Heterotopic bone formation by nano-apatite containing poly(D,L-lactide) composites

Area of Science:

• Biomaterials Science
• Materials Engineering
• Regenerative Medicine

Background:

• Polymeric materials often lack inherent osteoinductivity for bone regeneration applications.
• Calcium phosphate apatite particles (CaP) are known for their biocompatibility and potential to enhance bone healing.
• Developing osteoinductive polymeric composites is crucial for advanced bone graft substitutes.

Purpose of the Study:

• To investigate the osteoinductive potential of poly(D,L-lactide) composites incorporating nano-sized calcium phosphate apatite particles (CaP).
• To evaluate the effect of varying CaP content on material properties and in vitro/in vivo biological responses.
• To determine the optimal CaP concentration for achieving osteoinductivity in a poly(D,L-lactide) matrix.

Main Methods:

• Fabrication of homogenous poly(D,L-lactide)/CaP composites with 10%, 20%, and 40% apatite content.
• Creation of porous samples (300-400 µm pores, 60% porosity) and sterilization.
• In vitro assessment of calcium ion release and surface mineralization in simulated body fluid (SBF).
• In vivo intramuscular implantation in dogs for 12 weeks to evaluate ectopic bone formation.

Main Results:

• Calcium ion release correlated with CaP content in vitro.
• Significant surface mineralization was observed only in 40% CaP composites after 14 days in SBF.
• Only the 40% CaP composite implant maintained structural integrity and demonstrated ectopic bone formation within its pores after 12 weeks in vivo.

Conclusions:

• A 40% apatite content in poly(D,L-lactide) composites renders the material osteoinductive.
• The 40% CaP composite shows promise as a potential bone graft substitute due to its ability to induce ectopic bone formation.
• Further research is needed to elucidate the mechanisms of material-directed osteoinduction for clinical translation.