Characterization of resilin-based materials for tissue engineering applications.

Modular proteins have emerged as powerful tools in tissue engineering because both the mechanical and biochemical properties can be precisely controlled through amino acid sequence. Resilin is an attractive candidate for use in modular proteins because it is well-known for having low stiffness, high fatigue lifetime, and high resilience. However, no studies have been conducted to assess resilin's compressive properties, cytocompatibility with clinically relevant cells, or effect on cell spreading. We designed a modular protein containing repeating sequences of a motif derived from Anopheles gambiae and cell-binding domains derived from fibronectin. Rapid cross-linking with tris(hydroxymethyl)phosphine was observed. The hydrogels had a complex modulus of 22 ± 1 kPa and yield strain of 63%. The elastic modulus in compression, or unconfined compressive modulus, was 2.4 ± 0.2 MPa, which is on the same order as human cartilage. A LIVE/DEAD assay demonstrated that human mesenchymal stem cells cultured on the resilin-based protein had a viability of 95% after three days. A cell-spreading assay revealed that the cells interacted with the fibronectin-derived domain in a sequence-specific manner and resulted in a mean cell area ~1.4-fold larger than when cells were seeded on a sequence-scrambled negative control protein. These results demonstrate that our resilin-based biomaterial is a promising biomaterial for cartilage tissue engineering.