In vitro growth of tissues has great potential for a wide range of medical applications. Tissues can be grown in the lab and then used to replace damaged or lost tissues in the body. However, in order to successfully grow tissues, biomedical scientists need extracellular matrices (ECMs) that mimic bodily conditions.
An artificial ECM helps to ensure cells survive, migrate, and differentiate. ECMs serve as a substrate on which cells can grow, the ECM provides the structure for the growth of the tissue as well as the growth factors necessary for artificial tissue generation in three dimensions. However, designing an ideal artificial ECM remains a challenge.
Scaffolds consisting of proteins and polysaccharides offer a number of advantages, helping with cell attachment, proliferation, and the regeneration of tissues. Biomedical scientists have investigated a wide range of materials for constructing scaffolds of proteins and polysaccharides for tissue generation with varying degrees of success. Some natural polymers have been shown promise, yet there are many undesirable properties that hamper efforts to construct effective, practical scaffolds with all of the required properties.
Silk offer a number of advantages over other materials for use in scaffolds. Silk – which is composed of sericin and fibrocin – has excellent mechanical properties, is easy to produce, is biocompatible and has low immunogenicity. Silk-based scaffolds have potential for use in growing skin, nerves, and cartilage. However, silk-based scaffolds are brittle and are therefore impractical.
Alginate-based scaffolds offer strength and flexibility. Alginates are extracted from seaweed and the material has been shown to accelerate healing of wounds making them ideal for growing tissues to repair damaged skin. However, alginate-based scaffolds also have disadvantages. They are flexible, but they are prone to swell, leading to deformation of the scaffold. Consequently, they are blended with other natural macromolecules such as elastin, gelatin, and collagen to make them better suited for use in tissue engineering scaffolds. These scaffolds have far superior properties, although these composite scaffolds lack one or more desirable properties.
Research into composite scaffolds from silk fibrocin (SF) and sodium alginate (SA) have shown some promise. SF and SA have been blended into films and hydrogels which have been used for a number of tissue engineering applications, although the scaffolds have not been extensively studied for use in tissue engineering to repair damaged soft tissues.
However, a team of researchers lead by Yiyu Wang has developed a stable, cytocompatible scaffold of SF/SA that combines the best features of both compounds. The scaffold has an ideal pore diameter, has excellent mechanical strength, and ideal degradation and swelling capacity. Furthermore, these parameters can be easily altered to suit specific tissue engineering applications.
The team was able to create the scaffolds in an aqueous solution at room temperature and the technique would easily allow the combination of growth factors or drugs into the scaffold. The team reports that two blends in particular have a remarkably similar structure to skin tissue and closely mimic natural ECMs. The scaffolds were also shown to enhance cell adhesion and proliferation in vitro, making them ideal candidates for use in soft tissue engineering applications.
The study has recently been published in Nature.