or regeneration of tissue. These foam structures are particularly useful for the generation of tissue junctions between two or more different types of tissues. For a multi-cellular system in the simplest case, one cell type could be present on one side of the scaffold and a second cell type on the other side of the scaffold. Examples of such regeneration can be (a) skin: with fibroblasts on one side to regenerate dermis, and keratinocytes on the other to regenerate epidermis; (b) vascular grafts: with an endothelial layer on the inside of the graft and a smooth muscle cell layer on the outside.

Problems solved by technology

However, the above techniques have limitations in producing a scaffold with a gradient structure.

Further, it is the limitation of prior art to make 3D scaffolds that have the ability to control the spatial distribution of various pore shapes.

However, the interface between the cartilage and bone in the human body is not a discrete junction of two dissimilar materials with an abrupt change in anatomical features and / or the mechanical properties.

In this technique which is quite cumbersome, a porous membrane is first prepared by drying a polymer solution containing leachable salt crystals.

One of the major weaknesses of the prior art regarding three-dimensional porous scaffolds used for the regeneration of biological tissue like cartilage is that their microstructure is random.

Further, current scaffolds do not provide adequate nutrient and fluid transport for many applications.

Finally, the laminated structures are not completely integrated and subjected to delamination under in vivo conditions.

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