A new method to produce macroporous Mg-phosphate bone growth substitutes

- We report a new real time, in situ technique to fabricate macroporous bone grafts.
- Self-corroding Mg granules act as porogens.
- Compositions containing AMP and PVA self-set within a reasonable time.
- The final bone graft substitute showed promising biocompatibility.
- The results provide important information on the porosity content and bioactivity.

This paper is a sequel to our previous effort in developing Mg-phosphate orthopedic cements using amorphous Mg-phosphate (AMP) as the precursor. In this paper, we report a new real-time in situ technique to create macroporous bone growth substitute (BGS). The method uses biodegradable Mg-particles as the porogen. As opposed to the conventional wisdom of providing corrosion protection layers to biodegradable Mg-alloys, the present method uses the fast corrosion kinetics of Mg to create macropores in real time during the setting of the cement. An aqueous solution of PVA was used as the setting solution. Using this technique, a macroporous cement containing up to 91% porosity is obtained, as determined by pycnometry. Due to formation of H2 gas bubbles from corrosion of Mg, the cement becomes macroporous. The pore sizes as big as 760 μm were observed. The results of SBF soaking indicated change in crystallinity as confirmed via scanning electron microscopy (SEM) and X-ray diffraction (XRD). Our in vitro cytocompatibility evaluation also revealed that the macroporous bone growth substitute composed of bobierrite is cytocompatible and can improve gene expression.