Improving Degradable Biomaterials for Orthopedic Fixation Devices

Abstract

Current degradable orthopedic fixation devices do not typically facilitate tissue integration during healing. Proposed here is a novel combination of processing methods to enhance the tissue integration capability of degradable thermoplastics used in temporary orthopedic fixation devices. The provision of open pores in devices used to affix reconstructed hard tissues would allow for local cells to infiltrate during the healing process. Any openly porous structure is inherently weakened in comparison to its monolithic peers (i.e. decreased relative bulk modulus), such that the matrix materials must be made more resilient in keep the device from becoming friable. These processing methods aim to improve degradable surgical fixation devices at multiple levels of design: both through the inclusion of porous morphology, processing changes, and additives to regain mechanical integrity. Biomimetic pores are added for cellular infiltration by dissolving a porogen’s interpenetrating polymer network. The addition of open pores significantly reduces the bulk stiffness. More uniform phase separation has led to better pores, but the objects still need more resilience. Carbon nanomaterials are used to improve on the mechanics and surface chemistry of the polymer matrix material, composites of polylactide/nanodiamond are produced through cryogenic milling and solid state polycondensation. The addition of minute amounts of functionalized nanodiamond has remedied the brittle failure of the material, by cryogenic milling and solid state polycondensation of poly((D,L)lactide-co-glycolide) and hydroxyl functionalized detonation nanodiamonds. This composite has also demonstrated increased cytocompatability with 7F2 osteoblasts, as analyzed by cellular adhesion through fluorescence microscopy and alamar blue assay.