Poly-Lactic Acid Reinforced Magnesium Alloy Nanowires
Poly-lactic acid (PLA) is another common biomaterial used as it is naturally biodegradable since it is derived from plants, such as starch and sugarcane. In using it for orthopedic applications several drawbacks must be overcome, such as poor mechanical strength, heterogeneous degradation [36, 37], and formation of acidic hydrogen ions during degradation, which lower the pH giving rise to bone resorption. Various materials have been used to create PLA composites with enhanced properties, including hydroxyapatite [36, 38], titania nanoparticles , and magnesium alloy fibers. In this section a summary will be given of PLA-Mg alloy composites.
Mg based fillers are biodegradable and have a very high biocompatibility. They are preferred for orthopedic applications since the density and elastic modulus of Mg are similar to those of cortical bone. Mg, however, cannot be used in its pure form as it is highly corrosive, and therefore it is either alloyed with another metal [40, 41] or coatings are deposited on its surface [42, 43]. A recent promising alloy that has been used to reinforce PLA is AZ31, which is comprised of 96 wt% Mg, 3 wt% Al and 1 wt% Zn, and will be described in the sequel .
Fig. 4.7 Scanning electron microscopy images illustrating the Mg-alloy reinforced scaffolds, with either treated or non-treated alloy surface (Reproduced with permission from Ref. )