In situ polymerization of tropoelastin in the absence of chemical cross-linking.

Tropoelastin, the polypeptide monomer precursor of elastin, is covalently cross-linked to give stable elastic structures. We show here that elastic biomaterials can be generated from tropoelastin in the absence of the classically accepted cross-linking pathway. Under alkaline conditions tropoelastin proceeds through a sol-gel transition leading to the formation of an irreversible hydrogel. This does not occur at neutral pH. The resulting biomaterial is stable, elastic and flexible. Scanning electron microscopy revealed that the hydrogel forms through the coalescence of approximately 1 microm quantized protein spheres. These spheres resemble the tropoelastin-rich globules that accumulate on cultured cell surfaces during elastin formation. In vitro cell culture studies demonstrate that the hydrogel can support human skin fibroblast proliferation. In vivo studies demonstrate that following injection, the tropoelastin solution undergoes rapid localized gelation to form a persistent mass. These subcutaneous rodent injection data establish the material's potential as a novel cell-compatible elastic scaffold that can be formed in situ.