Dissolution behavior of Mg/Si-doped vaterite particles in biodegradable polymer composites

Abstract

Tuning the ion release ability of bioactive materials is one of the key factors for bone repair and regeneration. Calcium (Ca2+), magnesium (Mg2+), and silicate ions were reported to enhance the activity of bone-forming cells. In this work, the dissolution behavior of magnesium- and silicate-doped calcium carbonate (vaterite), denoted as MgSiV, embedded in three kinds of biodegradable polymers in Tris buffer solutions (TBS) were examined to find an effective ion releasing system. Poly(L-lactic acid) (PLLA) and poly(D,L-lactide-co-glycolide) (PDLLG, lactide:glycolide = 75:25 or 50:50; denoted as PDLLG75 and PDLLG50, respectively) were chosen as the matrix polymers. The Mg2+ and silicate ions were released rapidly within 3 d of soaking. Continuous release of Ca2+ ions from the composites induced the formation of aragonite on the film surfaces in the presence of Mg2+ ions. The amount of ions released from the MgSiV-PLLA composite was lesser than those released from the PDLLG-based composites. The fast degradation of PDLLG50 induced a decrease in the pH of TBS. The MgSiV-PDLLG75 composite exhibited a rapid release of Mg2+ ions, a continuous release of Ca2+ ions, and a controlled release of silicate ions with no reduction in the pH of TBS. Such release phenomena are caused by the formation of pathways for ion release, originating from the water uptake ability of PDLLG75.

Keywords

• Polymer composites
• Biodegradable polymers
• Calcium carbonate
• Ion release
• Biomaterials