MECHANICAL-PROPERTIES OF A SELF-ASSEMBLING OLIGOPEPTIDE MATRIX

We have begun studies of a novel type of biomaterial derived from a re cently-discovered class of ionic self-complementary oligopeptides. The se short peptides (typically 8, 16, 24, or 32 amino acid residues with internally-repeating sequences) self-assemble in aqueous salt solutio n into three-dimensional matrices capable of favorable interactions wi th cells, and offer promise for useful bioengineering design based on rational changes in sequence. In this paper we present preliminary res ults on mechanical properties, combining experimental and theoretical approaches, of one particular example of these peptide materials, EFK8 . The static elastic modulus was measured using an apparatus designed to allow sample fabrication and mechanical testing in the same system with the sample in aqueous solution. The material microstructure was e xamined by SEM and the measurements interpreted with the aid of a mode l for cellular solids. Values for the elastic modulus increased from 1 .59 +/- 0.06 to 14.7 +/- 1.0 kPa for peptide concentrations increasing from 2.7 to 10 mg ml(-1) SEM photographs showed the microstructure to consist of a relatively homogeneous lattice with fiber thickness of 1 0-30 nm independent of peptide concentration, but with fiber density i ncreasing with peptide concentration. This behavior is consistent with scaling predictions from the cellular solids model and yields an esti mate for the individual fiber elastic modulus in the range of 1-20 MPa . We therefore have provided some initial physical principles for guid ing improvement of the mechanical properties of these new materials.