Bioelastic Materials as Matrices for Tissue Reconstruction

Abstract

Bioelastic materials are elastomeric polypeptides whose origins are repeating peptide sequences in mammalian elastic fibers (Sandberg et al., 1985; Yeh et al., 1987; Indik et al., 1987). Physical properties of synthetic high polymers of the repeats have been extensively studied (Urry, 1991;1988), and they have been designed to exhibit properties not present in elastic fibers. A key property is that these elastomeric polypeptides exhibit reversible transitional behavior in which they become more-ordered on increasing the temperature through a critical temperature range (Urry, 1992). This is called an inverse temperature transition; its onset temperature is designated as Tt; and it is due to hydrophobic folding and assembly. The reverse process of hydrophobic unfolding and disassembly on lowering the temperature is well-known in proteins as cold denaturation (Privalov, 1990). The temperature, Tt, at which the transition occurs depends on the amino acid composition allowing for a Tt-based hydrophobicity scale to be developed (Urry et al., 1992a) which allows the bioelastic material to be designed to have its transition temperature set as desired within the available aqueous range or returned to a desired temperature when functional peptide sequences have been added that change the value of Tt. In spite of becoming more-ordered on raising the temperature, the more-ordered state in cross-linked matrices is a dominantly entropic elastomer (Urry, 1991) with the potential for great durability to sustain repeated stretch/relaxation cycles.