The disclosed subject matter can provide a nanotube-reinforced polymer composite material comprising a plurality of nanotubes, each nanotube being formed of a plurality of cyclic peptide molecules, disposed within a polymer matrix, such as a biodegradable polymer matrix. A cyclic polymer, such as a cyclic 8-mer, composed of amino acid residues of alternating absolute configurations (D/L, R/S), can self-assemble into nanotubes useful for preparation of the composite polymer material of the invention. For example, the cyclic peptide (QL)4, wherein the glutamine and leucine residues are of opposite absolute configuration, self-assembles into nanotubes, which when formed into a reinforced polymer composite including poly(caprolactone), provides a biocompatible material of greater tensile strength and Youngs modulus compared to the poly(caprolactone) material alone. The nanotubes can be prepared by a vapor equilibration technique or by a solvent-nonsolvent precipitation technique. The materials of the invention can be used for implants, stents and the like as well as for synthetic ligaments, tendons, cartilage, and bone for use in the living tissue of a patient in need thereof. For example, a spinal fusion cage comprising a PDLLA polymer matrix with a plurality of nanotubes of the invention can exhibit enhanced stiffness.
