Abstract
Abstract As biodegradable orthopedic implant materials, magnesium alloys have been attracted enough attentions recently. However, too fast degradation in vivo, limited biocompatibilities, and insufficient antibacterial properties are three main challenges at present. In order to solve these problems, a multifunctional composite coating of Chi(Zn/BMP2)/HA was constructed on AZ31B magnesium alloy surface, successively by the alkali heating treatment, self-assembly of 16-phosphonyl-hexadecanoic acid, in situ immobilization of Chi(Zn/BMP2) (chitosan, zinc ions, and bone morphogenetic protein 2), and the deposition of HA (hydroxyapatite). The results of ATR-FTIR (attenuated total reflection Fourier transform infrared spectrum) spectra and elemental compositions confirmed that 16-phosphonyl-hexadecanoic acid, Chi(Zn/BMP2), and HA were successfully immobilized on the surface. Compared with Mg, Mg-OH, Mg-16, and Mg-Chi(Zn/BMP2), Mg-Chi(Zn/BMP2)/HA with the concave–convex structure surface significantly enhanced the hydrophilicity and corrosion resistance. On the other hand, Mg-Chi(Zn/BMP2)/HA coating also showed excellent biocompatibilities, which not only significantly promoted the osteoblast adhesion and proliferation, but also upregulated ALP and OCN expression of osteoblasts. Furthermore, due to the synergistic antibacterial effect of zinc ions and chitosan, Mg-Chi(Zn/BMP2)/HA showed a good antibacterial property against Escherichia coli (E. coli). Therefore, it can be said that the method used in this work has a good application prospect in improving the corrosion resistance, biocompatibility of magnesium alloys, and inhibiting infections against E. coli.
Highlights
There are increasing demands on clinical implants for orthopedic diseases [1]
After being washed thrice by PBS, the attached bacteria were fixed by 2.5% glutaraldehyde followed by dehydrating with 50, 70, 90, and 100% ethanol solutions for 10 min each time
The evaluation on bactericidal activities was carried out according to ISO22196-2007 and E. coli (ATCC 25922) was chosen for the antimicrobial tests
Summary
There are increasing demands on clinical implants for orthopedic diseases [1]. Compared with ceramics and polymers, biomedical metals are more suitable for hardtissue implants, especially in load-bearing application, owing to their excellent strength and toughness [2,3]. Cobalt–chromium-based alloys, and titanium alloys are commonly used to repair serious bone fracture or replace the bone tissue. Their mismatched elastic modus with natural bone tissue contributes to occurrence of the stress-shielding effect and restrains the growth of new bone [4]. Harmful metallic ions or particles released through corrosion or wear can lead to inflammation, cell apoptosis, and other destructive tissue reactions [5,6]. The three metallic materials, called as permanent rigid metals, must be removed from the human body by a second surgical
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