Abstract
Over the past few decades there has been great interest in the use of orthopedic and dental implants that integrate into tissue by promoting bone ingrowth or bone adhesion, thereby eliminating the need for cement fixation. However, strategies to create bioactive implant surfaces to direct cellular activity and mineralization leading to osteointegration are lacking. We report here on a method to prepare a hybrid bone implant material consisting of a Ti-6Al-4V foam, whose 52% porosity is filled with a peptide amphiphile (PA) nanofiber matrix. These PA nanofibers can be highly bioactive by molecular design, and are used here as a strategy to transform an inert titanium foam into a potentially bioactive implant. Using scanning electron microscopy (SEM) and confocal microscopy, we show that PA molecules self-assemble into a nanofiber matrix within the pores of the metallic foam, fully occupying the foam's interconnected porosity. Furthermore, the method allows the encapsulation of cells within the bioactive matrix, and under appropriate conditions the nanofibers can nucleate mineralization of calcium phosphate phases with a Ca:P ratio that corresponds to that of hydroxyapatite. Cell encapsulation was quantified using a DNA measuring assay and qualitatively verified by SEM and confocal microscopy. An in vivo experiment was performed using a bone plug model in the diaphysis of the hind femurs of a Sprague Dawley rat and examined by histology to evaluate the performance of these hybrid systems after 4 weeks of implantation. Preliminary results demonstrate de novo bone formation around and inside the implant, vascularization around the implant, as well as the absence of a cytotoxic response. The PA-Ti hybrid strategy could be potentially tailored to initiate mineralization and direct a cellular response from the host tissue into porous implants to form new bone and thereby improve fixation, osteointegration, and long term stability of implants.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 161-171 |
| Number of pages | 11 |
| Journal | Biomaterials |
| Volume | 29 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jan 2008 |
Funding
The authors gratefully acknowledge funding support from the National Science Foundation, under Award no. DMR-0505772 and the National Institutes of Health, under Award no. 5R01DE015920. Electron microscopy was performed in the Electron Probe Instrumentation Center (EPIC) facility of the NUANCE Center at Northwestern University, and is supported by NSF-NSEC, NSF-MRSEC, Keck Foundation, the State of Illinois, and Northwestern University. Confocal microscopy was performed in the Biological Imaging Facility (BIF) at Northwestern University. Portions of the cell work were performed in the Institute for Bionanotechnology in Medicine (IBNAM) at Northwestern University. We thank Mr. Ben Myers for his technical help with experiments at EPIC and Dr. William Russin for his technical help with experiments at BIF. We thank Dr. Catherine Ambrose for histological preparation performed at The University of Texas Houston Health Science Center, and Dr. Sue Crawford and Dr. Philip Fitchev at Northwestern University for her help with histological analysis.
Keywords
- Bone
- Foam
- MC3T3-E1
- Self-assembly
- Ti-6Al-4V
- Tissue engineering
ASJC Scopus subject areas
- Mechanics of Materials
- Ceramics and Composites
- Bioengineering
- Biophysics
- Biomaterials