| AVS 63rd International Symposium & Exhibition | |
| Biomaterial Interfaces | Tuesday Sessions |
| Session BI+PB-TuP |
| Session: | Biomaterial Interfaces Poster Session (preceded by Oral Flash Presentations) |
| Presenter: | David Florian, University of Virginia |
| Authors: | M.A. Melia, University of Virginia D.C. Florian, University of Virginia W. Steuer, University of Virginia J.R. Scully, University of Virginia J.M. Fitz-Gerald, University of Virginia |
| Correspondent: | Click to Email |
Until recently, biodegradable implants have exclusively been used in non-load bearing applications such as stents and sutures. Mg-Al-Zn alloys like AZ31B are currently being considered as biodegradable materials because of their similar mechanical properties to that of bone. In addition, the corrosion product resulting from Mg alloys in body fluid contains Mg and Ca-phosphates (hydroxyapatite) and has been shown to stimulate bone regeneration. The degradation of Mg alloys is also considered non-toxic when corroding in the human body. However, the structural integrity is poor due to rapid corrosion caused by microstructural heterogeneities in the form of electrochemically noble secondary phases leading to micro-galvanic couples and preferential dissolution of the α-Mg matrix in physiological media. Laser surface processing of the Mg-Al-Zn alloy, AZ31B, reduced the corrosion rate in simulated body fluid (SBF) experiments by minimizing the impact of secondary phases.
Experiments utilized a pulsed excimer laser (λ = 248 nm and FWHM = 25 ns) in combination with a novel surface modification chamber. Samples of AZ31B in the as-received and laser processed condition were submerged in a 27 mM HCO3- Tris ((HOCH2)3CNH2) variant of SBF. The corrosion resistance was investigated through optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), gravimetric mass loss, and polarization measurements.
No major corrosion product variations were observed for the as-received / laser processed specimens by SEM and EDS, both showing a similar amount of Ca and P. The laser processed alloy exhibited a reduction in anodic kinetics compared to the as-received material, suggesting the corrosion product is more compact and passivating. Furthermore, the laser processed surface exhibited a 50% reduction in mass loss after 24 hours immersion in SBF in comparison to the as-received samples. Optical micrographs of samples immersed in SBF reveal a reduction in the H2 evolution rate of the laser processed versus as-received material. In addition, the laser treated specimens exhibited a significant increase in wettability with a 10o contact angle compared to the 45o angle of the as-received materials. The increased wettability of the laser processed samples may decrease the time required for osseointegration through allowing cells to more readily bind to the surface of an implant.