Magnesium with micro-arc oxidation coating and polymeric membrane: an in vitro study on microenvironment.

Numerous modification methods have been reported to enhance the corrosion resistance of magnesium with positive results. However, little attention has been paid on their impact on micro-environment, particularly the ion concentration and local pH value. In this study, two different coatings were prepared on magnesium, one with porous micro-arc oxidation (MAO) coating alone, and the other with additional polymer polyhydroxybutyrate (PHB) membrane using spinning technique. Their in vitro corrosional and biological behaviors were investigated and compared. Both coatings were found to reduce the degradation rate of magnesium, but an additionally deposited PHB membrane was superior to MAO-coated magnesium since it could produce a micro-environment with preferable local pH value and ion concentration for osteoblast proliferation. Our study suggests that micro-environment should be another critical issue in evaluation of a modification method for orthopaedic implants.

Biological Fixation of Bioactive Bone Cement in Vertebroplasty: The First Clinical Investigation of Borosilicate Glass (BSG) Reinforced PMMA Bone Cement.

PMMA bone cement has been clinically used for decades in vertebroplasty due to its high mechanical strength and satisfactory injectability. However, the interface between bone and PMMA is fragile and more prone to refracture in situ because PMMA lacks a proper biological response from the host bone with minimal bone integration and dense fibrous tissue formation. Here, we modified PMMA by incoporating borosilicate glass (BSG) with a dual glass network of [BO3] and [SiO4], which spontaneously modulates immunity and osteogenesis. In particular, the BSG modified PMMA bone cement (abbreviated as BSG/PMMA cement) provided an alkaline microenvironment that spontaneously balanced the activities between osteoclasts and osteoblasts. Furthermore, the trace elements released from the BSGs enhanced the osteogenesis to strengthen the interface between the host bone and the implant. This study shows the first clinical case after implantation of BSG/PMMA for three months using the dual-energy CT, which found apatite nucleation around PMMA instead of fibrous tissues, indicating the biological interface was formed. Therefore, BSG/PMMA is promising as a biomaterial in vertebroplasty, overcoming the drawback of PMMA by improving the biological response from the host bone.