(268d) The Effects of Elastin on the Mechanical Properties of Collagen-Gag Membranes for Tissue Engineered Skin

Tissue engineered skin is one of the few tissue engineered products that is currently being used clinically. The success of tissue engineered skin comes from advances in keratinocyte harvesting, keratinocyte culturing and tissue engineering scaffolds. Procedures have been well developed to produce tissue engineered artificial skin substitutes with controlled characteristics. Collagen glycoaminoglycan (CG) is often used in tissue engineering constructs because of its biocompatibility and cell adhesion properties. Also, because collagen is a natural biological structural unit it is easy for cells to rearrange the collagen into a native ECM. Traditional CG scaffolds for skin tissue engineering use membranes created by filtering a CG suspension. The advantages of the filtration method are the uniformity and strength of the resulting membranes. Membrane strength is important when integrating the tissue engineered skin with the host skin, but other mechanical properties are also important for a successful tissue engineered product. Tissue engineered skin must also have an elastic modulus comparable to skin to be able to withstand the stretching and bending of the host. Elastin is a natural protein that increases the elasticity of connective tissues by forming a spring like cross-linked array. Adding elastin to CG membranes could increase their compatibility and promote integration with the host tissue. The formation of constructs starts by preparing a CG solution. The basic procedure for preparing solutions was adapted from that of Yannas, et al. In short, 0.55 g of type I bovine collagen is added to a 0.05 M acetic acid solution. The solution is homogenized in a cooled jacketed blender. After 45 minutes of blending 0.055g of the glycosaminoglycan Chondroitin-6 Sulfate dissolved in 10 mL of 0.05M acetic acid solution is added to the solution drop-wise. The solution is then blended for an additional 5 minutes. The filtering method for producing CG membranes is accomplished by placing the homogenized CG solution into a vacuum flask. A vacuum flask with a filter size of 0.4 microns is used to separate the solution from the CG. The solution is then filtered overnight. After the liquid is filtered away a thin continuous collagen membrane remains. This membrane is strong enough to be removed with a tweezers as a single coherent unit. When a solution 0.55g of collagen is filtered in a 350 ml flask with an 8 cm diameter the resulting membrane is approximately 400 microns. This procedure was altered by incorporating varying amounts of elastin into the collagen suspension. The weight percentage of elastin in the membrane was varied from 0% to 10%. The membranes were then completed using the same filtration method as stated previously. The mechanical properties of the CG/elastin membranes were tested using a universal materials testing machine (Instron. Norwood, MA). It was found that adding elastin to the CG membranes increased the stress and strain at breakage and increased the elastic modulus of the membrane. Membranes with 10% elastin by weight showed a 27% increase in strain at breakage and a 76% increase in stress at breakage. Cell viability for creating tissue engineered skin from these membranes is currently being assessed.