Preparation of poly(lactic acid) composite hollow spheres containing calcium carbonates

Poly(lactic acid) composite hollow spheres containing calcium carbonate were prepared by oil-in-water emulsion evaporation to develop injectable bone substitutes incorporated with cells. The spheres were ∼1.2 mm in diameter and had a shell with a thickness in the range of 50–150 μm. The hollow in the spheres was presumed to be formed by CO2 gas generated by the decomposition of vaterite used as a starting material. An open channel ∼800 μm in diameter was formed in the spheres by chemical etching utilizing the rapid dissolution of poly(lactic acid) at the thin portion of the shell. Cells could migrate into the hollow spheres through the open channel and attach to the inner surface.