Polymerization of L-lactide within the pores of anorganic mammalian bone is described. No additional solvent or catalyst is used. The resulting composites exhibit macroscopic morphologies and mechanical properties similar to that of the original bone. We observe an average compressive strength of 194 MPa and an elastic modulus of 8.8 GPa for composites comprised of poly-L-lactide and anorganic bone derived from bovine femurs. Modeling of the reaction kinetics with synthetic sources of crystalline hydroxyapatite powder suggests that polymerization proceeds via a surface-initiated mechanism that is first order in surface area of hydroxyapatite and first order in mole fraction of L-lactide.

Biomimetic composites were constructed using anorganic bone to initiate the polymerization of cyclic lactones. The resulting anorganic bone/polylactone composites preserve the inorganic structure and the mechanical properties of the original bone. Thermal conditions used to prepare the anorganic bone were shown to control the surface functionalities, surface area, and crystallinity, all of which influence the rates of subsequent polymerizations. Thermal pretreatment of anorganic bone was examined as a function of time and temperature, ranging from 400°C to 800°C. Polymerization rates of different monomers were also compared. Additionally, in vitro evaluations of anorganic bone/poly-L-lactide and anorganic bone/polyglycolide composites for osteoblast and osteoclast competence suggest that these composites are good candidates for potential in vivo use, since both composites promoted osteoblast differentiation. The anorganic bone/poly-L-lactide composite also promoted osteoclast differentiation.